БЪЛГАРСКА АКАДЕМИЯ НА НАУКИТЕ ИНСТИТУТ ПО ЕЛЕКТРОНИКА “АКАДЕМИК ЕМИЛ ДЖАКОВ”
BULGARIAN ACADEMY OF SCIENCES INSTITUTE OF ELECTRONICS “ACADEMICIAN EMIL DJAKOV”
EMIL DJAKOV INSTITUTE OF ELECTRONICS
ANNUAL REPORT 2012
Dedicated to the Institute’s 50th Anniversary
Editors: Ch. Ghelev and N. Guerassimov
Contents Page 50th Anniversary of Academician Emil Djakov Institute of Electronics 4 Institute of Electronics on the Eve of its 50th Anniversary 8
Laboratories: 11 ● Plasma Physics and Engineering 13 ● Physical Problems of Ion Technologies 20 ● Physical Problems of Electron Beam Technologies 24 ● Superconductivity and Cryoelectronics 32 ● Micro- and Nano-Photonics 36 ● Biophotonics 41 ● Laser Systems 51 ● Nonlinear and Fiber Optics 56 ● Laser Radars 59 ● Microwave Physics and Technologies 69 ● Microwave Magnetics 73 ● Physical Technologies 79
Selected Projects: 81 ● Modeling and Simulation of Gyrotrons for ITER 83 ● Regeneration of Materials by Electron Beam Melting and 91 Refining of Refractory Metals and Alloys in Vacuum ● Plasmon and Optical Properties of Metal Nanoparticles and 97 their Application to High-Sensitivity Raman Spectroscopy and Biophotonics ● High-Resolution Spectroscopy of Cs Vapor Confined in 100 Micron-Thickness Optical Cells ● Aerosols, Clouds, and Trace-Gasses Research Infrastructure 106 Network (ACTRIS) ● Improving the Resolution of Thomson Scattering Lidars by 114 Application of Novel Deconvolution-Based Algorithms ● Development and Introduction of Optical Biopsy System for 119 Early Diagnostic of Malignant Tumors ● Coherent Optics Sensors for Medical Applications (COSMA) 124
Scientific Events: 125 ● Tenth Anniversary International Conference on Electron Beam 127 Technologies (EBT’2012) ● Seventeenth International School on Quantum Electronics Laser 129 Physics and Applications (ISQE’2012)
Awards 133
4 50th Anniversary of E. Djakov Institute of Electronics
50th ANNIVERSARY OF ACADEMICIAN EMIL DJAKOV INSTITUTE OF ELECTRONICS
In 2013, the Academician Emil Djakov intellectual and material enrichment and to Institute of Electronics of the Bulgarian widening humankind’s scientific horizons. Academy of Sciences turns 50. It was Through the years, the Institute’s established on September 27, 1962, by a research field and structure have Resolution of Bulgaria’s National developed dynamically in response to the Assembly and began its independent changes taking place in the main trends existence in 1963 based on the Physical in applied physics and technologies: and Applied Electronics Section formed materials science and technologies, in 1948 at the Institute of Physics of the physics of nano-sized objects and BAS by the Institute of Electronics’ nanotechnologies, nanoelectronics, founder, first Director and builder, photonics, opto-electronics, quantum Academician Emil Djakov. Initially, the optics, environmental physics and Institute had 30 employees and comprised monitoring, biomedical photonics and two sections and two laboratories located biomedical applications. on the fourth floor of the Institute of The Institute’s main areas of scientific Physics’ new building. According to the development have been preserved, while Resolution of September 27, 1962, the the specific research today takes into Institute of Electronics’ scope of activities account the contemporary problems and was academic research in the fields of requirements, the world-wide tendencies cathode electronics, electro-vacuum and Bulgaria’s specificity and traditions. microwave devices, quantum electronics The research efforts in physical and applied electronics. At the time, the electronics are concentrated on studying term Electronics included the set of and solving the problems of generating fundamental knowledge, technologies and and controlling electron and ion beams algorithms for the development and and their interaction with materials. This manufacture of the electronic components includes theoretical modeling, modern necessary for creating modern techniques, research and industrial communications, computing equipment equipment for micro- and nano- and information technologies. The structuring, thin films deposition and Institute was relied on to become the study, modification of surfaces, vacuum academic motor in the drive of laying the melting and welding of metals by intense scientific foundations and forming the electron beams. The physical basis is research cadres necessary for the nascent being formed of creating nanostructures, electronic stage of Bulgaria’s nanomaterials and nanoelements by development. using electron and ion beams. In its quality of a part of the Bulgarian Furthermore, fundamental properties are Academy of Sciences, the Institute’s being investigated of gasses and gas mission is to acquire, accumulate and plasma, plasma arcs and plasma torches disseminate scientific knowledge and in view of developing diagnostic technologies in its research field, thus techniques and applications in thin films contributing to Bulgarian people’s deposition and plasma chemistry. 5 Annual Report IE 2012
The research in photonics and quantum for gas lasers; particularities in the electronics comprises theoretical and interaction of electron and ion beams with experimental studies on the interaction of materials; electromagnetically induced short and ultrashort lasers pulses with absorption in Hanle configuration. matter; development of novel During the 50 years of the Institute’s nanostructuring technologies; laser thin- existence, its scientists have published films deposition and treatment; light- over 7000 scientific papers that have been induced absorption and transmission in cited more than 4500 times. The Institute alkaline vapors; development of complex has taken an active part in the international laser systems for analysis and modification scientific cooperation by establishing of semiconducting and superconducting partnerships with scientific research materials; theoretical and experimental institutions of the USA, Russia, France, investigation of non-linear optical Germany, Japan, India, Italy, Poland, the phenomena; biomedical photonics. Czech Republic, Slovak Republic, The research efforts in radiophysics are Sweden, Ukraine, Canada, Finland, and directed to clarifying the processes of Vietnam. In recent years, in its interaction of optical and microwave collaboration with the European scientific electromagnetic radiation with the research institutions, the Institute has atmosphere and the Earth’s surface; placed the accent on joint work within the developing experimental systems for laser framework of the European priority remote sensing and monitoring of the research programs. atmosphere; microwave remote The Institute has represented Bulgaria radiometric measurement of soil moisture in international scientific organization, content; developing algorithms and such as the International Institute for techniques for signals and information Weights and Measures, the International processing; constructing microwave units Laboratory of Low Temperatures and High and systems for radar and communication Magnetic Fields in Wroclaw, Poland, the applications; studying non-linear processes European Physical Union, the International in optical communication media. New Union for Pure and Applied Physics, the ferrite devices with micrometric International Union on Vacuum Physics dimensions were developed with and Applications, the International possibility for higher degree of integration. Radiosciences Union, the NATO Active research on gyro-magnetic Advanced Study Institute, as well as in the materials is underway, in view of reaching editorial boards of reputable international higher frequency ranges, especially mm- scientific journals. waves for wireless communications and The following important innovative protection from powerful microwave technologies and devices have been radiation. developed for the first time in Bulgaria in In all three fields of research, the laboratory conditions, mastered Institute’s scientists have achieved technologically and made available to the internationally-recognized priority by Bulgarian industry and economy: lasers, discovering new physical phenomena and lidars, plasma torches, electro-optical relations, among which are ion channeling converters with a micro-channel plate; in the semi-channels of a crystal surface technology for optical fibers production; and hyperchanneling at grazing angles; electron and ion projectors; ion ion-stimulated sorption; plasma electrodes technologies and systems for deposition of 6 50th Anniversary of E. Djakov Institute of Electronics
thin wear-resistant coatings; low-noise sensing of soil moisture, electron beam parametric solid-state microwave and plasma technologies, microwave solid- amplifiers; line- and stripline circulators; state electronics. In this context, a series converters; microwave absorbers; of expeditions have been organized microwave amplifiers, SQUID devices; and temporary stationary measuring portable microwave moisture meters for laboratories established in different parts bulk materials; microwave radiometers of Bulgaria with the purpose of laser and systems for remote soil moisture remote studies of the atmospheric sensing; a mobile laboratory for remote pollution intensity and dynamics over microwave sensing of sea and land urban areas (Velingrad, Razlog, Devnya, surfaces; magnetometers based on various Silistra (BG) - Kalarash (RO)); remote principles; electron lithography systems microwave remote soil moisture sensing and installations and technologies for near Pavlikeni, Vidin, Knezha, Plovdiv; electron beam melting, welding and remote radar observation of oil spills near refining of metals; ultra-high vacuum the ports of Burgas and Varna. pumps and installations; devices and Through the years, the Institute has installations for studying the surfaces and provided the scientific ambiance and properties of semiconducting materials; a opportunities that allowed the formation scanning field microscope; automated and successful scientific carriers of one systems for measuring and adjusting the academician and three corresponding parameters of electronic components; members of the Bulgarian Academy of optical gas sensors; technologies and Sciences, 18 professors, 21 doctors of systems for nanoparticles and sciences and 111 PhDs; 37 former nanostructures formation; a technology members of the Institute’s research staff and installation for nanopowders are now working on leading positions at production; industrial and medical laser research institutions in the USA, Sweden, and plasma technologies and installations; Canada, France, Great Britain, optical and microwave communication Switzerland, Germany, Vietnam. systems. Proofs of the above achievements The Institute has participated in the have been participation in and awards preparation of a White Book, a strategy from numerous industrial exhibitions and numerous basic documents concerning and fairs and a large number of the development of science in Bulgaria practical developments and industrial and high-technologies mastering under the implementations resulting in revenues for conditions of a transition to and the Bulgarian economy measured in establishment of a market economy; the millions of BGN or foreign currency. Institute was leading in the development Gradually, the Institute acquired the role of and application of modern criteria for a secondary center for education of assessment of scientific research work. scientists and dissemination of knowledge Scientists from the Institute took part in and methodologies in Bulgaria and abroad. the Management Committee of the Under the conditions of a free and fierce Fundamentals of Nanoelectronics Program competition, the Institute won the status of of the European Science Foundation. a center for and a coordinator of the The Institute’s staff has been research on lasers and lidars, remote instrumental in the development and microwave sensing of sea and land advancement of highly efficient techniques surfaces, remote radiometric microwave for and approaches to implementing 7 Annual Report IE 2012
scientific products in the industry, To quote part of the evaluation given by agriculture, public health and defense by the European Scientific Foundation’ way of joint development programs, inter- Commission which performed in 2009 a branch and joint laboratories, experimental comprehensive assessment of the installations and workshops for pilot Institute’s condition and results, its production; research and development of “prospects are related with overcoming the technologies, measuring and technological problems having to do with generational equipment, single devices and changes, improving the age structure of the technologies; training of specialists. The staff by attracting and training a larger Institute is now by and large the leading number of young scientists, and National Academic Center in its traditional adequately adapting to the quickly priorities and fields of competence. changing conditions in the country”. During the Institute’s existence, its The Institute of Electronics’ history work and staff have been evaluated several proves under Bulgarian conditions and times by the Bulgarian Academy of without any doubt the proposition of the Science and other national institutions efficacy of a multi-profile academic having the relevant authority, as well as institution where national competence is twice by prestigious international being created and reproduced at the commissions. With no exceptions, the highest possible level, where interaction marks have been high, accompanied by and harmony is guaranteed between the recommendations for further development specialists who share the existing and expansion. equipment so that new knowledge is born The Institute of Electronics is now a and makes its first steps in Bulgaria and research institution carrying out a wide higher technologies are developed that will range of fundamental research but eventually change our country and the nonetheless maintaining strong ties with world. The free exchange of ideas, results the industry. Its primary priorities are at and methodologies creates unique present the fields of photonics, conditions for comprehensive approaches nanoelectronics and new materials, optical to solving even the most complex and microwave technologies. The Institute scientific research task in ways has won a world-wide recognition with its inaccessible to other types of important and valuable contributions to the organizations. international scientific community: tens of Since year 2000, following the wish of monographs and books and thousands of all its collaborators and a Resolution of the scientific papers in international scientific General Assembly of the Scientists of the journals whose high scientific level is BAS, our Institute has carried with pride reflected in the thousands of citations in and dignity, recognition of the past, the scientific literature. The Institute confidence in the present and a pledge for enjoys strong contacts with universities the future, the name of its founder, and research institutions both in Bulgaria ACADEMICIAN EMIL DJAKOV and abroad and with the national industry, INSTITUTE OF ELECTRONICS OF thus playing an important role in THE BULGARIAN ACADEMY OF Bulgaria’s social and economic progress. SCIENCES.
8 Institute of Electronics on the Eve of its 50th Anniversary
INSTITUTE OF ELECTRONICS ON THE EVE OF ITS 50th ANNIVERSARY
STRATEGIC PLAN AND PRIORITIES Optical and radio-wave FOR 2013 - 2015 technologies: lidar monitoring and diagnostics of the atmosphere and The development is envisaged of research thermonuclear plasma; radio-wave subjects and short- and long-term plans, sounding of land and sea; optical sounding including the prospects for strengthening the of turbid media; imaging and interdisciplinary co-operations within the characterization of small objects. Academy, at national level and Active participation in a broad internationally (in Europe and worldwide). international collaboration in the The physical and engineering sciences framework of the European Research are key driving forces for research and Area, European Framework Programs innovation, providing fundamental insight (FP7 & FP8), EURATOM, as well as in and creating new applications. The Institute other international projects worldwide. of Electronics’ strategic plan for scientific Alongside with these strategic priorities, research is based on the results and the Institute plans to preserve and extend achievements obtained by the most further its leadership in many other competitive researchers and laboratories. It traditional research fields of the physical coincides nowadays with several emerging electronics and radio-physics such as fields. The research activity of the Institute vacuum, electron, ion and plasma physics has the tendency of becoming more complex and technologies. and interdisciplinary. The following priority fields will be basic for the next five years: Photonics: femtosecond INSTITUTE’S LEADERSHIP photonics; plasmonics; bio-medical photonics; optoelectronics; new optical DIRECTOR sensors; and coherent laser spectroscopy. Assoc. Prof. Sanka Gateva, Ph.D. This research will correlate with the study of Tel: +359 2 875 0077 new advanced materials and structures, novel e-mail: [email protected] nanotechnologies and optical communications. They cut across many DEPUTY DIRECTORS research activities, including applied physics, ● Assoc. Prof. Tanja Dreischuh, Ph.D. materials science, and nanoelectronics. Tel: +359 2 979 5867 Nanoelectronics and new e-mail: [email protected] materials: nanostructuring technology; ● Assoc. Prof. N. Nedyalkov, Ph.D. fabrication and characterization of nano- Tel: +359 2 979 5924 dimension films, quantum wires and e-mail: [email protected] quantum dots; applications of the new generation of field-effect nano transistors; SCIENTIFIC SECRETARY electron spin transport and modification of Assoc. Prof. Ekaterina Borisova, Ph.D. magnetic walls, as well as interaction of Tel: +359 2 979 5894 magnetic and superconducting thin film e-mail: [email protected] structures. Based on the experience and the results obtained, the efforts will also be ADMINISTRATIVE DIRECTOR focused on creating advanced materials for Mrs. Dora Mladenova new generation of photovoltaic cells and Tel: +359 2 875 2678 displays. e-mail: [email protected] 9 Annual Report IE 2012
SCIENTIFIC COUNCIL*
Chairman: Prof. P. Atanasov, Dr.Sc., Corresponding Member of BAS, IE BAS, e-mail: [email protected] Deputy Assoc. Prof. O. Yordanov, Ph.D., Chairman: IE BAS, e-mail: [email protected] Secretary: Assoc. Prof. T. Koutzarova, Ph.D., IE BAS, e-mail: [email protected] Members: Prof. L. Avramov, Dr.Sc., Assoc. Prof. T. Dreischuh, Ph.D., IE BAS, e-mail: [email protected] IE BAS, e-mail: [email protected] Prof. A. Dreischuh, Dr.Sc., Assoc. Prof. S. Gateva, Ph.D., Sofia University, e-mail: [email protected] IE BAS, e-mail: [email protected] Prof. V. Gerjikov, Dr.Sc, Assoc. Prof. Y. Georgiev, Ph.D., INRNE BAS, e-mail: [email protected] IE BAS, e-mail: [email protected] Prof. G. Mladenov, Dr.Sc., Corresp. Member of BAS Assoc. Prof. N. Guerassimov, Ph.D., IE BAS, e-mail: [email protected] IE BAS, e-mail: [email protected] Prof. I. Nedkov, Dr.Sc., Assoc. Prof. L. Gurdev, Ph.D., IE BAS, e-mail: [email protected] IE BAS, e-mail: [email protected] Prof. M. Nenchev, Dr.Sc., Assoc. Prof. S. Kartaleva, Ph.D., TU Sofia, e-mail: [email protected] IE BAS, e-mail: [email protected] Prof. P. Petrov, Dr.Sc., Assoc. Prof. L. Kovachev, Ph.D., IE BAS, e-mail: [email protected] IE BAS, e-mail: [email protected] Prof. N. Sabotinov, Dr.Sc., Member of BAS, Assoc. Prof. N. Nedyalkov, Ph.D., ISSP BAS, e-mail: [email protected] IE BAS, e-mail: [email protected] Prof. D. Stoyanov, Dr.Sc., Assoc. Prof. S. Sabchevski, Ph.D., IE BAS, e-mail: [email protected] IE BAS, e-mail: [email protected] Assoc. Prof. E. Alipieva, Ph.D., Assoc. Prof. I. Sirkova, Ph.D., IE BAS, e-mail: [email protected] IE BAS, e-mail: [email protected] Assoc. Prof. E. Balabanova, Ph.D., IE BAS, e-mail: [email protected]
*Abbreviations: IE BAS – Institute of Electronics of the Bulgarian Academy of Sciences INRNE BAS – Institute for Nuclear Research and Nuclear Energy of the Bulgarian Academy of Sciences TU Sofia – Technical University of Sofia ISSP BAS – Institute of Solid State Physics of the Bulgarian Academy of Sciences 10 Institute of Electronics on the Eve of its 50th Anniversary
LABORATORIES:
PLASMA PHYSICS AND ENGINEERING HEAD: Assoc. Prof. S. Sabchevski, Ph.D.
PHYSICAL PROBLEMS OF ION TECHNOLOGIES HEAD: Prof. S. Tinchev, Dr.Sc.
PHYSICAL PROBLEMS OF ELECTRON BEAM TECHNOLOGIES HEAD: Prof. K. Vutova, Dr.Sc.
SUPERCONDUCTIVITY AND CRYOELECTRONICS HEAD: Prof. T. Nurgaliev, Dr.Sc.
MICRO- AND NANO-PHOTONICS HEAD: Prof. P. Atanasov, Dr.Sc., Corresponding Member of BAS
BIOPHOTONICS HEAD: Prof. L. Avramov, Dr.Sc.
LASER SYSTEMS HEAD: Assoc. Prof. S. Gateva, Ph.D.
NONLINEAR AND FIBER OPTICS HEAD: Assoc. Prof. L. Kovachev, Ph.D.
LASER RADARS HEAD: Prof. D. Stoyanov, Dr.Sc.
MICROWAVE PHYSICS AND TECHNOLOGIES HEAD: Assoc. Prof. O. Yordanov, Ph.D.
MICROWAVE MAGNETICS HEAD: Prof. I. Nedkov, Dr.Sc.
PHYSICAL TECHNOLOGIES HEAD: Prof. P. Petrov, Dr.Sc.
LABORATORIES
● Plasma Physics and Engineering ● Physical Problems of Ion Technologies ● Physical Problems of Electron Beam Technologies ● Superconductivity and Cryoelectronics ● Micro- and Nano-photonics ● Biophotonics ● Laser Systems ● Non-linear and Fiber Optics ● Laser Radars ● Microwave Physics and Technologies ● Microwave Magnetics ● Physical Technologies
13 Annual Report IE 2012
LABORATORY
PLASMA PHYSICS AND ENGINEERING
HEAD: Assoc. Prof. S. P. Sabchevski, Ph.D.
TOTAL STAFF: 9 RESEARCH SCIENTISTS: 6 Assoc. Prof. E. Balabanova, Ph.D.; M. Dimitrova, Ph.D.; M. Damyanova, Ph.D.; P. Ivanova, Ph.D.; E. Vasileva; K. Raykov; I. Bozhinova; E. Hasan.
RESEARCH ACTIVITIES characteristics was used to retrieve the plasma potential; the EEDF was then 1. Diagnostics of edge plasma in evaluated applying the first derivative tokamaks probe method (FDPM). The results obtained after processing the probe Recently, a novel advanced technique characteristics demonstrated that, for a for diagnostics of magnetically confined poloidal arrangement, the EEDF near the plasma based on the classical Langmuir wall of the tokamak is a bi-Maxwellian in probe method was developed and applied the inner (high-field side) and in the outer to the experimental investigations carried (low-field side) divertor regions, while it is out in the new COMPASS tokamak at the a Maxwellian (with a single temperature of Institute of Plasma Physics of the 9 eV) in the middle between the two strike Academy of Sciences of the Czech points (where the D-shaped plasma is in Republic (IPP-ASCR) as well as in the contact with the divertor). ISTTOK tokamak and the TJ-II stellarator An important task that has been pursued in Spain. Some of the theoretical during 2012 was to study the plasma considerations and the experimental results parameters in the so-called scrape-off layer obtained by the research group, which (SOL) region that is located between the includes scientists from the Faculty of last closed surface of the magnetic field Physics of University of Sofia, IE-BAS, (LCFS) and the wall of the tokamak. In the and IPP-ASCR. were summarized in the experiments, two reciprocating manipula- Ph.D. thesis of Dr. P. Ivanova entitled tors were used, the first one being a “Langmuir probe investigation of the vertical one with a single Langmuir probe, electron energy distribution function while the second one was positioned (EEDF) in a tokamak plasma”, defended horizontally and had three ball-pen probes successfully in April, 2012. and two single Langmuir probes. Such an In 2012, during the experimental experimental set-up allows one to collect campaigns on the COMPASS tokamak, a rich information about the plasma series of measurements were carried out in parameters in this zone which is of great order to register Langmuir probe importance for the operation of the currentvoltage characteristics in the tokamaks. In particular, the results show plasma edge region using a novel 60- that the EEDF is Maxwellian in the channel probe system (designed and proximity of the wall. At the same time, it installed in 2012 by the Bulgarian team) was found that the distribution changes its alongside with the standard (embedded shape towards the plasma depth and can be initially in the plasma vessel) 39 graphite approximated by a bi-Maxwellian profile probes. The electron branch of these that corresponds to two groups of particles. 14 Laboratory Plasma Physics and Engineering
The first one (with a higher concentration) Power and Microwave Technology at KIT consists of slow electrons with a (IHM-KIT), Karlsruhe, Germany and temperature of about 5 eV, while the Centre de Recherches en Physique des second group comprises faster electrons Plasmas École Polytechnique Fédérale de with a temperature of 10 – 22 eV. Lausanne (CRPP-EPFL), Switzerland. This data provide a better physical The main activities of the work on Task insight in the underlying physical 2.1.2 during 2012 included: (i) theoretical processes that affect the operation of the investigations focused on the development COMPASS tokamak. The techniques of adequate, self-consistent and applied in this investigation can be used to informative physical models formulated in study other similar reactors for fusion 2D and 3D; (ii) improvement, research. maintenance, upgrade, testing and This work was performed under Task benchmarking of the available computer 2.2.1 “Edge plasma diagnostics” of the codes and the underlying numerical Association EURATOM-INRNE. libraries, compilers, integrated development environments; (iii) 2. Modeling, simulation and computer development of novel software tools for aided design (CAD) of powerful simulation of the electron-optical system gyrotrons for fusion research (EOS) of the tube (GYREOSS package) and the electro-dynamical system As the most powerful sources of (resonant cavity) using efficient numerical coherent radiation in the millimeter and methods and algorithms, advanced sub-millimeter wavelength region of the computing environments and electromagnetic spectrum that can operate programming techniques as well as (iv) in both continuous wave (CW) and long- conducting numerical experiments for pulse regimes, the gyrotrons are analysis, computer aided design (CAD) considered as indispensable components of and optimization of megawatt class the systems for heating and diagnostics of gyrotrons. magnetically confined plasmas in various The work during 2012 was focused on reactors for controlled thermonuclear two of the problemoriented software fusion (e.g. tokamaks, stellarators), and packages, namely GYROSIM (which most notably in the International stands for Gyrotron Simulation) and Thermonuclear Experimental Reactor GYREOSS (Gyrotron Electron Optical (ITER) and its sequel – the DEMO project. System Simulation). Many planned In these plasma facilities for fusion improvements of the program realization research, the gyrotrons are used for of their modules that resolve problems electron cyclotron resonance heating identified in the course of the preceding (ECRH) and electron cyclotron current debugging and benchmarking tests were drive (ECCD), for plasma start-up, implemented successfully and the novel stabilization etc. Modeling, simulation and versions installed on the maintained computer aided design (CAD) based on workstations. The updated versions were numerical experiments are essential tools used in a number of numerical for development, optimization and study experiments carried out to produce of such high-power gyrotrons. The informative examples that illustrate both research on this topic is being pursued as a the functionality and the productivity of Task 2.1.2 of the scientific program of the the numerical codes. They were included Association EURATOM-INRNE by a in a report (delivered at the 5th Bulgarian team from IE-BAS and from the International Workshop and Summer Faculty of Physics of University Sofia in School on Plasma Physics), which collaboration with the Institute for Pulsed presented the current status of both the 15 Annual Report IE 2012
computational infrastructure and the technologies. One of the leaders simulation tools (physical models and their worldwide in the field of development, implementations in computer programs) investigation and application of such for numerical analysis, optimization and gyrotrons is the Research Center for CAD of gyrotrons. Development of the Far-Infrared Region An important task of the work plan for (FIR FU Center) at the University of 2012 was the realization of a novel field Fukui, Japan. IE-BAS has a longstanding solver in 2D and 3D for the GYREOSS (more than 14 years) and fruitful package. A great number of possible collaboration with FIR FU in the combinations of FEM formulations, finite framework of an Agreement for Academic elements, linear solvers, mesh Exchange and a Memorandum of optimizations and data structures were understanding for creation of an studied in order to select the most international consortium for “Promoting appropriate one. As a result, an efficient international collaboration for solver was programmed and tested. This development and application of sub- was followed by the development of a millimeter gyrotrons”. novel second-order relativistic leapfrog In recent years, one of the central topics Boris-Buneman particle pusher which is of the collaboration was the development consistent with the data structures of the of the problem-oriented software package electromagnetic field components at the GYROSIM and its application to current particle positions provided by the numerical studies for analysis and design field solver. It is also consistent with our of high-frequency gyrotrons for many strategy for a prospective future novel and, in fact, pioneering applications. parallelization of the PIC algorithm In parallel, a concept for both standard and implemented in GYREOSS. innovative CAD of specialized gyrotron More information about the current tubes was developed. The results in this status of GYREOSS is available on-line broad field were summarized and from the collaborative website of the presented in a review paper published project at http://gyreoss.wikidot.com, as during 2012 in a special issue of the well as in the Project’s section of this Journal of Infrared, Millimeter, and Annual Report. Terahertz Waves devoted to “High Power THz Technologies Opened by High 3. Development, investigation and Frequency Gyrotrons”. application of high-frequency gyrotrons The gyrotrons developed in FIR FU Center form the so-called Gyrotron FU The so-called THzgap of the Series, which includes several groups of electromagnetic spectrum situated between devices, namely FIR FU (pulsed tubes), microwaves and light has long been FIR FU CW (oscillators operating in a characterized by a lack of efficient and continuous wave mode), FIR FU CW C sufficiently powerful sources of coherent (compact tubes), and FU CW G (radiation radiation. In recent years, however, the sources with an output beam of a Gaussian gyrotrons have demonstrated a remarkable type). Among the novel applications of potential for operation at the millimeter, these gyrotrons presented in the Special subTHz and THz ranges and have begun Issue, as well as in the rest of the papers to bridge successfully this gap. The published during 2012, are several progress in the development of high advanced spectroscopic techniques (most frequency gyrotron oscillators makes notably ESR spectroscopy, DNP enhanced possible many novel and prospective NMR spectroscopy), X-ray detected attractive applications in both the magnetic resonance, and studies on the fundamental physical research and the energy levels of positronium (Ps). It 16 Laboratory Plasma Physics and Engineering
should be mentioned that the latter is the quantum beam and will facilitate the only direct method for measurement of the development of effective methods and hyperfine splitting (HFS) of Ps and is in tools for cancer treatment. fact a demonstration of a new horizon of a precision spectroscopy using a gyrotron as 4. Investigation of the potentials of a powerful source of coherent radiation. In interaction and the thermo-physical 2012, results were published from the first properties of gases and binary mixtures direct observation of the hyperfine at low pressures transition of ground-state positronium in a Fabry-Perot cavity driven by a sub- Investigations on the interactions terahertz gyrotron with an output between particles in pure gases and gas frequency of 203 GHz that corresponds to mixtures have always been among the the difference in the energy levels of central research topics of the Laboratory in orthopositronium (o-Ps) and the recent years. As a result of these parapositronium (p-Ps). The stimulated studies, novel data for the intermolecular transition from o-Ps to p-Ps is observed interactions and the thermo-physical with a significance of 5.4 standard properties of various gases and mixtures deviations. This result is a significant step were obtained and published. The physical towards a direct measurement of the Ps- model used for calculating the most HFS for which however, a frequency important parameters affecting their tunability of the gyrotron radiation is thermo-physical properties is based on the mandatory. In order to satisfy such a well-known (n-6) Lennard-Jones requirement and additionally increase the temperature dependent potential developed statistics, several improvements to the by Stefanov and Zarkova. The results measurement system (most notably of the obtained form a data base of recommended gyrotron and the cavity) are in progress values for the potential well depth, now. equilibrium distance, second virial A good example of a pioneering coefficient, viscosity and diffusion in the application of a gyrotron in a medical temperature range 200 – 1200 K. The technology is the recently developed gases studied included halogens (F2, Cl2, concept of a dual-beam irradiation facility Br2, I2), alkanes (CnH2n+2, n<6) and binary for an experimental cancer therapy based mixtures of alkanes. The systematized and on the simultaneous and/or sequential tabulated values compensate the lack of application of two beams, namely a beam systematic experimental data in such wide of neutrons and a CW or intermittent sub- temperature interval and can be used for terahertz wave beam produced by a both interpolation and extrapolation, as gyrotron (forming the so called “quantum well as for calculation of other potential- beam”). The conceptual design and the dependent properties of pure gases and feasibility study of the hybrid (dual-beam) mixtures. system were carried out using the software The main results obtained during this package GYROSIM. The first prototype of study in recent years were summarized and the gyrotron for this facility was presented in the PhD thesis of Mrs. M. manufactured, tested and prepared for Damyanova entitled “Interaction potentials embedding in the complex for BNCT and thermo-physical properties of gasses (Boron Neutron Capture Therapy). It is and binary mixtures at low pressures”. In believed that building such novel 2012, Dr. Damyanova defended irradiation facility will open many new successfully her dissertation and opportunities for experimenting with formulated some ideas for a further different therapeutic techniques utilizing a continuation of the research in this field. 17 Annual Report IE 2012
PUBLICATIONS precision spectroscopy using gyrotrons 2012 J. Infrared, Millimeter 1. Popov Tsv K, Ivanova P, Dimitrova M, and Terahertz Waves 33/7 766-76 Kovačič J, Gyergyek T and Čerček M, DOI: 10.1007/s10762-011-9864-8 2012 Langmuir probe measurements (ISSN: 1866-6892) of the electron energy distribution 7. Yamazaki T, Miyazaki A, Suehara T, function in magnetized gas discharge Namba T, Asai S, Kobayashi T, Saito T, plasmas Plasma Sources Sci. Ogawa I, Idehara T and Sabchevski S Technol. 21 2012 Direct observation of the DOI:10.1088/0963-0252/21/2/025004 hyperfine transition of ground-state (Online ISSN: 025004) positronium Phys. Rev. Lett. 108 2. Dimitrova M, Ivanova P, Kotseva I, 253401 DOI: 10.1103/PhysRevLett. Popov Tsv K, Benova E, Bogdanov T, 108.253401 (Online ISSN: 1079- Stöckel J and Dejarnac R 2012 7114) Evaluation of the plasma parameters 8. Yamazaki T, Miyazaki A, Suehara T, in COMPASS tokamak divertor area Namba T, Asai S, Kobayashi T, Saito H, J. Phys.: Conf. Series 356 DOI: Urushizaki Y, Ogawa I, Idehara T and 10.1088/1742-6596/356/1/012007 Sabchevski S 2012 First observation (Online ISSN: 012007) of o-Ps to p-Ps transition and first 3. Mitov M, Bankova A, Dimitrova M, direct measurement of positronium Ivanova P, Tutulkov K, Djermanova N, hyperfine splitting with sub-THz light Dejarnac R, Stöckel J and Popov Tsv K Hyperfine Interaction 212/1-3 141-7 2012 Electronic system for Langmuir DOI: 10.1007/s10751-011-0399-0 probe measurements, J. Phys.: Conf. (ISSN: 03043843) Series 356 DOI:10.1088/1742- 9. Sabchevski S, Idehara T, Ishiyama S, 6596/356/1/012008 (Online ISSN: Miyoshi N and Tatsukawa T 2013 012008) A dual-beam irradiation facility for a 4. Damyanova M, Balabanova E, Kern S, novel hybrid cancer therapy Illy S, Sabchevski S, Thumm M, J. Infrared, Millimeter and Terahertz Vasileva E and Zhelyazkov I 2012 Waves 34/1 71-87 Simulation tools for computer-aided DOI: 10.1007/s10762-012-9945-3 design and numerical investigations of (Print ISSN 1866-6892). high power gyrotrons J. Phys.: Conf. 10. Aripin H, Mitsudo S, Prima E S, Series 356 012044. Sudiana I N, Tani S, Sako K, Fujii Y, DOI:10.1088/1742-596/356/1/012044 Saito T, Idehara T, Sano S, Sunendar B (Online ISSN: 012008) and Sabchevski S 2012 Structural and 5. Idehara T and Sabchevski S 2012 microwave properties of silica xerogel Development and applications of glass-ceramic sintered by sub- high-frequency gyrotrons in FIR FU millimeter wave heating using a covering the sub-THz to THz range, gyrotron, J. Infrared, Millimeter and J. Infrared, Millimeter and Terahertz Terahertz Waves 33 1149-62 Waves 33/7 667-94 DOI: DOI 10.1007/s10762-012-9925-7 10.1007/s10762-011-9862-x (ISSN: (ISSN 1866-6892) 1866-6892) 11. Suehara T, Yamazaki T, Miyazaki A, 6. Asai S, Yamazaki T, Miyazaki A, Akimoto G, Ishida A, Namba T, Asai S, Suehara T, Namba T, Kobayashi T, Kobayashi T, Saito H, Idehara T, Saito H, Idehara T, Ogawa I and Ogawa I and Sabchevski S 2012 The Sabchevski S 2012 Direct first direct observation of positronium measurement of positronium hyperfine splitting AIP Conf. Proc. hyperfine structure: a new horizon of 1441 pp 549-51 (19th Particles and 18 Laboratory Plasma Physics and Engineering
Nuclei Int. Conf. 24–29 July 2011 M. Dimitrova, R. Dejarnac, Tsv. K. Cambridge Massachusetts USA) Popov, J. Stöckel, J. Havlicek, DOI: 10.1063/1.3700613 (ISBN 978- F. Janky, P. Ivanova, K. Tutulkov, 0-7354-1035-0) N. Djermanova, M. Mitov and 12. Yamazaki T, Miyazaki A, Suehara T, A. Bankova, Determination of the Namba T, Asai S, Kobayashi T, edge plasma parameters by divertor Saito H, Ogawa I, Idehara T and probes in the COMPASS tokamak; M. Dimitrova, J. Horacek, Tsv. K. Sabchevski S 2012 Direct observation Popov, J. Stöckel , R. Dejarnac, of the hyperfine transition of the P. Bílková, J. Havlicek, F. Janky, ground state positronium arXiv: P. Ivanova and I. Kotseva, Plasma 1204.1129 [hep-exp] 5 April 2012 potential and electron energy pp 1-4. Available on-line at: distribution function measured by arxiv.org/pdf/1204.1129 vertical reciprocating Langmuir probe 13. Idehara T and Sabchevski S P 2012 in the COMPASS tokamak edge Development and applications of high plasma. frequency gyrotron with harmonic 25th Symp. Plasma Phys. and Technol., 18–21 operation promoted by international June 2012, Prague, Czech Republic: collaborative project JAIRO 13 pp M. Dimitrova, R. Dejarnac, Tsv. K. 38–65 (in Japanese) Available on-line at: Popov, J. Stöckel, J. Havlicek and http://jairo.nii.ac.jp/0039/00005815/en F. Janky, Determination of the edge 14. Raykov K T and Videkov V H 2012 plasma parameters by divertor probes on the COMPASS tokamak. Problems in wire bonding process st Annual J. Electronics 6 43-5 (ISSN 21 Europhysics Conference on Atomic 1314-0078) and Molecular Physics of Ionized Gases, 10 – 14 July 2012, Viana do Castelo, 15. Balabanova E and Mileva E eds 2012 Portugal: Nanoscience & Nanotechnology: Tsv. K. Popov, M. Mitov, Nanostructured materials application A. Bankova, P. Ivanova, and innovation transfer 12 (Prof M. Dimitrova, S. Rupnik, J. Kovačič, Marin Drinov Publ. House BAS- T. Gyergyek, M. Čerček and F. M. NCNNT) (ISSN 1313-8995) Dias, Langmuir probe evaluation of the negative ion density in oxygen gas discharge magnetized plasma. CONFERENCES 26th Summer School and International Symposium on the Physics of Ionized 5th Int. Workshop & Summer School on Gases, 2012, Zrenjanin, Serbia: Plasma Physics, 25 – 30 June, 2012, Tsv. K. Popov, M. Dimitrova, Kiten, Bulgaria: P. Ivanova, J. Horacek, J. Stöckel, M. Damyanova, S. Sabchevski, R. Dejarnac and COMPASS tokamak I. Zhelyazkov, E. Vasileva, team, Evaluation of plasma potential E. Balabanova, P. Dankov, and P. and electron energy distribution Malinov, Problem-oriented simulation function by Langmuir probes in packages and computational infra- magnetized plasma. structure for numerical studies of powerful gyrotrons; DEFENDED PhD DISSERTATIONS Tsv. K. Popov, M. Dimitrova, P. Ivanova, R. Dejarnac, J. Stöckel, 1. P. Ivanova, Langmuir probe J. Kovačič, T Gyergyek, M Čerček investigation of the electron energy and F. M. Dias, Langmuir probe distribution function (EEDF) in a measurements of the electron energy tokamak plasma (23 April 2012, distribution function in magnetized Faculty of Physics, St. Kliment plasma; Ohridski University of Sofia. 19 Annual Report IE 2012
2. M. Damyanova, Interaction potentials 4. Edge plasma diagnostics, Task 2.2.1 and thermophysical properties of of the Association EURATOM–INRNE rarefied gases and binary mixtures (30 in collaboration with the Institute of May 2012, Institute of Electronics of Plasma Physics, Czech Academy of the Bulgarian Academy of Sciences). Sciences, Prague, Czech Republic. 5. Langmuir probe diagnostics of ONGOING RESEARCH PROJECTS electron energy distribution functions in fusion edge type magnetized Funded by EC as 7FP projects through plasmas, Project under the Bilateral Contract of Association with Association Scientific Cooperation between St. EURATOM-INRNE Kliment Ohridski University of Sofia and Faculty of Electrical Engineering, 1. Task 2.1.2: Development of numerical University of Ljubljana, Slovenia. codes to describe the behavior of high 6. Edge plasma diagnostics on the power gyrotrons. COMPASS Tokamak, Inter-academic 2. Task 2.2.1: Edge plasma diagnostics. collaboration BAS – ASCR, Bulgaria - Czech Republic. Funded by the Bulgarian Academy of Sciences LABORATORY VISITS
1. Edge plasma diagnostics on the 1. M. Dimitrova, Institute of Plasma COMPASS tokamak 2012-2015. Physics, Czech Academy of Sciences, 2. Investigations in the field of the Prague, Czech Republic – Feb 2012 controlled thermonuclear fusion Dec 2012 – Postdoc researcher. powerful gyrotrons for plasma heating 2. M. Damyanova, 21 Nov 2012 30 and probe plasma diagnostics in Nov 2012, Institute of Plasma Physics, tokamaks 2011-2013. Czech Academy of Sciences, Prague, Czech Republic. COLLABORATIONS 3. P. Ivanova, 21 Nov 2012 30 Nov 2012, Institute of Plasma Physics, 1. Analysis and optimization of electron Czech Academy of Sciences, Prague, guns for compact shower devices and Czech Republic. submillimeterwave gyrotrons, in the 4. E. Vasileva, 9 Sep 2012 10 Oct framework of the Agreement for 2012, Institute of Plasma Physics, academic exchange between IE-BAS and Czech Academy of Sciences, Prague, FIR FU Research Center in Fukui, Japan. Czech Republic. 2. Promoting international collaboration for development and application of GUESTS submillimeter-wave gyrotrons, in the framework of the Memorandum of 1. R. Panek, Institute of Plasma Physics, Understanding between IE-BAS and Czech Academy of Sciences, Prague, FIR FU Research Center in Fukui, Czech Republic. Japan for establishing an international 2. J. Stockel, Institute of Plasma Physics, consortium. Czech Academy of Sciences, Prague, 3. Development of numerical codes to Czech Republic. describe the behavior of high power 3. R. Dejarnac, Institute of Plasma gyrotrons, Task 2.1.2 of the Association Physics, Czech Academy of Sciences, EURATOM – INRNE in collaboration Prague, Czech Republic. with KIT-IHM, Karlsruhe (Germany) and EPFL-CRPP, Lausanne (Switzerland).
20 Laboratory Physical Problems of Ion Technologies
LABORATORY
PHYSICAL PROBLEMS OF ION TECHNOLOGIES
HEAD: Prof. S. Tinchev, Dr.Sc.
