CPPA 2019 Xviiith International Conference on Plasma Physics and Application Th Nd 20 –22 June 2019, Ias, I, Romania

CPPA 2019 XVIIIth International Conference on Plasma Physics and Application th nd 20 –22 June 2019, Ias, i, Romania

Book of Abstracts

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LaTeX Template adapted from: A Basic Conference Abstract Booklet under License Creative Commons CC BY 4.0 www.overleaf. com CONFERENCE CHAIRS

Gheorghe DINESCU INFLPR, Bucharest

Lucel SIRGHI UAIC, Ias, i

HONORARY CHAIR

Gheorghe POPA UAIC, Ias, i

INTERNATIONAL SCIENTIFIC COMMITTEE

F. AREFI-KHONSARI, Paris, France T. BELMONTE, Nancy, France H. BIEDERMAN, Praga, Czech Republic A. BOGAERTS, Antwerpen, Belgium M. BRAIC, Bucharest, Romania V. COLOMBO, Bologna, Italy M. ECHIM, Brussels, Belgium P. FAVIA, Bari, Italy E. GOGOLIDES, Athens, Greece H. KERSTEN, Kiel, Germany L. KRAVETS, Dubna, Russia A. LACOSTE, Grenoble, France C. LEYS, Ghent, Belgium D. MARIC, Belgrade, Serbia T. MINEA, Orsay, France M. MOZETIC, Ljubljana, Slovenia M.C.M. van de SANDEN, Nieuwegein, The Netherlands D.C. SCHRAM, Eindhoven, the Netherlands E. STAMATE, Roskilde, Danemark F. SPINEANU, Bucharest, Romania

SCIENTIFIC SECRETARIES

Claudiu Costin UAIC, Ias, i Bogdana Mitu INFLPR, Bucharest

iii LOCAL ORGANIZING COMMITTEE MEMBERS

T. ACSENTE, INFLPR, Bucharest

C. AGHEORGHIESEI, UAIC, Ias, i

R. APETREI, UAIC, Ias, i M. BAZAVAN, University of Bucharest ˘ A. BES, LEAGA, UAIC, Ias, i

C. BORCIA, UAIC, Ias, i

G. BORCIA, UAIC, Ias, i V. BRAIC, INOE, Bucharest ˘ A.L. BREABAN, UIAC, Ias, i

A.S. CHIPER , UAIC, Ias, i

M. DOBROMIR, UAIC, Ias, i

N. DUMITRAS, CU, UAIC, Ias, i

C. GERBER, UAIC, Ias, i A. LAZEA-STOYANOVA, INFLPR, Bucharest

D. LUCA , UAIC, Ias, i C.P. LUNGU, INFLPR, Bucharest M. MAGUREANU, INFLPR, Bucharest ˘ ˘ I. MIHAILA, UAIC, Ias, i ˘ ˘ A. NASTUT, A UMF, Ias, i M. NISTOR, INFLPR, Bucharest M. OSIAC, University of Craiova ˘ V. POHOAT, A, UAIC, Ias, i S.D. STOICA, INFLPR, Bucharest C. TICOS, INFLPR, Bucharest

V. TIRON, UAIC, Ias, i ˘ I. TOPALA, UAIC, Ias, i

I.-L. VELICU, UAIC, Ias, i S. VIZIREANU, INFLPR, Bucharest R. VLADOIU, Ovidius University, Constanta G. VOITCU, INFLPR-ISS, Bucharest

CPPA 2019 Web-Page:

Alexandru Ioan Cuza University, Faculty of Physics

Ias, i Plasma Advanced Research Centre (IPARC)