TOTAL STAFF: 5 RESEARCH SCIENTISTS: 3 T. Milenov Ph.D.; P. Nikolova; E. Petrova.
RESEARCH ACTIVITIES carbon surface can crystallize to graphene as a result of point defect creation and 1. Plasma surface modification of enhanced diffusion caused by the ion diamond-like carbon films to graphene bombardment. Different ions can be used to modify diamond-like carbon films, for Graphene, the first 2D atomic crystal example, carbon and hydrogen ions as ever known, possesses interesting inherent to the starting material (a-C:H). In electrical properties, in particular, a high our experiments we chose argon ions, carrier mobility, thus holding promises for which are widely used in the a “bright future” in electronics. However, microelectronic technology and, beng a a suitable technology is yet to be devised noble gas, would not react with the carbon. for fabrication of graphene for general The Monte Carlo SRIM-2008 program electronic applications. Today, the most was used to estimate the energy and doses widely used fabrication technology of the ions necessary to modify a few comprises CVD on metals followed by a monolayers only on the surface of the transfer process on insulating substrates, as amorphous carbon films. We found that for usually needed in electronics. This process argon ions energy of 1 keV the dose is quite successful – up to 30-inch should be 4.5×1015 Ar+/cm2 in order to graphene sheets have been fabricated and break all surface bonds of the amorphous successfully transferred to plastic carbon films. This estimated value is in substrates . good agreement with the experimental Although such a technology is suitable values found in the literature. for transparent electrodes, the necessity In our first experiments, the films were exists for a technology that would be modified in a DC magnetron system at generally applicable for fabrication of unipolar pulsed discharges. Pulse biasing graphene on insulating substrates. One of the magnetron is needed because the should mention here that the fabrication of diamond-like carbon films are highly graphene from SiC by thermal insulating and ion bombardment with DC decomposition is not an alternative, voltage would cause charging of the films. because the high temperatures (≥ 1300 ºC) The reason for using a magnetron in the needed to sublimate Si atoms make this film modification was the possibility for technology incompatible with the existing easy production of argon ions with low silicon electronics. energy and high density. However, this We recently proposed a technique for choice had also a drawback. It was found fabrication of graphene on top of that to achieve the necessary dose of about insulating amorphous carbon films by low- 4.5×1015 Ar+/cm2, the modification time energy ion modification. In this low- should be shorter than 1 s. Although these temperature process, the amorphous first experiments were quite successful, the 21 Annual Report IE 2012
short modification time was difficult to annealing at temperatures 800–900 ºC. It is control and vary in order to optimize the well known that in graphite or graphene, technology. the presence of the D peak indicates This is why we proceeded to build disorder. However, in amorphous carbon, another setup, namely, a simple diode the development of a D peak indicates system. Both electrodes were copper strips ordering. The D-peak’s intensity rose with fixed on an alumina substrate; the samples increasing the plasma treatment time, i.e. could be placed on/or near the cathode. the crystallization was enhanced. The cathode and samples were not cooled, However, its position remained stable. In since, to our estimates, heating during the contrast, the G-peak showed an upshift ion bombardment should not be (~12 cm-1) from 1572 cm-1 to 1584 cm-1, significant. The voltage amplitude was close to the typical G-peak of graphene. 400 V, at pulse frequency of 66 kHz and As the plasma treatment time was pulse duration of 10 µs. The system was increased, the G-peak became narrower, evacuated by a combination of a diffusion indicating again enhanced ordering and a mechanical pump. During the (crystallization) of the amorphous carbon modification, the pressure in the chamber modified. -1 was 3×10 Torr. The ID/IG ratio, widely used for Raman spectra of the samples were characterization of carbon materials, was obtained before and after sample also investigated. As the implantation time modification at room temperature using was increased, this ratio rose up to ~0.96, laser wavelength of 633 nm and laser indicating an sp2 cluster size of about power of less than 0.9 mW in order to 1.5 nm. However, such conclusions should prevent modification of the films by the be drawn very carefully, because laser radiation. The Raman spectra of the interpreting Raman signals of such plasma treated (but not annealed) samples complicated system, as graphen on showed small differences only in amorphous carbon, is not an easy task. comparison with the non-implanted The single and sharp second-order samples. This is only to be expected, Raman band (2D) is widely used as a because, at room temperature, the simple and efficient way to confirm the diffusion coefficient of carbon is not presence of single-layer graphene. In the sufficiently high for its crystallization. Raman spectra of our samples in the 2D Obviously, annealing is needed after the band region, one can recognize a peak at plasma treatment. Raman spectra of the 2700 cm-1,which, however, is not as sharp samples were measured again after as expected. These broad Raman spectra annealing at 350ºC for 6 hours. This are typical for defective graphene. temperature was chosen as the maximal Increasing modification time (ion dose) temperature that could not affect the leads to an increase in this peak’s underlaying amorphous carbon. Without intensity, and of that of two other small plasma treatment, the annealing of a peaks at about 2000 cm-1 and 2900 cm-1. sample did not change the Raman The peak at 2900 cm-1 can be identified as spectrum significantly. a D + D’ combination. At the moment, the The most significant change of the origin of the peak at about 2000 cm-1 is not Raman spectra observed after annealing clear. was a splitting of the broad amorphous These results show that surface spectrum into two distinct D- and G-peaks. modification by low-energy pulsed argon This is typical for partial crystalline carbon plasma can be used for fabrication of with small crystalline size. Without plasma graphene on top of insulating diamond-like treatment, such partial crystallization of carbon films. It was shown that by low amorphous carbon can be achieved by temperature thermal annealing at 350 ºC 22 Laboratory Physical Problems of Ion Technologies
one can achieve partial crystallization of desired operating temperature could be amorphous carbon to graphene. The precisely adjusted. Raman spectra observed are typical for Using such weak links, RF SQUIDs defective graphene – splitted D- and G- operating at 77 K were fabricated and used peaks and a broad 2D-peak. This result is in some measurements systems – a very encouraging and we hope that by scanning SQUID magnetometer, a spinner improving this technology it will be magnetometer, etc. A chip with 16 RF possible to fabricate defect-free graphene, SQUID made by oxygen ion implantation which can be used in electronics without was the first high-Tc electronic device transfer to other substrates. launched in space on board of Discovery Space Shuttle in 1993. A very important property, the current- 2. Ion-modified HTc-Josephson junc- phase relation of these weak links, was tions and SQUIDs successfully measured in a non-hysteretic All results published in this field since mode of operation of a RF SQUID. No our first demonstration in 1990 until the significant deviations from the sinusoidal recent successfull fabrication in Berkeley Josephson relation were found, which of more then 15 000 junctions with a indicates that oxygen-ion irradiated critical current spread of about 16 % were junctions are probably of the S-N-S type. summarized in a book chapter. In fact, this was the first measurement of Following the discovery of high-Tc the current-phase relation in high-Tc superconductivity, considerable efforts junctions. have been directed to preparing Josephson Using ion modification, Josephson junctions and SQUIDs. Various fabrication junctions and SQUIDs were successfully techniques have been developed since fabricated not only from YBCO but also then. The most successful structures from MgB2 thin films. produced were grain boundary junctions During these 22 years, some significant (bicrystal and step-edge) and ramp improvements were made in this junctions. However, they all have technology, for example, reducing the drawbacks – a large variation of the width of the irradiated region down to junction’s parameters and a limited large- 30 nm and improving the long-time scale integration capability. stability of these devices. Some drawbacks More then twenty years ago we of these junctions, as the small temperature proposed and demonstrated an alternative range of operation, still remain and need technology – ion-modified Josephson further work. Recently, results were junctions, whereby ion irradiation was reported of measurements of ion-modified used to reduce the Tc in a narrow region of junctions after years of storage at room a superconducting bridge and, thus, a S-N- temperature. It was shown that these S operation became possible. An important devices have excellent temporal stability point was the choice to use oxygen ions over a time period of eight years. for irradiation, which are inherent to YBCO and do not introduce additional 3. Investigation of the influence of effects. Thus, operation at liquid nitrogen Eu2O3 on the crystallization process of temperature was possible. However, later glasses in the system BaO-Bi2O3-B2O3 + + on, other kinds of ions (Ne and H ) have also been successfully used. The critical We studied the crystallization behavior temperature of the irradiated area and, of 30 mol. % BaO – 25 mol. % Bi2O3 – thus, the operatiing temperature of the 45 mol. %B2O3 glasses doped with Eu2O3 junction could be predicted quite well to different levels. At a Eu2O3 content of using the TRIM (SRIM) program and the 7 mol % or higher, the glasses underwent 23 Annual Report IE 2012
volume crystallization. The only 2. Tinchev S S 2012 Surface precipitating phase was a solid solution of modification of diamond-like carbon europium and bismuth oxides. As the films to graphene under low energy europium concentration in the glass was ion beam irradiation Appl. Surf. Sci. increased, the structure of the crystallites 258 2931 ISSN: 0169-4332 changed from cubic to rhombohedral. We 3. Egorysheva A V, Volodin V D, investigated the morphology, the physico- Milenov T, Avdeev G, Rafailov P and chemical properties, and the luminescence Skorikov V M 2012 Influence of spectra of the glasses and the glass- Eu2O3 on the crystallization process of ceramics. glasses in the system BaO-Bi2O3-B2O3 Inorganic Materials 48 948–52 4. Study of the magnetic behavior of a 4. Milenov T I, Rafailov P M, I. Urcelay- La2CoMnO6-δ crystal doped with Pb Olabarria, Ressouche E, García- and Pt Muñoz J L, Skumryev V and Gospodinov M M 2012 Magnetic A La2CoMnO6-δ crystal doped with Pb behaviour of La2CoMnO6-δ crystal and Pt was successfully grown. The lattice doped with Pb and Pt Materials Res. parameters were determined by X-ray Bulletin 47. 4001- 5 diffractometry, while polarized Raman 5. Tinchev S S 2012 Low temperature spectroscopy and magnetic measurements crystallization of diamond-like carbon were used to probe the Co/Mn positional films to graphene by low energy order and to suggest the most likely crystal plasma surface treatment and magnetic structures. The magnetic arXiv:1207.0837v1 [cond-mat.mtrl-sci] response of the crystal to ac- and dc- magnetic fields was discussed in terms of CONFERENCES possible occupation of crystallographic positions by the constituent ions and S. Tinchev, Plasma surface modification of valence state disproportion in the Mn/Co diamond-like carbon films to graphene, ions. The results were explained within a 13th International Conference on Plasma framework of statistically randomly Surf. Engin. PSE 2012, Garmisch- distributed Mn3+-O-Mn4+ and Co2+-O-Pt4+ Partenkirchen, Germany, Sept. 10–14, 2012. chains within the predominantly ordered Co2+/Mn4+ double perovskite structure. ONGOING RESEARCH PROJECTS
PUBLICATIONS Financed by the BAS
1. Tinchev S S 2012 Ion-modified high- Nanofunctional thin films and structures. Tc Josephson junctions and SQUIDs chapter in the book Super- conductivity: Theory, Materials and Application (Nova Science Publishers Inc) ISBN: 978-1-61324-843-0
24 Laboratory Physical Problems of Electron Beam Technologies
LABORATORY
PHYSICAL PROBLEMS OF ELECTRON BEAM TECHNOLOGIES
HEAD: Prof. K. Vutova, Dr.Sc.
TOTAL STAFF: 10 RESEARCH SCIENTISTS: 7
Prof. P. Petrov, Dr.Sc.; Assoc. Prof. V. Vassileva, PhD; Assoc. Prof. E. Koleva, Ph.D.; Assoc. Prof. Y. Gueorgiev, Ph.D.; Assoc. Prof . M. Beshkova, Ph.D.; V. Donchev, R. Nikolov, D. Tabakov. Ph.D. Student: D. Dimitrov.
RESEARCH ACTIVITIES fully CMOS-compatible top-down fabrication process, Si nanowire (SiNW) 1. Nanolithography and nanoelectronics sensing devices of various number (1, 3, and 20 NWs), length (0.5, 1, and 10 µm), We studied the contrast curves of two and width (10, 20, 30, and 50 nm and electron sensitive resists: the positive tone 5 µm) of the nanowires were fabricated. resist polymethyl methacrylate (PMMA), a The devices are based on the field-effect widely used organic resist with important transistor (FET) principle, but, in contrast applications in nanolithography, and the with most sensors of this type, they have a epoxy-based negative resist SU-8. The junctionless architecture. Such devices are negative resist SU-8 shows a very high easier to fabricate since they do not require sensitivity at exposure by 20 keV electrons separate doping of the source and drain that makes it suitable and attractive for regions and possess number of other high-throughput photomasks fabrication advantages over the conventional using electron-beam lithography (EBL). inversion-mode FETs. Their electrical More detailed knowledge of these resists’ characterization showed a very good characteristics is needed due to their performance as backgated junctionless diverse applications in nanolithography. nanowire transistors (JNTs). In addition, The experiments performed showed that results from pH sensing experiments the resist behavior, including its sensitivity demonstrated a high sensitivity to the pH and contrast, is influenced by the energy of level of the different pH buffers used. the beam electrons, by the nature of the Using EBL, RIE, and consecutive resist and substrate, by the type and oxidation and wet etching of the NWs, a composition of the developer, as well as technology was developed for fabrication by the conditions of development. of sub-5 nm suspended SiNWs This tech- During the year, a member of our team nology can be used for fabrication of core- (Assoc.Prof. Dr. Y.Georgiev) has been shell materials (NWs) and gate-all-around working in Ireland on nanotechnology and FETs. nanoelectronics, mainly on top-down A well-functioning Ge JNT was fabri- nanofabrication of nanowire (NW) cated on substrates of a novel material, structures and devices on silicon (Si), germanium on insulator (GeOI), by a silicon on insulator (SOI), germanium simple 5-step CMOS-compatible top-down (Ge), and germanium on insulator (GeOI) process; it exhibited a good transistor substrates. performance in terms of sub-threshold By means of EBL and reactive ion slope (SS), Ion/Ioff current ratio and drain- etching (RIE) on SOI wafers, and using a induced barrier lowering (DIBL). 25 Annual Report IE 2012
Arrays of well-ordered vertical SiNWs along the domain boundary or inside the (nanopillars) having diameters of 100, 150, domains. This suggests that the formation and 200 nm and lengths of ~1 µm were of 6H-SiC inclusions has started at fabricated on large areas by EBL and RIE. different moments of the growth process; These arrays can be used as nano-scale this is related to a growth instability or a photovoltaic (PV) cells for energy surface irregularity, respectively. A harvesting. 2 theta-omega scan showed a high intensity of the 111 peak of the 3C-SiC 2. SiC thin films study grown under Si-rich conditions, which is related to the continuous character of 3C- 3C-SiC films were grown by SiC domains. sublimation epitaxy at a source The results demonstrate that the vapor temperature of 2 000 oC in vacuum environment (Si- or C-rich) is a crucial (<105 mbar) for 30 min at a temperature factor in growing 3C-SiC. The conditions gradient of 6C/mm on on-axis 6H-SiC can be controlled by the presence of a Ta (0001) substrates under Si- and C-rich foil in the reaction space during the growth conditions. Polycrystalline SiC was used process. as a source material, the clearance between the source and substrate being kept at 1 mm by a graphite spacer. Mass spectro- 3. New materials and technologies scopic investigations showed that the main reactive species after SiC sublimation are 3.1. Research and development of new Si, Si2C, SiC2 and SiC. The content of the materials by electron beam recycling of other reactive species (Si2, C, C2, C3) in scrap the vapor is insignificant and can be Using the ЕLIT-60 equipment, neglected. experiments were conducted on evaluating The 3C-SiC epilayers studied were the influence of the technological grown in different growth environments - parameters (e-beam power, casting either under Si-rich conditions (sample A) velocity, refining time) on the alloy or C-rich conditions (sample B). In order components in the case of e-beam melting to maintain Si–rich conditions, a Ta foil and refining (EBMR) of high-speed steel was inserted inside the crucible, which acts and bearing tool steel from waste products. as a carbon getter due to transformation of The optimal process conditions were Ta into TaC. To ensure C-rich conditions, determined for alloy steel regeneration, an annealed Ta-foil at the same growth whereby the proportion of the alloy conditions was used. Since the Ta foil is components remains unchanged and the partly transformed into TaC before the weight losses are minimal. Technological growth, the carbon’s gettering efficiency is schemes were proposed for sample reduced. preparation and selection of conditions that The morphological studies by optical result in the steel samples treated having microscopy in a transmission mode concentrations similar to the initial ones. revealed continuous 3C-SiC domains with Optimizing the EBMR technology and 0.4 % 6H-inclusions, more often formed the quality and price of the new materials along the 3C-SiC boundary for the layers obtained require a detailed study of the grown under Si-rich conditions. Under C- heat processes and an adequate rich conditions, the studies revealed mathematical modeling. A time-dependent separated 3C-SiC domains only. The AFM mathematical model was developed of the images showed different types of 6H-SiC heat transfer during EBMR of metals and inclusions for the sample grown under Si- alloys. The model allows simulation of the rich conditions, with a hill and a pit nature, thermal processes in the metal solidified in 26 Laboratory Physical Problems of Electron Beam Technologies
the water-cooled crucible, as well as in the Optimization of the molten pool feeding rod, assuming three mechanisms geometry as connected with per- of heat transfer. A cor-responding forming the refinement processes. numerical method (modified Pismen- Furthermore, the process was studied of Rekford method) and a computer program 60-kW EBMR of tantalum. The were developed. The numerical scheme is refinement was carried out at various absolutely stable and implicit in terms of power densities for different periods of the time. The heat model was validated by time. The initial concentration of conducting numerical experiments for impurities in the prepared test melted disks wide ranges of regime conditions variation (ingots) was similar to that in the raw (e-beam power, beam diameter, casting material composition utilized in industrial velocity, heating time, ingot dimensions, EBMR. The level of refining the base etc.) and for different metals. A good material by EB treatment in vacuum was correspondence between the simulation considered, as described by the and the experimental data was demon- purification coefficient . A way was strated. proposed of optimizing the final impurity Data and dependencies of practical concentration, based on an appropriate importance were obtained concerning the choice of parameters and an estimation of liquid pool geometry, the energy losses, the purification coefficient. the temperature field, etc. In the case of By varying the processing parameters, EBMR of copper by a 10-kW e-beam, the data were obtained on the material weight geometry of the liquid pool becomes stable losses, the molten pool geometries and on at higher casting velocities (V = 9, the cast material compositions of the test 10 mm/min), which is a condition for a samples. These experimental data, together more efficient refining process. In the case with the calculated physical characteristics of 24-kW EBMR of tantalum at different of the molten pools and the test disks casting velocities (V = 0, 3, 6 and during melting, were analyzed by a 9 mm/min) and ingot heights, the liquid statistical approach, which allowed pool depth stabilizes after five minutes. As modeling of the relationships of the the casting velocity is increased, a fully liquid top surface of the ingot is observed process parameters with the characteristics earlier (for shorter heating times) and an investigated. A multi-criterion optimiza- earlier stabilization of the depth of the tion, concerning fulfilling simultaneously formed molten pool is achieved, which the requirements for several ensures better conditions for the refining characteristics, was performed and Pareto- processes. optimal compromise solutions were found. On the basis of the heat model The data accumulated, the complex developed and the simulation results relations found and the optimization obtained, conclusions were drawn performed will be applied to improving the concerning the influence of a variety of process of EBMR of tantalum. regime parameters and recommendations were given for ensuring the proper process 3.2. Electron beam welding conditions. A model-based quality optimization of 3.2.1. The geometry parameters of the the process EBMR of tantalum was weld cross-section were studied in detail in considered as connected with two aspects: the case of e-beam welding of Optimization of the level of 38Cr2Ni2Mo high-strength steel. refinement by choosing appropriate Longitudinal or transverse beam deflection values of the process parameters and with respect to the non-deflected beam estimation of the purification coeffi- position was applied during welding. The cient ; welded seam parameters were investigated 27 Annual Report IE 2012
for deflection oscillation frequencies in the PUBLICATIONS range of 90 – 1600 Hz and amplitudes in the range of 0.7 – 2.7 mm at a beam 1. Vutova K, Donchev V, Vassileva V accelerating voltage of 60 keV, beam and Mladenov G 2012 Influence of current of 45 mA and 50 mA and distance process and thermo-physical from the end of the electron gun to the parameters on the heat transfer at welded sample of 100 mm. By varying the electron beam melting of Cu and Ta frequency, the amplitude and the shape of Supplem. Proc. Materials Processing the beam deflection oscillations, one can and Interfaces TMS (Wiley USA) effectively control the weld cross-section 125-32 geometry while preserving the weld-depth 2. Oane M, Vutova K, Mihailescu I N, value. The behavior observed of the weld Donchev V, Florescu G, Munteanu L shape in the case of the higher beam and Georgescu G 2012 The study of energy density was less dependent on the vacuum influence on spatial- oscillations; we assume that this is due to a temporal dependence of thermal self-focusing of the beam by the metal distributions during laser-optical vapors in the key-hole part near the weld components interaction Vacuum 86 root. Models for the dependence of the 1440-42 welds’ geometry parameters on the process 3. Vutova K ed 2012 Research and parameters (focusing current, frequency, development of new materials on the amplitude and shape of the oscillations) base of recycling of reactive and were considered and applied to e-beam refractory metals scrap through welding parameters optimization in view electron beam method Proc. IE-BAS of fulfilling specific requirements to the 172 pages weld parameters. 4. Beshkova M, Birch J, Syväjärvi M and Yakimova R 2012 Sublimation 3.2.2. The monograph “Fundamentals of epitaxy of 3C-SiC grown at Si- and Welding” was published by the Stroitelni C-rich conditions Vacuum 86 1595-9 Konstrukcii OOD (in Bulgarian). It 5. Beshkova M, Grigorov K, Nedkov I, presents the fundamentals of the present- Massi M, Sismanoglu B, Maciel H day welding technologies in five chapters: and Velchev N B 2012 Properties of Review of the Welding Processes, Physics thin silicon carbide films prepared of Welding, Heat Transfer and by rapid thermal annealing Temperature Fields During Welding, J. Physics 356 012039 Welding Metallurgy, and Stress and 6. Lotty O, Petkov N, Georgiev Y M Deformation During Welding. and Holmes J D 2012 Porous to The mechanism was studied of molten nonporous transition in the pool formation during e-beam welding of morphology of metal assisted nuclear reactor steels, together with the etched silicon nanowires Jap. J. influence of the technological parameters Appl. Phys. 51 11PE03 on the defect formation, such as cold and 7. Hobbs R G, Schmidt M, Bolger C T, hot cracks. Specimens were prepared for Georgiev Y M, Xiu F, Wang K L, experimental determination of the stress Fleming P, Morris M A, Djara V, Yu R, arising in the weld and in the heat-affected Colinge J-P, Petkov N and Holmes J D zone by e-beam reconstitution of Charpy 2012 Resist-substrate interface specimens. tailoring for generating high density Experiments on determining the arrays of Ge and Bi2Se3 nanowires nanoparticles’ influence on the micro- by electron beam lithography structure of the welds were also J. Vac. Sci. Technol. B 30/4 performed. 041602(1)-041602(7) 28 Laboratory Physical Problems of Electron Beam Technologies
8. Ščajev P, Onufrijevs P, Manolis G, Innovative Materials, Processes, Karaliūnas M, Nargelas S, Jegenyes N, Products and Applications) pp 23-32 Lorenzzi J, Ferro G, Beshkova M, 16. Bencurova A, Nemec P, Kostic I, Vasiliauskas M, Syväjärvi M, Vutova K, Koleva E and Mladenov G Yakimova R, Kato M and Jarašiūnas K 2012 Investigation of sensitivity of 2012 Metrological potential of time electron resists J. Electrotechnica resolved optical techniques for and Electronica 47/5-6 10-13 characterization of differently grown 17. Mladenov G, Koleva E and Vutova K 3C-SiC crystals and heterostructures 2012 Nanotechnology and Materials Sci. Forum 771 159-63 nanomaterials – a collaboration 9. Vutova K and Donchev V 2012 between Bulgaria (IE-BAS) and Time-dependent thermal model for Ukraine (National Technical electron beam melting of metals and University "KPI") Annual Report alloys J. Electrotechnica and 2011 Institute of Electronics, BAS, Electronica 47/5-6 273-9 Eds. Ch. Ghelev and N. Guerassimov 10. Donchev V, Oane M, Vutova K, pp 87-95 Mihailescu I N, Vassileva V, Koleva E, 18. Koleva E, Mladenov G, Trushnikov D Mladenov G and Toader D 2012 and Belenkiy V 2012 Model-based Heat transfer study based on time- approach for investigation of dependent mathematical model and electron beam welding of high- experimental data at EBMR of Ta strength J. Electrotechnica and J. Electrotechnica and Electronica Electronica 47/5-6 115-8 47/5-6 pp 280-84 19. Trushnikov D, Koleva E, Belenkiy V 11. Petrova D, Koleva E and Voutchkov I and Mladenov G 2012 Experimental 2012 Model-based robust parametric investigation of the weld cross design of automatic cleaning process section at electron beam J. Pharmaceutical Innovation 7/1 welding of high-strength steel 30-7 J. Electrotechnica and Electronica 12. Petrov P 2012 Surface modification 47/5-6 108-14 of aluminum alloys using hybrid 20. Mladenov G, Vutova K, Vassileva V, treatment techniques J. Phys.: Conf. Georgieva E, Petrov E, Pankov V Series 356 012035 and Petrov D 2012 Recycling of 13. Schmidt M, Nazneen F, Georgiev Y, refractory and reactive metals scrap Herzog G, Galvin P and Petkov N and their alloys through electron 2012 FIB patterning of stainless steel beam method; exploring the for the development of nano- availability of metal scrap and structured stent surfaces for marketing analysis, economic and cardiovascular applications environmental effect evaluation of J. Phys.: Conf. Series 371 012065 application of EBM for recycling of 14. Vassileva V, Vutova K and Donchev V refractory and reactive metals Proc. 2012 Recycling of alloy steel Research and Development of New by electron beam melting Materials on the Base of Recycling J. Electrotechnica and Electronica of Reactive and Refractory Metals 47/5-6 285-91 Scrap through Electron Beam 15. Vutova K 2012 Mathematical Method ed K. Vutova (IE-BAS) pp modeling of sub-micron and nano- 9-20 (in Bulgarian) structures at electron beam 21. Toader D, Oane M, Mihailescu I, lithography Plenary and Keynote Ticos C, Serban N, Ristoscu C, Proceedings “Nanocon 012” (2nd Vutova K, Georgescu G and Int. Conf. Nanotechnology - Donchev V 2012 Beam dynamics: a 29 Annual Report IE 2012
new computational approach ONGOING RESEARCH PROJECTS J. Electrotechnica and Electronica 47/5-6 33-5 Financed by the National Science Fund 22. Petrov P 2012 Techniques for on- line monitoring and inspection of 1. DO 02-200 New materials electron beam welding process regeneration through electron beam nd Proc. 2 Int. Electron Beam melting and refining of refractory and Welding Conf. pp 114-7 reactive metals and alloys in vacuum. 23. Yu R, Das S, Hobbs R, Georgiev Y, 2. DNTS/Slovakia01/10 Robust Ferain I, Razavi P, Dehdashti lithography of submicron and nano- Akhavan N, Colinge C A and dimensional structures, with the Colinge J-P 2012 Top-down process Institute of Informatics, Slovak of germanium nanowires using EBL Academy of Sciences, under exposure of hydrogen silsesquioxane Bulgarian-Slovak inter-governmental resist Proc. 13th Int. Conf. Ultimate program of cooperation in science and Integration on Silicon (ULIS) IEEE technology. Conf. Publications pp 145-8 3. BIn-5 New materials regeneration 24. Mihailov V, Karhin V and Petrov P through electron beam melting and 2012 Fundamentals of welding refining of refractory metal wastes in (Stroitelni Konstrukcii OOD) 197 vacuum, with the Centre for Materials pages (in Bulgarian) for Electronics Technology (C-MET), Hyderabad, India, under Bulgarian- Indian inter-governmental program of CONFERENCES cooperation in science and technology.
1. E.Koleva Financed by the BAS Workshop Nanomaterials for solar energy, 26-29 Jan. 2012, Gothenburg, 1. Pure metal obtaining, investigation of Sweden. processes at electron beam 2. K. Vutova modification of materials, modeling of 141 TMS2012, 10–17 March 2012, nano-lithography processes and thin Orlando, USA. film deposition and study. 3. K. Vutova, E. Koleva, V.Donchev and D.Dimitrov 10th Anniversary Int. Conf. Electron COLLABORATIONS Beam Technologies, 1-4 June 2012, EU, NATO and other international Varna, Bulgaria. organizations projects 4. K. Vutova and E. Koleva Int. Conf. High-Power Electron Beam 1. Contract No MRTN-CT-2006-035735 Technology, 14-16 Oct. 2012, Reno, Promoting and structuring a USA. multidisciplinary academic-industrial 5. K. Vutova network through the heteropolytype IInd Int. Conf. Nanotechnology - growth, characterization and Innovative Materials, Processes, application of 3C-SiC on hexagonal Products and Applications, 17-18 Oct. substrates, Dr. Gabriel Ferro, 2012, Pune, India. Coordinator, Financed by the 30 Laboratory Physical Problems of Electron Beam Technologies
European Community through the LECTURE COURSES Marie Curie RTN MANSiC project 2. Semiconducting nanowire platform for 1. Assoc. Prof. Dr. E. Koleva: Lecture autonomous sensors (SiNAPS), 7 FP courses on Statistics (in English) – 30 h and seminars – 20 h, Univ. Chem. of EU (grant agreement no. 257856), Technol. and Metallurgy, Sofia, Bulgaria. Dr. Y.Fagas Coordinator 2. Assoc. Prof. Dr. E. Koleva: Seminars on methods for experimental Other scientific institutions and companies investigations – 75 h, Univ. Chem. Technol. and Metallurgy, Sofia, Bulgaria. 1. Computer simulation of the processes 3. Assoc. Prof. Dr. E. Koleva: Seminars of electron, ion and X-ray irradiation on modeling and optimization of of electronic materials, Hiroshima technological objects – 60 h, Univ. Chem. Technol. and Metallurgy, Sofia, Institute of Technology, Hiroshima, Bulgaria. Japan. 4. Assoc. Prof. Dr. E. Koleva: Seminars 2. Electron beam nanolithography, on industrial management - 69 h, Institute of Electrical Engineering Univ. Chem. Technol. and Metallurgy, (IEE), Chinese Academy of Sciences, Sofia, Bulgaria. Beijing, China. 5. V. Donchev: Seminars on 3. Investigation of physical and heat biomathematics – 30 h, St. Kliment Ohridski University of Sofia. processes at interaction of focused 6. V. Donchev: Seminars on algebra 1 – energy flows with materials, National 90 h, St. Kliment Ohridski University Institute for Lasers, Plasma and of Sofia. Radiation Physics, Romanian 7. V. Donchev: Seminars on Academy of Sciences, Bucharest, mathematical analysis – 45 h, St. Romania. Kliment Ohridski University of Sofia. 4. Investigation of nanosystems and new materials by neutron scattering, JINR, LABORATORY VISITS
Dubna, Russia. 1. K. Vutova and E. Koleva 5. Novel nanowire structures for devices, Institute of Electrical Engineering financed by the Science Foundation (IEE), Chinese Academy of Sciences, Ireland (SFI), (grant agreement no. 09- Beijing, China. IN1-I2602). 2. E. Koleva 6. Agreement between IE-BAS and IPPK State National Research Polytechnic EOOD, Sofia for join forces for University of Perm, Perm, Russia. 3. K. Vutova and E. Koleva development of technologies for Institute of Informatics, Slovak electron beam melting and refining of Academy of Sciences, Bratislava, metals and alloys in Bulgaria and for Slovakia. training of specialists for high- technological work. GUESTS 7. Agreement between IE-BAS and 1. Prof. Takeshi Tanaka, Targets OOD, Plovdiv for join forces Hiroshima Institute of Technology, for development of technologies for Hiroshima, Japan, June 2012. electron beam melting and refining of 2. Eng. Dorina Toader, precious metals and alloys in Bulgaria National Institute for Lasers, Plasma and and for training of specialists for high- Radiation Physics, Romanian Academy of technological work. Sciences, Bucharest, Romania, June 2012. 31 Annual Report IE 2012
3. Phys. Eng. Colin Ribton, 7. Dr. Tatiana V. Olshanskaia, TWI, Cambridge, UK, June 2012 State National Research Polytechnic 4. Dr. Ivan Kostic, Univ. of Perm, Perm, Russia, Nov. 2012. Institute of Informatics, Slovak 8. Prof. Dr. Ion N. Mihailescu, Academy of Sciences, Bratislava, National Institute for Lasers, Plasma Slovakia, June 2012. and Radiation Physics, Romanian 5. Eng. Anna Bencurova, Academy of Sciences, Bucharest, Institute of Informatics, Slovak Romania, Dec. 2012. Academy of Sciences, Bratislava, 9. Dr. Carmen Ristoscu, Slovakia, June 2012. National Institute for Lasers, Plasma 6. Dr. Dmitriy N. Trushnikov, and Radiation Physics, Romanian State National Research Polytechnic Academy of Sciences, Bucharest, Univ. of Perm, Perm, Russia, Nov. 2012. Romania, Dec. 2012.
32 Laboratory Superconductivity and Cryoelectronics
LABORATORY
SUPERCONDUCTIVITY AND CRYOELECTRONICS
HEAD: Prof. T. Nurgaliev, Dr.Sc.
TOTAL STAFF: 7
RESEARCH SCIENTISTS: 6 Assoc. Prof. E. S. Mateev, Ph.D.; Assoc. Prof. N. Donkov, Ph.D.; B. S. Blagoev, Ph.D.; L. I. Neshkov, MS; Pl. Petkov, MS.
RESEARCH ACTIVITIES voltage drop in four-probe measurements. The electrical characteristics of the The laboratory’s team is working in the microstrips located in the central area of fields of “Nanoscience, New Materials and the substrates were close to those of the as Technologies” and “Nanoelectronics and prepared YBCO/LSMO bi-layer. They New Materials”, which are among the exhibited a nearly linear temperature priorities of the 2009-2013 National dependence of the resistance R and a Scientific Program. Some of team’s tasks superconducting transition temperature of were described in the Annual Report IE Tc ~ 85 K. These microstrips were found 2011. to be suitable for further focused ion beam (FIB) machining in order to use them in 1. Supeconductor - ferromagnetic more complex devices. The microstrips at YBa2Cu3O7/La0.7Sr0.3MnO3 bilayers and the corners of the chip were degraded to a nanostrips prepared on SrTiO3 different degree – some of them even substrates fully, with a lower value of the critical temperature or absence of a Superconductor/ferromagnetic (S/F) superconducting transition. YBa2Cu3O7/La0.7Sr0.3MnO3 (YBCO / As a next step, FIB (using 30 keV Ga LSMO) bilayers were grown by magnetron ions and current about 10 pA) was applied sputtering on SrTiO3 (STO) substrates; the to realize nanostrips of length 5 μm and parameters of nanostrips with SFS weak width below 0.5 . Strong deterioration of links, formed on such bilayers, were the YBCO film properties after FIB investigated in collaboration with the application was observed if the bilayer had Institute of Electroengineering of the not been covered by a protecting film. Slovak Academy of Sciences. The Curie Covering the bilayer by a 50-nm thick gold temperature TCurie of the samples exceeded layer was sufficient to suppress the impact 320 K. The critical temperature Tc of the of the focused Ga ion beam. To complete YBCO film in the as-prepared the superconductor - ferromagnet - super- YBCO/LSMO/STO bilayers was about conductor (SFS) structures, cross-lines of 85 K. To study the homogeneity of the length L ≤ 100 nm were iplemented. The samples, 28 YBCO/LSMO microstrip final aim of these efforts was to remove configurations of width 10 μm and length completely the YBCO film in the cross- 5 μm were formed by photolithography line to observe the so-called long-range and Ar ion beam etching on 10×10 mm2 proximity effect (LRPE) in FS structures. SrTiO3 substrates. The configuration A critical temperature of the nanostrip of comprised current carrying microstrips, Tc0n > 76 K, a resistance of the weak link narrow microstrip lines and square-shaped plateau of R ≈ 4 Ω and a critical contact areas used for measuring the temperature of the weak link of 33 Annual Report IE 2012
TcWL ≈ 57 K were found from R-T thick. The LSMO films (with a thickness dependence measurements in the SFS of 40 nm) grown on the ALO substrate junctions prepared. The studies will be were polycrystalline and consisted of continued with the aim of clarifying grains of submicron size. whether the coupling of the YBCO The complex surface impedance of the through LSMO of length L < 100 nm is the single-crystal layer exhibited a slightly result of a residual YBCO film in the inductive behavior, while the impedance cross-line or indicates the presence of of the polycrystalline layer showed a LRPE. capacitive one. The time constant of the intergrain transition was τ = 587.32 ps. 2. Magnetic Properties of La1-xCax The contribution of the grain volume to the MnO3/La1-xSrxMnO3 thin films grown DC resistance of the polycrystalline layer on LaAlO3 and Al2O3 substrates (3.435 kΩ) was substantially higher than the DC resistance of the single-crystal Ferromagnetic La0.7Ca0.3MnO3(35nm) layer. The contribution of the grain /La0.7Sr0.3MnO3(30 nm) manganite bi- boundaries to the DC resistance of the layers were grown on LaAlO3 (LAO) and polycrystalline layer was found to be Al2O3 (ALO) substrates (i.e., predominant. Such a contribution is LCMO/LSMO/LAO and LCMO/LSMO expected to be smaller in the films with /ALO structures) using magnetron larger grains. sputtering. The individual Curie temperatures of the LSMO and LCMO 4. Biocompatibility of e-beam evapo- sublayers were 325 K, 225 K for the rated Ta2O5 films LCMO/LSMO/LAO sample, and 325 K, 210 K for the LCMO/LSMO/ALO sample. The effects were studied of the structure The zero-field-cooled (ZFC) and properties of e-beam evaporated Ta2O5 magnetization of the samples exhibited films on the cell/material response and maximums at 150 K and 170 K, behavior in in-vitro and in-vivo tests. The respectively. The difference between the Ta2O5 films were formed on titanium ZFC and field-cooled (FC) magnetizations substrates (Ti4Al6V). The film deposition was greater for the bilayer deposited on rate was 28 nm/min. The surface ALO substrate due to its polycrystalline properties and the structural characteristics nature. The coercive field of the of the films were analyzed in detail. The LCMO/LSMO/LAO sample was greater at advancing contact angle of the film, the room temperature (298 K) than at 150 K. surface free energy (SFE) and its polar and This was interpreted as being due to a dispersion components were determined. change of the magnetic state of the LCMO The good cyto-compatibility was sublayer in this temperature interval. demonstrated of e-beam evaporated Ta2O5 coatings, especially in the case of annealed 3. Investigation of the complex surface films with nearly stoichiometric Ta2O5 impedance of epitaxial and composition. polycrystalline LSMO thin films The cyto-toxicity and the cyto- compatibility were estimated in in-vitro The complex surface impedance of La1- tests, while the tissue ingrowths were xSrxMnO3 (LSMO) single- and analyzed in in-vivo tests. In the process of polycrystalline films were investigated in cell cultivation with coated samples, the the frequency range 1 – 100 kHz at cell cytology, morphology and temperatures bellow the Curie proliferation activity were determined by temperature. The LSMO layer grown on means of optical microscopy after 24 h, 3 the STO substrate was epitaxial and 30-nm and 5 days cultivation. Rat hypodermic 34 Laboratory Superconductivity and Cryoelectronics
cellular tissue was extracted to obtain 6. Safonov V, Zykova A, Smolik J, initial fibroblast culture. The in-vivo test Donkov N, Rogovska R, Goltsev A, showed that the osteo-genesis front was Dubrava T and Rassokha I 2012 uniform. The titanium implants with Nano scale biomaterial interface annealed Ta2O5 coatings exhibited the best modifications for advanced bio-compatibility, together with an tissue engineering applications improvement of the remodeling process J. Phys.: Conf. Series 356 012046. and absence of inflammatory reactions on doi:10.1088/1742-6596/356/1/012046 the bone-implant interface in comparison 7. Radeva E, Georgieva V, Lazarov J, with uncoated samples. Vergov L and Donkov N 2012 Plasma deposited polymers as gas sensitive films J. Phys.: Conf. Series PUBLICATIONS 356 012013 doi:10.1088/1742- 6596/356/1/012013 1. Nurgaliev T, Topal U, Blagoev B and 8. Georgieva V, Donkov N, Stefanov P, Mateev E 2012 Magnetic properties Sendova-Vassileva M, Grechnikov A of LCMO/LSMO thin films on LAO and Gadjanova V 2012 NO2 sensing and ALO substrates J Supercond. properties of amorphous silicon films Nov. Magn. 25 2495-8 doi: J. Phys.: Conf. Series 356 012027 10.1007/s10948-012-1676-0 doi:10.1088/1742-6596/356/1/012027 2. Nurgaliev T, Blagoev B, Mateev E, 9. Nurgaliev T 2012 Preparation and Štrbík V, Beňačka Š, Šmatko V, investigation of high-temperature Gaži Š and Chromik Š 2012 Planar superconducting thin films in the homogeneity of the electrical pro- Superconductivity and Cryoelectro- perties of YBa2Cu3O7/La0.7Sr0.3MnO3 nics Laboratory of the Institute of bi-layers J. Phys.: Con. Series 356 Electronics, Bulgarian Academy of 012020 doi:10.1088/1742-6596/356/1/012020 Sciences BM-Trade Ltd Sofia 100-8. 3. Mateev E, Blagoev B and Nurgaliev T ISBN 978-954-91198-4-8 2012 Impedance measurements of 10. Ivanova G, Stoyanova-Ivanova A, epitaxial and polycrystalline LSMO Terzieva S, Kovacheva D, Mladenov M, thin films J. Phys.: Conf. Series 356 Blagoev B and Dimitrov D 2012 012022. doi:10.1088/1742-6596/356/1/012022 Opportunities for improving the 4. Štrbík V, Beňačka Š, Šmatko V, Gaži Š, electrochemical characteristics of Ni- Chromik Š, Mateev E, Blagoev B Zn batteries using high temperature and Nurgaliev T 2012 Properties superconducting ceramic Proc. 12th of SFS heterostructures prepared Cryogenics Int. Conf. (Dresden by a focused-ion-beam technique Germany 11-14 Sept) 0151-1637 J. Phys.: Conf. Series 356 012021. doi:10.1088/1742-6596/356/1/012021 CONFERENCES ISSN 1742-6588 5. Ghelev Ch, Koutzarova T, Kolev S, 1. Nurgaliev T, Topal U, Blagoev B and Nedkov I, Krezhov K, Kovacheva D, Mateev E, Magnetic properties of Blagoev B, Vertruyen B, Henrist C, LCMO/LSMO thin films on LAO and Cloots R, Zaleski A and ALO substrates, Int. Conf. Nizhankovskii V 2012 Magnetic Superconductivity and Magnetism, properties of nanosized MgFe2O4 May, 2012, Istanbul, Turkey. powders prepared by auto 2. Ivanova G, Stoyanova-Ivanova A, combustion J. Phys.: Conf. Series Terzieva S, Kovacheva D, Mladenov 356 012048 doi:10.1088/1742- M, Blagoev B and Dimitrov D, 6596/356/1/012048 Opportunities for improving the 35 Annual Report IE 2012
electrochemical characteristics of Ni- 4. Preparation and spintronic property of Zn batteries using high temperature perovskite оxide materials, superconducting ceramics, 12th (2012-2014) Cryogenics Int. Conf., 11-14 Sept., Shanghai Institute of Ceramics, China 2012, Dresden, Germany. Academy of Sciences, Shanghai, 3. Stoyanova-Ivanova A, Ilievska I, China. Terzieva S, Ivanova G, Kovacheva D, Mladenov M, Blagoev B and Zaleski A, LABORATORY VISITS Application of HTS ceramic in Ni/Zn batteries, 17th Int. School on Dr. B. Blagoev, Condensed Matter Physics, 2-7 Sept., Institute of Low Temperature and 2012, Varna, Bulgaria. Structure Research, Polish Academy of Sciences, Wroclaw, Poland. COLLABORATIONS Institute of Electrical Engineering, Slovak Academy of Sciences, 1. Investigation of the electrical current Bratislava, Slovak Republic. flowing conditions in HTS/manganite Shanghai Institute of Ceramics, China heterostructures and the electrical Academy of Sciences, Shanghai, current effects on the resistivity China. (2012-2014), Institute of Solid State Physics, VISITS OF FOREIGN SCIENTISTS Russian Academy of Sciences, Chernogolovka, Russia. 1. Assoc. Prof. V. Strbik, 2. Elaboration of technology for Institute of Electrical Engineering, deposition of nanostructure dielectric Slovak Academy of Sciences, oxide covers of new generation, used Bratislava, Slovak Republic, 7 days. as biomaterials and biosensors, 2. Prof. Anhua Wu, ЕР - 12а (2011-2013), Shanghai Institute of Ceramics, China National Scientific Center “Kharkov Academy of Sciences, Shanghai, Institute of Physics and Technology”, China, 7 days. Ukraine. 3. Assoc. Prof. Feng Wu, 3. Investigation of the proximity effect Shanghai Institute of Ceramics, China and spin injection in epitaxial bi-layer Academy of Sciences, Shanghai, structures of ferromagnetic manganites China, 7 days. and high temperature superconductors, (2012-2014), Institut of Electroengineering, Slovak Academy of Sciences, Bratislava, Slovakia.