Bd. Carol I nr. 11, 700506-Ias, i, Romania http://www.plasma.uaic.ro/cppa2019/

iv Contents

Invited Lectures 1

I-01 Kinetic effects induced in a plasma crystal by an electron beam (C.M. Ticos, , D. Ticos, , A. Scurtu, J.D. Williams)...... 3 I-02 Plasma polymer films with high similarity to their classical counterparts (J. Kousal, Z.K. Raˇsková, Z. Krtouˇs, J. Sedlaˇr´ıková, L. Kuˇcerová, P. Solaˇr, S. Ali-Ogly, A. Choukourov, L. Hanyková,H. Biederman, M. Lehocký )...... 4 I-03 Challenges and opportunities in transparent conducting oxide thin films deposited by magnetron sputtering (E. Stamate)...... 5 I-04 Synthesis of tungsten based nanoparticles by means of magnetron sputtering combined with gas aggregation (T. Acsente, L.G. Carpen, E. Matei, G. Dinescu)...... 6 I-05 Bipolar HiPIMS: a step further in exploring new perspectives and horizons in coatings deposition (I.-L. Velicu, V. Tiron, D. Cristea, I. Mih˘ail˘a,D. Munteanu, G. Popa).7 I-06 Inverted Fireballs (R. Schrittwieser, C.T. Teodorescu-Soare, C. Ionita, D.G. Dimitriu, O. Vasilovici, S. Gurlui, S.A. Irimiciuc, B. Hodoroaba, T. O’Hara, L. Amarandi, F. Enescu, F. Mazzanti, R. Stenzel, J. Gruenwald)...... 8 I-07 Particle modelling of HiPIMS plasma (T. Minea, A. Revel, C. Costin)...... 9 I-08 Double layers and oscillatory phenomena in laser ablation transient plasmas: optical

and electrical investigations (C. Focs, a)...... 10 I-09 Laser and plasma processing of thin ﬁlms and nanostructures for applications in opto-/micro-electronic devices (A. Bercea, C. Constantinescu, C. Champeaux, F. Dumas-Bouchiat)...... 11

Oral Presentations 13 O-01 Electromagnetic model for simulations plasma wall-touching kink and vertical modes in ITER tokamak (C.V. Atanasiu, L.E. Zakharov, K. Lackner, M. Hoelzl)...... 15 O-02 Dynamic generation of shear of the velocity at the L to H transition (F. Spineanu, M. Vlad, A. Croitoru)...... 16 O-03 Electron-impact excitation and dissociative recombination of molecular cations + + in cold plasma: application to BeH ,H2 and their isotopomers (F. Iacob, N. Pop, J. Zs Mezei, S. Niyonzima, M.D. EpéeEpée,O. Motapon, K. Chakrabarti, I.F. Schneider)...... 17 O-04 Investigation of direct and resonance contributions to the electron-impact excitation of neon-like Mo ion (C. Iorga, V. Stancalie)...... 18 O-05 Efficient algorithms for 3D modeling of fusion technology relevant superconductor cables from X-ray tomography data (D. Dumitru, I. Tiseanu)...... 19 O-06 On the Penning processes in atmospheric pressure plasma jet in helium with

oxygen impurities (I. Topal˘a, A.S. Chiper, V. Pohoat,˘a,I. Mih˘ail˘a,C. Anastassiou, C. Lazarou, G.E. Georghiou)...... 20 O-07 Pulsed Solid-State Lasers for Plasma Diagnostics and Processing (E. Colin, R. Sade) 21 O-08 Non-Maxwellian velocity distributions within plasma jets interacting with increasing magnetic ﬁelds: particle-in-cell simulations (G. Voitcu, M. Echim)...... 22 O-09 Hidden drifts, a source of heavy impurity pinch in tokamak plasmas (M. Vlad, F. Spineanu)...... 23

v O-10 Stochastic transport in strongly turbulent plasmas (D.I. Palade, M. Vlad, F. Spineanu) 24 O-11 Interstellar carbonaceous dust analogs obtained in plasma. Morphology and chemical

characterization (I.C. Gerber, I. Mih˘ail˘a,L.V. Soroaga, A.S. Chiper, V. Pohoat,˘a, I. Topal˘a)...... 25 O-12 Multilayered all-oxide plasma coatings for colored glazed solar thermal collectors

(I. Pana, C. Vit,elaru, M. Dinu, N.C. Zoita, A.E. Kiss, M. Braic)...... 26 O-13 Study of TID propagation parameters using Dynasonde measurements from Wallops Island, VA (C. Negrea)...... 27 O-14 Cold atmospheric plasma as an associative agent for chemotherapy of breast cancer (C.T. Mihai, I. Mih˘ail˘a,I.C. Gerber, D. Gherghel, G. Vochita, C. Anastassiou, I. Topal˘a)...... 28 O-15 Surface dielectric barrier discharge micro-plasma in humid air at atmospheric

pressure (A. Dascalu, V. Pohoat,˘a,K. Shimizu, L. Sirghi)...... 29 O-16 Magnum-PSI plasma parameters mapping by electrical probes (C. Costin, I. Mih˘ail˘a,