36 Laboratory Micro- and Nano-photonics
LABORATORY
MICRO- AND NANO-PHOTONICS
HEAD: Prof. Dr.Sc. P. A. Atanasov, Corresponding member of BAS
TOTAL STAFF: 12 RESEARCH SCIENTISTS: 7 Assoc. Prof. N. N. Nedialkov, Ph.D.; Assoc. Prof. A. Og. Dikovska, Ph.D.; M. E. Koleva, Ph.D.; N. E. Stankova, Ph.D.; A. S. Nikolov, Ph.D.; E. L. Pavlov, MS; Т. R. Stoyanchov, MS. Ph.D. students: Ro. G. Nikov; Ru. G. Nikov.
RESEARCH ACTIVITES from the samples was investigated. High SERS signal enhancement was observed 1. Nanoscience and nanotechnologies from all Au-coated ZnO nanostructures. The properties of ZnO films are 1.1. Preparation and study of ZnO strongly dependent on the synthesis nanostructures. Applications to SERS and process and the experimental conditions. biophotonics Thus, the samples were prepared by PLD, which allows excellent control over the These studies deal with different types stoichiometry and surface morphology. of nanostructured ZnO films produced by Cell suspensions of the same concentration pulsed laser deposition (PLD). The and volume (i.e. same number of cells) influence was investigated of the surface were seeded on each sample. The subjects morphology on the physicochemical and of interest were 3T3 fibroblast, MCF-7 and optical properties of the nanostructured HeLa cancer cells. The influence of the films. X-ray photoelectron spectroscopy ZnO surface morphology on the viability was used to study the composition and of these three different cell cultures was chemical state of the nanostructured ZnO. studied. The cell type defines the The changes occurring on the surface of appropriate surface morphology for cell the films after prolonged exposure to air culturing. The nanoscale morphology of were considered in the light of practical the samples supports the HeLa cell applications of ZnO films. The change in viability, while only a small quantity of the number of adsorbed species on the MCF-7 cells are able to adhere, spread and surface with the time affects the surface survive on them. conductivity, the latter in turn modifying the optical properties of the samples. 1.2. Optical scattering and plasmonic Thin ZnO nanostructured films were nanopatterning of the material surfaces produced by PLD for surface enhanced Raman spectroscopy (SERS) studies. The The optical properties of gold experimental conditions used for nanoparticle clusters were studied from the preparation of the samples were chosen in point of view of their biophotonic view of obtaining different types of ZnO applications, where the absorption and nanostructures. The Raman spectra of scattering spectra are of particular rhodamine 6G (R6G) were measured at an importance. The generalized multiparticle excitation wavelength of 785 nm after Mie theory and the finite-difference time- coating the ZnO nanostructures with a thin domain (FDTD) technique were used for Au layer. The influence of the surface theoretical description of the far- and near- morphology on the Raman signal obtained field optical properties of two-dimensional 37 Annual Report IE 2012
nanoparticle ensembles. The system under as on the excitation energy. The structures consideration consisted of spherical gold are characterized by markedly reduced nanoparticles from 20 to 200 nm in dephasing times of about 3 fs. We thus diameter forming 2D clusters in water. The showed that laser annealing of thin Au properties of the far-field absorption and films provides a reliable and cost-effective the scattering spectra as functions of the method for controlled preparation of semi- cluster size, particle dimensions, and regular NP arrays favourable for photonic interparticle distance were investigated for applications. an ordered hexagonal structure of the We also studied the processes of laser- particle arrays. It was found that the driven nanostructuring of bimetallic thin absorption efficiency can be shifted to the films. The thin films were deposited by the IR spectral range by increasing the array classical on-axis PLD technology with size and decreasing the interparticle targets consisting of two sections distance. The increase in the array size composed of different metals. Gold/nickel results also in an enhancement of the or gold/silver thin films were thus scattering efficiency while the absorption deposited on quartz substrates. By is reduced. The near-field intensity changing the area of the different sections distribution is inhomogeneous over the of the target, thin films with different array, as formation of zones with intensity concentrations of the two metals were enhancement of about two orders of produced. The as-fabricated films were magnitude is observed in specific areas. then annealed by nanosecond laser pulses The optical properties of an ensemble delivered by a Nd:YAG laser system whose configuration is reproduced from operating at λ = 355 nm. The modification real experiments of gold nanoparticle of the films produced was studied as deposition onto cancer cells are also functions of the incident irradiation presented. The results obtained can be parameters, such as pulse number and laser used in designing nanoparticle arrays with fluence, the composition of the thin films, applications in biophotonics, bioimaging and the ambient characteristics. It was and photothermal therapy. found that laser annealing leads to We further studied semi-regular arrays nanostructuring of the films if, under of Au nanoparticles (NPs) obtained via certain conditions, the thin films are UV laser irradiation of thin Au films on decomposed into a monolayer of glass substrates. The NP structures were nanoparticles with a narrow size prepared from films of a thickness up to distribution. The EDX analyses performed 60 nm produced by discharge sputtering or indicated that the fabricated particles are PLD, and annealed by nanosecond laser composed of a bimetallic system of the pulses at 266 or 308 nm at fluences in the basic metals used. The extinction spectra range of 60 – 410 mJ/cm2. For the rare- of the structures obtained show plasmon and close-packed NP structures, consistent excitation, while the resonance wavelength description of optical properties was can be efficiently tuned in a wide range by derived from microscopic observation, changing the ratio of the basic metals in measurements of the absorption and the films. The structures obtained can be Raman spectra, and modelling of the near- used in SERS and magneto-optics. field intensity distributions. The absorption bands centred at 540 – 570 nm are 1.3. Nanosecond laser heating of gold ascribed to resonant absorption by surface NPs. Application to photo-thermal cancer plasmons. For the band positions, half cell therapy widths, and intensities, dependences are An application of gold nanoparticles in observed on the NPs shape (partial in-vitro photothermal cancer cell therapy spheres), size and size distribution, as well was demonstrated. Gold nanoparticles with 38 Laboratory Micro- and Nano-photonics
different diameters – 40, 100 and 200 nm, stored at a constant temperature, as a were mixed with HeLa cancer cells. After function of the time after preparation were incubation, the nanoparticles were found monitored. The analyses were based on to have been deposited on the cell’s optical transmission spectroscopy in the membrane or penetrated the cells. Pulsed UV and VIS regions. The change of the laser radiation at wavelength of 532 nm plasmon resonance wavelength as a delivered by a Nd:YAG system was used function of time was studied. Zeta to irradiate the samples. The experiments potential measurement was also utilized to were performed at fluences ranging from measure the charge of the NPs in the 50 mJ/cm2 up to the established safety colloids. The size distribution of the NPs standard for medical lasers of 100 mJ/cm2. and its change in time was determined by The cell viability as a function of the transmission electron microscopy (TEM). particle dimensions and the laser fluence On the basis of the results obtained, the was estimated. The nanoparticles heating optimal conditions of post fabrication and cooling dynamics was traced by a manipulation of gold and silver colloids numerical model based on the heat were defined in view of producing stable diffusion equation combined with the Mie NPs with a narrow size distribution. theory for calculation of the nanoparticles’ An Ag target was immersed in the optical properties. The particles’ response liquid and irradiated by the fundamental, to the nanosecond laser heating was second, third and fourth harmonics of the investigated experimentally as gold Nd:YAG laser system to create different colloids were irradiated at different colloids. Two specific boundary values of fluencies. The threshold fluences for the laser fluence were applied for each particle’s melting and boiling were wavelength. The properties of the determined. We showed that within the nanoparticles at different wavelengths of range of fluencies quoted the particles are the laser radiation were examined. The decomposed into smaller fragments and characterization of the colloids was even a short irradiation time leads to a performed immediately after their decrease in the cell viability. fabrication. Spherical and spherical-like shapes of the nanoparticles formed were 2. Noble metal nanoparticles production established. The formation of nanowires by laser ablation in a liquid was observed when the second and the environment third harmonics of the laser were used. This has to do with absorption of the Preparing noble metal NPs colloids incident laser light by the already-created using pulsed laser ablation in water has an nanoparticles and depends on the laser inherent advantage compared to the fluency. The size distribution of the different chemical methods used, nanoparticles was estimated by TEM. especially when biological applications of Generally, their mean size and standard the colloids are considered. We applied the deviation decreased as the wavelength of technique of laser ablation of a solid target the incident laser light was increased, and in water in order to obtain gold and silver increased with the increase of the laser NP colloids. The experiment was fluency. The substantial discrepancy performed by using the fundamental between the results already commented on wavelength (1064 nm) of a Nd:YAG laser for the two characteristics considered and system. The target immersed in double those obtained by dynamic light scattering distilled water was irradiated for 20 min by was discussed. The structure of the laser pulses with duration of 15 ns at a nanoparticles was established to be single repetition rate of 10 Hz. The sedimentation and polycrystalline, and the phase and aggregation of NPs in the colloids, composition in both cases was identified 39 Annual Report IE 2012
as consisting of cubic silver. The nanostructuring of Ag underlayer nanoparticles are slightly oxidized. Appl. Surf. Sci. 258/23 9181-5 4. Atanasova G, Dikovska A Og, Stankova M, Stefanov P and 3. Enhancement of the ZnO photo- Atanasov P A 2012 XPS study of luminescence by laser nanostructuring ZnO nanostructures prepared by of an Ag underlayer laser ablation J. Phys.: Conf. Series 356 012036 Results are presented on the synthesis 5. Dikovska A Og, Nedyalkov N N, and characterization of nanocomposite Imamova S E, Atanasova G B and Ag/ZnO hetero-structures on fused quartz Atanasov P A 2012 Au-coated ZnO nanostructures for surface enhanced substrates. The experiments were Raman spectroscopy applications performed by PLD using a third harmonic Quantum Electronics 42/3 258–61 Nd:YAG laser in a vacuum chamber. The 6. Koleva M E, Dikovska A Og, ablation of a rotating Ag target was Nedyalkov N N and Atanasov P A followed by laser modification of the 2012 Structural and photo- deposited layer and subsequent deposition luminescent properties of Ag/ZnO nanocomposite heterostructures of ZnO. The process factors, such as the J. Phys.: Conf. Series 356 012002 silver film thickness and the post- 7. Nedyalkov N N, Atanasov P A, deposition annealing procedures, were Toshkova R A, Gardeva E G, varied in view of controlling the diameter Yossifova L S, Alexandrov M T and and size distribution of the Ag Karashanova D 2012 Laser heating nanoparticles. The annealing regimes were of gold nanoparticles: Photothermal modified by varying the laser fluence on cancer cell therapy Progress in Biomedical Optics and Imaging – the Ag layers. The effect on the Ag/ZnO Proc. SPIE 8427 84272P properties was discussed. It was 8. Dikovska A Og, Tsankov N Ts, demonstrated that the photoluminescence Toshkova R, Gardeva E, Yossifova L, intensity of ZnO nanolayers is Nedyalkov N N and Atanasov P A significantly enhanced by plasmon 2012 Fabrication of ZnO absorption in the Ag nanoparticles and a nanostructures and their application shift to the lower wavelengths. in biomedicine Proc. SPIE 8424 8424Q1-7 9. Nikolov A S, Nedyalkov N N, PUBLICATIONS Nikov R G, Atanasov P A, Alexandrov M T and Karashanova D B 1. Nedyalkov N N, Nikov Ru, 2012 Investigation of Ag Dikovska A Og, Atanasov P A, nanoparticles produced by Obara G and Obara M 2012 Laser nanosecond pulsed laser ablation in annealing of bimetal thin films: a water Appl. Phys. A 109/2 315-22 route of fabrication of alloyed 10. Nedyalkov N, Atanasov P, Nikov Ru nanostructures Appl. Surf. Sci. and Imamova S 2012 Structures of 258/23 9162-66 multi-component nanoparticles and 2. Nikov R G, Nikolov A S, Nedyalkov N N, Dimitrov I G Atanasov P A method for their production and Alexandrov M T 2012 Stability Application for BG Patent № of contamination-free gold and 111351/26.11.2012 silver nanoparticles produced by 11. Nedyalkov N N, Dikovska A, nanosecond laser ablation of solid Dimitrov I, Nikov Ru, Atanasov P A, targets in water Appl. Surf. Sci. Toshkova R A, Gardeva E G, 258/23 9318-22 Yossifova L S and Alexandrov M T 3. Koleva M E, Dikovska A Og, 2012 Far- and near-field optical Nedyalkov N N, Atanasov P A and properties of gold nanoparticle Bliznakova I A 2012 Enhancement ensembles Quantum Electronics of ZnO photoluminescence by laser 42/12 1123–27 40 Laboratory Micro- and Nano-photonics
ONGOING RESEARCH PROJECTS 2. Ms. Katarzina Grohovska, Institute of Fluid-Flow Machines, Polish Financed by the Bulgarian Academy of Academy of Sciences, Gdansk, Sciences Poland, 7 days, 23.09.2012. 3. Prof. Gerard Slivinski, Institute of Fluid-Flow Machines, Polish Pulsed laser deposition of thin films. Academy of Sciences, Gdansk, Poland, 7 days, 23.09.2012. Financed by the National Science Fund 4. Prof. Jon Mihailescu, National Institute for Lasers, Plasma and FNI – DО 02 -293 Plasmon and optical Radiation Physics, Magurele, properties of metal nanoparticles and their Romania, 5 days, 14.12.2012. 5. Dr. Felix-Nicolae Sima, National application to high-sensitivity Raman Institute for Lasers, Plasma and spectroscopy and biophotonics. Radiation Physics, Magurele, Romania, 5 days, 14.12.2012. COLLABORATIONS 6. Dr. Gabriel Sokol, National Institute for Lasers, Plasma and Radiation 1. Femtosecond laser processing and Physics, Magurele, Romania, 5 days, novel methods for nanofabrication, 14.12.2012. Department of Electronics and 7. Dr. Carmen-Georgeta Ristoscu, Electrical Engineering, Keio National Institute for Lasers, Plasma University, Yokohama, Japan. and Radiation Physics, Magurele, 2. Nanoparticles generation by Romania, 5 days, 14.12.2012. ultrashort laser ablation of metals and dielectrics: theory and LABORATORY VISITS experiments, Coherentia-INFM, Istituto Nazionale per la Fisica della P. A. Atanasov: Materia; 80126 Napoli, Italy. Institute of Fluid-Flow Machines, 3. Fabrication and characterization of noble metal nanoparticles arrays, Polish Academy of Sciences, Institute of Fluid-Flow Machines, Gdansk, Poland, 10 days, Polish Academy of Sciences, 24.05.2012. Gdansk, Poland. Coherentia-INFM, Istituto Nazionale 4. Pulsed laser deposition of thin oxide per la Fisica della Materia; Napoli, films, Institute of Lasers, Plasma and Italy, 14 days, 19.03.2012. Radiation Physics, Romanian Academy of Sciences, Bucharest, N. N. Nedyalkov: Romania. Institute of Fluid-Flow Machines, 5. Laser nanostructuring of different Polish Academy of Sciences, materials and nanoparticles Gdansk, Poland, 10 days, generation, Institute of Physics, 24.05.2012. Czech Academy of Sciences, Prague, Coherentia-INFM, Istituto Nazionale Czech Republic. per la Fisica della Materia; Napoli, Italy, 14 days, 19.03.2012. GUESTS
1. Ms. Anna Iwulska, Institute of Fluid- Flow Machines, Polish Academy of Sciences, Gdansk, Poland, 7 days, 23.09.2012.
41 Annual Report IE 2012
LABORATORY
BIOPHOTONICS
HEAD: Prof. Latchezar Avramov, Dr.Sc.
TOTAL STAFF: 12 RESEARCH SCIENTISTS: 5
Assoc. Prof. E. G. Borisova, Ph.D.; Assoc. Prof. D. G. Slavov, Ph.D.; A. T. Daskalova- Shivarova, Ph.D.; A. I. Gisbrecht; I. A. Bliznakova; Al. Zh. Zhelyazkova; D. S. Petkov; L. P. Angelova; Zh. D. Dimitrov; Ts. I. Genova; I. I. Balchev.
RESEARCH ACTIVITIES these two techniques in a clinical trial investigation in view of introducing a skin 1. Biophotonics: Laser medical and cancer optical biopsy system into the biomedical research and development of clinical practice of Queen Jiovanna – new diagnostic and therapeutic methods ISUL University Hospital. and equipment In the LIAFS measurements, multiple wavelength excitation was used of the 1.1. Initial diagnosis of skin cancer endogenous fluorescence of benign and using optical biopsy malignant cutaneous lesions. Initially, the lesions were classified visually by an Biomedical optics is one of the fastest experienced dermatologist and growing areas of medical and biomedical dermatoscopically using ABCD scoring research. The non-ionizing nature of light criteria. The second step was detection of applied for investigation and detection of autofluorescence originating from the abnormalities in human tissues make this lesion and the surrounding normal skin area very attractive for development of using different excitation wavelengths, new diagnostic techniques and modalities. namely 365, 385, and 405 nm, emitted by Many optical techniques have recently several narrow-band light-emitting diodes. been applied in the clinical practice to An optical fiber probe was used to deliver obtain qualitatively and quantitatively new the light from the LEDs and to collect the data. Due to their high sensitivity in fluorescence signals from the skin surface. detecting small changes, spectroscopic It consists of 7 fibers in a circular techniques are widely used for detection of geometry. The central fiber is used for early changes in biological tissues. Such autofluorescence signal detection; it is techniques based on the recent progress in connected to a microspectrometric system, optics have been developed for laboratory while the surrounding six fibers are used to and clinical applications. deliver the excitation light from the LEDs The term “optical biopsy” can be found to the skin under investigation. The same in the description of different optical fiber-optic probe was used for reflectance spectral techniques, such as fluorescence, measurements. In the DRS mode of absorption, scattering, reflectance, Raman examination, the illumination source was a scattering, NIR luminescence of biological broad-band halogen lamp. We thus tissues, but its most popular usage is when acquired cutaneous diffuse reflectance light-induced autofluorescence (LIAF) and spectra within the 380-900 nm spectral diffuse reflectance spectroscopic region. techniques for tissue detection and The routine calibration involved determination are described. We applied measuring an optical standard, e.g., a 42 Laboratory Biophotonics
block of Spectralon® (Ocean Optics Inc., from each lesion. The histological Dunedin, FL, USA). The subsequent examination results were used as a “gold reflectance measurements of the skin ere standard” to which all data acquired were normalized with respect to this standard compared. Up to now, more than 500 measurement. Such normalization patients with different skin pathologies eliminates the influence of the source and have been investigated, including 143 the detector response, both of which are cases of basal cell carcinoma (BCC), 48 wavelength dependent. Immediately prior cases of squamous cell carcinoma (SCC), to each patient data collection session, the 12 cases of keratoacanthoma, 62 cases of fiber end was placed in front of a malignant melanoma, dysplastic and Spectrslon® block to obtain the reference benign lesions. The spectral properties of a reflectance spectrum. Measurements of the variety of benign cutaneous lesions have dark current, Dλ, were performed by also been evaluated in order to develop closing an external shutter in front of the more accurate discrimination algorithms spectrometer input. The dark and reference for cancer lesions diagnosis. All subjects signals were then recorded automatically, were Caucasian volunteers – patients of after which the probe end was placed flat the National Oncological Medical Center – against the skin investigated. Both the Sofia, and Queen Giovanna – ISUL LIAFS and DRS spectra were recorded University Hospital, with skin phototypes and stored using a fiber-optic I, II and III according to Fitzpatrick microspectrometer (USB4000, Ocean classification. Optics Inc., Dunedin, FL, USA). A The specific features observed in the personal computer was used to control the cutaneous lesions investigated were as system and store and display the data using follows: the specialized microspectrometer 1) Basal cell carcinoma lesions have lower software OOI Base (Ocean Optics Inc., fluorescence than normal skin; Dunedin, FL, USA). 2) Squamous cell carcinoma lesions have Several spectra were measured from higher fluorescence than normal skin; each suspicious area and averaged to reduce 3) Keratoacantoma lesions have strong the influence of the lesions’ inhomogeneity. keratin fluorescence signal in the green Five to seven spectra were recorded and spectral region; averaged from every lesion, depending on 4) Compounds that fluoresce are collagen its size, and three to five, from a given type I – at 400-405 nm; its cross-links – at normal skin area. The averaged spectra 460-490 nm; elastin – with maxima at 400- from the healthy skin were used as an 420, 460 nm; elastin cross-links – about indicator of the spectral changes in the 500 nm; NADH – at 440-470 nm; keratin pathological areas and for evaluation of – at 430-460, and around 500-520 nm, and effects related to inter- and intra-patients flavins; spectral variations. The spectra were 5) Red-band fluorescence, related to smoothed using a Savitzky-Golay algorithm endogenous porphyrins accumulation in in order to reduce the instrumental noise of the lesions, is also observed for advanced the spectrometric system. stage BCC lesions and in dysplastic Before every spectroscopic lesions with a high metabolic activitiy; measurement, a clinical observation and 6) The influence of the hemoglobin and dermatoscopic evaluation of the lesion of melanin pigments is well pronounced in interest was performed by an experienced the in vivo fluorescence spectra acquired, dermatologist (Elmira Pavlova, MD). namely, a relative decrease of the short- After these initial medical and wavelength vs. long-wavelength intensity, spectroscopic measurements, cytological as well as the appearance of minima at and/or histological samples were taken 420, 543 and 575 nm; 43 Annual Report IE 2012
7) Reflectance spectroscopy exhibits a sensitivity, easy-to-use measurement higher specificity compared to methodology, lack of need for contrast fluorescence spectroscopy in agents application on the tissue under differentiating pigmented skin pathologies, investigation, possibilities for real-time including malignancies; this technique is measurements and non-invasive tumor thus very useful for early detection of the detection. However, no reliable and appearance of malignant melanoma and universal systems for fluorescence for monitoring and evaluation of changes detection of skin cancer have so far been occurring in dysplastic nevi; offered on the medical market. The 8) The fluorescence technique is very problems in developing such a system are sensitive (>85%) for non-melanoma skin related to the great variety of benign and pathologies and could be applied in routine malignant forms of skin pathologies; e.g., clinical practice for early diagnosis of basal cell carcinoma lesions have more BCC and SCC. than 15 sub-types, squamous cell Our work proceeded with assessing the carcinoma lesions have about 10 different origins of diagnostically significant subtypes, and all of them have a variety of spectral features; differentiation schemes benign and dysplastic forms; moreover, were developed and examined. A clinical they are different, including by their trial for initial diagnosis of skin cancer is fluorescence properties, at the different currently being performed at Queen stages of the lesion growth. Another very Giovanna – ISUL University Hospital; by important disadvantage is the fact that expanding the database of fluorescence different endogenous fluorophores appear spectra of major skin benign and in the integral autofluorescence signal malignant pathologies, we expect to originating from the skin under excitation develop an objective tool for cancer at different wavelengths, which makes this detection and treatment monitoring. We type of spectra difficult to analyze and are curently processing the spectral data compare with the fluorescence signals obtained for subsequent medical statistical detected from various pathological skin analysis. The results indicate that the lesions. optical biopsy method yields extremely The use of autofluorescence high sensitivity (> 95 %) and specificity spectroscopy for early detection of (~97 %) in differentiating carcinoma from cutaneous pathologies has been reported in other pathologies, and SE = 92 % and a large number of publications. To SP = 100 %, in differentiating malignant stimulate in vivo autofluorescence melanoma. The results also revealed a very emission from skin tissues, the research good correlation with the histological skin groups have applied a variety of excitation analysis, as well as a repeatability of the sources (and wavelengths), such as lasers, features of the fluorescence and LEDs, narrow-filter broad-band lamps. reflectance signals from patient to patient, However, a comprehesive review of the with the same type of lesion being autofluorescence spectra emitted in vivo by obtained by the LIAFS and DRS normal human skin under excitation at measurements. different wavelengths is yet to appear in the literature. 1.2. Excitation-emission matrices for In the beginning of 2012, we started studying intrinsic fluorescent properties of investigations on determining the cutaneous and mucosa tumors endogenous fluorescent properties of cutaneous and mucosal (lower Autofluorescence spectroscopy of gastrointestinal tract) tissues normal and human tissues is a very attractive tool for diseased. The research is financed by the early diagnosis of cancer due to its high National Science Fund at the Ministry of 44 Laboratory Biophotonics
Education, Youth and Science of Republic mechanical, and structural properties is an of Bulgaria (DMU-03-46/2011 – important consideration in designing Development and introduction of optical tissues for biomedical applications. biopsy for early diagnosis of malignant Natural and synthetic polymers are used tumors). as substitute biomaterials in tissue The studies involved two systems – for engineering applications. It is known that point spectroscopic measurements and for the laser-modified surface of a thin film of 2-D imaging of the tissues and lesions biomaterial exhibits better investigated. Excitation-emission matrices biocompatibility, greater roughness, were constructed for a variety of tumors enhanced cell attachment and proliferation, and normal samples. thus being an adequate host for cells The excitation applied in the point- differentiation, as compared with an measurements was in the range from 250 unmodified scaffold. It is also known that to 550 nm, with a 5-nm step between the femtosecond laser pulses induce the excitation bands (2 nm); the emission was formation of micro-pores on the surface of detected in the 260 – 800 nm region using thin gelatine and collagen films. We a FluoroLog3 spectrofluorimetric system studied the effect of the laser pulse energy in a steady-state mode with a F3000 fiber- and the number of laser pulses on the optic stand and a probe attached to the development of micro-pores. We showed spectrometric system (HORIBA that applying laser pulses at various JobinYvon, France). In the EEMs formed, repetition rates modifies considerably the one can address all detected in vivo major thin film surface. The results revealed that skin fluorophores existing in the normal femtosecond laser pulse treatment of thin cutaneous tissues based on their films of biomaterials (gelatin and collagen) coordinates (excitation max; emission results in creation of nanostructures and max). A complete picture is thus obtained micro/nano pores of different size. The in vivo of the autofluorescence properties experiments demonstrated the possibility of normal Caucasian skin; it can be used as to vary the pore size (ranging from 5 µm to a diagnostic basis for comparison with 100–450 µm) by varying the laser autofluorescence signals from different parameters. The surface properties of thin cutaneous pathologies. Detection of EEM biopolymer films before and after Ti- data from cutaneous tumors and mucosal sapphire laser irradiation at 800 nm were neoplasia is in progress, as our first results investigated by means a field emission showed very good repeatability for the scanning electron microscope (FESEM). same type of samples with specific The results showed a direct correlation changes that correlate with our previous between the nanostructured gelatine foam investigations and our knowledge on the and the laser pulse duration, τ, the number biochemical and morphological changes of pulses, N, and the pulse energy. Thus, occurring in pathological tissues. decreasing τ affected the size of the pores; secondly, N can affect the quality of the 1.3. Femtosecond modification of foam surface expansion. Collagen biopolymers for application in tissue irradiation by a larger N results in a greater engineering ejection of melt products on the circumferential areas, which subsequently The ability to produce idealized cellular leads to a higher degree of surface constructs is essential for understanding roughness. Controlling the processing of a and controlling intercellular processes and, biocompatible collagen-based foam may ultimately, for producing engineered tissue lead to a better understanding of the replacements. The fabrication of artificial cellular requirements necessary for scaffolds with the appropriate biological, successfully regenerating new tissue 45 Annual Report IE 2012
scaffolds. Moreover, good data (the distribution of the light power understanding/knowledge will be achieved received proportional to the light intensity) of the thermodynamics and phase was obtained by a transversal radial scan transformations during laser surface of the fiber at each stepwise-varied depth modification aimed at enhancing the of interest and for each of the turbid media functionality of the laser-treated surfaces. prepared. Scanning in three mutually Further, the problems associated with laser perpendicular (x, y, and z) directions was processing, such as microcracks and heat- implemented by using three long-travel affected zones, will be minimized. Apart stages Thorlabs LTS 300/M ensuring a from this, proper in situ monitoring and minimum sampling step of 4 μm. The control of the laser surface engineering cross-sectional distribution of the laser- should be incorporated into the setup for beam intensity and the receiving effective feedback analysis of the directional diagram of the fiber in air were operations. also measured and shown to have an approximately Gaussian shape. The angle 1.4. Determination of the optical of view of the fiber in air was estimated to properties of turbid media based on the be γ ~ 12°, or 0.21 rad, so that its characteristics of propagating laser numerical aperture NA sin ~ 0.21. If radiation beams the diluted Intralipid emulsion is considered as a watery medium with a An experimental setup was built with refractive index n ~ 1.34, the angle of view the aim of measuring the forward spatial of the fiber in these media will intensity distribution of laser light be arcsin(NA / n) ~ 90 , i.e. 0.16 rad. propagating in turbid media. A laser diode The turbid media investigated was used as near-infrared (NIR) light experimentally were prepared by dilution source emitting a nearly collimated of different amounts (from 17.5 ml to 433 continuous-wave optical beam of about ml) of 20% IL emulsion in 14 l distilled 1 mm radius and wavelength of 850 nm. water. Correspondingly, the IL The total emitted light power could be concentration varied from 0.025% to varied from 20 mW to 50 mW. The tissue- 0.6%. The investigations performed are like phantoms of different optical important in view of developing methods properties were prepared by diluting for measuring the optical characteristics of different amounts of Intralipid (IL)-20% turbid media, such as tissues and (Fresenius Kabi AB, Sweden) in 14 l experimental tissue-like phantoms. They distilled water placed in a cubic (edge of would also be especially useful in the 25 cm) plexiglass container. The axis of process of establishing the laws governing the incident laser beam was perpendicular the radiative transfer inside the optically to the “frontal” face of the container. It investigated biological objects. The further may be considered as being forward- work on the subject will be directed to oriented, in the direction of beam increasing the experimental accuracy and incidence. The forward spatial intensity refining the theoretical models. distribution of the light propagating inside the container was measured by using a 1.5. Laser-induced tissue oxygenation scanning optical fiber of 0.1 mm core diameter. The fiber was oriented The value of the relative antiparallel to the beam axis and connected oxyhemoglobin concentration (saturation) to an optical radiometer (Laser Precision in arterial (SаO2) and venous blood (SvO2) Corp., USA) with a RqP-546 silicon probe plays a significant role in the oxygen in external locking regime, a 14-bit ADC exchange in tissues and is used as a and a data-processing computer. A set of criterion for oxygen delivery adequate to 46 Laboratory Biophotonics
the needs of tissue cells. A reduction of the 2. Mantareva V, Kril A, Angelov I, of blood flowrate, as well as a reduction of Dimitrov R, Borisova E and Avramov L the oxygen concentration in arterial blood, 2012 Effects of the position of cause hypoxia – a deficit of oxygen in the galactose units to Zn(II) respective tissue. One of the main phthalocyanine on the uptake mechanisms of eliminating hypoxia is and photodynamic activity towards based on compensating the oxygen deficit breast cancer cells Biophotonics: by increasing the oxygen extraction from Photonic Solutions for Better arterial blood, which leads to oxygen Health Care III, Popp J, Dexler W, reduction of in the venous blood. We used Tuchin V and Matthews L eds. two optical techniques for venous blood Proc. SPIE 8427 8427-43 saturation measurement. The first one is ISSN:16057422 ISBN:978-081949119-0 based on the pulseoximetry with artificial mechanical modulation of the tissue doi: 10.1117/12.923794 volume, while the second one, on 3. Gurdev L, Dreischuh T, Bliznakova I, spectrophotometry of the human Vankov O, Avramov L and Stoyanov D respiratory rhythm. Good correlation 2012 Scattering of a laser beam in between the results obtained with both turbid media with forward-peaked techniques was observed. Henyey–Greenstein indicatrices Phys. Numerical simulations were performed Scripta 149 014074 doi:10.1088/0031- of the effect of laser radiation on the gas 8949/2012/T149/014074 exchange processes in biological tissues. It 4. Asimov M M, Asimov R M, Rubinov was shown that the photodissociation of A N and Gisbrecht A I 2012 The oxyhemoglobin in the blood vessels and physics of biomedical effect of blood myoglobin in muscle tissue can increase oxyhemoglobin photodissociation the molecular oxygen extraction, which J. Basic and Applied Phys. 1 33-48 allows one to regulate the local oxygen ISSN: 2304-9340 concentration in the tissue in the 5. Damyanov Ch, Sirova J, Gerasimova D, immediate area of radiation exposure. It is Maslev I, Avramov L and Gisbrecht A predicted that photodissociation of 2012 Intravenous laser (405 nm) oxymyoglobin in the condition of low irradiation of blood for treatment of oxygen supply may cause deep hypoxia in oncological diseases. Initial muscles and have a negative effect in the investigations Laser Medicine 16/3 application of multi-wavelength laser 25-8 ISSN: 2071-8004 therapy. This factor should be taken into 6. Sargsyan D, Leroy C, Pashayan- account when the combined effects of Leroy Y, Sarkisyan D, Slavov D and laser therapy at two or more wavelengths, Cartaleva S 2012 Electromagnetically including IR radiation, are considered. The induced transparency and optical development of the optical method holds pumping processes formed in Cs sub- promises for improving the laser therapy micron thin cell Optics Commun. efficiency. 285/8 2090–5 doi: PUBLICATIONS http//dx.doi.org/10.1016/j.optcom.2012.01.00 2 ISSN: 00304018 1. Borisova E, Pavlova P, Pavlova E, 7. Borisova E, Pavlova E, Troyanova P and Avramov L 2012 Optical biopsy Troyanova P and Avramov L 2012 nd Optical biopsy of human skin – tool of cutaneous tumours Proc. 2 Int. for cutaneous tumours’ diagnosis Int. Conf. Laser Surgery and Medicine J. Bioautomation 16/1 53-72 ISSN: CLSM'2012 (23-30 April 2012 1314-2321 (on-line) 1314-1902 Yokohama Japan) CLSM6-2 pp 2-3 47 Annual Report IE 2012
8. Borisova E, Uzunov T and Avramov L CONFERENCES 2012 Laser-induced breakdown spectroscopy of dental lesions – tool Prof. Dr.Sc. L. Avramov
for real time optical feedback during Int. Symp. Radiobiology and Medicine, nd laser ablation of caries Proc. 2 Int. Dubna, Russia, 05 March 2012: Conf. Laser Surgery and Medicine ● Biophotonics technologies in CLSM'2012 (23-30 April 2012 anticancer therapy. Yokohama Japan) CLSM7p-3 pp 48-9 Int. Conf. Biophotonics in Dermatology and 9. Borisova E, Pavlova E, Troyanova P, Cardiology, Riga, Latvia, 30 April 2012: ● Fluorescence spectroscopy for skin Nikolova B and. Tsoneva I 2012 cancer diagnosis. Autofluorescence of skin cancer – Int. Conf. Integrative Medicine, Vienna, tool for initial diagnosis and Austria, 04-09 May 2012: monitoring of therapy Proc. 15th Int. ● Biophotonics in integrative cancer Conf. Laser Optics-2012 (Sankt treatment. th Petersburg, Russia, 25-29 June 2012) 17 Int. School on Quantum Electronics, 24-28 September 2012, Nessebar, 10. Borisova E, Pavlova E, Troyanova P, Bulgaria: Nikolova B and Tsoneva I 2012 ● Endogenous and exogenous Optical biopsy – tool for initial cancer fluorescence of gastro-intestinal tumors diagnosis and monitoring of therapy – initial clinical observations; Proc. European Medical Phys. Conf. ● Light-induced auto-fluorescence and pp172-9 ISBN: 978-954-91589-3-9 diffuse reflectance spectroscopy of cutaneous tumors – clinical study; 11. Asimov M, Asimov R, Rubinov A ● Laser-induced breakdown spectroscopy and. Gizbreht A 2012 Influence of of caries. oxyhemoglobin photo-dissociation on oxygenation of muscle tissues Proc. Assoc. Prof. Dr. E. Borisova 9th Int. Conf. Laser Phys. and Optical Technol. (Grodno Belarus) pp 240-3 Member of the Program Committee of ISBN: 978-985-515-597-4 th ● 20 Int. Conf. Advanced Laser 12. Asimov M, Asimov R, Rubinov A Technologies ALT'2012, 03-09 Sept. and. Gizbreht A 2012 Physical basis 2012, Thun, Switzerland; of biomedical effect of ● 21th Int. Conf. Advanced Laser oxyhemoglobin molecules dissoci- Technologies ALT'2013, Sept. 2013, ation Proc. Int. Conf. Molecular Budva, Montenegro; ● Int. Conf. Photonics, Optics and Laser Membrane and Cell Functionalizing Technologies PHOTOPICS'2013, February of Biosystems (Minsk Belarus) pp 2013, Spain; 241-4 ISBN: 978-985-027-6 ● Int. Conf. Laser Applications and Technologies LAT2013, June 2013, PATENTS Moscow, Russia. Participation in conferences, symposia, A. Gizbrecht, 2012, System for schools photodynamic therapy of oncological 2nd Int. Conf. Laser Surgery and Medicine diseases, Official Patent Bulletin of CLSM'2012, 23-30 April 2012, Yokohama, Republic of Bulgaria 10 pp 18-19. Japan: 48 Laboratory Biophotonics
● Optical biopsy of cutaneous tumours Assoc. Prof. Dr. D. Slavov (invited report); ● Laser-induced breakdown spectro- 17th Int. School on Quantum Electronics, scopy of dental lesions – a tool for 24-28 September 2012, Nessebar, real time optical feedback during laser Bulgaria: ablation of caries (poster). ● Second-harmonic generation from Laser Optics 2012 - LO'2012, 26 June- 01 complex chiral samples; July 2012, Sankt Peterburg, Russia: ● Sub-natural width resonances in Cs ● Autofluorescence of skin cancer – a vapor confined in micrometric tool for initial diagnosis and thickness optical cell; monitoring of therapy (invited ● Velocity selective optical pumping lecture). resonance sign reversal; 20th Int. Conf. Advanced Laser ● Bi-chromatic spectroscopy in Technologies ALT'2012, 03-09 September micrometric optical cells. 2012, Thun, Switzerland: ● Endogenous and exogenous fluorescence of biological tissues for Dr. A. Daskalova clinical applications (invited lecture). Int. School on Optics, Lasers and 17th Int. School on Quantum Electronics, Biomedical Photonics (Saratov Fall 24-28 September 2012, Nessebar, Meeting - SFM’2012), 23-30 Sept. 2012, Bulgaria: Saratov, Russia: ● Surface modification of collagen- ● Optical biopsy – a clinical tool for based biomaterial induced by initial diagnosis and therapeutic femtosecond laser pulses of variable monitoring of cutaneous tumors duration. (invited lecture); ● Autofluorescence spectral features of normal skin – basis for comparison A. Gisbrecht with cutaneous pathologies (oral report). 9th Int. Conf. Laser Phys. and Optical 17th Int. School on Quantum Electronics, Technol., Grodno, Belarus, 30 May - 02 24-28 September 2012, Nessebar, June 2012: Bulgaria: ● Influence of oxyhemoglobin photo- ● Light-induced auto-fluorescence and dissociation on the oxygenation of diffuse reflectance spectroscopy of muscle tissues. cutaneous tumors – clinical study Int. Conf. Molecular Membrane and Cell (poster); Functionalizing of Biosystems, Minsk, ● Endogenous and exogenous Belarus, 19-21 June 2012: fluorescence of gastro-intestinal ● Physical basis of biomedical effect of tumors – initial clinical observations oxyhemoglobin molecules dissociation. (poster); 17th Int. School on Quantum Electronics, ● Laser-induced breakdown spectroscopy 24-28 September 2012, Nessebar, of caries (poster). Bulgaria: European Medical Phys. Conf. – ● Venous saturation and blood flow EMPEC’2012, 18-20 October 2012, Sofia, behavior during laser-induced Bulgaria: photodissociation of oxyhemoglobin; ● Optical biopsy – a tool for initial ● The impact of myoglobin on the cancer diagnosis and monitoring of therapeutic efficiency of low-intensity therapy (invited lecture). laser radiation.