H. van der Meiden, V. Anit,a, S. Brons, J.M.W. Vernimmen, J. Scholten)..... 30

Posters Topic 1 Fundamental processes in plasmas, modelling and simulation. 31 P1-01 Transient inward helical orbits and heavy impurity accumulation in tokamak (A. Croitoru, F. Spineanu, M. Vlad)...... 33 P1-02 Nonlinear dynamics of non-concentric multiple double layers as a source of low- temperature plasma instabilities (D.G. Dimitriu, S.A. Irimiciuc, M. Agop)..... 34 P1-03 High–β plasmas: from space observations to lab experiments (M Lazar)...... 35 P1-04 Turbulence in planetary plasmas, at the interface with the solar wind: Observations and Techniques (M. Echim, P. Kovacs, N. Dwivedi, E. Yordanova, E. Teodorescu, C. Munteanu)...... 36 P1-05 Minimum entropy production in the process of ﬁreball formation (S. Popescu, D.G. Dimitriu)...... 37

Posters Topic 2 Plasma diagnostics. Gas discharge physics, dusty plasma, plasma sources and reactors at low and atmospheric pressure. Laser plasmas. 39 P2-01 Time-space evolution of pulsed dielectric barrier discharge in presence of ﬁber-based woven substrate (I.C. Gerber, I. Topal˘a,G. Borcia)...... 41 P2-02 Preliminary Characterization of a Plasma Driven Shock Tube (D. Bivolaru, G. Papadopoulos)...... 42

P2-03 Stretching and compression of double plasma vortex (A. Scurtu, D. Ticos, , E. Con-

stantin, C.M. Ticos, )...... 43 P2-04 Particle Tracking Velocimetry of Plasma Crystal Rotation Induced by Electron

Beams (D. Ticos, , A. Scurtu, E. Constantin, C. M. Ticos, )...... 44 P2-05 Ion propulsion based on microwave vaporization and ionization of the metal wires (C.P. Lungu, M. Mogildea, G. Mogildea, C.M. Achim (Popa), C. Porosnicu, P. Dinca, B. Butoi, O. Pompilian, C. Staicu, P. Chiru)...... 45 P2-06 Mass spectrometry investigation during magnetron sputtering of PTFE (S.D. Stoica, B. Mitu, V. S˘atulu,G. Dinescu)...... 46 P2-07 Vacuum Ultra-Violet irradiance measurements of an atmospheric pressure AC high voltage driven plasma jet (A.V. Nastuta, T. Gerling, P. Holtz)...... 47 P2-08 Experimental study of an atmospheric pressure piezoelectric plasma jet (J. Orejas, C. Muja, C. Tendero, F. Pigache, Ph. Guillot)...... 48

Posters Topic 3 Plasma material processing. Surface treatments, thin ﬁlm deposition, plasma assisted nano-fabrication techniques. 49 P3-01 Structural characterization of Au-incorporated tungsten trioxide used for improving gas sensing (I. Tirca, M. Jigau, M. Osiac)...... 51 P3-02 On the erosion of Tungsten surfaces exposed to an atmospheric pressure microdischarge (V. M˘ar˘ascu,C. Stancu, A. Bonciu, V. S˘atulu,G. Dinescu)...... 52

vi P3-03 Silicon based coatings for composite membranes with tunable wettability properties (V. S˘atulu, B. Mitu, L. Kravets, G. Dinescu)...... 53 P3-04 Surface properties of polymers treated by air atmospheric-pressure discharge (E. Birleanu, I. Mih˘ail˘a,I. Topal˘a,G. Borcia)...... 54 P3-05 Morphology and structural investigations of graphene / graphite nanowalls grown by capacitively coupled RF-PECVD at various substrate temperatures (O.-G. Simionescu, A. Avram, R. Popa, O. Tutunaru, C. Pachiu, G. Dinescu)...... 55 P3-06 Conduction anisotropy in carbon nanowall layers obtained by a low-pressure

plasma jet (B.I. Bit,˘a, S. Vizireanu, S.D. Stoica, S.A. Yehia, A. Radu, S. Iftimie, G. Dinescu)...... 56 P3-07 Atmospheric pressure plasma treatment of surfaces for cleaning and modiﬁcation

(M. Zarif, S.A. Yehia, S. Vizireanu, V. S˘atulu,V. M˘ar˘ascu, B.I. Bit,˘a,G. Dinescu) 57 P3-08 Effect of nitrogen content on physical and mechanical properties of tungsten films deposited by CMSII (F. Baiasu, M. Gherendi, E. Grigore)...... 58 P3-09 Wearing and friction properties of octadecyltrichlorosilane layers deposited by chemical vapour deposition on plasma activated silica surfaces (S. Teodoroff-Onesim,

A. Bes, leag˘a,L. Sirghi)...... 59 P3-10 Chemical vapour deposition of octadecyltrichlorosilane on plasma activated silica

surfaces (A. Bes, leag˘a, S. Teodoroﬀ-Onesim, L. Sirghi)...... 60

P3-11 The use of HiPIMS for DLC deposition of micrometer thick coatings (C. Vit,elaru, A.E. Kiss, A.C. Parau, M. Dinu, L.R. Constantin, A. Sobetkii, T. Kubart )..... 61 P3-12 CNW/WO3 hybrid nanostructures obtained by plasma assisted thermal evaporation

(L.G. Carpen, T. Acsente, S. Vizireanu, B.I. Bit,˘a,V. S˘atulu,E. Matei, G. Dinescu) 62 P3-13 Chitosan-based patches obtained by atmospheric pressure dielectric barrier discharge plasma treatment (B. Mitu, S. Iorgoaia, C. Chifiriuc, C.M. Saviuc, G. Dinescu) 63 P3-14 Carbon-based thin films for high-power laser applications (L. Dinc˘a, B. Diaconescu, V. S˘atulu,V. M˘ar˘ascu,C. Gheorghiu, B. Mitu)...... 64 P3-15 Plasma dry etching, a critical step in SiC device technology. Physico-chemical mechanisms, and applications (M. Lazar, J. Béal,F. Marty, A. Rumyantseva)... 65 P3-16 Plasma modification of vertically graphene for energy storage ( S. Vizireanu,

S.D. Stoica, B.I. Bit,˘a,A. Trefilov, A. Achour, M. Iordoc, G. Dinescu)...... 66 P3-17 Indium oxide thin films by pulsed electron beam deposition: growth and plasma investigation (F. Gherendi, N.B. Mandache, M. Nistor)...... 67 P3-18 Fabrics with electromagnetic shielding properties achieved by magnetron sputtering deposition (A.A. Ardeleanu, C. Stancu, L. Surdu, E. Visileanu, I-R. R˘adulescu, M. B˘adic,C. Morari, B. Mitu)...... 68 P3-19 Copolymerized films under atmospheric pressure plasma conditions (V. Chiriac,

I. Topal˘a,L. Curecheriu, M. Dobromir, N. Dumitras, cu)...... 69 P3-20 Enhanced optical and mechanical properties of silicon dioxide thin ﬁlms deposited by reactive HiPIMS (V. Tiron, I.-L. Velicu, A. Ceban, D. Cristea, G. Bulai, D. Munteanu) 70 P3-21 Synthesis and characterization of ZnO-loaded TiO2 nanotube array layers for enhanced photocatalytic application (M. Dobromir, C.T. Teodorescu-Soare, R. Apetrei,

G. Stoian, V. Pohoat,˘a,D. Luca)...... 71 P3-22 Properties of multilayer coatings obtained by pulsed laser deposition (V. Ion, N.D. Scarisoreanu, A. Andrei, A. Bonciu, M. Dinescu)...... 72 P3-23 Characterization of chlorinated polythiophene ﬁlms obtained under the plasma

conditions (I. Mih˘ail˘a,V. Chiriac, V. Tiron, L. Curecheriu, N. Dumitras, cu).... 73 P3-24 Modiﬁcation of elasticity modulus and work of adhesion of PDMS surface by treatment in negative glow plasma of a luminescent discharge in argon at low pressure (G. Tifui, S. Teodoroﬀ-Onesim, L. Sirghi)...... 74