49 Annual Report IE 2012
L. Angelova Financed by ministries, departments, and companies 17th Int. School on Quantum Electronics, 24-28 September 2012, Nessebar, 1. Agreement between Institute of Bulgaria: Electronics, Bulgarian Academy of ● Endogenous and exogenous Sciences, and Institute of Organic fluorescence of gastro-intestinal Chemistry with Photochemistry tumors – initial clinical observations Center, Bulgarian Academy of (poster). Sciences, Application of biologically- active compounds for improvement of tumor tissues’ fluorescent abilities. ONGOING RESEARCH PROJECTS 2. Bilateral agreement between Institute of Electronics, Bulgarian Academy of Financed by the National Science Fund Sciences and Institute of Nuclear Research – Dubna, Russian 1. Contract № DMU 03/15 3D Federation, Radiation and Femtosecond laser microprocessing of radiobiological investigations in the biomaterials for application in irradiation fields of Joint Institute of medicine. Nuclear Research Facilities and in the 2. Contract № DMU-03-46/2011 environment. Development and introduction of an optical biopsy system for early COLLABORATIONS diagnostic of malignant tumors 2011- 2013. 1. In the framework of the National 3. Contract № DNTS-Ukraine Center on Biomedical Photonics 01/0006/2012 – Investigation of laser Project: interaction with peripheral blood Center for Optical Diagnostics circulation for development of highly and Therapy, Erasmus Medical efficient phototherapy Center, Rotterdam, the 4. Contract #DO-02-112/2008 - National Netherlands; Center on Biomedical Photonics – School of Pharmacy & Bio- completed in 2012. molecular Sciences, University of 5. Contract #DO-02-58/2008 - Brighton, UK; Development of infrastructure for University of Ioannina, Greece; neutron therapy in Bulgaria – Institute of General Physics, completed in 2012. Technical University of Vienna, 6. Contract № BIN-04/07 Inactivation of Austria; pathogenic bacteria of periodontal Optics and Biomedical Physics diseases – fluorescence diagnostics Department, Research-Educa- and photodynamic therapy – tional Institute of Optics & completed in 2012. Biophotonics, Saratov State University, Russia; Department of Electrical Financed by the European Social Fund Engineering and Electronics, University of Liverpool, Contract #BG 051РО001-3.3.04/56/28.08.2009 Liverpool, UK; Development of interdisciplinary thinking Frederick University, Department and training of young researchers in the of Mechanical Engineering, field of light-matter interactions, Cyprus; completed in 2012. University of Siena, Italy; 50 Laboratory Biophotonics
Organic and Natural Products LECTURE COURSES Chemistry Group, Chemistry Department, University of Aveiro, Assoc. Prof. Dr. Ekaterina Borisova Portugal; ● Photochemical interactions in Institute of Organic and biomedicine – lectures (15 h) and Macromolecular Chemistry, practice (30 h), MS degree course, for University of Bremen, Germany; the Medical Physics Program of the Biophotonics Laboratory & Head Faculty of Physics, St. Kl. Ohridski Atmospheric Sciences Division, University of Sofia. Centre for Earth Science Studies, ● Optical methods and technologies used India; in medicine – practice (24 h), BS Biophysics and PDT group, degree course, at the Physics and Institute for Cancer Research, Engineering Technologies Department Norwegian Radium Hospital, of the University of Plovdiv. Norway; A.M. Prokhorov General Physics LABORATORY VISITS Institute, Russian Academy of Sciences, Moscow; L. Avramov, School of Science and ● Joint Institute of Nuclear Researches, Technology, University of Sussex, Dubna, Russia, 04-08 March 2012; UK; ● Institute of Spectroscopy, Riga, Physics Department, National Latvia, 29 April – 04 May 2012. Technical University of Athens, Greece; E. Borisova, Department of Constructive and General Physics Institute of the Russian Technological Engineering, Academy of Sciences, Moscow, Russia, National Institute of Research and Sept. 2012. Development for Optoelectronics – INOE - 2000, Romania; A. Daskalova, 2. Institute for Electronic Structure and Technical University of Vienna, Institute Laser, FORTH, Heraklion, Greece. of Applied Physics, Vienna, Austria, 14-21 3. Coherent Population Trapping Effect Oct. 2012. in Potassium” – CNR, Pisa, Italy. 4. Atomic vapors in metamatherials – I. Bliznakova, University of Leuven, Belgium. Technical University of Vienna, Institute 5. High resolution spectroscopy in of Applied Physics, Vienna, Austria, 14-21 quantum optics and metrology” - Oct. 2012. Institute of Physics, Belgrade. 6. P09073A: HCI-induced ToF-SIMS studies of hard dental tissues, France. 7. ITSLEIF-exchange programme of the EU Study of mechanisms of ultra- short laser ablation and desorption of biomolecules, 2010. 8. Development of new methods for laser diagnostics and therapy of dermatological and oncological diseases, Institute of Physics, National Academy of Sciences of Belarus, Minsk, Belarus. 51 Annual Report IE 2012
LABORATORY
LASER SYSTEMS
HEAD: Assoc. Prof. S. Gateva, Ph.D.
TOTAL STAFF: 12 RESEARCH SCIENTISTS: 9 Assoc. Prof. S. Cartaleva, Ph.D.; Assoc. Prof. E. Alipieva, Ph.D.; Ch. Andreeva, Ph.D.; E. Taskova, Ph.D.; P. Todorov, Ph.D.; O. Vankov; K. Vaseva; N. Petrov; V. Sarova; A. Krasteva; T. Kalaidjiev.
RESEARCH ACTIVITIES features in the spectra of 1D confined atoms, when the nanometric dimension The growing interest in coherent- approaches the wavelength of the population-trapping (CPT) resonances, irradiating light. The application of the prepared and detected under different nanometric cell provides a new conditions, is stimulated by their numerous opportunity for significant enhancement of applications in high-resolution the resolution of the laser spectroscopy of spectroscopy, quantum information thermal cells, without application of storage and processing, metrology (atomic complex atomic beam or laser cooling clocks), magnetometry, lasing without systems. This simple approach makes it inversion, laser cooling, ultraslow group also possible to study the dynamic velocity propagation of light, etc. Building processes in absorption and fluorescence. miniature and high sensitivity sensors It was shown that when the Cs vapor layer ensuring reliable operation requires good thickness is about the wavelength of the knowledge of the CPT resonance shape irradiating light , the fluorescence and the processes influencing it. During spectrum is significantly narrower than the 2012 at the Laser Systems Laboratory, absorption one and the absorption systematic investigation of the contrast and coefficient does not grow linearly with the width of the CPT resonances was thickness of the atomic layer. The coherent performed in conventional vacuum cells, Dicke narrowing of atomic transitions cells with antirelaxation coating, micro- observed in the optical domain is strongest and nanometric cells, and of laser cooled at L = /2, while expanding further the atoms. vapor layer thickness results in periodical High-resolution laser spectroscopy of collapse and revival of this coherent effect. alkali vapor contained in optical cells with The significant difference was centimeter dimensions is widely used for demonstrated and analyzed between the various applications in photonic sensors, saturation of open and closed transitions where the reduction of the sensor under conditions of very well-expressed dimensions is of significant importance. Dicke revival (L = 1.5 ). The appearance One of the main concerns is to keep the of a narrow structure in the sub-Doppler parameters of the sensor when reducing its fluorescence profile was studied both size. Interesting experimental and experimentally and theoretically, while theoretical results were obtained distinguishing between open and closed concerning high-resolution spectroscopy transitions. The theoretical simulations of Cs vapor layer with nanometric predicted a significant enhancement with thickness. The practical importance of this the cell thickness of the amplitude of the study is accompanied by numerous new narrow dip observed in the fluorescence 52 Laboratory Laser Systems
profile. The prediction was confirmed experimental shapes. The results show that experimentally; it was demonstrated that the theoretical modeling developed can be the narrow structure in the fluorescence at applied for analysis of the influence of the L = 6 has a very good potential for different factors and of the cell quality. development of frequency references. The Rayleigh scattering can be used to To miniaturize the cells, a series of analyze the cell’s vacuum cleanness and measurements of micro- and nano-size the quality of its walls. On the other hand, cells were performed with colleagues from these narrow resonances can be applied for Armenia. The effect of electromagnetically building magneto-optical sensors. From induced transparency (EIT) in a Λ-system the point of view of applications in formed by Cs atoms confined in magnetometry, where narrow signals and nanometric cell (L varying in the range high signal-to-noise ratios are important, 800 nm – 3 μm) was studied both the narrow Rayleigh structure of the CPT experimentally and theoretically. It was resonance measured in fluorescence offers demonstrated that when the coupling laser good possibilities: it is not power- frequency is in exact resonance with the broadened, its width does not depend on corresponding atomic transition, the EIT the position of the detector and its resonance parameters depend weakly on L, amplitude increases with the power. The which allows one to detect the effect at complex structure of the resonance L = λ = 852 nm. The EIT process reveals a expands the range of the magnetic fields striking peculiarity in the case of detuning measured. the coupling laser from the atomic Peculiarities in the D1 87 Rb line CPT transition, namely, the width of the EIT resonance obtained in fluorescence in a resonance rapidly increases upon an paraffin-coated cell were studied as well. increase of the detuning. The opposite The transformation was investigated from effect is observed in centimeter-scale cells. black to bright resonances, together with The strong broadening of the EIT and its dependence on the laser power and resonance for large detuning values is experimental geometry. In the case of a caused by the influence of the atom-wall weak (1 mG) laboratory magnetic field collisions on the dephasing rate of applied in the laser light polarization coherence. We also demonstrated that the direction, a good qualitative agreement nanometric cell is well suited for was obtained between the theoretical curve measuring strong and non-homogeneous constructed by numerical calculations magnetic fields in a large range of based on the irreducible tensor operator intensities. formalism and the experimental curve. The investigations of the influence of The studies on the CPT resonance different factors on the shape of the CPT shapes performed at the Institute of resonances excited in a Hanle effect Physics in Warsaw with laser cooled configuration in an uncoated room- atoms in a magneto-optical trap (MOT) are temperature vacuum cell and registered in of principal interest, since they concern fluorescence were generalized in a chapter small volumes without Doppler of a monograph. The numerical broadening. In the past year, modeling was calculations performed by taking into conducted of the pump-probe spectra and account the Gaussian distribution of the the different spectral features were laser beam intensity, the experimental attributed to various levels-fields’ geometry of the excitation, the velocity configurations with respect to the mF-mF’ distribution of the atoms, the high-rank transitions realized under the conditions of polarization moments, the stray magnetic an operating magneto-optical trap. fields influence, and the Rayleigh These investigations are of importance scattering, describe very well the complex for the development of new sensors for 53 Annual Report IE 2012
photonics, their miniaturization and 8. Gateva S and Todorov G 2012 Shape application to precise magnetic field of the coherent population trapping measurements and metrology. resonances registered in fluorescence Photodetectors (InTech) 417-440 PUBLICATIONS ISBN: 978-953-51-0358-5 9. Polischuk V, Domelunksen V, 1. Todorov P, Slavov D, Vaseva K, Alipieva E and Todorov G 2012 Taslakov M, Cartaleva S and Saltiel S. Modelling of nonlinear interaction 2012 High-resolution spectroscopy of of Rb87 atoms with polarized a cesium-vapor layer with radiation Bulg. J. Phys. 39 150-64 micrometric thickness for the ISSN: 1310-0157 development of frequency reference 10. Taskova E, Alipieva E and Todorov G Physica Scripta 149 014014 ISSN: 2012 Transformation of the coherent 0031-8949 population trapping resonance 2. Sargsyan A, Leroy C, Pashayan- into enhanced fluorescence in a Leroy Y, Sarkisyan D, Slavov D and paraffin coated Rb vacuum cell Cartaleva S 2012 Electro- J. Phys.: Conf. Series 356 012030 magnetically induced transparency ISSN: 1742-6588 and optical pumping processes 11. Cartaleva S, Krasteva A, Sargsyan A, formed in Cs sub-micron thin cell Sarkisyan D, Slavov D and Opt. Commun. 285 2090–95 ISSN: Vartanyan T 2012 High resolution 0030-4018 spectroscopy of Cs vapor confined in 3. Nasyrov K A and Cartaleva S 2012 optical cells of few-micron Magnetooptical resonances in cells thicknesses J. Phys.: Conf. Series with residual buffer gas in elliptical 397 012062 ISSN: 1742-6588 polarization of radiation 12. Gurdev L, Dreischuh T, Bliznakova I, Optoelectronics, Instrumentation and Vankov O, Avramov L and Stoyanov D Data Processing 48 389-95 ISSN: 2012 Scattering of a laser beam in 8756-6990 turbid media with forward-peaked 4. Nasyrov K A and Cartaleva S 2012 Henyey-Greenstein indicatrices Magnetooptical resonances in cells Physica Scripta 149 014074 with residual buffer gas in elliptical DOI:10.1088/0031-8949/2012/T149/ polarization of radiation Avtometriya 014074 48 79-87 ISSN: 0320-7102 (in Russian) PATENTS SUPPORTED 5. Moi L and Cartaleva S 2012 Sensitive magnetometers based on 1. Biancalana V, Dancheva Y, Mariotti E, dark states Europhysics news 43 6 Moi L, Cartaleva S and Andreeva Ch 24-7 ISSN 0531-7479 Method and device for measurement 6. Cartaleva S, Krasteva A, Sargsyan A, of magnetic induction, BG Patent Reg. Sarkisyan D, Slavov D, Todorov P No 107350/03122008. and Vaseva K 2012 High resolution 2. Biancalana V, Dancheva Y, Mariotti E, laser spectroscopy of cesium vapor Moi L, Cartaleva S and Andreeva Ch layers with nanometric thickness Method and device for measurement Adv. Photonic Sci. Fadhali M ed of magnetic induction, Eur. Patent No 9 255-84 (InTech) ISBN: 978-953- EP1570282 Priority 03122002/2009. 51-0153-6 3. Stoyanov D, Gurdev G, Dreischuh T, 7. Gateva S ed 2012 Photodetectors Vankov O and Protochristov Ch (InTech) ISBN: 978-953-51-0358-5 Radar on single spontaneously emitted 460 pages gamma-photons, Reg. № 65770 В1/2009. 54 Laboratory Laser Systems
4. Stoyanov D, Gurdev G, Dreischuh T, Gateva S, Taslakov M, Sarova V, Vankov O, Avramov L and Borissova E Marriotti E and Cartaleva S, Optical multichannel transceiving Light-induced atomic desorption for system, Reg № 65769 В1/2009. miniaturization of magneto-optical sensors; EUROPEAN PATENTS PENDING Żaba A, Paul-Kwiek E, Kowalski K, Szonert J, Gateva S, Long V C and 1. Stoyanov D, Dreischuh T, Gurdev L, Głódź M, Vankov O, Avramov L, Borisova E Pump-probe spectra modeled with and Bliznakova I, Method for inclusion of a dipole-coupled but not determining optical and spatial dipole-probed F' state, for the case of characteristics of an inclusion in a 85Rb 5S1/2(F)↔5P3/2(F') transitions. turbid medium using multiple- scattering optical tomography, 21st Int. Conf. Spectral Line Shapes Patent No.EP2153772A1, (ICSLS 2012), 3-9 June 2012, St. Applicant - Siemens AG, Germany. Petersburg, Russia: 2. Stoyanov D, Dreischuh T, Gurdev L, Cartaleva S, Krasteva A, Sargsyan A, Vankov O, Avramov L, Borisova E Sarkisyan D, Slavov D and and Bliznakova I, Apparatus for Vartanyan T, determining optical and spatial High resolution spectroscopy of Cs characteristics of an inclusion in a vapor confined in optical cells of turbid medium using multiple- few-micron thicknesses. scattering optical tomography, Patent No.EP2165647A1 11th Int. Conf. Solid State Chem.: Applicant - Siemens AG, Germany. Nanomaterials, Nanotechnol., 22-27 April 2012, Stawropol, Russia: Slavov D, Krasteva A, Subov P and CONFERENCES Cartaleva S, Dark and bright velocity selective 17th Int. School on Quantum Electronics, optical pumping resonances in 24-28 September 2012, Nessebar, nanometric cells filled with Cs vapor. Bulgaria: Cartaleva S, Krasteva A, Sargsyan A, 15th Winter Seminar of the Young Sarkisyan D, Slavov D and Scientist and PhD Students, 07-09 Vartanyan T, December 2012, BAS House of Scientists, Sub-natural width resonances in Cs Vitosha, Sofia, Bulgaria: vapor confined in micrometric Krasteva A, thickness optical cell; Electromagnetically induced trans- Sargsyan A, Mirzoyan R, Cartaleva S, parency in micrometric thickness and Sarkisyan D, optical cell containing cesium vapor. Simultaneous observation of N- and EIT- resonances in a 40-micron thin cell filled with Rb and buffer gas; ONGOING RESEARCH PROJECTS Slavov D, Krasteva A and Cartaleva S, Bi-chromatic spectroscopy in Financed by the National Science Fund micrometric optical cells; Krasteva A, Slavov D, Todorov G, 1. Grant No: DO-02-108, Vartanyan T and Cartaleva S, Coherent spectroscopy of alkali nano- Velocity selective optical pumping layers for miniaturization of photonics resonance sign reversal; sensors. 55 Annual Report IE 2012
2. Grant No: BIn-2-07, 2. Coherent spectroscopy of alkali nano- All–optical diode-laser-based magnetometer: layers for miniaturization of photonics miniaturization and parameters sensors. optimization, Bulgarian-Indian inter- 3. Nonlinear magnetooptical effects on governmental program of cooperation Zeeman sublevels of alkali atoms in in science and technology (2008- antirelaxation coated cells. 2011). 3. Grant No: DMU-02-17, COLLABORATIONS Velocity distribution of alkali atoms in micrometric thin cell. 1. University of Siena, Siena, Italy, 4. Grant No: DO-02-112/2008, Framework agreement of academic National Center on Biomedical cooperation, Establishment of PhD Photonics. School on Laser Spectroscopy – 5. Grant No: DO-02-107/2009, Common Doctorate. Improving the resolution of Thomson 2. National Institute of Optics (INO- CNR), Pisa, Italy. scattering lidars by deconvolution- 3. University of Calcutta, Kolkata, India based algorithms. 4. Jadavpur University, Kolkata, India. 5. Institute for Physical Research, NAS of Armenia, Ashtarak-2, Armenia. Financed by the European Funds 6. Institute of Automation and Electrometry, Siberian Branch RAS, 1. Coherent optics sensors for medical Novosibirsk, Russia. applications (COSMA) 7FP 2012- 7. Swansea University - College of 2016. Human and Health Sciences – UK. 2. Improving the resolution of Thomson 8. University of California at Berkeley - scattering LIDARs by application of Department of Physics, USA. novel deconvolution-based algorithms, 9. University College London, - Department of Physics and Contract of Association between the Astronomy, - UK. European Atomic Energy Community 10. Bar-Ilan University - Department of (EURATOM) and INRNE under the th Chemistry – Israel. 7 Framework Program of the 11. Jagiellonian University - Department European Atomic Energy Community of Physics, Poland. (Euratom), No.FU07-CT-2007-00059. 12. Institute of Physics, Polish Academy of Sciences, Warsaw, Poland.
Financed by the BAS LABORATORY VISITS
1. Coherent processes under conditions Vaseva K, of strong optical excitation of Institute of Physics, Polish Academy of multilevel atomic structures. Sciences, Warsaw, Poland, 20 days.
56 Laboratory Nonlinear and Fiber Optics
LABORATORY
NONLINEAR AND FIBER OPTICS
HEAD: Assoc. Prof. L. Kovachev, Ph. D.
TOTAL STAFF: 5 RESEARCH SCIENTIST: 2
Assoc. Prof. L. M. Ivanov, Ph.D.; K. L. Kovachev. Ph.D.; A. Dakova; V. Slavchev.
RESEARCH ACTIVITIES positron pairs appears at the beginning. If we compare the nonlinear vacuum shock 1. High-intensity laser pulses in wave with a spherically symmetric nonlinear vacuum solution of the linear wave equation, the difference becomes obvious. While the The modern high-power laser facilities spherically symmetric solution of the can generate optical pulses with intensities linear wave equation forms inside and in the order of I ~ 1022 W/cm2. At the same outside wave fronts and the amplitude time, the critical power for observation of significantly decreases, the nonlinear self-action effects due to virtual electron- shock wave preserves the amplitude positron pairs in vacuum is in the order of maximum and is self-compressed in the P ~ 2.5 4.4×1024 W at a wavelength 1 µm. r direction. Thus, for a laser pulse with waist r0 = 1 mm, the corresponding intensity for observation of self-action effects in vac 26 vacuum becomes I cr ~ 2.5 – 4.4×10 W/cm2, which is above the range of the new high-power lasers. The nonlinear addition to the refractive index in vacuum Figure 1. Evolution of the intensity profile of a depends also on the magnetic field. This is pulse as solution of the nonlinear vector wave why new different nonlinear effects can be equation in vacuum for normalized time t = 0 and expected. t = 10 respectively. Euler, Heisenberg and Kockel predicted one intrinsic nonlinearity of the The nonlinear wave exhibits an entirely electromagnetic vacuum due to the different evolution as compared with the electron-positron nonlinear polarization. linear spherical one: the shock wave In [1], the nonlinear vector wave preserves its amplitude maximum and equations in nonlinear vacuum was solved self-compresses in the r direction. through the method of separation of the variables in a pseudo-spherical coordinate 2. Filamentation of femtosecond laser system. The analytical solution obtained pulses represents a spherical shock wave with its own angular momentum l = 1 for the Studies conducted in the past two electric field. decades have revealed that the evolution of Such a high-intensity wave can be ultra-short laser pulses with high intensity generated not only by laser sources, but in solid, liquid and gaseous transparent also in a nuclear reaction, where a media is a rich source of highly nonlinear nonlinear polarization of virtual electron- effects. The filamentation of FS optical 57 Annual Report IE 2012
pulses and the possibility to transfer superbroad spectrum kz ~ k0 with a energy to considerable distances is the carrier wavelength of 0 = 800 nm. The reason why this mode attracts considerable stability of the long-range filament is attention. In order to explain this new achieved via a combination of two effects phenomenon, the first theory proposed was generating opposite phase transformations based on the combination of two effects in one short broad-band pulse – non- with opposite direction in terms of the paraxial diffraction and third-order focusing – cyclic self-focusing and plasma nonlinearity. defocusing. The brief preliminary analysis made of the theoretical and experimental 3. Broad-band optical pulses in optical studies of the nonlinear evolution of FS fibers laser pulses showed that this model could not explain the stability of a single A theoretical model was presented of filament with intensity in the order of the evolution of femtosecond pulses with I ~ 1012 W/cm2 in the far area. superbroad spectrum in single-mode The main effect accompanying the optical fibers (DSF and W-fibers) with propagation of filaments in nonlinear anomalous dispersion of the group mode described and observed in the velocity; the accompanying effect of experiments is the generation of coherent coherent THz emission was also analyzed. THz and GHz radiation around the optical We used the one-dimensional scalar pulses. Various theoretical models have nonlinear amplitude equation, which been developed to describe the THz describes the evolution of optical pulses generation. They have a limited with superbroad spectrum in isotropic application, as it appears that coherent dispersive medium in a Cartesian THz generation can be observed without coordinate system. Due to the waveguide ionization. The light pulse near the characteristics of propagation of the laser nonlinear focus emits incoherent and pulses, the transverse structure of the beam non-homogenous plasma, while the is determined by the mode structure of the coherent THz radiation requires fiber. This is why we were not interested homogenous plasma with fixed electron in the evolution of the transverse size 16 -3 2 2 2 density in the order of 10 cm Only (r0 = x + y ) of the pulses. We assumed homogenous plasma can generate coherent that the geometric axis of the fiber THz emission, but such kind of plasma is coincides with the axis Oz of the Cartesian absent in the process of filamentation. The coordinate system. contribution from ionization in the faraway Our results demonstrated that the zone is negligible; this is the reason for coherent THz generation is proportional to seeking other physical mechanisms that the difference between the phase and could lead to emission of coherent THz or group velocities of the pulse. The GHz radiation. Our analysis of the third- nonlinear mechanism is the same as the order nonlinear polarization of pulses with one that was observed during the broadband spectrum indicated that the propagation of the pulses in air. nonlinear term in the corresponding A new soliton solution was found of the envelope equation oscillates at a frequency amplitude equation, describing the proportional to the difference between the evolution of FS pulses with broadband group and phase velocities. Actually, it is spectrum in single-mode optical fibers three times as large as the well-known (DSF and W-fibers) with anomalous Carrier-to-Envelope Phase (CEP) dispersion. It was shown that the soliton difference. This oscillation induces intensity value calculated in our work is fluctuations in the nonlinear refractive much greater than the magnitude of the index, where the generated frequency is intensity of the Schrödinger's soliton. The exactly nl = 93 GHz for a pulse with a results will be investigated further. 58 Laboratory Nonlinear and Fiber Optics
PUBLICATIONS ONGOING RESEARCH PROJECTS
1. Kovachev L M, Georgieva D A and Financed by the Bulgarian Academy of Kovachev K L 2012 Electromagnetic Sciences shock wave in nonlinear vacuum: exact solution Opt. Lett. 37 4047-9 Propagation of ultra-short optical pulses in DOI: 10.1364/ OL.37. 004047 media with non-stationary optical and 2. Kovachev L M and Georgieva D A magnetic response (2012-2015). 2012 A class of localized solutions of the linear and nonlinear wave equation LECTURE COURSES J. Geometry and Symmetry in Physics 27 67-82 ISSN: 1312-5192 Fiber Optic Communication Systems; 3. Kovachev L M and Georgieva D A Optics; Electricity and Magnetism, 2012 Analytical solution of the linear South-Western University, Blagoevgrad, wave equation with finite energy Bulgaria. AIP Conf. Proc. 1487 264 DOI: 10.1063/1.4758967
59 Annual Report IE 2012
LABORATORY
LASER RADARS
HEAD: Prof. D. Stoyanov, Dr.Sc.
TOTAL STAFF: 13 RESEARCH SCIENTISTS: 11 Assoc. Prof. L. Gurdev, Ph.D.; Assoc. Prof. T. Dreischuh, Ph.D.; Assoc. Prof. V. Mitev, Ph.D.; Assoc. Prof. V. Pencheva, Ph.D.; Z. Peshev, Ph.D.; S. Penchev, Ph.D.; N. Kolev, Ph.D.; A. Deleva, Ph.D.; Ts. Evgenieva, Ph.D.; I. Grigorov.
RESEARCH ACTIVITIES aims to improve the daytime capabilities of lidar instruments, to 1. Lidar remote sensing of the develop and apply integrated atmosphere within the European observation strategies for lidar and Aerosol Lidar Network (EARLINET) sun-photometer measurements in view of the best possible use of Lidar systems are being used widely for complementary information on remote studies of atmospheric parameters. atmospheric aerosols gained from The importance of the lidar information active and passive remote-sensing provided by a single lidar station is instruments. enhanced considerably if working within a Since 2011, the two elastic backscatter a lidar network. Sofia Lidar Station at the lidar systems of the Laser Radar Institute of Electronics, being one of the Laboratory (the aerosol lidar with a CuBr- stations operating under EARLINET, has vapor laser and the aerosol lidar with a been involved mainly in the following Nd:YAG-laser) have accomplished tasks research activities: of the ACTRIS project (Aerosols, Clouds, Regular lidar measurements with the and Trace gasses Research Infra Structure aim of establishing a common database Network) of the EC’s FP7. This project is of atmospheric aerosol backscatter aimed at integrating European ground- coefficient profiles; based stations equipped with advanced Observation of special phenomena, atmospheric probing instrumentation for such as unusually high concentrations aerosols, clouds, and short-lived gas-phase of aerosols in the troposphere species. ACTRIS is building the next (transportation of mineral dust from generation of the ground-based component Sahara desert over the Mediterranean of the EU observing system by integrating Sea to Europe, volcanic eruptions, three existing research infrastructures formation of smoke layers resulting EUSAAR, EARLINET, CLOUDNET, from forest or industrial fires, intense and a new trace-gasses network photochemical smog, etc.); component into a single coordinated Measurements in conjunction with framework. satellite missions aimed at conducting As a part of the European lidar network, a detailed comparison of ground-based for about a month (18.06-17.07.2012) both and spaceborne lidar data sets over lidars participated in the Pan-European Europe; Gas-Aerosol-Climate Inter-action Study Lidar measurements combined with campaign (PEGASOS) that aims to simultaneous sun-photometer and explore and provide knowledge on the gas- ceilometer measurements with the aerosols-climate interactions on a conti- 60 Laboratory Laser Radars
nental scale. PEGASOS brings together and characterized by multi-wavelength most of the leading European research measurements using the two lidars. Two of groups with state-of the-art observational the fires were of local origin (in Vitosha and modeling facilities to (a) quantify the mountain close to Sofia), whereas the third magnitude of regional-to-global feedbacks one was localized to be in the USA. The between the atmospheric chemistry and a spatial density distribution, composition, changing climate and reduce the spreading, and temporal evolution of the corresponding uncertainty of the major fire-smoke layers were characterized in ones and (b) identify mitigation strategies terms of valuable lidar backscatter-based and policies to improve the air quality and optical and microphysical parameters. limit the climate changes. Special attention was paid to the Both lidars were involved in several range/height profiles of the backscatter- observations on Saharan dust presence in related Ångström exponent (BAE) and its the atmosphere over Sofia in order to occurrence-frequency distributions, in follow the concentration, spreading, and order to characterize better the temporal evolution of Saharan dust composition, size ranges, and aging transported over the European continent. processes of the fire-smoke aerosols, in The measurements were synchronized view of their impact on the human health. with the Barcelona Supercomputing The prompt processing of the fire-related Centre (BCS) DREAM model forecasts for lidar data and announcing the results in dust loadings and transport. The public media contributed to informing the investigations performed during an community and authorities for proper episode of Sahara dust transport, 02-07 decision making. April 2012, involved also ceilometer Systematic two-wavelength (1064∕532 (CHM 15k) data and satellite data from the nm) lidar investigation and analysis were CALIPSO lidar. A conclusion was drawn carried out on the spatial distribution, on the atmospheric aerosol’s origin made structure, composition, and temporal upon analyzing the information of the evolution of close-to-surface atmospheric weather-forecast maps provided by the aerosol fields over heterogeneous BCS. Additional information was provided orographic areas (adjacent city, plain, and by calculating the backward air mass mountain) near Sofia. Range profiles, trajectories using the online NOAA histograms, and evolutional range-time HYSPLIT model. The comparison diagrams of the aerosol backscatter between the data from the two lidars and coefficients, range-corrected lidar signals, the ceilometer showed similar behavior of normalized standard deviations, and aerosol layers development in the backscatter-related Ångström exponents atmosphere above Sofia. The information (BAE) were displayed and analyzed, as on the aerosol layers origin and their related to the orographic zones altitude above ground and persistence investigated. A near-perfect correlation during the lidar observations confirmed the between the aerosol density distribution conclusion for a long-distance Sahara dust and the orographic differentiation of the transport beyond Sofia and the Balkans. underlying terrain was established, as An interesting case of complementing the expressed in a sustained horizontal CALIPSO lidar and the ground-based lidar stratification of the atmospheric domains data took place when a thick opaque cloud probed. Distinctive features of the spatial layer was present, which sliced the lidar distribution and temporal evolution of both remote sensing paths in both directions. the fine- and coarse aerosol fractions were As a part of the special-event lidar revealed in correlation with the terrain’s observations, in the summer of 2012, three orography. Zonal aerosol particle-size wild forest fires were detected, studied, distributions were qualitatively 61 Annual Report IE 2012
characterized by using an approach based profiles. This algorithm is based on on BAE occurrence-frequency distribution matching synthesized profiles of lidar analysis. Justified assumptions were made returns from hypothetical Rayleigh about the aerosol particles type, origin, and atmosphere with real lidar data. The dominating size, as connected (by procedure is used in pre-processing lidar transport-modeling data) to local pollution data to determine the background noise sources and meteorological conditions. magnitude which should be removed Specifics and patterns of temporal before starting the inversion processing dynamics of the fine- and coarse aerosol (by Klett or Fernald algorithms) to retrieve fraction density distributions and motion atmospheric backscatter or extinction were discussed, as revealed by using profiles. Application of the Rayleigh-fit statistical analysis of the lidar data. The procedure was demonstrated on some results obtained can be used to help examples on synthetic and real lidar data monitor the air quality, particularly over profiles. A way of justifying the large industrial and densely populated correctness of the Rayleigh-fit approach areas, as a part of the general ecological procedure was offered. The justification monitoring. used calculations of the backscatter ratio Two-wavelength remote measurements between a retrieved attenuated atmospheric and characterization were performed of backscatter profile and a model molecular aerosols originating from burning biomass backscatter profile. The closer the values observed in the low troposphere (altitudes of the backscatter ratio calculated oscillate 2-5 km) over Sofia. By using air-transport to the value of a backscatter ratio for modeling data (NOAA ARL HYSPLIT altitudes in the free troposphere, the more Model), the aerosols were identified as correctly the Rayleigh-fit approach consisting mainly of over ten-day-aged procedure has been performed, assuming a smoke of wildfires in the USA in the last correct algorithm of further data third of July 2012. The long-range processing of noise-free lidar profiles. transport of the smoke aerosols was A study of aerosol-cloud interactions determined to be driven by the Northern was carried out on the basis of complex Hemisphere Polar Jet Stream. The spatial measurements with an arsenal of advanced distribution and temporal evolution of the measuring instruments: lidars, a sun observed aerosols were obtained and photometer, a ceilometer and a displayed. The aerosol particles size-range meteorological station. The data acquired was characterized qualitatively by using by the different devices were used for a vertical profiles and distributions of more complete description of the backscatter-related Ǻngström exponents. meteorological conditions and the Processes of considerable aggregation parameters of the atmosphere related to and/or coagulation of the finest particle distinguishing between aerosol and cloud size modes during the aging period were fields as observed by lidars. revealed and discussed. The results can A series of experimental campaigns was contribute to clarifying peculiarities and launched using a CMH 15 ceilometer and specifics of fire-smoke aerosol behavior a sun photometer for measuring the and aging under conditions of long-range aerosol optical depth and the total ozone transport. content in the atmosphere. Our aim was to The Rayleigh-fit algorithm as applied to continue the monitoring of the total ozone improving the background noise removal concentration and possibly reveal a trend from lidar data, which was developed in to a reduction of the atmospheric ozone 2011, was tested repeatedly in the over the region. These studies are related processing of lidar data aimed at retrieving to the hypothesis of the North Pole ozone atmospheric aerosol backscatter coefficient hole expansion and its impact on the ozone 62 Laboratory Laser Radars
concentrations above Eastern Europe. The lution-based algorithms for improving the measurements during the summer range resolution of the fusion plasma campaign from 31.05.2012 to 09.07.2012 temperature Te and density ne profiles showed preservation of the total ozone measured by using TS LIDAR diagnostics content values in the range 220 – 390 DU. in JET (Joint European Torus), the Another major task was accumulation of analysis of the sensitivity of the pedestal data on the height of the stable boundary and core plasma parameters to the edge layer, the residual layer and the mixing localized mode (ELM) evolution layer. The purpose of this research was to processes, as well as the systematic and evaluate the impact of factors, such as the statistical error analysis of basic plasma closure of Kremikovtzi Steel Works and parameters. the climate changes on a number of local Different methods were analyzed and phenomena, e.g., pollution from increasing implemented for deconvolution of the traffic and from fires. The atmospheric signals registered in each spectral channel boundary layer height is often identified of the TS LIDAR in order to improve the by the mixing layer height, one of the most range resolution of the measured Te and ne important parameters governing the profiles. The core LIDAR spatial concentration and dispersion of trace resolution at the moment (~ 12 cm) is gasses and aerosol particles. practically insufficient for accurate Comparisons were conducted of the registration of the narrow pedestal area. data obtained by lidar measurements at IE The lidar signals deconvolution is and by ceilometer measurements at the important not only for retrieving the Te and Astronomical Observatory, Borisova ne profiles with an improved range Gradina Park. The comparison between resolution, but also as a first necessary step the data for the mixing layer height in for studying the pedestal evolution on the clear sunny days showed similar behavior basis of the TS LIDAR data. Our attention at the two observation sites. The effect on was mainly focused on the performance of the mixing layer development was also the deconvolution algorithms developed revealed of local summer phenomena, by us (proved earlier analytically and by such as forest fires in the nearby Vitosha computer statistical modeling) when Mountain. Aerosol layers due to a dust processing real lidar data. The problem storm over Sahara desert were also was solved of the correct determination of detected. the shape of the system instrumental function on the basis of the information 2. Lidar diagnostics of thermonuclear from raw LIDAR data. Two methods for plasma deconvolution of TS LIDAR data were analyzed – the Fourier deconvolution Efficient observation and control of the approach and the stabilized inversion fusion process is only possible on the basis method. Both methods showed good of adequate plasma diagnostics involving performance and led to a more accurate the determination with high accuracy and recovering of the electron temperature and (spatio-temporal) resolution of the electron concentration profiles. The expected shift temperature Te and concentration ne in the was also observed of the seeming edges of reactive zone. Тhe most appropriate the profiles from the torus walls to the approach to their simultaneous fast internal torus zone. After deconvolution, determination in a remote contactless way the electron concentration pedestal is is the Thomson scattering (TS) LIDAR observed to be steeper compared to the approach. The main results obtained in this initially registered one. As a whole, after field in 2012 were the development and deconvolution, the lidar signals are close successful implementation of deconvo- to those obtained by other diagnostics, 63 Annual Report IE 2012