Posters Topic 4 Plasma Chemistry. Plasma applications in environment management, biology, medicine and agriculture. 75 P4-01 Atmospheric pressure plasma jet submerged in liquid for dyes decomposition

(S.A. Yehia, M. Zarif, L.G. Carpen, B.I. Bit,˘a,S. Vizireanu, G. Dinescu)...... 77

vii P4-02 Removal of organic dyes by air atmospheric pressure plasma (A.L. Breab˘an,

I. Mih˘ail˘a,V. Pohoat,˘a,I. Topal˘a)...... 78 P4-03 Enhanced biocompatibility properties of poly(ethylene terephthalate) foils after

AC He DBD plasma jet exposure (A.V. Nastuta, M. Butnaru, V. Pohoat,˘a,V. Tiron, I. Topal˘a)...... 79 P4-04 Black pepper (Pipper nigrum) decontamination using low pressure plasma (C. Muja, A. Kais, T. Maho, L. Th`erese, Ph. Guillot)...... 80 P4-05 An atmospheric plasma source for seed treatment and biological decontamination (C. Muja, M. Soulier, Ph. Guillot, P. Belenguer)...... 81

Posters Topic 5 Fusion plasma physics and technology. 83 P5-01 Enhanced XRF method applied on fusion plasma high Z materials integrated in marker lamellae (M. Lungu, C. Dobrea, I. Porosnicu, A. Sima, I. Tiseanu)..... 85 P5-02 Collisions between electrons and molecular cations at extreme energy (N. Pop, F. Iacob, R. Bogdan, J. Zs Mezei, S. Niyonzima, M.D. Ep´eeEp´ee,O. Motapon, K. Chakrabarti, V. Laporta, I.F. Schneider)...... 86 P5-03 Momentum transfer from fast particles to the H-mode plasma layer (C. Dumitrescu, D.I. Palade, F. Spineanu)...... 87

Sponsors 89

Author Index 93

viii Invited Lectures

Kinetic effects induced in a plasma crystal by an electron beam I-01 1,* 1 1 2 C.M. Ticos, , D. Ticos, , A. Scurtu , J.D. Williams 1National Institute for Laser, Plasma and Radiation Physics, Bucharest 077125, Romania 2Wittenberg University, Physics Department, Springfield, OH 45501, USA *catalin.ticos@inflpr.ro

The kinetic effects on the dust particles are studied experimentally in a plasma crystal locally irradiated by a narrow pulsed electron beam with an energy 10 to 14 keV and a peak current of 4 mA [1]. We observe in the top layer of the plasma crystal the formation of a stable dust flow along the irradiation direction in the first ≈ 200 ms of the interaction, as in Figure 1. The dust flow eventually becomes perturbed later in time, with the dust particles having chaotic trajectories as they are still drifting in the beam direction. The speed of the dust flow is mapped in a horizontal plane using the particle image velocimetry (PIV) technique. The kinetic energy of the flow and its vorticity are deduced based on the speed vectors provided by PIV. Vortices and tripolar vortices are observed when the dust flow becomes perturbed [2]. It is shown that the force associated with the electron momentum transfer is consistent with the observed acceleration of the dust particles in gas at low pressure [3]. Numerical estimates show that the electron drag force does not depend on the dust charge. The interaction of the electron beam is described in terms of the electron penetration depth, deposited energy and heating of a dust particle, as well as the effect of the beam on the discharge. This study has implications in dusty plasmas and beyond, in instances where microparticles interact with sufficiently intense electron fluxes, and shows the potential to use an electron beam as a tool for manipulation of microparticles.

Figure 1: Top view of plasma crystal irradiated by a collimated electron beam (EB). Keywords: plasma physics Acknowledgement: This work was supported by ROSA on project STAR # 123 (C3-2016), the MCI on Project No. PN-16-47-01-02 and LAPLAS VI 16N/08.02.2019 and by U.S. NSF Grant No. PHY-1615421. References: [1] Ticos, D., et al., “Setup for plasma crystal interaction with an electron beam” (unpublished). [2] Ticos, C.M., et al., Physics of Plasmas 26 (2019) 043702. [3] Ticos, C.M., et al., “Pushing microscopic matter in plasma with an electron beam” (submit- ted).