such as high-resolution Thomson fitting procedure, the correlation between scattering. the estimates of the electron temperature The possibility to analyze the effects of and concentration leads to an increase in the ELM evolution on the basic plasma the rms errors in determining the parameters by the JET Core Lidar is of concentration and the pressure compared great importance because of the to the case of no correlation. In the non- simultaneous range-resolved probing of linear fitting procedure, the same plasma parameters – temperature, density, correlation increases the ne–measurement pressure, etc along the entire torus length. error, while influencing only slightly the This is also of interest when considering error in determining the pressure. the ITER Core Lidar performance. Novel The investigations were performed as a algorithms were developed for precise part of the implementation of a project single-shot determination of the pedestal under the 7-th FP of the EC. parameters – position, width and amplitude, and of some integral core 3. Photothermal characterization of plasma parameters (temperature, density, magnetoelectric nanofilms and pressure), by applying an improved deconvolution technique combined with a Experimental and theoretical studies set of algorithms for regressive & were conducted on photothermal correlation analysis of the plasma characterization of magnetoelectric parameters and the ELM time evolution. In nanofilms of large magnetoresistance. general, the numerical modeling and the These included measurements of processing of real data by the algorithms photomodulated surface reflectance and developed revealed the mutual correlation displacement of various nanostructures. between the pedestal and core plasma The possibility was confirmed of applying parameters and the ELM time evolution. photothermal microscopy by modulated The results obtained for the cross- optical reflectance (MOR) for correlation coefficient of the density characterization of conductive media. A pedestal amplitude to the ELM-slice further application was developed for film intervals exhibited a good sensitivity to the thickness assessment by measuring the ELM evolution. optical absorption coefficient. The method Using a fitting approach, the rms errors refers to nanofilms deposited on were investigated, analytically and by transparent substrates, where the laser computer simulations, in the determination power is absorbed selectively in the film. by a Thomson scattering lidar of the The analytical approach is based on an electron temperature Te, the concentration ultrasensitive laser double-heterodyne ne and the pressure in fusion plasmas. probe featuring a thickness resolution of Unlike previous such studies, we up to fractions of a nanometer at improved accounted for the correlation between the translational resolution compared to fluctuations of the statistical estimates of ellipsometry. the electron temperature and Films of homogeneous chemical concentration. Analytical expressions of composition were evaluated by following the errors as functions of the electron small variations in the film thickness temperature were derived for the cases of during a laser scan. The minimal log-linear and non-linear fitting procedures detectable thickness gradient is inversely at a high measurement signal-to-noise proportional to the signal-to-noise ratio ratio. Computer simulations were also (SNR) by a factor determined by the performed of the nonlinear fitting absorption coefficient and the mean procedure, which confirmed the analytical thickness of the given sample film. The results. It was shown that, in the log-linear resolution of measuring the film thickness 64 Laboratory Laser Radars
of a 100-nm film at 55 dB SNR was The MOR signal correlates well with the evaluated at 0,2 nm. High-resolution thermal derivative as theoretically measurements require calibration of the predicted, but its profile is shifted to the heating laser power absorbed, which was lower temperatures due to the thermal performed by means of high-quality gradient introduced by the heating laser reference AlBK7 and AgBK7 mirrors. The pulses. use of a mirror of higher reflection raises the measurable range and, respectively, 4. Laser probing of turbid media for lowers the film thickness resolution. optical tomography applications Experimental measurements were conducted employing a computerized laser A further, extended, analysis was system for photothermal non-destructive performed of the results of the theoretical analysis based on the modulated optical and experimental studies on laser radiation reflectance (MOR) effect. It was found scattering in tissue-like turbid media – that the modulated reflectance of suspensions of different concentrations magnetoelectric nanofilms depends C (%) of Intralipid in distilled water. The linearly on the optical conductivity. The quadratic dependence obtained of the Drude model concerning the reflectance extinction coefficient on C is interpreted as modulation by electric carrier density due to the distance between the variation explains well the experimental neighboring effective scatterers being results. Photothermal characterization by reduced below the laser radiation the modulated reflectance method was wavelength as C increases. At the same applied to ferroelectric La1-xSrxMnO3 time, the experimental dependence at low (LSMO) nanofilms with compositional concentrations (C < 0.3 %) is practically parameter x 0,3. The sample films of linear and closely follows the data 100 nm thickness were grown in situ on obtained by linear extrapolation of the sapphire monocrystalline substrates by results of van Staveren et al. for Intralipid- magnetron sputtering. The experimental 10% at a wavelength of 850 nm. On the data were recorded at a constant basis of this linearity, a linear with respect temperature by heating uniformly the to C expression was derived for absorption whole sample. The LSMO films resistivity coefficient determination. Such a linear was evaluated by the resistance measured expression may also be obtained for all using the four-probe method. The spatial wavelengths within the interval resolution of the laser scans was limited by 400 nm < λ < 1000 nm, using the same a step of 50×100 µm between adjacent methodology. The reduced-scattering measurement points within a confined coefficient at low Intralipid concentrations region of the sample film. A good (0.075 % 0.25 %), as well as the g-factor agreement was demonstrated between the for Gaussian and Henyey-Greenstein (HG) theoretical model and the experimental indicatrices were also determined precisely results. The MOR technique distinguishes on the basis of the data for the e-1 effectively between the conductive layer halfwidth w(z) of the light beam at a depth and the dielectric substrate. The resistivity z in the turbid medium. The value obtained rises with the temperature in the for g for a HG indicatrix (0.81) proved to ferromagnetic phase and reaches saturation be closer to that for a Gaussian indicatrix as the Curie point is approached (360Co) than the value of 0.607 predicted by van due to a deterioration of the manganite Staveren et al. and even closer than the spin alignment. The thermal derivative value of 0.78 obtained by other authors. calculated from the experimental data on The values of the absorption coefficient at film the resistivity approaches zero with low Intralipid concentrations (0.075 % and the transition to the paramagnetic phase. 0.1 %) were determined by a log-linear fit 65 Annual Report IE 2012
of data on the scattered light power profile packets, which are proprotional to the detected on-axis. The values obtained optical signal back-scattered from the exceed the absorption coefficient of pure section chosen. water and are below the ones determined The work was continued on developing by the empiric linear expression. a prototype of a remote-sensing The results obtained are of essential hygrometer based on a lidar system importance for the development of comprising a pair of two complementary methods for measuring the optical high-power pulsed laser diodes. The laser characteristics of turbid media, such as diodes employed possess a number of tissues and tissue-like experimental advantages, namely, they are phantoms. They are also especially useful commercially available and used widely, in the process of establishing the relations e.g., as rangefinders. The high-power governing the radiative transfer in radiation of these lasers is particularly optically investigated biological objects. advantageous for monitoring the The further investigations in this field will atmospheric humidity in the optimal range be directed to increasing the experimental of water vapor rotational-vibrational accuracy and refining the theoretical absorption spectrum of 0,9 – 0,915 µm. model. The optimal absorption spectrum selected is free of spectral species of other gasses. 5. Lidar hardware & software The method is independent from variations in the atmospheric pressure and The need to continue the operation of temperature. The lidar characteristics the CuBr-vapor laser lidar necessitated that combine high measurement resolution we revert to using a higher laser pulse with operational efficiency supplemented repetition rate, from ~9 kHz to 10.5 kHz. by a compact and low-energy consumption A higher frequency allows for better design suitable to atmospheric and climatic heating of the laser tube and, thus, for a monitoring. The progress in the more stable laser operation. Unfortunately, technology of fabricating lasers in the the maximal altitude of sounding infrared range offers possibilities for decreased to ~14 km. The mechanics used developing similar remote-sensing for adjusting the lidar optics was upgraded techniques for other gases, such as carbon by changing the bearing elements with a dioxide and methane, which are of system designed especially for the type of considerable environmental interest. telescope used, thereby achieving precision and repeatability of the lidar PUBLICATIONS tuning. A new mechanical design of the wave- 1. Gurdev L, Dreischuh T, Bliznakova I, separating module of the combined Vankov O, Avramov L and Stoyanov D aerosol-Raman lidar was developed; the 2012 Scattering of a laser beam in module is being incorporated in the lidar turbid media with forward-peaked system and adjusted accordingly. Henyey-Greenstein indicatrices An adjustable image receiver was Physica Scripta 149 014074 especially designed in view of laser remote doi:10.1088/0031-8949/2012/T149/014074 sensing applications (patent pending). In 2. Peshev Z, Dreischuh T, Toncheva E order to receive the back-scattered laser and Stoyanov D 2012 Two- light from a pre-selected distance along the wavelength lidar characterization of sounding path, a pulsed control unit lowers atmospheric aerosol fields at low the potential of the overflow channel, so altitudes over heterogeneous terrain that the photo-sensitive elements of the J. Appl. Remote Sensing 6/1 063581 image receiver start accumulating charge doi:10.1117/1.JRS.6.063581 66 Laboratory Laser Radars
3. Grigorieva V, Kolev N, Donev E, aerosol optical depth, and planetary Ivanov D, Mendeva B, Evgenieva Ts, boundary layer height determined by Danchovski V and Kolev I 2012 sun photometer, lidar and ceilometer Surface and total ozone Proc. 26-th Int. Laser Radar Conf. investigations in the region of Sofia, ILRC 2012 (25-29 June 2012 Porto Bulgaria Int. J. Remote Sensing Heli Greece) II 849-53 33/11 3542-56 10. Kolev N, Grigorov I, Evgenieva Ts, doi:10.1080/01431161.2011.621904 Deleva A, Donev E, Ivanov D and 4. Meier J, Tegen I, Mattis I, Wolke R, Petkov D 2012 Observation in the Alados Arboledas L, Apituley A, troposphere over mountain valley by Balis D, Barnaba F, Chaikovsky A, ceilometer, sunphotometer and lidars Sicard M, Pappalardo G, Pietruczuk A, Proc. 26-th Int. Laser Radar Conf. Stoyanov D, Ravetta F and Rizi V ILRC 2012 (25-29 June 2012 Porto 2012 A regional model of European Heli Greece) II 969-72 aerosol transport: evaluation with 11. Mona L, Papagiannopoulos N, sun photometer, lidar and air quality D’Amico G, Giunta A, Hiebsch A, data Atmos. Environ. 47 519-32 Wandinger U, Amodeo A, Apituley A, doi:10.1016/j.atmosenv.2011.09.029 Alados-Arboledas L, Balis D, 5. Stoyanov D, Grigorov I, Kolarov G, Chaikovsky A, Comeron A, De Peshev Z and Dreischuh T 2012 Tomasi F, Freudenthaler V, Grigorov I, Lidar atmospheric sensing by metal Iarlori M, Linnè H, Papayannis A, vapor and Nd:YAG lasers Advanced Pietruczuk A, Schnel F, Spinelli N, Photonic Sciences Fadhali M ed Wiegner M and Pappalardo G 2012 (Intech) chapter 14 345-74 ISBN: Investigation of representativeness of 978-953-51-0153-6 Calipso aerosol optical properties 6. Kolev N, Grigorov I, Evgenieva Ts, products by EARLINET correlative Donev E, Ivanov D, Kolarov G, measurements Proc. 26-th Int. Laser Kolev I and Stoyanov D 2012 Radar Conf. ILRC 2012 (25-29 June Combined lidar-ceilometer measure- 2012, Porto Heli Greece) II 717-20 ments in the troposphere over Sofia (Bulgaria) Comptes Rendus de PATENTS SUPPORTED l'Academie Bulgare des Sciences 65/4 491-8 ISSN 1310-1331 1. Stoyanov D, Gurdev L, Dreischuh T, 7. Pеnchev S, Pencheva V and Naboko S Vankov O and Protochristov C, 2012 Atmospheric remote sensing Radar on single spontaneously emitted hygrometer employing powerful gamma-photons, broad-line laser diodes Comptes Patent No 65770 B (2009) Rendus de l'Academie Bulgare des 2. Stoyanov D, Gurdev L, Dreischuh T, Sciences 65/5 667-72 Vankov O, Avramov L and Borisova E, 8. Pencheva V and Penchev S С 2012 Optical multichannel transceiving Nanomaterials and nanotechno- system, logies – consensus concerning the Patent No 65769 B (2009) benefits/risks ratio of their impact on human health Ecological engineering EUROPEAN PATENTS PENDING and environmental protection 1 19- 25 (in Bulgarian) 1. Stoyanov D, Dreischuh T, Gurdev L, 9. Kolev N, Evgenieva Ts, Petkov D, Vankov O, Avramov L, Borisova E Donev E, Devara P C S, Raj P E, and Bliznakova I, Miloshev N, Wiman B L B and Method for determining optical and Kolev I 2012 Water vapor content, spatial characteristics of an inclusion 67 Annual Report IE 2012
in a turbid medium using multiple- Peshev Z, Dreischuh T, Toncheva E scattering optical tomography, and Stoyanov D, Patent No.EP2153772A1, Lidar observations and character- Applicant - Siemens AG, Germany. ization of biomass burning aerosols 2. Stoyanov D, Dreischuh T, Gurdev L, over Sofia: Long-range transport of Vankov O, Avramov L, Borisova E forest wildfire smoke. and Bliznakova I,
Apparatus for determining optical and th spatial characteristics of an inclusion 26 Int. Laser Radar Conf. 25-29 June in a turbid medium using multiple- 2012, Porto Heli, Greece scattering optical tomography, Kolev N, Evgenieva Ts, Petkov D, Patent No.EP2165647A1 Donev E, Devara P C S, Raj P E, Applicant - Siemens AG, Germany. Miloshev N, Wiman B L B and Kolev I, Water vapor content, aerosol optical PATENTS PENDING depth, and planetary boundary layer height determined by sun photometer, 1. Mitev V, Method and lidar system for lidar and ceilometer; registration of turbulences, Reg. No Kolev N, Grigorov I, Evgenieva Ts, 110786/04.11.2010. Deleva A, Donev E, Ivanov D and 2. Mitev V, Method and lidar for measurement of aerosol turbulence in Petkov D, the atmosphere. Reg. No 110925/ Observation in the troposphere over a 29.09.2011. mountain valley by ceilometer, 3. Mitev V, Adjustable imaging receiver. sunphotometer and lidars; Reg. No 111198/10.08.2012. Mona L, Papagiannopoulos N, D’Amico G, Giunta A, Hiebsch A, Wandinger U, Amodeo A, Apituley A, CONFERENCES Alados-Arboledas L, Balis D,
th Chaikovsky A, Comeron A, 17 Int. School on Quantum Electronics, De Tomasi F, Freudenthaler V, 24-28 September 2012, Nessebar, Grigorov I, Iarlori M, Linnè H, Bulgaria: Papayannis A, Pietruczuk A, Grigorov I and Kolarov G, Rayleigh-fit approach applied to Schnel F, Spinelli N, Wiegner M and improving the removal of background Pappalardo G, noise from lidar data; Investigation of representativeness of Stoyanov D, Grigorov I, Deleva A, Calipso aerosol optical properties Kolev N, Peshev Z, Kolarov G, Donev E products by EARLINET correlative and Ivanov D, measurements. Remote monitoring of aerosol layers over Sofia during a Sahara dust 30th Jubilee Colloqium – Physics in the transport episode (April, 2012); protection of man and its environment, Deleva A and Grigorov I, June 2012, Gyulechitsa, Bulgaria Lidar observations of high-altitude (organized by the Bulgarian Society of aerosol layers (cirrus clouds); Dreischuh T, Gurdev L and Stoyanov D, Biomedical Physics and Engineering) Efficiency of determining the electron Pencheva V, Penchev S and Grigorov I, temperature and concentration in The nanotechnologies of the future thermonuclear plasmas by Thomson and their impact on the human health scattering lidar; and the environment. 68 Laboratory Laser Radars
ONGOING RESEARCH PROJECTS European projects
Financed by the National Science Fund 1. Improving the resolution of Thomson scattering LIDARs by application of 1. DО- 224/2008, Novel magnetic and novel deconvolution-based algorithms, magnetoelectrical materials for the Task 2.2.2, Contract of Association next generation of electronic between the European Atomic Energy components. Community (EURATOM) and 2. DO 02-107/2009, Improving the INRNE, FP7, Project No. FU07-CT- resolution of Thomson scattering 2007-00059. LIDARs by application of novel 2. Aerosols, Clouds, and Trace gases deconvolution-based algorithms. Research Infrastructure Network 3. DO 02–112/2008, National Center on (ACTRIS), FP7, Project No.262254. Biomedical Photonics. 3. JET components of the EFDA 2011 and 2012 work programmes, FP7, Financed by the Steering Council of the Project No.FU07-CT-2011-00219-002. Bulgarian Academy of Sciences 4. Aerosols and clouds. Long-term data base from space-borne lidar 1. Investigation of the temporal measurements, CALIPSO Program, dynamics of fine and coarse aerosol European Space Agency, ESA. components in the troposphere by a two-wavelength lidar. COLLABORATIONS 2. Remote determination of some statistical characteristics of non- 1. Optical remote sensing studies of the uniform media by image processing. atmospheric boundary layer 3. Lidar-radiometric probing of aerosol characteristics using laser radar, characteristics in the PBL and the free Institute of Tropical Meteorology, atmosphere above a mountain valley. Pune, India (in the framework of the 4. Laser sensing of tissue-like turbid Indo-Bulgarian inter-governmental optical media for localizing program of cooperation in Science & characteristic inhomogeneities. Technology, Grant № INT/Bulgaria). 5. Laser system and methodology for 2. Advanced lidar technologies for optical probing of novel magnetic and tropospheric aerosol studies, magnetoelectrical materials for the next Istituto di Metodologie per l’Analisi generation of electronics components. Ambientale, CNR, Italy. 6. Lidar atmospheric system using high- 3. Lidar investigation of aerosol fields power diode lasers. transformations in urban industrial 7. Error analysis of the lidar Thomson zones, scattering probing of the electron Institute of Physics, National temperature and density of Academy of Belarus, Minsk, Belarus. thermonuclear plasma. 8. Lidar investigation of aerosol pollutions in the troposphere by Raman-aerosol lidar.
69 Annual Report IE 2012
LABORATORY
MICROWAVE PHYSICS AND TECHNOLOGIES
HEAD: Assoc. Prof. O. Yordanov, Ph.D.
TOTAL STAFF: 15 RESEARCH SCIENTISTS: 14
Assoc. Prof. V. Atanassov, Ph.D.; Assoc. Prof. I. Sirkova, Ph.D.; Assoc. Prof. M. Taslakov, Ph.D.; E. Krasteva, Ph.D.; P. Zabov, Ph.D.; B. Simeonova Ph.D.; I. Atanasov, Ph.D.; K. Kostov; V. Ranev; L. Mladenov; L. Vulkova; V. Iordanova; K. Omar.
RESEARCH ACTIVITIES 2. Emerging simple and extended chaotic systems
1. VHF and optical devices – design, 2.1. Methods based on asymptotic scaling optimization, implementation and for characterization of chaotic processes specifications and complex structures The general solution of a specific third- During 2012, the following devices order differential equation was obtained, were built and their performance studied with each particular solution representing a and specified: i) DC-DC transformers to different kind of scaling – exact, low-voltage with efficiency above 95 % asymptotic and multiplicative. Integral and output current of 10 A. The representations of all three functions were transformers can find a variety of developed and algorithms for fast and applications, in particular for supplying accurate evaluation in the entire domain high-power light emitting diodes; ii) an were studied and implemented. The latter electronic board of novel design are of key importance for improving the convenient for experiments on new analog methodology in question. or/and digital circuits. The design provides 2.2. Theoretical and numerical analysis of an apt visualization of the circuits regular and chaotic optical oscillators. implemented and is a well-suited tool for A multi-scale perturbation technique teaching in applied electronics; iii) a was employed to derive an expression for circuit generating two signals out of a the switch-on time of a variety of laser single harmonic signal. The circuit systems. In all dynamical cases, operates in a wide frequency band (20 Hz bifurcation diagrams were built and phase to 20 kHz). In addition to its ordinary portraits were calculated numerically and applications, the circuit can be used for traced. Resonant effects due to small- control of electric motors; iv) a set of amplitude periodic pumping were modeled electronic devices demonstrating basic and quantified. electronic principles and effects. Some of them were tested as educational tools. A 3. Bibliometric indicators and distributions methodology for measuring a variety of absorption materials under high-frequency Empirical distribution functions of conditions was substantially improved and several bibliometric indicators were extended. In particular, it allows real-time estimated for a sample of researchers characterization of fractal structures. working in a specific field of physical 70 Laboratory Microwave Physics and Technologies
research, but under different material, calibration was also tested with data financial and information-rich conditions. obtained in 2011 by the L-band radiometer The indicators include: the number of ELBARA II at the Selhausen experimental publications, P, the total number of site of the Institute of Bio- and citations, C, the number of citations per Geosciences, Research Center Jülich, publication, C/P, and the Hirsch index Germany. It was shown that the new (h-index). In addition, we calculated the calibration algorithm reduces significantly so-called mock Hirsch index, the bias of the brightness temperature 2 1/3 hm = (C /P) . We also worked with estimates and the RMSE between the alternative indicators based on the number measured and modeled sky brightness of independent citations (no self-citations), temperatures. C*, as in the case of the Hirsch index, h*. One-month data sets from a ploughed The outcome of such an analysis is to bare soil plot for five meteorologically suggest an adequate and statistically different measurement periods were used justified assessment of the contribution of in a coupled-model inversion routine to a given scientist within his or her area of derive the soil hydraulic parameters and research. the soil surface roughness at the field scale We also studied some problems from measured rainfall and brightness involved in the analysis of Pareto- temperatures at 1.4 GHz (L-band) and distributed scientometric data (series of modeled potential evaporation. Two citations versus paper ranks). The different models for the soil hydraulic problems include appropriate choices of i) properties were considered, namely, the the distribution type (continuous, discrete unimodal model of Mualem van or finite-size discrete) and ii) statistical Genuchten and the bimodal model of methods to obtain unbiased estimates for Durner. Two reflectivity models with the power-law exponent (a maximum different complexity were used, namely, likelihood procedure or a least-squares the Fresnel equation based on the averaged regression). Since relatively low dielectric permittivity of the first 2-cm soil magnitudes of the power exponent (less layer and a coherent radiative transfer than 2) are predominantly observed in model (CRTM). A correction for the soil scientometric databases, the finite-size surface roughness effects on the discrete Pareto distribution (citations microwave emission was also applied. The distributed to a finite number of paper laboratory-derived water retention curve of ranks) appears to be more adequate for the ploughed soil showed a bimodal data analysis than the traditional ones. This behavior which could be retrieved conclusion is illustrated by two examples consistently from the brightness (for synthetic and for actual data). We also temperatures for the different periods. The derived empirical relationships, in estimated soil hydraulic properties were in particular, for the dependence of the good agreement with the hydraulic maximum and the total number of citations properties obtained from laboratory on the Hirsch index. The latter was a analysis of soil samples. The surface soil generalization of results of previous moisture simulated using retrieved soil studies. hydraulic parameters was compared with the soil moisture calculated from the 4. Microwave radiometers for remote dielectric permittivity measured at 2 cm sensing applications and 5 cm using 5TE sensors. The effect of depth averaging by the in-situ moisture The recently proposed algorithm for sky sensors and the use of soil and depth- calibration of L-band radiometers by built- specific calibration relations were in cold and hot noise sources for internal evaluated and found to be of importance 71 Annual Report IE 2012
for the comparison with the L-band Kovacheva D, Ghelev Ch, Bliznakova I, retrieved soil moisture. Krezhov K and Nedkov I 2012 These investigations in the field of Structural and magnetic properties of microwave radiometry were carried out multiferroic Y-type hexaferrites jointly with scientists from the Institute of Proc. 11th Int. Conf. Solid State Bio- and Geosciences (IBG-3 Agrosphere), Chemistry: Nanomater. & Nano- Research Center Jülich, Germany. technol. (Kislovodsk Russia) pp 181–3 4. Slavov D, Krasteva A, Subov P and 5. Tropospheric ducting Cartaleva S 2012 Dark and bright velocity selective optical pumping The theory and current status of one of resonances in nanometric cells filled the most widely used advanced methods with Cs vapor Proc. 11th Int. Conf. for microwave propagation channel Solid State Chemistry: Nanomater. & modeling, the parabolic equation (PE) Nanotechnol. (Kislovodsk Russia) pp method, was overviewed with emphasis on 183 –5 its applications to the planning and 5. Atanassov V and Detcheva E 2012 operation of different radio systems in Theoretical analysis of empirical coastal and maritime regions. The relationships for Pareto-distributed approximations of the method, its scientometric data Int. J. Information numerical solutions and possible sources Models & Analyses 1/3 271-82 ISSN: of errors related to the accuracy of the 1314-6416 (print) 1314-6424 (CD) input data used were discussed. Recent 1314-6432 (online) achievements, some unresolved issues and 6. Sirkova I 2012 Brief review of the ongoing developments to further PE method application to propagation improvement of the PE method were channel modeling in sea environment pointed out. Central European J. Engin. 2 19-38 A classification of refractivity profiles DOI: 10.2478/s13531-011-0049-y made previously for the Bulgarian Black ISSN: 1896-1541 (print) ISSN: 2081- Sea coast and their organization in clusters 9927 (online) was revisited. The classification was 7. Dimitrov M, Kostov K G, Jonard F, complemented by metrics and new Jadoon K Z, Schwank M, “characteristic” profiles for the anomalous Weihermueller L, Hermes N, microwave propagation in the summer Vanderborght J and Vereecken H season were proposed for every cluster. 2012 New improved algorithm for sky calibration of L-band radiometers PUBLICATIONS Jülbara and Elbara II Proc. 12th Specialist Meeting on Microwave 1. Sirkova I 2012 Clustering of Radiometry and Remote Sensing of refractive index profiles - the Environment MICRORAD 2012 reconsidered COST IC0802 7th MCM (Frascati Italy) ISBN: 978-1-4673- (16-18 April 2012 Portsmouth UK) 1470-1 pp 1-4 2. Võ Thị Lan Anh, Chung D M, 8. Todorov P, Slavov D, Vaseva K, Kostov K G and Vichev B I 2012 Taslakov M, Cartaleva S and Saltiel S Design and development of a 2012 High-resolution spectroscopy of microwave X-band radiometer and its a cesium-vapor layer with utilization for environmental micrometric thickness for the investigations Proc. 6th Conf. development of frequency reference Mechatronics (December 14-15 2012 Phys. Scripta 149 014014 Hanoi Vietnam) pp 1-5 9. Simeonova B and Simeonov L 2012 3. Koutzarova T, Kolev S, Subov P, Express laser elemental and isotopic 72 Laboratory Microwave Physics and Technologies
analysis of hard samples Navigation & Earth Observation contaminated by heavy metals Systems. Ecological Engin. and Environmental Protection 1 12-8 ISSN: 1311-8668 LABORATORY VISITS (print) 10. Simeonova B and Simeonov L 2012 I. Sirkova In situ laser elemental and isotopic COST IC0802 7th MCM – Portsmouth, analysis of water samples UK, 16-18 April 2012. contaminated by heavy metals Ecological Engin. and Environmental O. Yordanov Protection 2 15-20 ISSN: 1311-8668 COST MP0801 – The Hebrew (print) University of Jerusalem, 24-28 March 2012. ONGOING RESEARCH PROJECTS COST MP0801 – The National University of Ireland, Galway, 1. COST Action: European Cooperation Ireland, 7-11 July 2012. in the Field of Scientific and COST MP0801 – The University of Technical Research: Action MP0801: East Anglia, Norwich, UK, 29 Physics of Competition and Conflicts August-9 September 2012. 2010/2013. 2. Action IC0802 Propagation Tools & Data for Integrated Telecommunication,
73 Annual Report IE 2012
LABORATORY
MICROWAVE MAGNETICS
HEAD: Prof. I. Nedkov, Dr.Sc.
TOTAL STAFF: 7 RESEARCH SCIENTISTS: 7 Assoc. Prof. T. Koutzarova, Ph.D.; Assoc. Prof. K. G. Grigorov, Ph.D.; S. Kolev, Ph.D.; L. Slavov, Ph.D.; Ch. Ghelev MS; R. Radicheva BS; M. Uliverova BS; R. Angelova MS student.
RESEARCH ACTIVITIES magnetic anisotropy and high permeability; they are thus attractive for The Microwave Magnetics Laboratory practical applications, such as microwave at the Institute of Electronics was devices. They possess a relatively high established in 1993; since then, a spiral-magnetic transition temperature predominant part of its team’s activities (~200 K), show multiferroic properties at has been aimed at preparing and studying zero magnetic field, and the direction of nanomagnetic materials – particles, the ferroelectric polarization can be hybride structures, composites, thick films controlled by a weak magnetic field – and studying their interaction with (< 0.02 T). A novel technology, namely, electromagnetic radiation in a wide range sonochemical synthesis, was adapted in of the MW spectrum. The scientific the Laboratory to the preparation of infrastructure and the potential of the complex magnetic oxides – laboratory staff have provided, and still Ba2хМхMe2Fe12O22, where М is Sr, and offer, opportunities for interdisciplinary Ме is Zn or Mg. The conditions were research and capabilities of combining optimized for producing Ba2Mg2Fe12O22 scientific studies with technological and Ba0.5Sr1.5Zn2Fe12O22. We then studied approaches. the magnetic properties of Ba2Mg2Fe12O22 In the past year, a priority among the powders obtained by sol-gel auto- Laboratory’s efforts was the preparation combustion synthesis and sonochemical and investigation of nanomagnetic synthesis. The magnetic phase transitions materials – particles, hybride structures, were monitored by measuring the composites, thick films. The rapid magnetization as a function of the development of the nanotechnologies temperature when an ac magnetic field with allowed the preparation of nanosized frequency 9967 Hz and amplitude 10 Oe magnetic particles, which, in turn, opened was applied. We observed changes in the possibilities for applications of magnetization behavior near 190 K and monodomain and superparamagnetic 50 K (figure. 1). The changes at 183 K in hybrid structures in electronic components. the magnetization curve of the sample prepared by sol-gel self-combustion, and at 1. Magnetic Multiferroics 196 K of the sample prepared by The main object of research in this area sonochemical synthesis, are related to a was the Y-type hexagonal ferrite with phase transition from ferromagnetic spin general formula Ba2Mg2Fe12O22 and its ordering to spiral spin ordering. Low- magnetic multiferroic properties. The Y- temperature transitions were also observed type hexagonal ferrites are an important at 40 K and 30 K for the sol-gel self- type of high-frequency soft magnetic combustion sample and the sonochemical materials due to their strong planar sample, respectively, which are due to spin 74 Laboratory Microwave Magnetics
reorientation to a longitudinal conical state differences in the particles’ sizes and along the c axis. The differences observed shapes in the samples, as well as to their in the values of these two types of orientation in the magnetic field. transitions in the two samples are due to the
0,6 a) 0,04 b)
0,5 0,03 0,4
0,3 0,02
M',emu/g
M",emu/g
0,2 0,01 0,1
0,0 0,00 0 50 100 150 200 250 0 50 100 150 200 250 T, K T, K
0,35 0,010 c) d) 0,30 0,008 0,25
0,20 0,006
0,15
0,004
M',emu/g
M",emu/g
0,10 0,002 0,05
0,00 0,000 0 50 100 150 200 250 0 50 100 150 200 250 T, K T, K
Figure 1. Magnetization measurements of Ba2Mg2Fe12O22 samples prepared by sol-gel combustion (a, b) and sonochemical synthesis (c, d) in an ac magnetic field. (а) and (c) M'(T) – the real part; and (b) and (d) M"(T) – the imaginery part of the differential magnetization.
Further, a methodology was developed of preparing thick Y-type hexaferrite films by way of spreading a gel-like paste, prepared in the Laboratory using an original technology and containing homogeneously distributed particles of Ba2Mg2Fe12O22 or Ba1.5Sr0.5Zn2Fe12O22. The magnetic coatings thus produced exhibited high degree of smoothness and adhesion. Figure 2 presents SEM images of one of the films prepared. These studies were conducted under BAS projects and financed in part by the National Science Fund – Project DO 02- 224/2008 New magnetic and magneto- electric materials for the new generation of electronic elements; and Project DHTC 01/4/2011 Room temperature multiferroics Figure 2. SEM images of thick films of based on Y-type hexaferrites. Ba2Mg2Fe12O22. 75 Annual Report IE 2012
In the past year, contacts were established laboratory conditions. In our experiments with colleagues of COST Action MP0904 we used several different nutrition media Single- and Multiphase Ferroics and aiming at collecting detailed information Multiferoics with Restricted Geometries about their influence on the end iron- (SIMUFER) and a Memorandum for containing bio-products. The studies on Mutual Interest was signed. neutrophilic FeOB showed the appearance of bacteries of the Leptothrix genus and identified a number of morphologically 2. New magnetic materials for distinct species from different study sites, electronics based on biogenic iron oxides including water iron seeps, hydrothermal This research dealt with the structure, vents, groundwater and rhizosphere of chemical content, morphology and wetland plants. electrical and magnetic properties of the The bactery subproducts were biogenic iron oxides produced by bacteria thoroughly examined by Raman micro- of the Leptothrix/Sphaerotius genus, as spectroscopy, SEM and XRD. The Raman well as with the possibilities of ecological, spectra were obtained using a LabRAM electronic and biomedical applications. HR visible single spectrometer equipped The studies are of interdisciplinary nature with a microscope and a Peltier-cooled and are conducted jointly with scientists of CCD detector. The 633-nm He-Ne laser the Faculty of Biology of St. Kliment line was used for excitation. We used Ohridski University of Sofia working on different acquisition times because of a the laboratory culturing of the iron strong luminescence signal at some of the oxidizing bacterial (FeOB) strains; the chosen spots for investigation and also efforts of the scientists of our Laboratory because of the different surface roughness. are combined with those of colleagues of The Raman measurements were performed the Institute of Catalysis and the Institute at room temperature and atmospheric of Electrochemistry and Energy Systems pressure. The structural identification was of the BAS in studying the structural, confirmed by XRD. physico-chemical and functional properties In Table 1 one can find all culture of the bioproducts produced. The project is media used with the corresponding iron coordinated by the Institute of Electronics. bio-products detected via Raman While numerous studies have been spectroscopy. No Raman signal was published on the properties of natural detected when focusing the laser beam on material, little has been reported on the naked glass (slides), signaling no selective culturing of these bacteria in interference from it.
Table 1. All culture media used with the corresponding iron bio-products. Sample’s Iron Luminescence Number/Culture oxides/hydroxides Type of (at 687 nm Source of Fe2+ media detected (by Raman Magnetism Raman line) scattering) lepidocrocite (γ- 1/Adler Antiferromagnetic (NH ) Fe(SO ) FeO(OH)) strong 4 2 4 4 (Fehrenbach) Ferrimagnetic . 6H2O magnetite (Fe3O4) 2/Isolation Iron cuttings, lepidocrocite (γ- media Antiferromagnetic strong FeCO and FeO(OH)) 3 (Fehrenbach) FeCl2 Iron cuttings, 3/Lieske goethite (α- Antiferromagnetic strong FeSO .7H O (Roux) FeO(OH)) 4 2 FeCO3 and FeCl2 76 Laboratory Microwave Magnetics
Biogenic nanotubes with length up to PUBLICATIONS 2 μm were produced (figure 3a), consisting of an organic matrix and nanostructured 1. Kolev S, Lisjak D, Ovtar S, Gyrgyek S magnetic compounds (figure 3b). Thanks and Drofenik M 2012 Thermal to the controlled metabolism of bacteria of treatment influence on the magnetic the Leptothrix genus, this technology properties and degree of orientation allows one to avoid the complicated and of BaFe12O19 films J. Supercond. Nov. Magn. 25 2819–24 energy-consuming processes for 2. Koutzarova T, Kolev S, Nedkov I, fabrication of nanostructured ferroxides Krezhov K, Kovacheva D, Blagoev B, and to prepare new basic materials as well. Ghelev Ch, Henrist C, Cloots R and Being of biological origin, these materials Zaleski A 2012 Magnetic properties are bio-compatible, with promising of nanosized Ba Mg Fe O powders applications in biology and medicine, such 2 2 12 22 obtained by auto-combustion J. Super- as bio-sensors, bio-engineering, bio- cond. Novel Magnetism 25 2631-2635 prosthetics, nervous tissue regeneration, 3. Ivanova T, Harizanova A, Koutzarova T etc. and Vertruyen B 2012 Preparation and characterization of Ag incorporating Al2O3 nano-composite films obtained by sol-gel method Crystal Res. and Technol. 47 579–84 4. Hoyer Y, Sismanoglu B, Grigorov K 2012 Measurements of spatially a) resolved electron number densities and modes temperature using optical emission spectroscopy of atmo- spheric pressure microplasma jet Biogenic ferroxide European Phys. J. D 66 art no 171 5. Ghelev Ch, Koutzarova T, Kolev S, Nedkov I, Krezhov K, Kovacheva D, Blagoev B, Vertruyen B, Henrist C, Cloots R, Zaleski A and b) Nizhankovskii V 2012 Magnetic Figure 3. а) SEM of bio-nanotubes produced via properties of nanosized MgFe2O4 bio-nanotechnologies, and b) ТЕМ of a nanotube powders prepared by auto-combustion structure (organic matrix and biogenic ferroxides). J. Phys.: Conf. Series 356 012048 6. Beshkova M, Grigorov K, Nedkov I, Massi M, Sismanoglu B, Maciel H In 2012, Research Assistant L. Slavov and Velchev N 2012 Properties of defended a thesis in the area of a thin silicon carbide films prepared nanostructured hybrid magnetic materials. by rapid thermal annealing His research was carried out under a J. Phys.: Conf. Series 356 012039 project financed by the Bulgarian National 7. Koutzarova T, Kolev S, Subov P, Science Fund (DID 02/38/2009 New Kovacheva D, Ghelev Ch, Bliznakova I, materials for electronics and ecology based Krezhov K and Nedkov I 2012 on biogenic iron oxides of nanosized Structural and magnetic properties of ferrite particles) and COST Action multiferroic Y-type hexaferrites TD1105 New Sensing Technologies for Proc. 10th Int. Conf. Solid State Air-Pollution Control and Environmental Chem.: Nano-materials and Technol. Sustainability – EuNetAir. (Stavropol Russia) 181-3 77 Annual Report IE 2012
8. Veleva S, Cherkezova-Zheleva Z, Financed by the National Science Fund Shopska M, Paneva D, Grudeva V, Iliev M, Slavov L, Nedkov I, 1. Project DID 02/38/2009 New Kadinov G, Mitov I, Mladenov M materials for electronics and ecology and Kovacheva D 2012 Study of based on biogenic iron oxides of new materials based on biogenic nanosized ferrite particles. iron oxides & physicochemical, 2. Project DO 02-224/2008 New electrochemical and catalyc magnetic and magneto-electric properties Nanosci. & Nanotechnol. materials for the new generation of E. Balabanova and I. Dragieva eds electronic elements. 12: 135-8 3. Project DHTC 01/4/2011 Room 9. van de Sanden M C M, Dimitrova M temperature multiferroics based on and Ghelev Ch 2012 VEIT 2011 Y-type hexaferrites. J. Phys.: Conf. Series 356 011001 10. Slavov L 2012 Magnetic properties and structural deviations on the COLLABORATIONS
surface of nanostructured magnetite 1. Structural and magnetoelectric effects and hybrid complexes in high temperature multiferroic magnetite/nonmagnetic shell (PhD Thesis IE BAS Sofia Bulgaria) materials, 11. Ghelev Ch and Guerassimov N eds University of Liege, Liege, Belgium. 2012 Institute of Electronics Annual 2. Magnetic Structural and Microwave Report 2011 (Sofia Bulgaria) properties of new thin films composite materials, Instituto Tecnologico de Aeronautica PATENTS (ITA), Brazil. 3. Cooperation in education and 1. Nedkov I and Merodiiska T scientific research with the Patent № 65609 Method for Communications and Physical preparation of nanosized ferrite Electronics Chair of the Faculty of particles Physics of St. Kliment Ohridski University of Sofia. ONGOING RESEARCH PROJECTS LABORATORY VISITS 1. COST TD1105 EuNetAir: Air- Pollution Control and Enviromental 1. I. Nedkov – Rome, Italy Mana- Sustainability. gement Committee Meeting of 2. COST MP0904 Single- and COST Action TD1105 (New multiphase ferroics and multiferroics Sensing Technologies for Air- with restricted geometries Pollution Control and Environmental (SIMUFER). Sustainability – EuNetAir), 4 days. 3. The use of grazing incidence X-ray 2. T. Koutzarova – University of Liege, diffractometry (Bruker D8) to Belgium, Structural and magneto- characterize the crystallographic electric effects in high temperature structure of polycrystalline magnetic multiferroic materials, 21 days. thin films, ERASMUS Lifelong 3. T. Koutzarova – University of Liege, Learning Programme. Belgium, The use of grazing 4. Investigation of polycrystalline incidence X-ray diffractometry multiferroic materials - training on (Bruker D8) to characterize the using equipment and techniques, crystallographic structure of ERASMUS Lifelong Learning polycrystalline magnetic thin films, Programme. 7 days. 78 Laboratory Microwave Magnetics
4. S. Kolev - Josef Stefan Institute, 2. P. Jenus, Josef Stefan Institute, Ljubljana, Slovenia, Project DHTC Ljubljana, Slovenia, 4 days, Project 01/4/2011 Room temperature DHTC 01/4/2011 Room temperature multiferroics based on Y-type multiferroics based on Y-type hexaferrites, 31 days. hexaferrites. 3. D. Primc, Josef Stefan Institute, GUESTS Ljubljana, Slovenia, 4 days, Project DHTC 01/4/2011 Room temperature 1. F. Stevens, University of Liege, multiferroics based on Y-type Belgium, 15 days, Joint Research hexaferrites. Project Structural and magnetoelectric effects in high temperature multiferroic materials between IE-BAS and University of Liege, Belgium.
79 Annual Report IE 2012
LABORATORY
PHYSICAL TECHNOLOGIES
Acting HEAD: Prof. Petar Petrov, Dr.Sc.