3 Plasma polymer films with high similarity to their classical I-02 counterparts J. Kousal1,*, Z.K. Raˇsková2, Z. Krtouˇs1, J. Sedlaˇr´ıková2,3, L. Kuˇcerová2, P. Solaˇr1, S. Ali-Ogly1, A. Choukourov1, L. Hanyková1, H. Biederman1, M. Lehocký2,3 1Charles University, Faculty of Mathematics and Physics, V Holeˇsoviˇckách 2, 180 00, Prague, Czech Rep 2Tomas Bata University in Zlin, Centre of Polymer Systems, tˇr´ıdaTomáˇseBati 5678, 760 01, Zlin, Czech Rep 3Tomas Bata University in Zlin, Faculty of Technology, Vavreˇckova 275, 76001 Zlin, Czech Rep *jaroslav.kousal@mff.cuni.cz

Classical “wet chemistry” methods can produce polymers with well-ordered chemical structure. However, in the case of highly crosslinked polymers, residues of the crosslinking agent can remain in the material. Plasma polymers are usually highly crosslinked, but the molecular structure of the precursor is mostly lost. Plasma assisted vapour thermal deposition (PAVTD) technique can combine these two approaches. Powder of classical bulk polymer (“precursor“) is placed into a heated crucible in a glow discharge. Macromolecular chains break into oligomers. These long fragments are much larger that would be practical to use in typical gas-phase plasma polymerization processes. They are released into the gas phase through a glow discharge and they form a plasma polymer film. In this way, PAVTD can preserve most of the molecular structure of the precursor that can be tuned by the plasma power and material deposition rate in Yasuda-like manner [1]. Plasma polymer films based on polyethylene oxide, poly-lactic acid and polyurethane were prepared under varying RF plasma power. The molar mass distribution of the resultant films gives and evidence both for the fragmentation and repolymerization of the oligomers. The chemical structure of the films, characterized using infrared spectroscopy, X-ray photoelectron spectroscopy and nuclear magnetic resonance, was found to correspond well to the original polymer “precursors“. Swelling, hydrolysis and permeation properties of the films were studied using liquid chromatography and in-situ spectroscopic ellipsometry. Properties of plasma polymers prepared by PAVTD can be tuned to significant degree by the deposition conditions. Such films can be used as a model materials that effectively bridge the gap between the classical and plasma polymers.

Keywords: plasma polymers, classical polymers, plasma-assisted vacuum thermal deposition

Acknowledgement: This work was supported by the grant GA17-10813S of the Czech Science Foundation.

References: [1] A. Choukourov et. al., Plasma Processes and Polymers, 1 (2011) 48-58.

4 Challenges and opportunities in transparent conducting oxide thin ﬁlms deposited by magnetron sputtering I-03 E. Stamate* Department of Energy Conversion and Storage, Technical University of Denmark, Roskilde 4000, Denmark *[email protected]

Thin film transparent conducting oxides (TCO) are widely used in large-area and big-market applications, such as solar cells, touch panels, organic-LED and smart windows, with indium tin oxide (ITO) as one of the most used material [1]. ITO has very good optoelectronic and mechanic properties but its high cost limits applications on smart windows, including low-emissivity glass or chromogenic effects. Therefore, resource and cost limitations for indium, requires a timely development of new materials, with aluminium doped zinc oxide (AZO) as one strong candidate [2]. Despite of intensive research, good optoelectronic properties (average transmittance above 88% and resistivity below 10-3Ω cm) for AZO thin films deposited by magnetron sputtering are limited to certain regions over the substrate surface. So far, the role of atomic oxygen and energetic negative ions during the film growth is not understood and this requires an in-depth investigation and correlation of plasma and thin film properties [3-7]. This work reviews the status of AZO deposition by magnetron sputtering and reports on spatially resolved properties of AZO thin films, with focus on plasma properties and spatially resolved thin film characterization by TOF-SIMS, XPS and XRD (see Figure 1). The targeted application relates to low-emissivity glass, for reducing the effect of radiation cooling on vacuum glazing windows.

Figure 1: XRD texture for a 50×50 mm AZO sample deposited at 3 mTorr discharge pressure and 30 W RF power. Keywords: Transparent conducting oxides, magnetron sputtering, plasma diagnostics Acknowledgement: This work was supported by the Innovation Fund Denmark through research project no 6151-0011B: “SmartCoating”. References: [1] Handbook of transparent conductors, ed. D. S. Ginley, Springer (2010). [2] K. Ellmer, Nat. Photon. 6 (2012) 809. [3] T. Minami, Semicond. Sci. Technol. 20 (2005) S35. [4] K. Ellmer, J. Phys. D: Appl. Phys. 33 (2000) R17. [5] A. Bikowski, T. Welzel K. and Ellmer, J. Appl. Phys. 112 (2013) 223716. [6] B.B. Sahu, J.G. Han, M. Hori and K. Takeda, J. Appl. Phys. 117 (2015) 023301. [7] A. Crovetto, T. S. Ottsen, E. Stamate, et.al, J. Phys. D: Appl. Phys. 49, (2016) 295101.

5 Synthesis of tungsten based nanoparticles by means of magnetron I-04 sputtering combined with gas aggregation T. Acsente1,*, L.G. Carpen1,2, E. Matei3, G. Dinescu1 1National Institute for Laser Plasma and Radiation Physics, 077125, Magurele, Romania 2University of Bucharest, Faculty of Physics, 077125, Magurele, Romania 3National Institute of Materials Physics, 077125, Magurele, Romania *tomy@inﬁm.ro

Cluster sources based on magnetron sputtering combined with gas aggregation (MSGA) are versatile devices for synthesis of nanoparticles from different types of materials. This method was introduced at the end of last century [1]. To the moment it was implemented by different groups for synthesis of nanoparticles from different materials, like metals, their compounds, and polymers. In this method the nanoparticles are produced by condensation in an inert gas flow of the supersaturated vapors of the sputtered material. The presentation will point out on the particularities of tungsten nanoparticles synthesis by MSGA process sustained by a radiofrequency (13.56 MHz) magnetron discharge in argon. Thus, by proper adjustment of the applied RF power (continuous or pulsed wave), various morphologies (nanoflowers, hexapodes [2] or cuboctahedrons [3]) of tungsten nanoparticles are obtained. Still, the drawback of the tungsten nanoparticles synthesis is the ceasing of the deposition rate in a finite time interval (up to 30 minutes for a new sputtering target). We will address this issue and we will present the solutions for increasing the nanoparticles production rate, while maintaining the control over their dimension and morphology. In view of applications of high interest are also tungsten oxide nanoparticles which were obtained to the moment by further oxidation of the as-synthesized metallic tungsten nanoparticles. Potential applications based on these nanoparticles will also be discussed.

Keywords: tungsten nanoparticles, magnetron sputtering, gas aggregation

Acknowledgement: This work was supported by a grant of the Romanian Ministery of Research and Innovation, CCCDI – UEFISCDI, project PCCDI 46/2018 within PNCDI III and by the INFLPR Nucleus programme LAPLAS VI - contract 4N/08.09.2019.

References: [1] Haberland, H., et al., J. Vac. Sci. Technol. A 10 (1992) 3266. [2] Acsente, T., et al., Eur. Phys. J. D 69 6 (2015) 161. [3] Acsente, T, et. al., Mater. Lett. 200 (2017) 121-12.

6 Bipolar HiPIMS: a step further in exploring new perspectives and horizons in coatings deposition I-05 I.-L. Velicu1,*, V. Tiron2, D. Cristea3, I. Mih˘ail˘a4, D. Munteanu3, G. Popa1 1Faculty of Physics, Alexandru Ioan Cuza University of Iasi, Iasi 700506, Romania 2Research Department, Faculty of Physics, Alexandru Ioan Cuza University of Iasi, Iasi 700506, Romania 3Faculty of Materials Science and Engineering, Department of Materials Science, Transilvania University, Brasov 500068, Romania 4Integrated Center of Environmental Science Studies in the North-Eastern Development Region (CERNESIM), Alexandru Ioan Cuza University of Iasi, Iasi 700506, Romania *[email protected]