TOTAL STAFF: 3 RESEARCH SCIENTISTS: 2
D. Dechev, Assistant Eng.; N. Ivanov, Assistant Eng.
RESEARCH ACTIVITIES (observed by a microscope) produced by a Rockwell hardness meter indentor under a 1. Multilayer tungsten nitride-titanium loading force G = 1471 N for 10 s. For nitride (WN/TiN) coatings system with a both types of tool steel, the adhesion was pure chromium (Cr) sublayer. found to be suitable with a mark of 2 (good adhesion with small cracks) as A technology was developed for estimated by the method’s six-grade scale. fabrication of multilayer coatings of The hardness (HV), the elasticity WN/TiN on tool steels P18 and У8. In module (E), and the plastic deformation view of improving the adhesion of the energy (Wr) were studied by means of a multilayer WN/TiN system to the FISHERSCOPE H 100 nanotester substrate, a sublayer of pure Cr was (Germany|. The following values were additionally introduced. The multilayer measured: WN/TiN coatings were prepared by - coating system on У8 steel – consecutive magnetron sputtering HV = 31 337 МРа, Е = 243 GPa, Wr equal deposition of single WN and TiN layers. to 18,7 % of the total energy of loading; The nitride layers were produced by - coating system on Р18 steel – sputtering targets of pure tungsten and HV = 36 791 МРа, Е = 236 GPa, Wr equal pure titanium in (Ar + N2) plasma in the to 10,9 % of the total energy of loading; working pressures range 10-2 10-1 Ра and The hardness values measured exceed condensation temperature T = 350 oС. The those of the tool steel by a factor of first layer deposited was of pure Cr. For 3,5 4. the purpose of the investigations, a The surface morphology was studied by multilayer system was fabricated a NICON OPTIPHOT HFX-DX consisting of 120 pairs of WN/TiN layers metallographic microscope. The coatings with a thickness of the single layers of were uniform, homogeneous, and lacking 6 nm and a 150-nm-thick Cr sublayer. The apparent cracks, pores and defects. total thickness of the coating was The multilayer systems fabricated can d = 1650 nm. find applications as hard and wear- The system’s adhesion, hardness (HV), resistant coatings on cutting tools (dies, elasticity module (E), and plastic punches, cutting blades, lathe knives, etc.) deformation energy (Wr) were measured, or on components subjected to intensive and the samples’ surface morphology was wear and large dynamic loads. studied. An analytic review was conducted of The adhesion was measured by the the major techniques for producing carbon Rockwell–C Impact Test method yielding nitride, with special emphasis on the the adhesion strength HF. This is a electron-beam evaporation in nitrogen quantitative method, with the adhesion plasma and the reactive magnetron being estimated by the type of impression sputtering techniques. Using the electron- 80 Laboratory Physical Technologies
beam technology, layers of carbon nitride 3. Dechev D, Ivanov N and Petrov P were synthesized on a Si substrate. The 2012 Obtaining and studying the Raman spectroscopy and XPS studies properties of multilayer films of revealed the presence of carbon nitride in WN/TiN, layered on materials for the form of inclusions in an amorphous cutting instruments with an underlayer matrix, as well as of the crystalline phase of pure chromium AMTECH pp 197- β-C3N4. 201 ISBN 978-954-438-494-9 The effect was studied of various doping elements, such as Fe, Cr, Ni, on the ONGOING RESEARCH PROJECTS properties of Al-Si alloys locally treated by a hybrid electron-beam technique. A Financed by the BAS considerable increase of the mechanical Mechanical characteristics of metal-nitride parameters was observed in the zone coatings fabricated in vacuum. treated. The layers’ characteristics Financed by the Joint Institute for Nuclear (geometry, defects, microhardness) were Research, Dubna, Russian Federation studied as functions of the manner, Study of nanosystems and new materials frequency and amplitiude of the electron- by neutron beams. beam sweep. Financed by the Scientific Research Fund of Asen Zlatarov University, city of Burgas PUBLICATIONS Using waste-water treatment end-products concentrates for metal coatings deposition 1. Petrov P. 2012 Surface modification on polymer materials. of aluminum alloys using hybrid treatment techniques J. Phys.: Conf. COLLABORATIONS Series 356 DOI: 10.1088/1742- 6596/356/1/012035 Chair of Welding and Joining Technology 2. Dechev D, Ivanov N and Petrov P at the Technical University of 2012 Carbon nitride thin films Brandenburg – Cottbus, Germany – produced by physical vapour Рroduction of new materials and deposition methods AMTECH pp191- nanotechnology. 6 ISBN 978-954-438-494-9
SELECTED PROJECTS
● Modeling and Simulation of Gyrotrons for ITER ● Regeneration of Materials by Electron Beam Melting and Refining of Refractory Metals and Alloys in Vacuum ● Plasmon and Optical Properties of Metal Nanoparticles and their Application to High- sensitivity Raman Spectroscopy and Biophotonics ● High Resolution Spectroscopy of Cs Vapor Confined in Micron-thickness Optical Cells ● Aerosols, Clouds, and Trace-gasses Research Infrastructure Network (ACTRIS) ● Improving the Resolution of Thomson Scattering Lidars by Application of Novel Deconvolution – Based Algorithms ● Development and Introduction of Optical Biopsy System for Early Diagnostic of Malignant Tumors ● Coherent Optics Sensors for Medical Applications (COSMA)
83 Annual Report IE 2012
EC–Project EURATOM of FP7
Contract № FU07-CT-2007-00059/Fusion CSA/EURATOM
MODELING AND SIMULATION OF GYROTRONS FOR ITER
S Sabchevski1, M Damyanova1, I Zhelyazkov2, P Dankov2, P Malinov2, E Balabanova1, E Vasileva1 and R. Enikov1
1Emil Djakov Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee, 1784 Sofia, Bulgaria, Association EURATOM-INRNE 2Faculty of Physics, St. Kliment Ohridski University of Sofia, 5 James Bourchier Blvd., 1164 Sofia, Bulgaria Association EURATOM-INRNE
1. Introduction: scope and main than 95%; (vi) frequency of power activities of the project modulation 3 5 kHz; (vii) reliability not As the most powerful sources of less than 95 %. The state-of-the-art of the coherent radiation operating in a gyrotrons for fusion is summarized in [5]. continuous wave (CW) mode in the Their high performance is a result of sub-terahertz frequency range (i.e., with several advanced concepts incorporated in millimeter and sub-millimeter the design of the tubes, most notably: wavelengths) the gyrotrons are considered (i) internal mode converter; (ii) CVD as indispensable components of the diamond output window; (iii) efficient systems for electron cyclotron resonance coupling of the gyrotron beam with the heating (ECRH) and electron cyclotron transmission line system through a MOU; current drive of magnetically confined (iv) depressed collector; (v) LHe and LHe- plasmas in various reactors (most notably free cryomagnets, etc. Gyrotrons with an of the tokamak type) for controlled output power exceeding 1 MW (in the thermonuclear fusion [1, 2]. Additionally, range 1.2 2 MW) represent well the they are used for startup (ignition), current power levels achieved worldwide stabilization (e.g., NTM suppression and [5, 6]. Among them is the coaxial MHD control) and diagnostics of the 170 GHz / 2 MW gyrotron developed by plasma [3, 4]. It should also be noted that the EGYC (European Gyrotron the gyrotrons are the only sources of RF Consortium, which includes CRPP, KIT, heating, which can be both localized and HELLAS, IFP-CNR) and is produced by steerable. The ECH system of ITER, for Thales Electron Devices (TED). The example, requires 24 MW installed RF short-pulse (in the millisecond range) power (20 MW launched in the plasma) at pre-prototype of this tube achieved at KIT 170 GHz for heating and 3 MW at the record power of 2.2 MW at 30 % 127 GHz for plasma startup. According to efficiency without SDC (and 45 % the technical specification of the ITER efficiency at 2 MW) and 96 % Gaussian project, the requirements to the gyrotrons mode purity [4]. However, despite these are: (i) output power not less than positive results, serious problems of 0.96 MW at the matching optic unit different nature have been encountered (MOU); (ii) output frequency of during the recent tests (internal tube 170 0.3 GHz; (iii) pulse length 3600 s; failure, operation on a wrong mode, (iv) RF efficiency not less than 50 %; (v) parasitic and after-cavity oscillations, Gaussian content of the wave beam greater lower-than-expected efficiency, arching, to 84 Selected Projects
mention just a few) [7, 8]. In order to tools (physical models and computer surmount these problems, it was decided in programs), as well as in the development 2012 (see, for example, Ref. [9]) to switch of novel ones. The work on this topic is to the development of 1 MW / 170 GHz being carried out in collaboration with the gyrotrons with a conventional (cylindrical) Institute for Pulsed Power and Microwave cavity using the experience gained during Technology at Karlsruhe Institute of the design and operation of other similar Technology, the Association EURATOM– tubes, e.g., 1 MW / 140 GHz for the W-7X KIT (KIT-IHM) and the Centre de stellarator [10]. At the end of this concise Recherches en Physique des Plasmas, introduction to the subject of our research École Polytechnique Fédérale de – powerful gyrotrons for fusion it should Lausanne, Association EURATOM– be mentioned that despite the remarkable Confédération Suisse (CRPP-EPFL). achievements demonstrated recently there The scope of the project (Task 2.1.2) are many challenges and problems encompasses all aspects of modeling and (physical, engineering and technological) simulation, namely: (i) theoretical work on that have to be addressed. They require the formulation of adequate, informative further theoretical, numerical and (but still numerically traceable) physical experimental investigations. In this models taking into account as much as respect, modeling and simulation, as well possible physical factors and phenomena; as numerical experiments, are essential (ii) selection of appropriate numerical tools for analysis, comparison and methods, programing libraries and optimization of different novel designs of environments for development of efficient the tube’s main subsystems and, algorithms describing mathematically the eventually, for computer aided design physical model; (iii) programming the (CAD) of the entire design. computational modules (program At present, the European gyrotron implementation of the algorithms); community uses a great number of (iv) numerical experiments for testing and stand-alone computer codes and several benchmarking of the simulation tools, as problem-oriented software packages for well as for analysis of concrete designs of numerical studies and CAD of various powerful gyrotrons. subsystems (electron-optical system; electrodynamical system; quasi-optical system) of powerful gyrotrons (see figure 1). In them, a wide variety of physical models with different levels of adequacy (ranging from self-consistent to phenomenological, time-dependent to static, etc.) is implemented. Most of them however, are static and are formulated in a two- dimensional coordinate space (2.5D physical models) and thus do not take into account a number of factors (e.g., violation of the axial symmetry; misalignment of the Figure 1. Structure of the simulation tools and coils, electrodes and so on; nonuniformity computational infrastructure for numerical studies of the emission, spacecharge and CAD of gyrotrons. compensation and many others). Our research team has been involved in the The work in the above-mentioned maintenance and further refinement directions follows a concept that has (improvement, optimization, and already been formulated in the preceding enrichment) of the available simulation investigations [11, 12], but which has been 85 Annual Report IE 2012
subject to a steady and continuous generator; the ASTRID finite element development ever since [1318]. solver, a graphic system for visualization, According to this concept, the most a command language and interfacing characteristic distinguishing features of the modules. DAPHNE is implemented as a next generation of codes are: (i) increased script written in ASTRID’s command physical content (i.e., more physical language and includes the two modules factors and phenomena taken into account CFI (for calculation of the magnetic field including a transition from 2D to 3D of the coils of the tube) and PART (for models); (ii) higher computational integration of the equations of particles efficiency (economical and optimized use motion) written in FORTRAN. The script of computational resources, such as run invokes successively both the particle time and memory); (iii) extensibility; pusher (PART) and the Poisson solver in (iv) portability to different platforms and an iterative loop until the process operating systems including execution on converges to a self-consistent solution. different parallel computers. 2.2 ESRAY (KIT) 2. Current status and functionality of the problem-oriented software packages ESRAY (KIT) [14, 17] is also a problem-oriented package for trajectory The hierarchy and structure of the analysis (ray-tracing) of EOS based on a simulation tools are presented in figure 1, fully relativistic 2.5D electrostatic physical together with the computational platforms model. Its most characteristic on which the different packages are distinguishing features are: (i) an object- operational. oriented program implementation in C++; (ii) an advanced mesh generator which 2.1 DAPHNE discretizes the computational domain with a great accuracy by structured boundary- DAPHNE package [14] (developed at fitted grids; (iii) versatile post-processing CRPP-EPFL) is a programming capabilities and visualization of all scalar environment for optimization of EOS of and vector physical fields by color maps; gyrotrons. It is based on an adequate (iv) a fast own solver for the boundary self-consistent physical model (formulated value problem by the finite difference in 2.5D) which consists of a field part method. The package consists of several (a boundary value problem with Dirichlet modules: GRIDGEN (for geometry and Neumann boundary conditions for the description and mesh generation), Poisson equation that governs the MAGGEN (for calculation of the magnetic electrostatic potential distribution taking field produced by a system of solenoids), into account the space charge) and a ESRAYS (for iterative solution of the dynamical part, which contains the self-consistent field problem), and OVIS. relativistic equation of motion of charged The latter module serves as a GUI and macro particles representing the electrons postprocessor that presents and visualizes of the beam. The computational region the results of the simulation. (2D meridional cross-section of an axially symmetric EOS) is discretized using a 2.3 CAVITY (KIT) structured mesh with rectangular cells. DAPHNE is embedded in the ASTRID The problem-oriented software package problem solving environment, which CAVITY (KIT) consists of a hierarchy of includes: a data base management system codes that begins with simple programs for memory and data handling (e.g., for an analysis of the mode (MEMCOM); a 3D adaptive mesh spectrum; cold-cavity code, single-mode 86 Selected Projects
self-consistent code) and culminates in the magnetron injection guns (MIG) with a most sophisticated self-consistent reversal of the magnetic field (e.g., a multimode time-dependent code SELFT. magnetic cusp) that form axis-encircling Both the structure of the package and the (aka uniaxial) beams to be simulated with physical models implemented in its an increased accuracy. Similarly, the codes modules have been reviewed recently [17]. of GYROSIM for simulation of the The codes are written in FORTRAN and electrodynamical system cover the same are invoked through a GUI. The GUI itself functionality as the CAVITY (KIT). At the is in fact a Tcl/Tk script for a Linux (Unix) same time, there are some notable bash shell that controls: (i) the interaction differences between them. For instance, with the codes, (ii) the specification of the the CAVITY (KIT) can treat both input data, and (iii) the visualization of the conventional and coaxial resonators but at results using a set of single commands in fundamental operation, while the cavity the menu window. codes belonging to GYROSIM are specialized only to cavities without an 2.4 GYROSIM insert but can simulate operation at the second (and in the case of a large orbit GYROSIM is a problem-oriented gyrotron (LOG), even higher) harmonic of software package which includes the cyclotron frequency. In its current numerical libraries and source codes of form, the GYROSIM is a heterogeneous various computational modules package and includes components written (standalone programs, subroutines, pre-, in different languages (Fortran 77, Fortran post-processing, and visualization codes) 90, C, C++, SciLab), operational and/or for solving a variety of problems pertinent portable to different computational to the simulation and CAD of gyrotrons platforms (ranging from laptops and using a rich set of adequate physical workstations to mainframe and models [18]. Unlike the other packages supercomputers), and executable under described above, it is not, however, different (genuine as well as specialized to only one subsystem of the emulated/virtualized) operating systems gyrotron tube. Rather, the individual (e.g., Unix, Linux, Windows, Cygwin). components of GYROSIM are designed Another characteristic feature of the for simulation of all main subsystems of package is that it is being built following a the gyrotron tube, notably: (i) the electron- concept of extensibility which allows us to optical system (EOS), (ii) the magnetic add/replace easily different computational system which includes the main magnet modules and in such a way modify both and an arrangement of additional coils, the numerical algorithms and the physical (iii) the electrodynamical system (resonant models implemented in the programs. The cavity), and (iv) the quasi-optical system latest upgrade of GYROSIM package has for mode conversion and transmission of been carried out in parallel with the the radiation. It should be mentioned that development of a novel module called the codes for numerical modelling of the GO&ART (which stands for Geometric EOS (GUN-MIG/CUSP) are based on a Optics and Analytic Ray Tracing). It 2.5D physical model, which is analogous consists of several codes (RAYS, to the one implemented in DAPHNE and COMODES, and TRACE) for analysis of ESRAY, and, therefore, provides results quasi-optical components (Vlasov and that are consistent and in a good agreement Denisov type launchers, reflectors and with each other. Besides the differences phase-correcting mirrors, etc.), as well as in their program implementation, systems based on them (e.g., internal mode GUN-MIG/CUSP, however, allows converters and transmission lines). 87 Annual Report IE 2012
2.5 GYREOSS was developed and tested. It is parameterized in such a way as to provide Initially, GYREOSS was conceived as a convenient data structures of the package of codes for simulation of EOS electromagnetic fields at the current using a physical model formulated in three particle positions in both 2D and 3D. space dimensions in order to take into Figure 3 presents several screenshots that account the departure from axial symmetry illustrate the visualization capabilities of due to various misalignments (for instance GYREOSS. Figure 3a shows a map of the of the electrodes, of the magnetic coils, electrostatic potential distribution obtained etc.) and non-uniformities [15]. Its initial in one of the test runs. The corresponding version was implemented using the Gmsh electrostatic field is shown in figure 3b. package for meshing, pre- and post- processing and GetDP as a solver. In the recent years, however, GYREOSS has evolved as a test bench for experimenting with different numerical methods, solvers and algorithms in 3D aiming at the final goal – a parallel 3D code for numerical simulation and CAD of EOS of gyrotrons. The latest version of GYREOSS is being developed using the FreeFEM++ problem solving environment and medit (a scientific visualization software) but the compatibility with Gmsh is preserved and the latter can be used for generation and optimization of the tetrahedral mesh (alongside with the mesher embedded in FreeFEM), as well as for post-operation, post-processing and visualization of the solution. As an illustration, some meshes generated and optimized by Gmsh and used in the recent numerical experiments are shown in figure 2. Figure 3. Electrostatic potential distribution (a); In 2012, a novel electrostatic field equipotential lines over the mesh (b); map and a solver of the GYREOSS software package vector representation of the electrostatic field near the emitting ring of the cathode (c), in a meridional cross-section of a coaxial magnetron injection gun (MIG) of the studied 2 MW/170 GHz gyrotron.
Another important task pursued during 2012 was the development of an efficient module for integration of the relativistic Newton–Lorentz equations of motion of beam electrons (usually referred to as a “particle pusher” aka “particle mover”) formulated in 2D and 3D. It uses the data structure of the electromagnetic field values at the current particle positions, Figure 2. Surface meshes representing the provided by the novel field solver electrodes of a coaxial gyrotron (2 MW/170 GHz) described above and realized with an simulated by GYREOSS. intended prospective parallelization of the 88 Selected Projects
PIC algorithm of GYREOSS. As a preparation, different methods for particle tracing were considered and analyzed. Among them were the schemes of Boris (Tajima’s Implicit Method), Boris– Bunneman, RungeKutta 4th order method, Verlet’s method, and the predictorcorrector method. As many researchers did before us, and having evaluated all important factors (accuracy, stability, CPU time etc.), we finally selected the leapfrog method of the Figure 4. Geometry of the coaxial magnetron relativistic BorisBunneman scheme. The injection gun (CMIG) of a 2 MW/170 GHz algorithm realized is convenient because it gyrotron (black color) and electron rays (red color), traced by the novel relativistic particle pusher of requires only one force evaluation per time the GYREOSS package. step and needs memory for storage of only one set of coordinates and velocities for stations of the Bulgarian research team each particle. It should be noted, however, (see figure 1), except DAPHNE, which is that several other advanced schemes available to us for remote execution and (e.g., Lorentz invariant advance) deserve maintenance on the PLEIADES2 cluster consideration and we plan to study them as from Sofia. Since the outstanding well. We also intend to implement an performance of PLEIADES2 is well adaptive calculation of the optimal time known, we will mention only the basic step (for an arbitrary gyro-frequency), characteristics of the most powerful of our which will minimize the consumed CPU workstations. ITER I has two CPU AMD time, while preserving a sufficient OpteronTM Dual Core 275, 2.2 GHz and accuracy. The more radical optimization, RAM 4 GB DDRAM with a MB however, is expected after realization of a Supermicro -Dual Opteron and SVGA parallel (multithreaded) implementation of Nvidia GeForce 6600 TD. The workstation the PIC algorithm of GYREOSS. As ITER II has 2 CPUs Intel Xeon X5680, mentioned above, a preparation for such 3.33 GHz,12 MB cache, 6 Cores; memory parallelization is in progress now and 4×4 GB DDR-31333. On both includes studies on MPI, multithreading workstations the operating system is and building of a computing clusters using Ubuntu 10.04 (lucid), Kernel Linux as nodes the workstations of the available 2.6.32-41-generic. Although some of them computational infrastructure at IE-BAS (e.g., DAPHNE, ESRAY-IHM, before going to the Pleiades cluster for CAVITY-IHM, and various components full-scale simulations. of GYROSIM) are well validated, As an illustration, in figure 4 we present benchmarked and debugged, they are several trajectories traced in a coaxial undergoing constant adaptation and magnetron injection gun (CMIG) for a upgrade to the ever-changing 2 MW/170 GHz gyrotron calculated by computational environments (hardware, GYREOSS using its novel particle mover. operating systems, novel versions of the
3. Computational platforms used for compilers and numerical libraries). code maintenance and development Alongside with the maintenance of these codes and their usage in numerical All packages outlined above (CAVITY, experiments, we are working on the further ESRAY, GYROSIM, GYREOSS) are development of the GYREOSS and installed and are operational on the work- GYROSIM packages. 89 Annual Report IE 2012
4. Conclusions and outlook References
The problem-oriented packages [1] Darbos C, Henderson M, Albajar F, outlined in the previous section are under Bigelow T et al 2009 Progress in continuous development and design and integration of the ITER improvement. Recently, they were used in Electron Cyclotron H&CD system a series of numerical experiments carried Fusion Eng. Des. 84 6515 [2] Omoria T, Henderson M A, Albajar F, out to study the designs of powerful Alberti S et al 2011 Overview of gyrotrons that are under consideration the ITER EC H&CD system and its and/or development at present. The capabilities Fusion Eng. Des. 86 951–4 simulations conducted give a deeper [3] Goodman T P, Felici F, Lauret M, Witvoet G, de Baar M R, physical insight into the operation of Vandersteen G, Canal G, Coda S, high-performance megawatt-class Duval B P, Kim D, Reimerdes H, J. gyrotrons and are good benchmarks that Rossel J X, Saute O and Silva M demonstrate the improved capabilities and 2012 Real-time control of MHD functionality of the upgraded codes. instabilities with multi-source EC actuators 39th EPS Conf. & 16th Int. Moreover, these results suggest some Congress Plasma Phys. (Stockholm, further experiments for more detailed Sweden, July 2–6, 2012) P2.029 study of the correlation between the [4] Bruschi A, Grossetti G, Grosso G, beam-quality parameters and efficiency, Lubiako L, Orsitto F, Peluso E, Tartari U, Bin W, Botrugno A, on one hand, and the particular design Buratti P, Calabrò G, D’Arcangelo O, (configuration of the electrodes, tailoring Granucci G, Pucella G, Moro A, of the magnetic field, etc.), on the other. It and Tudisco O 2012 Anomalous is expected that the novel and upgraded wave scattering in magnetic islands detected by CTS diagnostic in FTU versions of the simulation packages will tokamak 39th EPS Conf. & 16th Int. contribute to the development of the next Congress Plasma Phys. (Stockholm generation of powerful gyrotrons for Sweden July 2–6 2012) P1.041 fusion with an improved performance. [5] Thumm M 2012 State-of-the-art of high power gyro-devices and free electron masers (Update 2011) KIT Acknowledgements Sci. Reports 7606 pp 1–140 [6] Beringer M H 2011 Design studies towards a 4 MW 170 GHz coaxial- As a part of the scientific program of cavity gyrotron PhD thesis (Sci. the Association EURATOM-INRNE, the Publ. Karlsruhe Inst. of Technol. work on Task 2.1.2 has been supported by Karlsruhe) the European Atomic Energy Agency [7] Kern S, Hogge J-P, Alberti S, Avramides K, Gantenbein G, Illy S, (EURATOM) and the Bulgarian Science Jelonnek J, Jin J, Li F, Pagonakis I Fund through the Association Gr, Piosczyk B, Rzesnicki T, EURATOM-INRNE. The remote access to Thumm M K, Tigelis I and Tran M Q the resources of the Pleiades cluster at 2012 Experimental results and recent developments on the CRPP-EPFL, as well as the collaboration EU 2 MW 170 GHz coaxial cavity with the gyrotron teams at CRPP-EPFL, gyrotron for ITER Presentation at Switzerland and IHM-KIT, Germany are EC17 Workshop (Deurne The greatly appreciated. Netherlands May 7–11 2012) 90 Selected Projects
[8] Kern S, Hogge J-P, Alberti S, [13] Sabchevski S and Zhelyazkov I Avramides K, Gantenbein G, Illy S, 2007 Modelling and simulation of Jelonnek J, Jin J, Li F, Pagonakis I new generation powerful gyrotrons Gr, Piosczyk B, Rzesnicki T, for the fusion research J. Phys: Thumm M K, Tigelis I and Tran M Q Conf. Series 63 012003 2012 Experimental results and [14] Sabchevski S, Zhelyazkov I, recent developments on the EU 2 Thumm M, Illy S, Piosczyk B, MW 170 GHz coaxial cavity Tran T-M, Hogge J-Ph and gyrotron for ITER EPJ Web of Pagonakis I Gr 2007 Recent Conf. 32 04009 (17th Joint evolution of the simulation tools for Workshop on Electron Cyclotron computer aided design of electron- Emission and Electron Cyclotron optical systems for powerful Resonance Heating - Deurne The gyrotrons Computer Modeling in Netherlands 7-11 May 2012) Eng. and Sci. 20 203–20 9] Bonicelli T 2012 Neutral beam [15] Sabchevski S, Illy S, Piosczyk B, system and electron cyclotron Borie E and Zhelyazkov I 2008 power supplies and sources Towards the formulation of a Presentation at Business realistic 3D model for simulation of Opportunities for UK plc from magnetron injection guns for Fusion & ITER (Culham UK gyrotrons (A preliminary study) October 11 2012) Wissenschaftliche Berichte FZKA [10] Schmid M, Erckmann V, 7409 pp 1–34 Gantenbein G, Illy S, Jelonnek J, [16] Damyanova M, Sabchevski S and Kern S, Legrand F and Samartsev A Zhelyazkov I 2010 Pre- and post- 2012 Recent achievements on tests processing of data for simulation of of series gyrotrons for W7-X and gyrotrons by the GYREOSS planned extensions at the KIT software package J. Phys.: Conf. Gyrotron Test Facility 27th Symp. Series 207 012032 Fusion Technol. (Liege Belgium [17] Damyanova M, Kern S, Illy S, 2428 Sept. 2012) Thumm M, Sabchevski S, [11] Sabchevski S, Zhelyazkov I, Zhelyazkov I and Vasileva E 2012 Benova E, Atanassov V, Dankov P, Modelling and simulation of Thumm M, Dammertz G, Piosczyk B, gyrotrons for ITER J. Phys.: Conf. Illy S, Tran M Q, Alberti S and Series 356 012044 Hogge J-Ph 2006 Development of [18] Damyanova M, Sabchevski S, new generation software tools for Zhelyazkov I, Vasileva E, simulation of electron beam Balabanova E, Dankov P and formation in novel high power Malinov P 2012 Problem-oriented gyrotrons, J. Phys.: Conf. Series 44 simulation packages and 96–101 computational infrastructure for [12] Sabchevski S, Zhelyazkov I, numerical studies of powerful Benova E, Atanassov V, Dankov P, gyrotrons 5th Int. Workshop & Thumm M, Arnold A, Jin J and Summer School on Plasma Phys. Rzesnic Mki T 2006 Quasi-optical (Kiten Bulgaria June 25–30 2012) converters for high-power gyrotrons: a brief review of physical models, numerical methods and computer codes J. Phys.: Conf. Series 44 102–9
91 Annual Report IE 2012
REGENERATION OF MATERIALS BY ELECTRON BEAM MELTING AND REFINING OF REFRACTORY METALS AND ALLOYS IN VACUUM
Project DO 02/200 financed by the Bulgarian National Science Fund at the Ministry of Education, Youth and Science
K Vutova, V Donchev, V Vassileva, E Koleva and G Mladenov Emil Djakov Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee, 1784 Sofia, Bulgaria
The relevance of the problem of successful application and optimization of fabricating new materials by recycling of EBMR depend also on the adequate scrap by electron beam melting and mathematical modeling of the processes refining (EBMR) of refractory and reactive involved; this will assist one in studying metals and alloys is justified by the the influence of the large number of environmental friendliness of the method technological parameters and the various and the fact that it enables one to obtain limiting factors. The research tasks materials with new and improved chemical performed and some of the main results composition, structure, and properties. The obtained in 2012 in view of achieving the materials thus processed find numerous main objective of the present project are: applications in the nuclear power industry, A time-dependent heat model for medicine, space engineering, automotive simulation of the heat transfer in metal industry, tool engineering, etc. A sharp ingots solidified in a water-cooled crucible increase in the activities on designing, during EBRM (figure 1) that is a implementating and operating equipment continuation and extension of our quasi- for refractory and reactive metals and steady-state heat model [1,2,3] was alloys by EBMR has taken place in recent proposed and developed [4,5]. The years. Large manufacturers in countries temperature distribution along the cast such as the U.S., India, China, Russia, ingot (figure 1) was described by the heat France, Germany, have shown particular equation in cylindrical coordinates with interest in developing such technologies. angle symmetry: Despite the rapid development in the 2 field of EBMR, many unsolved problems 1 T T V T Cp T r (1) still remain. The study of mechanisms and r r r z2 z t relationships of macroscopic heat and mass transfer during heating a free liquid where T(r, z, t) denotes the temperature at surface by an intensive energy flux is a heating time t at points with height z and fundamental problem. Improving the polar distance r; ρ is the density of the energy efficiency is crucial in optimizing metal; the last term in the left-hand side of the technologies and reducing the price of equation (1) describes the casting process, the pure metals obtained. This requires i.e., the heat added by the molten metal detailed studies of the thermal processes poured (from the raw material being taking place in the zone of beam-material melted) into the crucible (figure 1), which interaction, thorough knowledge of the is given by the heat energy transfer from processes and factors limiting the the material moving with velocity V along geometry of the molten pool, and precise the z-axis; a is the thermal diffusivity. evaluation of the temperature distribution By assuming three mechanisms of heat and behavior of the metals and their transfer through the different boundaries compounds in the refining process. The (figure 1), i.e., three types of thermal contact 92 Selected Projects
ranges of variation of the values of the parameters involved in EBMR of tantalum, titanium, copper and aluminum. Important data were obtained about the heat fluxes through the boundaries, the geometry of the molten pool, the temperature distributions in vertical and/or horizontal cross-sections of the cylindrical metal samples, and recommendations were given concerning the choice of proper regime conditions in order to optimize the EBMR process.
Figure 1. Schematic of the drip EBMR method. G1- the top surface of the ingot; G2 – the molten ingot/crucible wall interface; G3- the ingot/vacuum interface; G4- the ingot/puller interface. interfaces, namely, areas with ideal thermal contact; areas with Newton’s type of heat transfer and areas where the radiation losses predominate, the corresponding boundary conditions were Figure 2. Temperature distribution in a vertical formulated taking into account the cross-section of a Cu ingot (2R = 60 mm, radiative and vaporization losses. A H = 100 mm). The yellow line (Tmelt = 1356 K) is the liquid/solid boundary (crystallization front). modified Pismen-Rekford method was Beam power P = 20 kW, beam radius rb = 12 mm, developed and applied to calculating the t = 10 min, V = 0 mm/min. temperature fields in the cast ingot. The numerical scheme developed is absolutely The temperature field calculated in a stable and implicit in terms of the heating vertical cross-section of the copper ingot at th time. The implicit nature of the scheme the 10 minute of the heating is shown in was overcome by applying the Thomas figure 2. The yellow line is the method for solving three-diagonal linear temperature contour corresponding to systems. The temperature dependencies of Tmelt = 1356 K, i.e., the liquid/solid the thermal conductivity λ and the specific boundary. The crystallization front (the heat capacity Cp for each metal liquid/solid boundary) shape is directly investigated were estimated using connected with the quality of the casting experimental data [6,7]. The metal ingot – a flat crystallization front corresponding functions obtained (on T) permits the formation of dendrite were included in the model. structures parallel to the ingot axis, as well The model proposed was modified and as uniform impurity displacement toward applied also to the simulation of the the block top surface. The simulation thermal processes in the feeding rod results showed that the lowest casting (figure 1). A corresponding computer velocity value, for which the molten metal program was developed and used to study pool starts contacting with the crucible the thermal processes during e-beam side wall (G2), is 5 mm/min (table 1). The melting and recycling of metals (figure 1). results presented in figure 3 demonstrate The model was validated and numerical the non-steady-state nature of the process experiments were performed for wide at the G2 interface (the interface molten 93 Annual Report IE 2012
Table 1. Dynamics of the contact molten metal The heating time t is up to 10 min and the pool/cooled side wall of the crucible (G2) for beam radius rb is 16 mm. The results EBMR of Cu. presented in figure 4 show that the casting First moment Total time velocity V influences strongly the volume V, of contact at of contact at of the molten pool Vm. mm/min G2, s G2, s 5 650 1 6 500 5 7 350 21 8 300 43 9 250 74 10 220 86
ingot/crucible wall – figure1) – alternation Figure 4. Variation of the molten volume th of contact molten pool/cooled side crucible Vm/Vingot×100 (in %) in Ta at the 10 minute and wall and withdrawal of the ingot surface. for P = 24 kW vs. the ingot height H for: The duration of the contact at G2 is only V = 9 mm/min – triangles; V = 6 mm/min – diamonds; 5 s from a total of 500 s for V = 6 mm/min V = 3 mm/min – squares; and only 86 s of 220 s for V = 10 mm/min V = 0 mm/min – circles. (table 1, figure 3). The liquid pool depth for V = 5÷10 mm/min is constant and is The results show that the liquid pool about 11 mm. For the higher values of depth hm stabilizes after five minutes casting velocities (V = 9, 10 mm/min), the heating and an almost fully molten top pool dimensions become stable (figure 3), ingot surface is achieved for H = 40 and which is a condition for more efficient 45 mm and V = 6 and 9 mm/min (table 2). refining processes. As V increases, a fully liquid top surface of the ingot is observed earlier (for a shorter heating time), e.g., for H = 45 mm – at the 230th s for V = 9 mm/min, and at the 500th s for V = 3 mm/min (table 2). This is seen even for shorter ingots. Furthermore, earlier stabilization of the liquid pool depth is achieved when the casting velocity is increased; this ensures better refining condition. A series of experiments implementing different technological regimes and methods were performed in our laboratory
Figure 3. Dynamics of the thermal losses through using the ELIT 60 equipment for EBMR the G2 boundary. Each jump corresponds to an of tantalum, titanium, copper, hafnium, actual contact molten pool/crucible wall (G2 aluminum, alloy steel, etc. The liquid pool interface) for 1 sec, V =10 mm/min. shape variation (experimental and simulation data) in titanium samples vs. The non-steady-state heat model was the refining time is shown in figure 5 for also applied to EBMR of the refractory heating e-beam power of 2.4 kW, metal tantalum for casting velocities V = 0, rb = 12 mm and V = 0 mm/min. A good 3, 6 and 9 mm/min and different ingot agreement is seen between the calculated heights H in order to study the pool and the experimentally obtained shapes of geometry changes and the ingot quality. the crystallization front. 94 Selected Projects
Table 2. Molten pool geometry data in Ta and time for stabilization of the liquid pool dimensions for different ingot heights H and casting velocities V.
H, mm V, mm/min 3 6 9 pool diameter/time 41 mm/400 s 45 mm/400 s 50 mm/350 s for stable pool 35 pool depth/ time 6.5 mm/430 s 9 mm/420 s 10 mm/400 s for stable pool pool diameter/time 45 mm/450 s 50 mm/380 s 50 mm/260 s for stable pool 40 pool depth/ time 9 mm/400 s 10 mm/400 s 10.7 mm/330 s for stable pool pool diameter/time 50 mm/500 s 50 mm/300 s 50 mm/230 s for stable pool 45 pool depth/ time 10 mm/400 s 11 mm/400 s 12 mm/340 s for stable pool
a) a)
b)
Figure 5. Dependence of the molten pool b) dimensions: (a) pool diameter dm and (b) pool depth hm on the heating time during EBMR of Ti, Figure 6. Comparison between experimental and where (●) represents simulation results and (■), simulation data for the diameter dm (upper curves) experimental data. and the depth hm (lower curves) of the molten pool in Cu during EBMR by: (a) 10 kW beam power; Experimental data for liquid pool (b) 15 kW beam power. (●) represents simulation dimensions – pool diameter dm (upper results and (■), experimental data. curves, figure 6) and pool depth hm (lower curves, figure 6) obtained for EBMR of seen, namely, less than 10 % mean copper ingots (2R = 60 mm, H = 50 mm) deviation value. with beam powers of 10 kW and 15 kW The crystallization front shape obtained are compared with calculated data and are experimentally and the calculated presented in figure 6. A good agreement is liquid/solid boundary are given on the 95 Annual Report IE 2012
metallographic photograph (figure 7) of a tantalum ingot cross-section after e-beam melting with beam power of 27 kW; a reasonable agreement can be seen. The temperature fields as calculated numerically and measured experimentally agree well, too – figure 8. Figure 8-a. Temperature level lines on the top sample surface at the first minutes of e-beam heating of Ta with a 6-kW e-beam. 1 - [975 K - 1025 K], 2 - [850 K - 975 K], 3 - [880 K - 850 K].
Figure 7. Comparison between the calculated (curve 1) and experimentally observed (curve 2) liquid/solid boundaries on a metallographic photo- graph of a Ta ingot.
Using experimental data for EBMR of copper, regression models for residual impurities concentration (after EBMR) Figure 8-b. Numerically calculated 2D tempe- were considered. The models obtained for rature distribution on the top surface of the ingot the impurities studied (Pb, Sb, Ni, Zn, As, at t ≈ 60 s. Sn, Bi) and the corresponding determination coefficients are given in A graphical user interface (GUI) for table 3. The variation of the concentration studying the EBMR of copper was of the impurities vs. the e-beam power and developed based on the regression models the refining time were studied and optimal considered. For concrete values of data for the concentration of the residual the refining time and the beam power, the impurities were obtained. residual concentrations of the impurities
Table 3. Regression models and determination coefficients.
Model R2 R2adj R2pred 2 y1=0.772-0.002x1-0.031x2-1.702x1 - As 3 4 3 0.77131 0.70271 0.61120 0.212x1 +1.751x1 +0.072x1 x2 2 y2=0.058-0.001x1-0.012x2-0.587x1 - Bi 3 4 3 0.73416 0.65441 0.55322 0.071x1 +0.603x1 +0.028x1 x2 2 y3=0.743+0.046x1-0.081x2-3.185x1 - Pb 3 4 3 0.87303 0.83494 0.76498 0.598x1 +3.440x1 +0.175x1 x2 2 y4=0.949+0.013x1-0.065x2-2.470x1 - Sb 3 4 3 0.81287 0.75673 0.65760 0.362x1 +2.587x1 +0.142x1 x2 y5=0.959-0.387x1-0.141x2- Ni 2 4 0.74330 0.69663 0.61149 3.161x1 +3.273x1
96 Selected Projects
joint research and development of technologies for EBMR of refractory metals and alloys, as well as for recycling of precious metals and alloys. Studying the processes involved in EBMR and developing better technologies and equipment for obtaining new materials by recycling waste products of refractory, reactive and other metals and alloys using EBMR form a good basis for technological transfer and for specialized industrial applications of the research results obtained.
References
[1] Vutova K, Vassileva V and Mladenov G Figure 9. Screenshot of GUI showing: (i) 3D 1997 Vacuum 48/2 143-8 dependence of the Pb concentration on the beam [2] Vutova K, Koleva E and Mladenov G power and refining time and (ii) residual 2011 IREME – Special Issue on Heat impurities’ concentration for EBMR of copper for Transfer 5 257-65 12 kW beam power and 1 min refining. [3] Vutova K, Donchev V, Vasileva V are calculated in the lower part (figure 9), and Mladenov G 2012 Supplemental while, in the upper part, a 2D or 3D Proceedings: Materials Processing graphical image can be drawn presenting and Interfaces (TMS Wiley USA) 1 the concentration dependence of the 125-32 chosen impurity on the beam power and on [4] Vutova K and Donchev V 2012 Proc. th the refining time (figure 9). Figure 9 10 Int. Conf. EBT’12 Varna presents an example for 1-min refining J. Electronics and Electrical Engin. time and 12-kW e-beam power for EBMR 47/5-6 273-9 of copper and a 3D visualization of the Pb [5] Vutova K, Donchev V, Vassileva V, impurity concentration variation. The GUI Amalnerkar D P, Munirathnam N and developed allows one to select more easily Prakash T 2013 EPD Congress 2013 the regime parameters thus achieving volume (TMS Wiley USA) accepted better process optimization. for publication On the basis of the experimental and [6] Samsonov G 1965 Chemo-physical theoretical studies performed, data and properties of elements (Kiev: dependencies of practical importance were Naukova Dumka Publ. House) 202- obtained and recommendations were 27 (in Russian) formulated for choosing the proper process [7] Gurevich S M 1982 Metallurgy and conditions. The results are important and technology of refractory metals and useful in view of studying, controlling and alloys welding (Kiev: Naukova optimizing the quality and purity of the Dumka Publ. House) 13 (in Russian) new materials obtained by EBMR. Agreements were signed between IE- BAS and two Bulgarian companies for
97 Annual Report IE 2012
PLASMON AND OPTICAL PROPERTIES OF METAL NANOPARTICLES AND THEIR APPLICATION TO HIGH-SENSITIVITY RAMAN SPECTROSCOPY AND BIOPHOTONICS
Project DO 02/293 funded by the Bulgarian National Science Fund Project coordinator: Assoc. Prof. Dr. Nikolay Nedyalkov Project period: 2009 – 2012
PARTNERS
Emil Djakov Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsaridradsko Chaussee, 1784 Sofia, Bulgaria, Micro and Nanophotonics Laboratory, group leader Prof. Dr.Sc. P. Atanasov Institute of Experimental Morphology, Pathology and Anthropology, Bulgarian Academy of Sciences, G. Bonchev Str., bl. 25, 1113 Sofia, Bulgaria, group leader Dr. R. Toshkova National Center of Oncology, 1756 Sofia, Bulgaria, group leader Prof. R. Balanski
PROJECT GOALS and 3D noble metal nanostructures and nanocomposites were defined and The objects of investigations in this analyzed; project were the mechanisms and effects of - various physical methods for interaction between the electromagnetic fabrication of nanoparticles and field and noble metal nanoparticles and nanostructures based on the interaction of nanostructures. The main efforts were laser radiation with matter were developed directed to a detailed description of the and studied. The experimental conditions optical properties of these structures in the that determine the fabrication of structures near- and far-field zones. The interest was with desirable properties were found for also focused on two applications of these the different methods: production of structures: gold-nanoparticles-assisted colloids by laser ablation of a solid target cancer-cell photothermal therapy and in a liquid; pulsed laser deposition of design of structures for surface enhanced nanostructures with different morphology: Raman spectroscopy (SERS). arrays of spherical particles, nanorods, and composite structures; direct laser RESULTS nanostructuring of metal thin films for fabrication of monolayers of spherical The main results of the activities particles on a substrate. The methods performed under the project can be developed showed high efficiency in terms summarized as follows: of speed, cost and flexibility. It was further - theoretical models were developed and shown that in some cases these physical applied to the description of the main methods are competitive alternatives of the characteristics of the plasmon resonance of well-developed, but still expensive, noble metals for wide ranges of electron- and ion-beam lithography and geometries, system parameters and multy-step chemical methods. incident irradiation. The critical Using the methods developed, noble parameters that influence significantly the metal nanostructures were fabricated in optical properties of noble metal view of SERS applications. The enhanced nanoparticles in the 20 – 200 nm range, 2D Raman signal obtained in some cases was 98 Selected Projects
an order of magnitude higher that the 3. Nedyalkov N N, Nikov Ru, Dikovska signals established as standard for this A Og, Atanasov P A, Obara G and technique. Obara M 2012 Laser annealing of Original results on the effects that arise bimetal thin films: A route to when gold nanoparticles are in a biological fabrication of composite nano- object or animals were obtained in-vivo. It structures Appl. Surf. Sci 258 9162 was found that the presence of gold 4. Balkanski R, Ganchev G, Ilcheva M, nanoparticles with size of 40 and 100 nm Toshkova R, Nedyalkov N, Atanasov P, in the body of adult mice does not induce Izzooti A and De Flora C 2012 clastogenic effects. However, such an Transplacental clastogenic effect of effect was observed in mice embryos, gold nanoparticles Oncology 4 35-42 where transplacental clastogenic effect was 5. Yossifova L, Gardeva E, Toshkova R, clearly expressed when 100-nm Nedyalkov N, Alexandrov M and nanoparticles were used. Such an effect Atanasov P 2013 Treatment of Graffi was not observed in the case of 40-nm tumor in hamsters using particles. A detailed analysis was also plasmonically activated gold performed on the effect of modification of nanoparticles Acta Morphoogica et micro RNA expression due to the presence Antrhropologica (in press) of gold nanoparticles in mice. 6. Dikovska A Og, Tsankov N Ts, The experiments on gold-nanoparticles- Toshkova R, Gardeva E, Yossifova L, assisted photothermal therapy of cancer Nedyalkov N and Atanasov P 2012 cells showed clearly a decrease of the cell Fabrication of ZnO nanostructures viability, especially for HeLa, Graffi, and and their application in biomedicine Hep-2 cells. The optimal conditions for Proc. SPIE 8424 84242Q-1 efficient treatment in in-vivo and in-vitro schemes were defined. 2012 CONFERENCE PARTICIPATION In general, the goals envisaged in the project’s working program were achieved EMRS 2012 Spring Symp. V, 14-18 May accordingly. The main results were 2012, Strasburg, France: published in 30 papers in journals and conference proceedings (16 of them with ● Dikovska A Og, Tsankov N Ts, impact factor). The scientific team Nedyalkov N N, Atanasov P A, presented 32 works at international Kocourek T and Jelinek M, conferences and meetings. Fabrication of ZnO nano-structures by PLD; ● Nikov Ru G, Nedyalkov N N and 2012 PUBLICATIONS Atanasov P A, Tuning of the optical properties of 1. Dikovska A Og , Nedyalkov N N, metal nanostructures fabricated on Imamova S E, Atanasova G B and flexible substrates; Atanasov P A 2012 Au-coated ZnO ● Nikolov A S, Nikov Ru G, Nedyalkov nanostructures for surface enhanced Raman spectroscopy applications N N, Atanasov P A and Alexandrov Quantum Electronics 42 258-61 M T, 2. Koleva M E, Dikovska A Og, Modification of the Ag and Au Nedyalkov N N, Atanasov P A and nanoparticles size-distribution by Bliznakova I A 2012 Enhancement of means of laser light illumination of ZnO photoluminescence by laser their water suspensions; nanostructuring of a Ag underlayer ● Nikov Ru G, Nikolov A S, Nedyalkov Appl. Surf. Sci. 258 9181 N N, Atanasov P A, Alexandrov M T 99 Annual Report IE 2012
and Karashanova D B, 17th Int. School on Quantum Electronics Processing condition influence on the 23 – 28 September 2012, Nessebar, characteristics of gold nanoparticles Bulgaria: produced by pulsed laser ablation in liquids; ● Nikov Ru G, Nedyalkov N N, ● Dikovska A Og, Alexandrov M T, Atanasov P A, Grochowska K, Atanasova G, Tsankov N Ts, Iwulska A and Sliwinski G, Nedyalkov N N and Atanasov P A, Laser nanostructuring of Au/Ag and Au/Ni films for application in SERS; Silver nanoparticles produced by PLD ● Nikov Ru G, Nedyalkov N N and in vacuum: role of the laser Atanasov P A, wavelength used; Near field intensity enhancement аnd ● Koleva M E, Nedyalkov N N, localization in noble metal Dikovska A Og and Atanasov P A, nanoparticle ensembles; Optical properties in plasmonic ● Nikolov A S, Nedyalkov N N, Nikov multultilayer structures; Ru G, Atanasov P A, Alexandrov M T ● Atanasov P A, Nedyalkov N N, and Karashanova D B, Amoruso S, Wang X and Bruzzese R, Fabrication of gold and silver Nanoparticles size control in nanowires by pulsed laser ablation in ultrashort-pulse laser ablation of gold double distilled water; thin film. ● Nikov Ru G, Nikolov A S, Nedyalkov N N, Atanasov P A, Alexandrov M T SPIE Photonics Europe 16 - 19 April and Karashanova D B, 2012, Brussels, Belgium: Investigation of Au nanoparticles produced by pulsed laser ablation of ● Dikovska A Og, Tsankov N Ts, solid targets in water; Toshkova R, Gardeva E, Yossifova L, ● Dikovska A Og, Nedyalkov N N, Nedyalkov N and Atanasov P, Avdeev, G V and Atanasov P A, Fabrication of ZnO nanostructures Fabrication of metal nanorod and their application in biomedicine; substrates for SERS application; ● Nedyalkov N N, Atanasov P A, ● Koleva M E, Dikovska A Og, Toshkova R A, Gardeva E G, Nedyalkov N N and Atanasov P A, Yossifova L S, Alexandrov M T and Ag/ZnO multilayer nano-composites Karashanova D, prepared by laser methods. Laser heating of gold nanoparticles: Photothermal cancer cell therapy.
100 Selected Projects
HIGH RESOLUTION SPECTROSCOPY OF CS VAPOR CONFINED IN -MICRON THICKNESS OPTICAL CELLS
S Cartaleva1, A Krasteva1, A Sargsyan2, D Sarkisyan2, D Slavov1 and T Vartanyan3
1Emil Djakov Institute of Electronics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee, 1784 Sofia, Bulgaria; 2Institute for Physical Research, National Academy of Sciences of Armenia, 0203 Ashtarak, Armenia; 3St. Petersburg National Research University of Information Technologies, Mechanics and Optics, 49 Kronverkskiy Blvd., 197101 St. Petersburg, Russian Federation.
1. Introduction Our research concerns high-resolution laser spectroscopy of Cs vapor confined in Laser spectroscopy of alkali vapor unique optical cells with thickness of a few contained in optical cells is widely used in microns, further on called micrometric various laboratory experiments and cells (MCs). The dimensions of such cells photonic devices. Reducing the cell differ significantly. The distance between thickness L is of importance not only for the high-quality cell windows L varies optical photonic sensor miniaturization, from 1 μm to 6 μm. At the same time, the but it also results in the observation of new window diameter is (12) cm. If the phenomena with L approaching the irradiating laser light is steered normally to wavelength of the irradiating light. the cell window, a strong spatial Recently, significant efforts have been anisotropy will be present for the time of devoted to the development of interaction between the atoms and the laser miniaturized atomic clocks and radiation. Two kinds of atoms, “slow” and magnetometers based on electro- “fast”, can then be distinguished. The slow magnetically-induced transparency (EIT) atoms are those flying in a direction nearly resonances. The EIT resonances have been orthogonal to the laser beam (typically of a prepared in Cs atoms confined in cells of millimeter diameter) and reaching a steady sub-millimeter thickness with a high- state in the interaction with the laser light. pressure buffer gas added to prevent The fast atoms have a significant velocity frequent collisions of alkali atoms with the component along the laser beam cell walls, which destroy the atomic propagation direction, which results in a coherence [1]. The EIT resonance contrast time of flight between the MC windows measured in such cells is similar in shorter than the lifetime of the excited magnitude to that obtained in centimeter- state of the atom. Due to transient effects, size cells, but a substantially higher laser this anisotropy leads to: (i) observation of intensity is needed when sufficient buffer- a significant difference between the gas pressure is used. The buffer gas fluorescence and transmission (absorption) broadens the optical transitions, which spectra [3] and (ii) appearance of velocity- limits the pumping efficiency and selective optical pumping (VSOP) compromises the performance of vapor resonances centered at hyperfine optical cell clocks and magnetometers. A transitions [4]. A series of VSOP promising strategy for increasing the atom- resonances have been observed and have light interaction time consists in the use of been the object of intensive studies anti-relaxation-wall coated cells. However, motivated by the possible applications for the atomic-vapor density is limited owing development of wavelength references, as to coating degradation with the well as for investigation of atom-atom and temperature [2]. atom-cell window collisions. 101 Annual Report IE 2012
More specifically, we report here a new orthogonally to one another. After careful behavior of the EIT and VSOP resonances overlapping, the two light beams observed in Cs vapor confined in L = 1.5 propagated in a direction orthogonal to the and L = 6 cells, where = 852 nm is the MC windows. The transmission wavelength of the laser light resonant with (absorption) and fluorescence (in a the Cs D2 line. The L = 1.5 cell provides direction orthogonal to the laser beam) of the possibility of studying the EIT jointly the Cs vapor were measured on the D2 with the Dicke-type coherent narrowing of resonance line. the optical transition, as the effect of Dicke coherent narrowing first revival has been 3. Sub-Doppler-width resonances of Cs observed in such an optical cell [4]. At the vapor confined in an optical cell with same time, for L = 6, the Dicke effect L = 1.5 vanishes, thus allowing one to compare the two different cases. Figure 2 illustrates the results for the In addition, we demonstrated that (i) in MC spectrum on the set of transitions a MC a reasonably narrow EIT resonance starting from the ground hyperfine level can be observed without a buffer gas, and F = 4 obtained by scanning the probe (ii) at the closed hyperfine transition, a g laser. high-contrast velocity-selective excitation
(VSE) resonance occurs, which has not been observed in conventional optical cells under the same experimental conditions.
2. Experimental set up for sub-Doppler and sub-natural width resonance study
Both micrometric cells used in the experiment were filled with Cs vapor and irradiated by a bi-chromatic laser light emitted by two narrow-band (with spectral
Figure 2. EIT and Dicke resonances at L = 1.5: (1) the probe laser is scanned within the Fg = 4 set of transitions, no pump; (2) the pump laser is fixed at the 3 - 4 transition and the probe is scanned as in (1); T = 105 oC, i.e. atomic density 2×1013 at/cm3, 2 2 Wprobe = 0.3 mW/cm , Wpump = 35.4 mW/cm .
Figure 1. Experimental setup for VSOP, EIT and VSE resonance observation by pump-probe Initially, the pump laser is switched off. spectroscopy. If the probe laser is of low intensity, narrow Dicke resonances occur centered at width of about 2 MHz) distributed the Fg = 4 Fe = 3,4,5 transitions – curve feedback (DFB) diode lasers – a pumping (1). The resonance at the closed one and a probing one (figure 1). Fg = 4 Fe = 5 transition is of the highest The frequency of the pump laser was amplitude, since it does not suffer any fixed at a certain hyperfine optical atomic population loss due to hyperfine transition, while that of the probe one was and Zeeman optical pumping. To obtain an scanned within a set of hyperfine EIT resonance, a pump laser is involved transitions starting from a single ground- and fixed at the Fg = 3 Fe = 4 transition. state level. The laser beams were polarized The EIT resonance centered at Fg = 4 Fe = 4 102 Selected Projects
transition – curve (2), is of natural width Fg = 4 Fe = 5 transition (figure 2, curve (ν = 5 MHz), proving that it is based (2)) is due to the Dicke phenomenon, the mainly on atoms flying parallel to cell second cell with L = 6 was used, where windows. In fact, the dephasing rate of the no Dicke effect is expected. ground levels for the atoms moving Moreover, our aim was also to make an orthogonally to the windows is ~ 70 MHz, accurate comparison of the effects in the as in the L = 1.5 cell the atomic L = 6 cell with those in a conventional interaction time with the laser beam is cell with L = 2.5 cm. For this purpose, a highly anisotropic. The atoms moving beam splitter, BS, was inserted (denoted in nearly parallel to the cell windows have blue in figure 1), directing the two precisely much longer interaction times compared to overlapped pump and probe beams to the the atoms moving in the direction centimeter cell as well. To make the perpendicular to the windows. The analysis simpler, we used very low powers advantage of this approach is that mainly of both lasers, thus working in a linear the slow atoms contribute to the EIT regime. As can be seen in figure 3a, even signal, which exhibits a very good without a Dicke effect, a significant contrast. accumulation of “slow” atoms occurs While it is clear that the laser light cycling at the Fg = 4 Fe = 5 transition. centered at the Fg = 3Fe = 4 transition Since in the L = 6 cell this narrow causes accumulation on the Fg = 4 level of resonance appears only with the pump Cs atoms with a small velocity component laser switched on, it is determined as being along the laser beam direction, it should be a VSE resonance. An EIT resonance is stressed that the Dicke resonance observed in the absorption at the Fg = 4 amplitude at the Fg = 4Fe = 5 transition Fe = 4 transition, as measured by the probe is strongly enhanced by the pump laser. beam (figure 3a). While the EIT resonance Moreover, some narrowing of the Dicke width remains constant (less than 2 MHz) resonance is observed. Hence, besides for as the atomic source temperature is raised, optical cell miniaturization, the two-laser the VSE resonance undergoes a noticeable approach proposed could be advantageous broadening (figure 3b). Further theoretical for further Dicke effect studies in MCs, as studies are in progress for clarifying the the contributions of the atoms of different physical processes behind the VSE velocity classes to the Dicke narrowing are resonance broadening under different still to be clarified experimentally. Our experimental conditions. experiment showed that if the pump laser The comparison of the EIT/VSE frequency is shifted out of exact resonance resonances for the L = 6 and L = 2.5 cm cells with the transition, the amplitude of the shows two unexpected results (figure 3c): narrow resonance decreases very quickly (i) despite the much higher rate of atomic and broadens considerably, i.e. the narrow collisions with the walls in the case of the L = 6 cell, the width of the EIT resonance Dicke resonance at the Fg = 4Fe = 5 transition is mainly due to the “slow” is similar in both cells (about 2 MHz, atoms flying along the cell window mainly determined by the laser line surface. widths); (ii) the thermalization of the atomic population at the Fe = 4 level selectively excited by the pump laser is 4. Sub-Doppler and sub-natural width dramatically lower for the L = 6 cell than resonances observed in cells with that observed in the L = 2.5 cm cell. Both L = 6 - difference between open and results will be analyzed theoretically in a closed optical transitions further study. In what concerns the different thermalization of the atoms In order to check if the large amplitude excited by the pump laser, we assume that of the sub-Doppler-width resonance at the it is due to the radiation trapping effect [5] 103 Annual Report IE 2012
Probe frequency detuning [MHz] Probe frequency detuning [MHz]
Figure 3. Probe absorption spectra in the L = 6 and the L = 2.5 cm cells: (a) EIT resonance at the 4-4 transition and VSE resonance at the 4-5 transition; (b) EIT and VSE resonance behavior with the atomic source temperature; (c) illustration of the striking difference between the thermalization of the atomic population selectively excited by the narrow-band pump beam in the L = 6and the L = 2.5 cm cells. Atomic density: (2.3×1012 – 5.3×1013) at/cm3.
L < 1 m) [4], it has been recently demonstrated [6] that even narrower dips appear in the already narrowed fluorescence profiles at an ETC thickness of L = . These saturation dips have only Probe frequency detuning [MHz] been reported for the open hyperfine
transitions of the Cs D2 line, which suffer which is much more pronounced in the atomic population loss due to hyperfine L = 2.5 cm cell than in the MC. In fact, the or/and Zeeman optical pumping. No dip extremely small thickness of the L = 6 has been observed in the fluorescence of cell reduces the probability for the Cs the completely closed 4-5 transition. For atoms re-absorbing the fluorescence, the latter transition, a tiny peak in the because of the extremely short time and distance of propagation of the fluorescence absorption has even been demonstrated [7] within the MC. using a narrow-band (few MHz) diode laser. In general, our experiments showed that The results presented here concern dark the MC is much less sensitive to the (reduced absorption) and bright (enhanced magnetic field gradients, the laser beam absorption) VSOP resonances observed in overlapping and the mutual coherence of a MC with thickness L = 6. The two open the two independent lasers. Fg = 4 → Fe = 3, 4 transitions show dark VSOP resonances in the transmission and 5. VSOP resonance sign reversal fluorescence spectra at all Cs source temperatures used in the experiments. In addition to the first observation of However, the profile of the closed narrow and well-resolved fluorescent Fg = 4 → Fe = 5 transition exhibits a VSOP spectra in extremely thin cells (ETC) (with resonance of different sign at different 104 Selected Projects
atomic source temperatures. At T = 60 oC, absorption (figure 4b). a very well-pronounced narrow bright Moreover, the fluorescence profile of VSOP is observed in absorption the Fg = 4 → Fe = 5 transition has a (i.e. enhanced absorption), together with a well-pronounced dip at T = 84 oC. At sharp top of the fluorescence profile lower Cs-source temperatures, increasing (figure 4a). This interesting absorption the light intensity results in the same effect peak is observed only at low atomic concentration and low light intensity. – a transformation of the bright resonance However, raising the temperature to about to a dark one. Note that no VSOP 84 oC leads to a sign reversal of the VSOP resonance broadening is observed during resonance, i.e. a narrow dip occurs in the the resonance sign transformation.
Figure 4. (a) Narrow VSOP resonances of different signs in the L = 6 cell fluorescence and transmission spectra for low atomic concentration (9.2×1011 at/cm3) and very low light intensity – comparison with a conventional L = 2.5 cm cell profile, where no sub-Doppler-width feature occurs; (b) Illustration of the bright resonance (in the fluorescence and absorption of the Fg = 4 Fe = 5 transition) transformation into a dark one (denoted by asterisks) as the atomic concentration is raised (5.2×1012 at/cm3).
The physical process behind the 6. Conclusions resonance sign reversal is assumed to be depolarization of the excited level, which VSOP, VSE and EIT resonances on the transforms the completely closed system at D2 line of Cs were experimentally low light intensity and atomic observed in a MC with a thickness of few concentration to one with effective loss in microns confining Cs atoms. The the excitation process at higher intensity resonances were detected by means of and Cs vapor pressure. Two main pump-probe spectroscopy using two processes can be responsible for the narrow-band DFB lasers. In the L = 6 population mixing of magnetic sublevels cell, a narrow VSOP resonance of of the excited state, namely: (i) elastic very high amplitude occurred at the interaction between Cs atoms at higher Fg = 4 Fe = 5 transition. In contrast, atomic vapor pressures and (ii) elastic such a narrow VSOP resonance was not interaction between the cell windows and observed in the L = 2.5 cm cell. This fact the Cs-atoms traveling parallel to the was attributed to the higher rate of window surface [8]. radiation trapping in the latter cell. 105 Annual Report IE 2012
A very interesting result concerns the References EIT resonance width, which for the L = 6 cell was about an order of magnitude [1] Knappe S, Hollberg L and Kitching J narrower than that estimated from the 2004 Opt. Lett. 29 388 [2] atomic collision rate with the cell Budker D and Romalis M 2007 Nat. Phys. 3 227 windows. The comparison with the EIT [3] Sarkisyan D, Bloch D, Papoyan A resonance in the L = 2.5 cm cell under the and Ducloy M 2001 Opt. Commun. same experimental conditions showed that 200 201 EIT resonances of similar width are [4] Sarkisyan D, Varzhapetyan T, observed in both cells. Sarkisyan A, Malakyan Yu, The experimental results obtained are of Papoyan A, Lezama A, Bloch D and significant importance for the further Ducloy M 2004 Phys. Rev. A 69 development of the spectroscopy of alkali 065802 atoms confined in optical cells with [5] Allegrini M, Huennekens J, micrometric thickness in view of the Namiotka R K, Sagle J and Jabbour Z J miniaturization of photonics sensor, as 1995 Phys. Rev. A 51 4472 [6] Andreeva C, Cartaleva S, Petrov L, well as for the study of new phenomena. Saltiel S, Sarkisyan D,
Varzhapetyan T, Bloch D and Acknowledgements Ducloy M 2007 Phys. Rev. A 76 013837 This work was supported in part by the [7] Cartaleva S, Saltiel S, Sargsyan A, Bulgarian National Science Fund (grant Sarkisyan D, Slavov D, Todorov P No: DO 02-108), as well as by a Marie and Vaseva K 2009 J. Opt. Soc. Am. Curie International Research Staff B 26 1999 Exchange Scheme Fellowship within the [8] Krasteva A, Slavov D and Cartaleva S 7-th European Community Framework 2011 Int. J. Opt. 2011 ID 683415 Program.
106 Selected Projects
AEROSOLS, CLOUDS AND TRACE GASSES RESEARCH INFRASTRUCTURE NETWORK (ACTRIS)
Research Infrastructure Action of the FP7 Capacities Specific Program for Integrating Activities, Grant Agreement # 262254
D Stoyanov, I Grigorov, Z Peshev, A Deleva, G Kolarov, N Kolev, Tz Evgenieva, E Toncheva and T Dreischuh
Emil Djakov Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee, 1784 Sofia, Bulgaria
ACTRIS (Aerosols, Clouds, and Trace quality information and services for gasses Research InfraStructure Network) the user communities (research, is a European Project aiming at integrating environmental protection agencies, European ground-based stations equipped etc.). with advanced atmospheric probing To develop new integration tools to instrumentation for aerosols, clouds, and fully exploit the use of multiple short-lived gas-phase species. ACTRIS has atmospheric techniques at ground- an essential role in supporting the based stations, in particular for the acquisition of new knowledge and in calibration/validation/integration of solving issues related to climate changes, satellite sensors and for the air-quality, and long-range transport of improvement of the parameterizations pollutants. ACTRIS is building the next used in global and regional scale generation of the ground-based component climate and air-quality models. of the EU observing system by integrating ACTRIS aims at providing time series three existing research infrastructures of climate and air-quality related EUSAAR, EARLINET, CLOUDNET, and variables not directly measured, which a new trace-gas network component into a are presently not available through the single coordinated framework. ACTRIS is existing data centers. funded by the European Community – To enhance the training of new Research Infrastructure Action of the FP7 scientists and new users, in particular Capacities Specific Program for students, young scientists and Integrating Activities under ACTRIS scientists from East European and non- Grant Agreement No. 262254. The project EU developing countries in the field of started on 1/4/2011 for a four-year period. atmospheric observation. The main objectives of ACTRIS are: To promote the development of new To provide long-term observational technologies for atmospheric data and to substantially increase the observation of aerosols, clouds and amount of high-quality data relevant to trace-gasses through close partnership climate and air-quality research on a with EU companies. ACTRIS aims at regional scale produced by contributing to more than four new standardized or comparable procedures operating standards for atmospheric throughout the network. monitoring by the end of the project. To provide a coordinated framework The ACTRIS Consortium is formed by for transnational access to advanced 28 contractors, representing 19 countries European infrastructures for atmo- across Europe, as Italy, France, Germany, spheric research thus strengthening Spain, Bulgaria, Greece, The Netherlands, high-quality collaboration in and Romania, Poland, Switzerland, Norway, outside the EU and access to high- United Kingdom, Belgium, Hungary, etc. 107 Annual Report IE 2012
(a) (b) Figure 1. Photographs of the CuBr-vapor (a) and Nd:YAG (b) laser-based aerosol lidars at the Laser Radar Laboratory (IE-BAS) involved in the European Lidar Network measurement programs.
Lidar remote sensing of the atmosphere WP22: A framework for cloud-aerosol in the framework of the European Lidar interaction studies. Network (EARLINET) The investigations at Sofia Lidar Station covered four categories of measurements, as follows: The lidar station in Bulgaria is 1. Regular lidar measurements with the positioned in the Laser Radar Laboratory objective to establish a common of the Institute of Electronics of the database of atmospheric aerosol Bulgarian Academy of Sciences (IE-BAS). backscatter coefficient profiles [1-3]; The Institute is located in the urban area of 2. Measurements in the framework of o the capital city of Sofia (42 39’14”North, cooperation with satellite missions o 23 23’14”East), at about 550 m above sea with the objective of a detailed level (ASL). Sofia lidar station is a comparison of ground-based and member of the European Lidar Network space-borne lidar data sets over (EARLINET) and has two functional Europe. These measurements are lidars [1]. The first one is based on a related to the Quid pro Quo (QPQ) CuBr-vapor laser, and the other one, on a validation measurements of the project Nd:YAG laser (see figure 1). Both lidars Cloud-Aerosol Lidar and Infrared are performing tasks of the work packages Pathfinder Satellite Observations (WP) of ACTRIS, in which the European CALIPSO Lidar Network is included. Those are: (http://calipsovalidation.hamptonu. WP2: Remote sensing of the vertical edu/QPQ_plan062206.htm). CALIPSO aerosol distribution; is a free-flying space lidar providing WP20: Lidar and sun-photometer – data on atmospheric clouds and improved instruments, integrated aerosols needed for climate studies. observation strategies and algorithms The ground EARLINET stations were for the retrieval of advanced aerosol deemed to be an optimal tool for microphysical products; validating CALIPSO lidar data and 108 Selected Projects
providing the necessary information to ceilometer measurements with the aim fully exploit the information from this of improving the lidar’s daytime mission [1,4]; capabilities, and developing and 3. Observation of special phenomena, such applying integrated lidar and sun- as unusually high concentrations of photometer observation strategies for aerosols in the troposphere. Their for the best use of complementary appearance may be due to transportation information on atmospheric aerosols of dust from Sahara over the gained from active and passive remote- Mediterranean Sea to Europe, volcanic sensing instruments and for retrieving eruptions, formation of smoke layers as a advanced information on the aerosol result of forest or industrial fires, intense microphysics from multi-spectral photochemical smog, etc. [1,3,5,6]; columnar sun-photometer and height- 4. Lidar measurements combined with resolved multi-wavelength lidar simultaneous sun-photometer and observations [7-9].
Figure 2. Lidar observations of a smoke layer spreading from a Vitosha forest fire in the atmosphere over Sofia (July 2012).
We present below some illustrative wild forest fire on July 3, 2012, in the results of lidar measurements conducted in Vitosha Mountain near Sofia. IE-BAS in 2012 during events of polluting The measurements were carried out by aerosol loadings. The multi-panel figure 2 using the two lidars mentioned above. The shows results of lidar observations of a lidar wavelengths used were 510.6 nm by 109 Annual Report IE 2012
the CuBr-vapor laser and 1064 nm by the 532 nm and 1064 nm related to lidar Nd:YAG laser. The photograph shows an observation of a forest fire in Vitosha episode of the smoke plume rising over the Mountain on October 9, 2012. The fire site and spreading along the mountain temporal evolution of the otherwise crest. The largest part of the aerosol field invisible smoke aerosol components remained invisible because of the low spreading down close to the surface of the concentration of smoke particulates in the city area is clearly seen [2]. air far from the source. The signals Another case of biomass-burning backscattered by the aerosol, however, aerosol intrusion into the atmosphere were reliably detected by the highly above Sofia was detected and sensitive lidar receivers, resulting in the characterized by means of the Nd:YAG- intense red layers seen on the height-time based lidar on August 6, 2012. By using color map diagrams displayed above the air-transport modeling data, the aerosols photograph. observed were identified as being more A vertical profile of the so-called than 10-day-aged organic smoke origi- Ångström exponent is shown in the left nating from wild forest fires raging in the upper panel of the figure. At the altitudes USA in July 2012, and subjected to trans- where the densest smoke layer appears (1 – Atlantic long-range transport driven by the 1.5 km), the Ångström exponent assumes Northern Hemisphere Polar Jet Stream. A values of about 1.5, indicating the presence backscatter-related Ångström exponents of coarse particles (soot) associated with the (BAE)-occurrence frequency distribution near fire source. At altitudes > 2 km, well analysis of the BMB aerosols considered above the smoke layer, the atmosphere is was conducted and used as an indirect clear as seen from the color maps and, approach to a qualitative characterization correspondingly, the Ångström exponent of the aerosol particle-size distribution. maintains nearly constant typical values of The lower left panel of figure 3 shows about 4. BAE distributions of the fire smoke layer The results obtained show that the (case B) and of other aerosols observed. smoke aerosols ejected into the Processes of coagulation and aggregation atmosphere by the fire in Vitosha of the finest particle size modes were thus Mountain on 3 July 2012 have spread found to have taken place during the long predominantly westward. This is supported aging time between the smoke emission by the air-mass transport model (NOAA and the lidar observation. The results can ARL HYSPLIT). The smoke layer has also contribute to the better understanding of expanded over the whole territory of the the composition and size evolution of city of Sofia at altitudes of 1.5 km. biomass aerosols subject to long-range Because of the absence of highly dynamic transport. atmospheric processes, the smoke layer Lidar observations of close-to-the- has remained at a nearly constant altitude, surface atmospheric domains located over without extending considerably down to a heterogeneous terrain, including adjacent the surface while gradually moving away city, plain, and mountain zones, were from the urban zone. carried out by using the two aerosol Two-wavelength (1064/532 nm) elastic- channels of the Nd:YAG-based lidar. The scatter lidar observations were also measurements revealed a strong and performed on the spatial distribution, specific influence of the underlying area composition, and temporal evolution over orography on the optical parameters and Sofia of atmospheric aerosols produced by dynamical behavior of the atmospheric burning biomass. The two upper panels in aerosols, resulting in an unusually distinct figure 3 present height-time coordinate zonal sectioning of these characteristics color maps of range-corrected lidar data at along the probing laser beam. The use of 110 Selected Projects
10 8 A Total 6
4 2
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 8 B City zone 6
4 2
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6
8 C Plain zone 6
4 2
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 3 D Mountain zone
2 Normalized BAE distribution (%) 1 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 Backscatter-related Angstrom exponent (a.u.)
Figure 3. Range-time diagrams of the range-corrected lidar signals (RCS) corresponding to 532 nm (upper left) and 1064 nm (upper right), illustrating smoke plume evolution resulting from the forest fire in Vitosha Mountain on 09.10.2012. Retrieved partial, zonal, and total distribution profiles of the backscatter-related Ångström exponent from a fire smoke layer transported over the Atlantic and detected over Sofia on 06.08.2012 (lower left) and a quasi-horizontal lidar study of close-to-the-surface aerosol layers over a heterogeneous orographic region (lower right). two considerably separated lidar qualitative aerosol particle size wavelengths, 532 nm and 1064 nm, distributions in terms of BAE for the allowed the fine and coarse aerosol differentiated orographic zones, as well as fractions to be distinguished and the overall one. characterized. A study of the aerosol The results presented above show that particle mode composition was performed two-wavelength lidar observations offer by range-resolved profiling of the BAE good opportunities for range- and time- and their frequency-count analysis. The resolved characterization of the spatial distributions obtained are shown in the distribution and temporal dynamics of both lower right panel of figure 3, revealing the the fine and coarse mode aerosol fractions 111 Annual Report IE 2012
over large areas, based mainly on lidar concerning the type, origin, and data. In combination with frequency-count approximate size distribution of the analysis of BAE, air-mass transport aerosol particles, as well as to identify the modeling data, and minor meteorological aerosol/pollution sources as a part of the data, the two-wavelength lidar approach air-quality monitoring. allows one to make valid assumptions
Figure 4. Lidar observation on April 4, 2012: A) retrieved backscatter coefficient profile and B) range-corrected lidar signal at wavelength 510.6 nm; C) and D) – the same, respectively, at wavelength 1064 nm; E) backscatter coefficient as calculated from data of the CALIPSO satellite lidar. The vertical red line marks the closest position to Sofia Lidar Station of the satellite’s trajectory projection.
Figure 5. METEO sounding at 12:00 h UTC on April 4, 2012 A), forecast maps of cloud cover and Sahara dust load B), and ceilometer time-height diagram C) with blank bands indicating intervals of simultaneous lidar measurements. 112 Selected Projects
Saharan dust transport from above when the cloud cover at 10 km disappeared. Figure 5 presents the meteorological Lidar observations of special situation during th lidar observation on phenomena, such as unusually high April 4. The close positions of the plots of concentrations of aerosols in the the atmospheric temperature and the dew troposphere, were carried out upon point, and the highest value of ~80 % of notification by the program coordinator for the atmospheric humidity, point to the upcoming dust events above the territory altitude of 5 km being critical for water of Europe. The notification is based on vapor condensation. We, therefore, satellite observations and weather concluded to have registered the forecast forecasts provided by the Atmospheric dust transport on April 4 (figure 5B) as a Modeling and Weather Forecasting Group wet aerosol layer at an altitude of ~4 – of the National Technical University of 5 km AGL, which was also confirmed by Athens (http://forecast.uoa.gr/) and the the time-height diagram of ceilometer data Forecast System of Barcelona Supercomputing Center (http://www.bsc. (figure 5 C). es/projects/earthscience/DREAM). Following such a notification, we performed a series of lidar measurements Conclusions from April 2 to 7, 2012, presented below [3]. The new ACTRIS project implemented The backward trajectories for April 4, under the FP-7 EU Program and some of 2012, show a well-expressed transport of the experimental results of the ACTRIS air mass from North Africa to Europe. team at IE-BAS were briefly presented. Unfortunately, we observed again a dense The high effectiveness was demonstrated cloud cover during our lidar measurements of the lidar measurements performed by presented on figure 4. On April 4, the the two lidars of Sofia Lidar Station CALIPSO satellite overflew the Balkans certified in EARLINET. We detected and and at 11:40 h UTC the projection of its analyzed different atmospheric processes trajectory passed close to Sofia. The graph (Saharan dust, volcanic ash, fires, etc., of the lidar atmospheric backscatter above Bulgarian territory originating from coefficient, measured by CALIPSO and three continents (Europe, Africa and provided by NASA, is presented in figure Northern America). Moreover, we 4 E. As it is clearly seen, the satellite lidar performed a large number of lidar provided data for the atmospheric measurements on the local distribution of backscatter coefficient from altitudes of the aerosol pollution due to fires in 30 km above see level (ASL) to the thick Vitosha Mountain in July 2012. We cloud cover over the Balkans at 10 km and showed that because of the absence of 5 km ASL. Data on the atmospheric highly dynamic atmospheric processes stratification from the ground to the during this period, the smoke layers from bottom of the same thick cloud were the Vitosha fires remained at a nearly provided by our ground-based lidar station constant altitude without considerable during the lidar observation on April 4. spread down to the surface and gradually Both lidars registered a cloud layer, very moved away from the urban zone. Thus, probably a wet Sahara dust layer, at Sofia (IE-BAS) Lidar Station was used for altitudes ~4 – 5 km AGL. This corre- the purposes of both the ACTRIS sponded well to the lower aerosol layers at measurements within the European Lidar 5 km ASL observed by the satellite lidar Network and local atmospheric monoring. 113 Annual Report IE 2012
Acknowledgements [5] Peshev Z, Dreischuh T, Toncheva E and Stoyanov D 2012 Two- The research leading to these results has wavelength lidar characterization of received funding from the EU, FP7/2007- atmospheric aerosol fields at low 2013, under grant agreement No. 262254. altitudes over heterogeneous terrain J. Appl. Remote Sens. 6/1 063581 References doi:10.1117/1.JRS.6.063581 [6] Peshev Z, Dreischuh T, Toncheva E [1] Stoyanov D, Grigorov I, Kolarov G, and Stoyanov D 2013 Lidar Peshev Z and Dreischuh T 2012 observations and characterization of Lidar atmospheric sensing by metal biomass burning aerosols over Sofia: vapor and Nd:YAG lasers Chapter Long-range transport of forest 14 in Advanced Photonic Sciences wildfire smoke Proc. SPIE 8770 Fadhali M ed (Intech) 345-74 87700Z ISBN: 978-953-51-0153-6 [7] Kolev N, Grigorov I, Evgenieva Ts, [2] Meier J, Tegen I, Mattis I, Wolke R, Donev E, Ivanov D, Kolarov G, Alados Arboledas L, Apituley A, Kolev I and Stoyanov D 2012 Balis D, Barnaba F, Chaikovsky A, Combined lidar-ceilometer measure- Sicard M, Pappalardo G, Pietruczuk A, ments in the troposphere over Sofia Stoyanov D, Ravetta F and Rizi V (Bulgaria) Comptes rendus de 2012 A regional model of European l'Academie Bulgare des Sciences 65/4 aerosol transport: evaluation with 491-98 ISSN 1310-1331 sun photometer, lidar and air quality [8] Kolev N, Grigorov I, Evgenieva Ts, data Atmos. Environ. 47 519-32 Deleva A, Donev E, Ivanov D and doi:10.1016/j.atmosenv.2011.09.029 Petkov D 2012 Observation in the [3] Stoyanov D, Grigorov I, Deleva A, troposphere over mountain valley by Kolev N, Peshev Z, Kolarov G, ceilometer, sunphotometer and lidars Donev E and Ivanov D 2013 Remote Proc. 26-th Int. Laser Radar Conf. monitoring of aerosol layers over Sofia ILRC 2012 (25-29 June 2012 Porto during Sahara dust transport episode Heli Greece) II 969-72 (April, 2012) Proc. SPIE 8770 87700Y [9] Kolev N, Evgenieva Ts, Petkov D, [4] Mona L, Papagiannopoulos N, Donev E, Devara P C S, Raj P E, D’Amico G, Giunta A, Hiebsch A, Miloshev N, Wiman B L B and Wandinger U, Amodeo A, Apituley A, Kolev I 2012 Water vapor content, Alados-Arboledas L, Balis D, aerosol optical depth, and planetary Chaikovsky A, Comeron A, De boundary layer height determined by Tomasi F, Freudenthaler V, Grigorov I, sun photometer, lidar and ceilometer Iarlori M, Linnè H, Papayannis A, Proc. 26-th Int. Laser Radar Conf. Pietruczuk A, Schnel F, Spinelli N, ILRC 2012 (25-29 June 2012 Porto Wiegner M and Pappalardo G 2012 Heli Greece) II 849-53 Investigation of representativeness of CALIPSO aerosol optical properties products by EARLINET correlative measurements Proc. 26-th Int. Laser Radar Conf. ILRC 2012 (25-29 June 2012 Porto Heli Greece) II 717-20
114 Selected Projects
IMPROVING THE RESOLUTION OF THOMSON SCATTERING LIDARS BY APPLICATION OF NOVEL DECONVOLUTION-BASED ALGORITHMS
EC-Project EURATOM of FP7 Contract № FU07-CT-2007-00059/Fusion CSA/EURATOM
Stoyanov D1,3, Dreischuh T1,3, Gurdev L1,3, Vankov O1,3 and Protochristov Ch2,3
1Emil Djakov Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee, 1784 Sofia, Bulgaria 2Institute of Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee, 1784 Sofia, Bulgaria 3EURATOM-INRNE Fusion Association, 72 Tsarigradsko Chaussee, 1784 Sofia, Bulgaria
1. Investigatory goals
Effective observation and control of the fusion process is only possible when based on effective plasma diagnostics involving the determination with high accuracy and (spatio-temporal) resolution of the electron temperature Te and concentration ne and of the pressure P in the torus. Thomson scattering (TS) methods are routinely used for measuring plasma temperature and density in fusion devices, but the only tokamak to have a LIDAR variant of this diagnostic (see figure1) is the Joint European Torus (JET), Culham, UK [1]. The TS lidar approach is based on the remote sensing of the plasma with an intense laser pulse and on the detection of the backscattered light from the plasma Figure 1. JET Thomson scattering Lidar system. electrons. It allows one to obtain light power) [6,7]. For this purpose, the simultaneously the Te and ne profiles along a lidar line of sight (LOS) through the single-scattering lidar equation which torus core. This diagnostic has been describes the relation between the successfully used for reliable measurement measured lidar profile, the parameters of the lidar system, and the characteristics of of Te and ne profiles at JET [2-4] and is intended to be used in ITER [5]. The the investigated high-temperature plasma investigations performed are of great along the LOS should be solved. There are different effective approaches for TS data importance for the ITER LIDAR development as JET is the only place in processing developed previously [8-10] the world where this measurement and recently [11-13], each one having technique can be tested. some advantages. It is usually accepted that the range The determination of Te and ne profiles by using TS lidar diagnostic is based on resolution of the lidars is of the order of the analysis of the information provided by the spatial size of the effective lidar pulse the TS lidar profiles (the time-to-range response, which is a convolution of the resolved profiles of the received back-scattered sensing laser pulse shape and the pulse 115 Annual Report IE 2012
response function of the receiving ensure considerably higher sensing signal- electronics. So, in order to achieve a better to-noise ratio due to higher electron resolution, shorter sensing pulses and concentration, sensing-pulse energy and faster registration electronics should be quantum efficiency of the photon used. The short-pulse lidar equation holds detectors, and to faster signal-receiving true when the effective pulse response electronics compared to the corresponding shape of the lidar is shorter than the least characteristics of JET. As an important longitudinal variation scale of the fusion new result, the simulations showed that the plasma characteristics. In the opposite theoretical estimates of the statistical error case, the lidar equation describing the lidar in the determination of the electron return has the form of the convolution of temperature from deconvolved lidar the short-pulse lidar profile with the profiles practically coincided with those system response shape. Then, different derived from the computer statistical deconvolution techniques may be used for modeling. In this way, a simulation-aided improving the sensing resolution [13,14]. explicit theoretical formulation was Such techniques concerning the TS lidar obtained of the temperature measurement sensing of electron temperature and error and the corresponding error bars. density profiles have already been In 2012 we continued our investigations investigated by us analytically and by in this field. We endeavored to reveal the computer statistical modeling [15,16]. influence of the system response shape on The research on this topic is carried out the distortions of the recovered electron under Task 2.2.2 Improving the resolution temperature and density profiles. Also, we of Thomson scattering lidars by investigated the performance of the application of novel deconvolution-based developed by us deconvolution algorithms algorithms of the Contract of Association and proved their efficiency by real data between the European Atomic Energy processing. Community (EURATOM) and INRNE in The upgrade of the JET Core LIDAR the frame of 7th Framework Programme of with more sensitive photon detectors the European Atomic Energy Community resulted in a substantial increase of the (Euratom) No. FU07-CT-2007-00059 by a signal-to-noise ratio in the output lidar Bulgarian team from the Institute of profiles [17], which gave rise to an interest Electronics and the Institute of Nuclear in the possibility of extracting information Research and Nuclear Energy at the about the plasma evolution (pedestal & Bulgarian Academy of Sciences in a core) from the lidar data. The collaboration with the JET Thomson attractiveness of such an analysis is of Scattering team, JET Electron Kinetics great importance for the plasma diagnostic Group at the Culham Centre for Fusion by the future ITER Core Lidar [5]. The Energy, UK. first results on testing the sensitivity of The statistical modeling of the improved Core Lidar data to the ELM deconvolution procedures confirmed their processes on the torus edge were obtained. capability in improving the resolution and The rms errors were investigated, accuracy of recovering Te profiles in analytically and by computer simulations, thermonuclear plasmas. The possibility in the determination by Thomson was confirmed as well of achieving scattering lidar of the electron temperature considerably higher recovery accuracy and Te and concentration ne and the pressure resolution in the new generation fusion in fusion plasmas, using fitting reactors (ITER, DEMO) intended to approach [18]. 116 Selected Projects
2. Research activities and results A program for acquisition, calibration, obtained in 2012 and processing of JET TS lidar data was adopted in view of performing 2.1. Deconvolution-based higher- deconvolution of the lidar profiles resolution processing of real TS Core registered and further determination with LIDAR data higher resolution of the electron temperature and density profiles. The performance was investigated of the deconvolution algorithms developed 2.2. Influence of the system response shape by us (and preliminarily proved on the convolution-due distortions of the analytically and by computer statistical electron temperature and density profiles modeling) when processing real lidar data. recovered by TS lidar The research was focused on the analysis and implementation of different methods The influence was analyzed of the for deconvolution of registered signals in system response shape on the convolution- each spectral channel of the JET Thomson due distortions of the electron temperature scattering LIDAR diagnostics in order to and density profiles as recovered by a TS improve the range resolution of the lidar. It was shown that in the case of profiles measured of the electron symmetric (Gaussian) laser pulses, far temperature Te and concentration ne. The from the pedestal area, the convolution total JET LIDAR system response time does not distort the information about the was estimated to be ~ 800 ps, which electron temperature and density. Such corresponds to a spatial resolution interval distortions exist in the pedestal areas, of ~ 12 cm that is practically insufficient concerning mainly the ne profiles and for accurate registration of the narrow depending on both the temperature and the plasma pedestal area. The deconvolution density profiles. These distortions could be of the lidar signals is important not only minimal only at sufficiently slant for registration of the Te and ne profiles temperature profiles. In the case of with higher resolution, but also as a first asymmetric (e.g., exponentially-shaped) necessary step in investigating the pedestal laser pulses, distortions of the information evolution on the basis of the TS lidar data. about ne exist along the whole line of sight Using lidar data, the problem was solved within the plasma torus. These distortions of the correct determination of the real depend again on the ne and Te profiles and system response function. Both methods could be minimal at sufficiently slant Te under investigation, the Fourier- profiles. The above conclusions are valid deconvolution method [13,16] and the when using the fitting approach to stabilized matrix method [19], showed measuring ne and Te. When using center- good performance, which will lead to of-mass wavelength (CMW) approach, the better recovering of the electron temperature information is also distorted in temperature and concentration profiles. the case of asymmetric sensing pulses, The expected shift was also observed of depending on the ne profiles and the the seeming edges of the profiles from the steepness of the Te profiles. torus walls to the internal torus zone. After deconvolution, the electron concentration 2.3. Analysis of sensitivity of JET Core pedestal was observed to be steeper LIDAR data to the ELM evolution compared to the initially registered one. As a whole, the deconvolved Te and ne The sensitivity was demonstrated for profiles are close to those obtained by the first time of JET Core LIDAR data other diagnostics, namely, high-resolution from the upgraded system (during JET Thomson scattering. experimental campaigns C28, C29 and 117 Annual Report IE 2012
C30) to the ELM processes on the plasma fitting procedure, the correlation between edge. To this purpose, the mean evolution the estimates of the electron temperature curves were created for the pedestal and concentration leads to an increase in electron density and temperature the rms errors in determining the amplitudes and the pressure amplitude. concentration and the pressure, compared Also, the mean evolution rates of to the case of no correlation. In the non- restoration of the pedestal density, linear fitting procedure, the same temperature and pressure were calculated. correlation increases the ne-measurement A comparison was performed between error while influencing only slightly the the mean electron temperature evolution error in the determination of the pressure. curves, created by the JET Core lidar data, and the ECE radiometer electron Acknowledgements temperature data, sampled in the same lidar slice instants. A relatively good This work, supported by the European agreement was demonstrated between the Atomic Energy Agency (EURATOM) and two evolution curves. the Bulgarian National Science Fund The approach developed provides an through the Association EURATOM- opportunity for a simultaneous analysis of INRNE, was carried out within the the sensitivity of a large set of JET plasma framework of the European Fusion parameters to the ELM evolution within Development Agreement. The views and the entire plasma torus. opinions expressed herein do not This approach is deemed as very necessarily reflect those of the European promising for the analysis of the ITER Commission. performance and the dynamics of the ITER core plasma on the torus edge. References 2.4. Errors in the determination of the electron temperature and density and the [1] Mlyná J. et al 2007 Focus on: JET pressure using a fitting approach for TS The European Centre of Fusion data processing Research EFDA JET report EFD- R(07)01 (Culham Science Centre The rms errors were investigated, UK) http://www.jet.efda.org/wp- analytically and by computer simulations, content/uploads/Focus_on.pdf in the determination by a Thomson [2] Salzmann H et al 1988 The scattering lidar of the electron temperature LIDAR Thomson scattering diagnostic on JET Rev. Sci. Te and concentration ne and the pressure P in fusion plasmas, using a fitting approach. Instrum. 59/8 1451-6 Unlike previous such studies, we [3] Kempenaars M, Flanagan J C, Giudicotti L, Walsh M J, accounted for the correlation between the Beurskens M and Balboa I 2008 fluctuations of the statistical estimates of Enhancement of the JET edge the electron temperature and LIDAR Thomson scattering concentration. Analytical expressions of diagnostic with ultrafast detectors the errors as functions of the electron Rev. Sci. Instrum. 79 10E728 temperature were derived for the cases of [4] Kempenaars M, Balboa I, log-linear and non-linear fitting procedures Beurskens M, Flanagan J C and at a high measurement signal-to-noise Maslov M 2010 The JET core ratio. Computer simulations were also LIDAR diagnostic Proc. Int. Conf. performed of the nonlinear fitting Plasma Diagnostics (Pont-à- procedure, which confirmed the analytical Mousson, France 12-16 April results. It was shown that in the log-linear 2010) paper P30 118 Selected Projects
[5] Walsh M J et al 2006 Design resolution of long-pulse lidars J. challenges and analysis of the Opt. Soc. Am. A 10/11 2296-2306 ITER core LIDAR Thomson [15] Stoyanov D, Beurskens M, scattering system Rev. Sci. Dreischuh T, Gurdev L, Ford O, Instrum. 77 10E525 Flanagan J, Kempenaaras M, [6] Naito O, Yoshida H and Matoba T Balboa I and Walsh M 2010 Analytic formula for fully Resolving the plasma electron relativistic Thomson scattering temperature pedestal in JET from spectrum Phys. Fluids B 5/11 Thomson scattering core LIDAR 4256-8 data Proc. 37th EPS Conf. Plasma [7] Mattioli M 1974 Incoherent light Physics (Dublin Ireland 2010) scattering from high temperature Contributed papers. ECA 34A plasmas EUR-CEA-FC-752 P5.133 (European Physical [8] Mattioli M and Papoular R 1975 Society) ISBN 2-914771-62-2 Analysis of light scattering data [16] Dreischuh T, Gurdev L and from relativistic plasmas Plasma Stoyanov D 2011 Statistical Phys. 17 165-72 modeling of deconvolution [9] Lasarus E A 1983 A comment on procedures for improving the the calculation of Te from resolution of measuring electron Thomson scattering data Plasma temperature profiles in tokamak Phys. 25 1271-3 plasmas by Thomson scattering [10] Nicholson M G 1984 A comment lidar Proc. SPIE 7747 77470T on ‘A comment on the calculation [17] New LIDAR detectors can take of Te from Thomson scattering the heat at ITER 2012 Fusion In data’ Plasma Phys. Control. Europe 2 14 Nieckchen P and Fusion 26 1035-6 Rüth C eds (EFDA Close Support [11] Gurdev L, Dreischuh T and Unit–Garching) ISSN 1818-5355 Stoyanov D 2008 Potential https://www.efda.org/newsletter/n accuracies of some new ew-lidar-detectors-can-take-the- approaches for determination by heat-at-iter/ Thomson scattering lidar of the [18] Dreischuh T, Gurdev L and electron temperature profiles in Stoyanov D 2013 Efficiency of thermonuclear plasmas Proc. determining electron temperature SPIE 7027 702711 and concentration in [12] Dreischuh T, Gurdev L, Stoyanov D, thermonuclear plasmas by Beurskens M, Walsh M and Capel A Thomson scattering lidar Proc. 2009 Statistical modeling of the SPIE 8770 error in the determination of the [19] Maslov C, Angioni H, Weisen and electron temperature in JET by a JET-EFDA contributors 2009 novel Thomson scattering LIDAR Density profile behavior in JET H- approach Proc. 36th EPS Conf. mode plasmas: experiments versus Plasma Phys. Contributed papers linear gyrokinetic predictions ECA 33E P-2.149 (European Nucl. Fusion 49 075037 Physical Society) ISBN:2-914771- 61-4 [13] Gurdev L, Dreischuh T and Stoyanov D 2011 Deconvolution of long-pulse lidar profiles Lasers – Applications in Science and Industry Jakubczak K ed (Intech) pp 249-76 ISBN 978-953-307-755-0 [14] Gurdev L, Dreischuh T and Stoyanov D 1993 Deconvolution techniques for improving the
119 Annual Report IE 2012
DEVELOPMENT AND INTRODUCTION OF OPTICAL BIOPSY SYSTEM FOR EARLY DIAGNOSTIC OF MALIGNANT TUMORS
Contract #DMU-03-46/2011 Project financed by the National Science Fund
E Borisova Institute of Electronics, Bulgarian Academy of Sciences, 72, Tsarigradsko Chaussee, 1784 Sofia, Bulgaria.
Project Coordinator: Assoc. Prof. Dr. Ekaterina Georgieva Borisova.
Project team members: Irina Angelova Bliznakova, PhD student, IE-BAS; Aleksandra Zhivkova Zhelyazkova, PhD student, IE-BAS; Momchil Dimitrov Keremedchiev, PhD student, Queen Giovanna – ISUL University Hospital; Liliya Plamenova Angelova, IE- BAS.
Project terms: 2011-2013. Web-site: http://www.ncbp.dir.bg/Projects.htm
1. Main objectives excisions (surgical removal) allowing precise determination of the tumor ● Development and optimization of borders and metastasized cells in tissue optoelectronic instrumentation and and adjacent lymph nodes. methodology for optical biopsy and ● To introduce into the clinical practice their approbation and introduction of Queen Giovanna – ISUL University into the clinical practice for early Hospital thee systems and methods diagnosis of malignant tumors of the developed for diagnosis and skin and mucosa. monitoring. To determine basic ● Optimization of fluorescent and spectral parameters of biological reflective diffuse spectroscopic tissues in norm and pathology, and techniques for obtaining maximum expand the database of human tissues diagnostic accuracy in identifying the optical properties. To obtain original main types of malignant neoplasias data on fluorescence temporal in dermatology and gastroenterology. parameters of the main types of cancers of the skin and the 2. Specific project objectives gastrointestinal tract. ● To assist the career progress of the ● To achieve a maximum diagnostic young scientists in the project team by accuracy in identifying the main types publishing the scientific research of malignant neoplasias in results in peer-reviewed journals and dermatology and gastro-enterology. To presenting them at prestigious apply the developed 1-D and 2-D international conferences. To include systems for spectroscopic analysis to the work on systems development and local measurement of the spectral the results of the clinical studies as characteristics and the topography of integral and significant parts of the skin and mucosa tumors, and to dissertations of the PhD students - intraoperative monitoring of tumor members of the team: A. Zhelyazkova 120 Selected Projects
(systems and methods for spectral The research results will be published analysis), and M. Keremedchiev in specialized international journals and (clinical research and approbation of reported at conferences as necessary for systems for fluorescence diagnostic their dissemination; this will contribute to and intraoperative monitoring of GIT the overall carreer development of the tumors). project team members. The methods and equipment developed will be used in the 3. Methods dissertations of two young scientists.
Fluorescence analysis methods are used 5. Preliminary results – both autofluorescence and introduction of exogenous markers, as well as time- and 5.1. Measurements “in vivo” frequency-domain spectroscopy. Diffuse The term “optical biopsy” can be found reflectance spectroscopy methods are used in the description of different optical to expand the diagnostic capabilities and spectral techniques, such as fluorescence, applied to pigmented neoplasms. The absorption, scattering, reflectance, Raman measurements are performed with fiber scattering, NIR luminescence of biological optic probes – one-dimensional point tissues, but its most popular usage is when spectroscopy (1-D) and topographic (2-D) light-induced autofluorescence (LIAF) and images of the distribution of fluorescence diffuse reflectance spectroscopic signals from tissues in norm and techniques for tissue detection and pathology. Databases of fluorescent and determination are described. We applied reflective properties are created and these two techniques in a clinical trial computer-processing methods are investigation in view of introducing a skin introduced, namely, development of cancer optical biopsy system into the diagnostic algorithms to differentiate the clinical practice of Queen Jiovanna – main types of malignancies by type, stage ISUL University Hospital. of development and from benign In the LIAFS measurements, multiple pathologies. The spectral data are wavelength excitation was used of the compared and verified with histological endogenous fluorescence of benign and results included in a "gold standard". malignant cutaneous lesions. Initially, the lesions were classified visually by an 4. Results expected experienced dermatologist and dermatoscopically using ABCD scoring Systems will be developed for optical criteria. The second step was detection of biopsy of skin and mucosa malignant autofluorescence originating from the neoplasias, for primary diagnosis and for lesion and the surrounding normal skin intraoperative monitoring. Methods for using different excitation wavelengths, diagnosis of the main types of skin namely 365, 385, and 405 nm, emitted by neoplasias and their differentiation from several narrow-band light-emitting diodes. benign and dysplastic lesions will be An optical fiber probe was used to deliver introduced. A system and methods for the light from the LEDs and to collect the fluorescent intraoperative monitoring of fluorescence signals from the skin surface. tumor resection of the colon and rectum It consists of 7 fibers in a circular will be established. The methodology geometry. The central fiber is used for developed in previous research for autofluorescence signal detection; it is fluorescence diagnosis of tumors of the connected to a microspectrometric system, upper and lower gastrointestinal tract will while the surrounding six fibers are used to be expanded and improved. The devices deliver the excitation light from the LEDs to and methodologies will be clinically the skin under investigation. The same fiber- approved. optic probe was used for reflectance 121 Annual Report IE 2012
measurements. In the DRS mode of expanding the database of fluorescence examination, the illumination source was a spectra of major skin benign and broad-band halogen lamp. We thus acquired malignant pathologies, we expect to cutaneous diffuse reflectance spectra within develop an objective tool for cancer the 380-900 nm spectral region. detection and treatment monitoring. In Both the LIAFS and DRS spectra were order to clarify the autofluorescence recorded and stored using a fiber-optic origins of the signal detected, excitation – microspectrometer (USB4000, Ocean emission matrices were constructed using Optics Inc., Dunedin, FL, USA). A in vivo measurements on normal human personal computer was used to control the skin, figure 2. One can thus address the system and store and display the data using major fluorophores and compare these data the specialized microspectrometer to all EEM data for different cutaneous software OOI Base (Ocean Optics Inc., pathologies. Dunedin, FL, USA). Fluorescent data acquired in vivo from cutaneous lesions are presented in figure 1.
Figure 2. Excitation-emission matrix of normal skin, phototype II.
We are currently processing the spectral Figure 1. Autofluorescence spectra of normal skin, data obtained for subsequent medical compared with these of different dysplastic and statistical analysis. The results indicate malignant cutaneous lesions using excitation at that the optical biopsy method yields 405 nm. extremely high sensitivity (> 95 %) and After these initial medical and specificity (~97 %) in differentiating spectroscopic measurements, cytological carcinoma from other pathologies, and SE and/or histological samples were taken = 92 % and SP = 100 %, in differentiating from each lesion. The histological malignant melanoma. The results also examination results were used as a “gold revealed a very good correlation with the standard” to which all data acquired were histological skin analysis, as well as a compared. All subjects were Caucasian repeatability of the features of the volunteers – patients of Queen Giovanna – fluorescence and reflectance signals from ISUL University Hospital, with skin patient to patient, with the same type of phototypes I, II and III according to lesion being obtained by the LIAFS and Fitzpatrick classification. DRS measurements. Our work proceeded with assessing the origins of diagnostically significant 5.2. Measurements “ex vivo” spectral features; differentiation schemes Autofluorescence spectroscopy of were developed and examined. A clinical human tissues is a very attractive tool for trial for initial diagnosis of skin cancer is early diagnosis of cancer due to its high currently being performed at Queen sensitivity, easy-to-use measurement Giovanna – ISUL University Hospital; by methodology, lack of need for contrast 122 Selected Projects
agents application on the tissue under investigated. Excitation-emission matrices investigation, possibilities for real-time were constructed for a variety of tumors measurements and non-invasive tumor and normal samples. detection. However, no reliable and The excitation applied in the point- universal systems for fluorescence measurements was in the range from 250 detection of skin cancer have so far been to 550 nm, with a 5-nm step between the offered on the medical market. The excitation bands (2 nm); the emission was problems in developing such a system are detected in the 260 – 800 nm region using related to the great variety of benign and a FluoroLog3 spectrofluorimetric system malignant forms of skin pathologies; e.g., in a steady-state mode with a F3000 fiber- basal cell carcinoma lesions have more optic stand and a probe attached to the than 15 sub-types, squamous cell spectrometric system (HORIBA Jobin carcinoma lesions have about 10 different Yvon, France). In the EEMs formed, one subtypes, and all of them have a variety of can address all detected in vivomajor skin benign and dysplastic forms; moreover, fluorophores existing in the normal they are different, including by their cutaneous tissues based on their fluorescence properties, at the different coordinates (excitation max; emission max). stages of the lesion growth. Another very As an example, figure 3 presents an important disadvantage is the fact that EEM of basal cell carcinoma ex vivo, different endogenous fluorophores appear where the signal originating from in the integral autofluorescence signal structural compounds is much higher than originating from the skin under excitation that from the co-enzyme component, due at different wavelengths, which makes this to enzymes reduction in excised tissues. type of spectra difficult to analyse and compare with the fluorescence signals detected from various pathological skin lesions. The use of autofluorescence spectroscopy for early detection of cutaneous pathologies has been reported in a large number of publications. To stimulate in vivo autofluorescence emission from skin tissues, the research groups have applied a variety of excitation sources (and wavelengths), such as lasers, LEDs, narrow-filter broad-band lamps. Figure 3. EEM of basal-cell carcinoma ex vivo. However, a comprehensive review of the autofluorescence spectra emitted in vivo by A complete picture is thus obtained in normal human skin under excitation at vivo of the autofluorescence properties of different wavelengths is yet to appear in normal Caucasian skin; it can be used as a the literature. diagnostic basis for comparison with In the framework of this project, in the autofluorescence signals from different beginning of 2012, we started cutaneous pathologies. Detection of EEM investigations on determining the data from cutaneous tumors and mucosal endogenous fluorescent properties of neoplasia is in progress, as our first results cutaneous and mucosal (lower showed very good repeatability for the gastrointestinal tract) tissues – normal and same type of samples with specific diseased. changes that correlate with our previous The studies involved two systems – for investigations and our knowledge on the point spectroscopic measurements and for biochemical and morphological changes 2-D imaging of the tissues and lesions occurring in pathological tissues. 123 Annual Report IE 2012
Publications Plamenova L, Endogenous and exogenous 1. Borisova E, Pavlova P, Pavlova E, fluorescence of biological tissues for Troyanova P and Avramov L 2012 clinical applications, Optical biopsy of human skin – tool 20th Int. Conf. Advanced Laser for cutaneous tumours’ diagnosis Int. Technologies ALT'2012, 03-09 J. Bioautomation 16/1 53-72 ISSN: September 2012, Thun, Switzerland. 1314-2321 (on-line) 1314-1902 4. Pavlova E., Borisova E, Troyanova P 2. Borisova E, Pavlova E, Troyanova P, and Avramov L, Nikolova B and. Tsoneva I 2012 Light-induced autofluorescence and Optical biopsy – tool for initial diffuse reflectance spectroscopy of cancer diagnosis and monitoring of cutaneous tumors – clinical study, therapy Proc. European Medical 17th Int. School on Quantum Phys. Conf. – EMPEC’2012 (18-20 Electronics, 24-28 September 2012, October 2012, Sofia, Bulgaria) Nessebar, Bulgaria. pp172-9 ISBN: 978-954-91589-3-9 5. Borisova E, Angelova L, 3. Borisova E, Pavlova E, Troyanova P Keremedchiev M, Vladimirov B and and Avramov L 2012 Optical biopsy Avramov L, of cutaneous tumours Proc. 2nd Int. Endogenous and exogenous Conf. Laser Surgery and Medicine fluorescence of gastrointestinal CLSM'2012 (23-30 April 2012 tumors – initial clinical observations, Yokohama Japan) CLSM6-2 pp 2-3 17th Int. School on Quantum 4. Borisova E, Pavlova E, Troyanova P, Electronics, 24-28 September 2012, Nikolova B and. Tsoneva I 2012 Nessebar, Bulgaria. Autofluorescence of skin cancer – 6. Borisova E, Pavlova E, Troyanova P, tool for initial diagnosis and Nikolova B and Tsoneva I, monitoring of therapy Proc. 15th Int. Optical biopsy clinical tool for initial Conf. Laser Optics-2012 (St. diagnosis and therapeutic monitoring Petersburg, Russia, 25-29 June 2012) of cutaneous tumors, Int. School on Optics, Lasers and Conferences Biomedical Photonics (Saratov Fall Meeting - SFM’2012), 23-30 Sept. 1. Borisova E, Pavlova E, Troyanova P 2012, Saratov, Russia. and Avramov L, 7. Borisova E, Optical biopsy of cutaneous tumours, Autofluorescence spectral features of 2nd Int. Conf. Laser Surgery and normal skin – basis for comparison Medicine - CLSM'2012, 23-30 April with cutaneous pathologies, 2012, Yokohama, Japan. Int. School on Optics, Lasers and 2. Borisova E, Pavlova E, Troyanova P, Biomedical Photonics (Saratov Fall Nikolova B and. Tsoneva I, Meeting - SFM’2012), 23-30 Sept. Autofluorescence of skin cancer – 2012, Saratov, Russia. tool for initial diagnosis and 8. Borisova E, Pavlova E, Troyanova P, monitoring of therapy, Nikolova B and. Tsoneva I, 15th Int. Conference Laser Optics – Optical biopsy – tool for initial LO’2012, 25-29 June 2012 St. cancer diagnosis and monitoring of Petersburg, Russia. therapy, 3. Borisova E, Pavlova E, Troyanova P, European Medical Phys. Conf. 18-20 Keremedchiev M, Vladimirov B and October 2012, Sofia, Bulgaria.
124 Selected Projects
COHERENT OPTICS SENSORS FOR MEDICAL APPLICATIONS (COSMA)
Project financed by the EC (7th FWP)
Duration of the project: 2012 – 2016
Project Partners: 1. University of Siena - Department of Physics - Italy 2. Swansea University - College of Human and Health Sciences - UK 3. University College London - Department of Physics and Astronomy - UK 4. Bulgarian Academy of Sciences - Institute of Electronics - Bulgaria 5. Bar-Ilan University - Department of Chemistry - Israel 6. Jagiellonian University - Department of Physics - Poland 7. National Academy of Sciences of Armenia - Institute for Physical Research - Armenia 8. Siberian Branch of Russian Academy of Sciences - Institute of Automation and Electrometry - Russia 9. University of Calcutta - Department of Physics - India 10. University of California at Berkeley - Department of Physics - USA
The Project aims to develop a class of will be conducted. The ultimate achievable optical atomic magnetometers (OAMs) result of the collaboration will be to specifically designed for medical provide to every hospital and clinic access applications, namely: direct detection of to biomagnetic diagnostics, which is not magnetic fields from the human body possible now with the very expensive through real-time and/or multichannel SQUID-based diagnostics whose use is magnetocardiography; detection of signals confined to a few major hospitals. This is in ultra-low-field nuclear magnetic not only because OAMs have potential for resonance (NMR) and in magnetic- providing high-precision measurements, resonance imaging (MRI). The project is but they also do not require the cryogenic being implemented with the participation temperatures intrinsic for the SQUID of ten research groups from Italy, the operation nor a large budget. OAMs make United Kingdom, Bulgaria, Israel, Armenia, it possible to achieve a much smaller size Russia, India, Poland and the USA. of the sensor, leading to better spatial Transfer of knowledge will be carried resolution and better coupling between the out to develop OAMs for clinical use, to sensor and the sample. Moreover, an train young researchers in the design of original approach will be adopted that novel instrumentation for medical consists of compensating rather than applications, to start a comprehensive and screening spurious magnetic fields. This coordinated research activity aimed to eliminates the need for an expensive mu- make biomagnetism detection and analysis metal isolated room, which will be a very important health issue. The activity replaced by coils powered by advanced will specifically include tests of the electronic equipment suitable for ultra- magnetometers in hospital environment low-noise current generation and active where magnetic-field-based diagnostics control of the atomic Larmor frequency.
SCIENTIFIC EVENTS
● Tenth Anniversary International Conference on Electron Beam Technologies (EBT’2012)
● Seventeenth International School on Quantum Electronics Laser Physics and Applications (ISQE’2012)
127 Annual Report IE 2012
Electron TENTH ANNIVERSARY Beam INTERNATIONAL CONFERENCE ON Technologies ELECTRON BEAM TECHNOLOGIES EBT’2012
International 1 – 4 June 2012, Varna, Bulgaria Conference Varna
The EBT’2012 was held from 1 to 4 efficiency of industrial production, June 2012 in Varna Grand Hotel in the creating new products and improving the Black Sea Resort Sts. Constantine and living standards. The studies presented at Elena near Varna, Bulgaria. This triennial the EBT’2012 Conference dealt with meeting brings together physicists, sophisticated modern e-beam nano- chemists, materials and electronics technologies for surface modification and engineers from universities, research deposition of functional coatings, recent institutions and the industry involved in work on e-beam physics and generation, various studies and applications of electron e-beam welding, cutting, melting and beam techniques and technologies. The refining, and electron accelerator conference is organized by the Institute of applications for various materials Electronics of the Bulgarian Academy of treatment. These was reflected in the Sciences in cooperation with the topics included during the EBT’12 Technological Center of Electron Beam Conference program: and Plasma Technologies Ltd., Sofia and physics of intense electron beams; the Union of Electronics, Electrical electron-optical systems and Engineering and Telecommunications, facilities for measurement and control of Bulgaria. The Chairman of the electron beams; International Organizing Committees of all free electron devices, electron ten EBT conferences has been Prof. beam welding; Dr.Sci. Georgi Mladenov, Corresponding electron beam melting and Member of BAS. refining, high-rate deposition of The conference is one of a series which metallurgical coatings; started in 1985 in Varna, the city that has surface modification; remained the venue for all subsequent thermal processing and thin films meetings. During the period since the First fabrication by electron beams; International Conference on EBT the field has seen considerable progress. The electron lithography; success of all ten events of series clearly electron beam curing of polymers demonstrated that the scientists and and composites; engineers working in academia and in ion lithography, ion implantation; industrial R&D laboratories have modeling of physical processes continued to make important contributions during the interaction of charged particle to the further development of the field. beams with materials; The papers presented at this anniversary applications of charged particles conference and the EBT’2012 Proceedings beams in nanotechnology and nano- published exhibit a wide scope of activities electronics, in medicine and industry; and the substantial potential of the electron beam equipment design technologies developed in increasing the and automation. 128 Scientific Events
The Conference proceeding was printed and distributed for the third time as a regular issue of the most respected Bulgarian scientific and technical journal in our field, Elektrotechnica & Elektronica (Electrical Engineering and Electronics – http://www.ceec.fnts.bg/sp- E+E.htm), v.5-6, 2012. The number of published papers is 62, presenting the research results of 176 scientists from academic institutions or industry of many countries: Germany, Russian Federation, Ukraine, Czech Republic, Slovak Republic, UK, Japan, Romania, France, Algeria, China, India, etc. Leading companies, such as ALD Vacuum following journals: Elektrotechnica & Technologies GmbH, Hanau, Germany; Elektronica, v.5-6, 2009; Elektrotechnica VON ARDENNE, Dresden, Germany; & Elektronica, v.5-6, 2006; Vacuum, v.77 JSC "NVO "Chervona Hvilya", Kiev, (4), 2005; Vacuum, v.62 (2- 3), 2001 and Ukraine; TWI, Cambridge, UK; Materials and Manufacturing Processes, TARGETS LTD, Plovdiv, had the v.14 (3), 1999, USA. opportunity to present their latest e-beam The latest, 10th, meeting, as all nine equipment and products. previous ones, provided an excellent The researchers in the e-beam forum for exchange of results, experience, technologies field now celebrate 50 years knowledge and ideas in the development since the first machines and industrial of EB technologies; as usual, it was also a technologies based on application of place for establishing personal and intense electron beams in vacuum were business contacts and finding partners for developed. The Proceedings of the EBT joint work programs and networks. The Conferences in Varna organized during 10th EBT Conference owes its success to the past 27 years trace the history of ideas all participants, to the International and the basic objectives in our field, as Organizing Committee and to the Local well as the personal successful careers of Organizing Committee. We would also three generations of researchers. The EBT like to thank all authors for their valuable Proceedings have been published in the contributions to the Proceedings.
INTERNATIONAL ORGANIZING COMMITTEE
R. Bakish (USA) E. Koleva (Bulgaria) E. M. Oks (Russia) J.-P. Bellot (France) I. Kostic (Slovak Republic) U. Seyfert (Germany) U. Gohs (Germany) N. Kuksanov (Russia) T. Tanaka (Japan) N. Grechanyuk (Ukraine) G. Mattausch (Germany) D. Trushnikov (Russia) V. Engelko (Russia) G. Mladenov (Bulgaria)-Chairman V. Vassileva (Bulgaria) A. Kaydalov (Ukraine) M. Nemtanu (Romania) K. Vutova (Bulgaria) K. Kawabata (Japan) O. Nazarenko (Ukraine) R. Zenker (Germany)
LOCAL ORGANIZING COMMITTEE
Co-chairs Members K. Vutova, E. Koleva V. Vassileva, V. Donchev, I. Kolev 129 Annual Report IE 2012
SEVENTEENTH INTERNATIONAL SCHOOL ON QUANTUM ELECTRONICS LASER PHYSICS AND APPLICATIONS (ISQE)
24-28 September 2012, Nessebar, Bulgaria
The International School on Quantum scientists. They participated in a Electronics Laser Physics and competition for the best poster Applications has been organized biennially presentation. The reports were evaluated by the Institute of Electronics of the by an international jury, which awarded Bulgarian Academy of Sciences since EPS, OSA and SPIE prizes to the eight 1980. best doctoral students. On the School’s last For more than 30 years now, the School day, these young researchers were given has been providing opportunities to young the opportunity to present orally their scientists to present the results of their works. It must be noted that the young research and discuss them with renowned people from the Institute of Electronics scientists from all over the world. Besides won four of the awards. becoming a well known center for training (http://www.isqe2012.dir.bg/awards.htm). of young scientists, over the years the Following a peer reviewing procedure, School has turned into a place for holding the works selected among those presented working meetings on current international at the 17th ISQE will be published in a programs and projects, as well as for special issue of Proceedings of SPIE. establishing new scientific contacts. The The School was accompanied by an results are the considerable number of exhibition of scientific equipment international collaborations and contracts manufactured by leading companies in the concluded with, and specializations laser physics and applications field, conducted in, prominent research centers. namely, Toptica Photonics AG, Coherent The 17th issue of the International Inc., ASTEL Ltd. and Andor Technology. School on Quantum Electronics took place The companies’ representatives scientific in Festa Panorama Hotel, Nessebar, from exhibition were given time for presenting 24 to 28 September 2012. It was attended the products and their applications in the by 97 participants from 17 countries: fields included in the School’s topics. Armenia, Austria, Belarus, Belgium, The 17th ISQE was announced in the Bulgaria, France, Germany, Greece, Italy, web-calendars of the cooperating and Poland, Romania, Russia, Spain, Sweden, participating organizations. Turkey, Ukraine, and the UK. In 2012, the School was supported by The participants were acquainted with the Optical Society of America (OSA), the the latest achievements in the fields of International Society for Optics and laser light-matter interaction, laser Photonics (SPIE), the Bulgarian Academy spectroscopy and metrology, remote laser of Sciences, the European Physical Society sounding of the atmosphere and ecology, (EPS), the Bulgarian National Science laser systems and non-linear optics and the Fund, the National Technical University of biological and medical applications of Athens, the IEEE Bulgarian Section, the lasers. VIVACOM Fund, the European Besides the 18 invited lectures Organization for Aerospace Research and delivered by eminent scientists in the Development (EOARD), SIEMENS respective fields, the School’s program Bulgaria and American Elements Co. included two poster sessions where over We are grateful to the sponsors and 80 works were presented by young cooperating organizations for their 130 Scientific Events
generosity that enabled us to support the correspondence, abstracts, and manuscripts attendance of students and provided support for the proceedings. with mailing, printing, renting the We would also like to thank all authors conference site, etc. for their valuable contributions to the 17th ISQE’12 was successful due to the proceedings and to the school, and all efforts of many people. The International reviewers for their hard and tedious, but Program Committee shaped the scientific very important, work. program and ensured high-quality plenary The next conference in the series will presentations by careful selection of the be held in 2014. invited speakers. The Local Committee bore the brunt of the organization, both at A. Daskalova, Chair of the School. the conference site and in dealing with
Website of the event: http://www.isqe2012.dir.bg
INTERNATIONAL ADVISORY COMMITTEE
Name Affiliation Country
Chairman:
Prof. Alexandros National Technical University of Athens Serafetinides (NTUA), Applied Physics Department GREECE
Members: University of California at Berkley, Prof. Dmitry Budker Department of Physics USA Lund University Medical Laser Center, Prof. Stefan Department of Physics, Lund Institute of Andersson-Engels SWEEDEN Technology, University of Lund
Dr. Marc Beurskens JET-EFDA, Culham Science Center UK
Prof. Wolfgang Institute of Applied Physics, Husinsky Vienna University of Technology AUSTRIA
Acad. Nikola Institute of Solid State Physics, Sabotinov Bulgarian Academy of Sciences BULGARIA Institute of Electronic Structure and Lasers - Prof. Costas Fotakis FORTH GREECE Department of Physics, Dr. Shane Mayor California State University, Chico USA 131 Annual Report IE 2012
Prof. Luigi Moi Department of Physics - University of Siena ITALY
Assoc. Prof. Dr. Institute of Electronics, Lubomir Kovachev Bulgarian Academy of Sciences BULGARIA Coherentia CNR-INFM and Dipartamento di Dr. Xuan Wang Scienza, Universita Degli Studi di Napoli Federico II ITALY Department of Physics and Astronomy, Dr. Peter Balling Aarhus University DENMARK Advanced Laser Research Section, Prof. Kenzo Institute of Advanced Energy, Miyazaki Kyoto University, Gokasho, Uji, Kyoto, Japan JAPAN Erasmus Medical Cener, Centrum voor Prof. Henricus Optische Diagnostiek en Therapie Afdeling Sterenborg Radiotherapie, Rotterdam The NEDERLANDS Laser Spectroscopy Laboratory, Prof. David Institute for Physical Research, Sarkisyan ARMENIA Armenian Academy of Sciences
Prof. Gerard The Szewalski Institute, Slivinski Polish Academy of Sciences POLAND
Prof. Stelios Institute of Electronic Structure and Lasers - Tzortzakis FORTH GREECE
Prof. Arnaud Centre de Physique Théorique, Couairon Ecole Polytechnique FRANCE National Institute for Lasers, Plasma and Dr. Maria Dinescu Radiation Physics NILPRP, Bucharest ROMANIA
LOCAL ORGANIZING COMMITTEE
Name Affiliation Country Chair: Institute of Electronics, Dr. Albena Daskalova Bulgarian Academy of Sciences BULGARIA Vice Chair: Institute of Electronics, Dr. Anna Dikovska Bulgarian Academy of Sciences BULGARIA Secretary: Institute of Electronics, Ms. Irina Bliznakova Bulgarian Academy of Sciences BULGARIA 132 Scientific Events
Members: Affiliation Country Institute of Electronics, Assoc. Prof. Dr. Tanja Dreischuh Bulgarian Academy of Sciences BULGARIA Institute of Electronics, Dr. Elena Taskova Bulgarian Academy of Sciences BULGARIA Institute of Electronics, Dr. Petko Todorov Bulgarian Academy of Sciences BULGARIA Institute of Electronics, Mr. Ivan Grigorov Bulgarian Academy of Sciences BULGARIA Institute of Electronics, Mr. Chavdar Ghelev Bulgarian Academy of Sciences BULGARIA Institute of Electronics, Mr. Nikolay Petrov Bulgarian Academy of Sciences BULGARIA Institute of Electronics, Ms. Aleksandra Zhelyazkova Bulgarian Academy of Sciences BULGARIA
MAIN SCIENTIFIC TOPICS
. Laser - matter interactions
. Laser spectroscopy and metrology
. Laser remote sensing and ecology
. Lasers in biology and medicine
. Laser systems and nonlinear optics
HONORARY AWARDS
● Assoc. Prof. Dr. Korneli Grigorov ● Prof. Dr.Sc. Petar Atanasov, Corresponding member of BAS ● Assoc. Prof. Dr. Ekaterina Borisova ● Assoc. Prof. Dr. Teodor Milenov ● Doctoral student Anna Krasteva ● Doctoral student Rumen Nikov ● Physicist Lilia Angelova ● Doctoral student Rosen Nikov ● Doctoral student Aneliya Dakova ● Mathematician Veliko Donchev
135 Annual Report IE 2012
The Scientific Council of the Emil E. DJAKOV INSTITUTE OF ELECTRONICS Djakov Institute of Electronics BULGARIAN ACADEMY OF SCIENCES presented the 2011 Academician Emil Djakov Annual Award to Assoc. Prof. Dr. Korneli Grigorov in recognition of the results of studies on thin films published in: Grigorov K G, Oliveira I C, Maciel H S, Massi M, Oliveira M S, Amorim Jr J and Cunha C A 2011 Optical and morphological properties of N-doped TiO2 thin LAUREATE films Surface Science 605 775 ACADEMICIAN DJAKOV AWARD 2011
Prof. Dr.Sc. P. A. Atanasov, Corresponding Member of BAS, was bestowed the Honorary Award of Keio University, Japan, for his great scientific contribution to the High Level Global Cooperation for Leading Edge Platform on Access Space Program.
Assoc. Prof. Dr. E. G. Borisova was conferred the Great Pythagoras Prize of the Ministry of Education, Youth and Science for 2012 in the Young Scientist Category for her studies in the field of photonics – development of non-invasive techniques for early cancer diagnostics.
136 Awards
Assoc. Prof. Dr. E. G. Borisova was awarded the Honorary Diploma of the D. S. Rozhdestvensky Optical Society for having met the highest standards of excellence in her presentation “Autofluorescence of skin cancer – a tool for initial diagnosis and monitoring of therapy” at the Fifteenth International Conference Laser Optics-2012 (Sankt Peterburg, Russia, 25-29 June 2012).
Assoc. Prof. Dr. Teodor Milenov was presented the Gold Medal of the National Chiao-Tung University, Hsin-Chu, Taiwan (ROC), for his contribution to the joint program of studies between the BAS and the National Chiao- Tung University on crystals of complex oxides and semicon- ductors.
Ms. Anna Krasteva, a doctoral student at the Institute of Electronics, won the SPIE First Prize for a Poster Presentation at the Seventeenth International School on Quantum Electronics (XVII ISQE’2012), 24-28 September 2012, Nessebar, Bulgaria.
137 Annual Report IE 2012
Mr. Rumen Nikov, a doctoral student at the Institute of Electronics, won the SPIE First Prize for a Poster Presentation at the Seventeenth International School on Quantum Electronics (XVII ISQE’2012), 24-28 September 2012, Nessebar, Bulgaria.
Ms. Lilia Angelova, a physicist at the Institute of Electronics, won the SPIE Third Prize for Poster Presentation at the Seventeenth International School on Quantum Electronics (XVII ISQE’2012), 24- 28 September 2012, Nessebar, Bulgaria.
Mr. Rosen Nikov, a doctoral student at the Institute of Electronics, won the the Optical Society of America Third Prize for Poster Presentation at the Seventeenth International School on Quantum Electronics (XVII ISQE’2012), 24-28 September 2012, Nessebar, Bulgaria.
Ms. Aneliya Dakova, an extramural doctoral student at the Institute of Electronics, won the European Physical Society Prize for Best Poster Presentation at the Seventeenth International School on Quantum Electronics (XVII ISQE’2012), 24-28 September 2012, Nessebar, Bulgaria. 138 Awards
Mr. Veliko Donchev, a mathematician at the Institute of Electronics, was awarded a St. Kliment Ohridski University of Sofia Honorary Diploma for scientific contributions.
Mr. Veliko Donchev, a mathematician at the Institute of Electronics, won Eureka Foundation’s Nikola Obreshkov Stipend for developments in the field of mathematical sciences.
On the occasion of the Bulgarian National Awakeners’ Day, November 1, Ms. Anna Krasteva, a doctoral student at the Institute of Electronics, was distinguished as a Finalist in the original doctoral student project category of The Bulgarian Contribution to the Contemporary Research Area Competition organized jointly by the Bulgarian Academy of Sciences and the Ikuo Hirayama Center.