The High Power Impulse Magnetron Sputtering (HiPIMS) has experienced the most spectacular development in the field of plasma-assisted physical vapor deposition techniques due to its tremendous potential in growing high-quality thin films from a wide range of materials with applications covering almost all the industries. In the last almost 10 years, we have made a significant contribution toward expanding the potential of this new technology and overcoming its drawbacks. Operating the HiPIMS discharge with an additional external magnetic field, ultra-short pulses, or multi-pulse sequences, we have succeeded in controlling the deposition rate by producing a plasma with a high ionization degree and high-energy film-forming species flux directed towards the growing film [1]. However, in order to meet the ever-increasing demands for new materials in form of thin films with combined innovative functionalities, new deposition technologies need to be developed and implemented in production. This paper intends to promote the opportunity to open new perspectives in coatings deposition for fresh technological applications by operating the HiPIMS discharge in bipolar mode when a positive voltage (reversed pulse) is applied on the cathode, just after the primary sputtering pulse (Bipolar HiPIMS). This will favour the accelerations of sputtered metal ions towards the growing film, giving excellent control over their flux and energy [2], even when working with insulating materials (both substrates and coatings) and no bias can be applied. The effect of the process parameters on the plasma energetics was investigated by means of energy-resolved mass spectrometry. Both metal and gas integrated ion fluxes and their mean energy were discussed as function of the duration and intensity of the pulses (both negative and positive) and the time delay between their ignition time. The three-dimensional spatial survey of the plasma potential was evaluated based on emissive probe measurements. The ion acceleration mechanism was discussed based on the ion energy and plasma potential distributions. During the reverse pulse, a dynamic double layer structure develops in the after-glow plasma and some ions gain extra-energy corresponding to the full positive target potential. The ion energy distributions of metal and gas ions depend on the spatial distribution of both plasma potential and ion species. The energetic enhanced deposition conditions of bipolar HiPIMS significantly improve the mechanical and tribological properties of the growing film.

Keywords: Bipolar HiPIMS, sputtering, ion energy distributions, plasma potential

References: [1] V. Tiron et al., Surf. Coat. Technol. 337 (2018) 484–491. [2] V. Tiron et al., Surf. Coat. Technol. 359 (2019) 97–107.

7 I-06 Inverted Fireballs R. Schrittwieser1,*, C.T. Teodorescu-Soare1,2, C. Ionita1, D.G. Dimitriu2, O. Vasilovici1, S. Gurlui2, S.A. Irimiciuc3, B. Hodoroaba4, T. O’Hara5, L. Amarandi2, F. Enescu2, F. Mazzanti5, R. Stenzel6, J. Gruenwald7 1Institute for Ion Physics and Applied Physics, University of Innsbruck, Austria 2Faculty of Physics, Alexandru Ioan Cuza University, Iasi, Romania 3National Institute for Laser, Plasma and Radiation Physics - NILPRP, Bucharest, Romania 4University of Bucharest, Faculty of Physics, Bucharest-Magurele, Romania 5Dublin Institute of Technology, Dublin 2, D08 X622, Ireland 6Department of Physics and Astronomy, University of California, Los Angeles, USA 7Gruenwald Laboratories GmbH, Taxberg 50, 5660 Taxenbach, Austria *[email protected]

Fireballs are localized space charge structures which often appear on additional electrodes of various shapes in thin cold plasmas with a certain neutral background pressure. The electrodes are usually biased positively with respect to the background plasma. The acceleration of electrons towards the electrode and additional ionization creates a region of higher luminosity, plasma potential and density in front of the electrode. These structures are more or less sharply confined by a Double Layer (DL) (see e.g. [1,2]). Recently ”inverted fireballs” have also been observed when the additional electrode consisted of a hollow spherical fine-mesh grid where the fireball structure appears inside the spherical grid. Conventional and inverted fireballs were intensively investigated in close collaboration of the Alexandru Ioan Cuza University and the University of Innsbruck, partly also in collaboration with the University of California, Los Angeles (see e.g. [3-6]). In this invited talk an overview of the research on inverted fireballs is presented. The diagnostic was usually carried out with plasma probes and spectrometry. Also constructions of two concentric spherical grids were investigated. Figure 1 shows a setup with one spherical grid with an orifice through which an electron beam is accelerated by the DL forming in the grid orifice.

Figure 1: Experimental arrangement with single spherical grid, the diameter is 68 mm. Keywords: cold plasma, ionization, space charge structures, hollow spherical grid Acknowledgement: This work was supported by a grant of Ministry of Research and Innova- tion, CNCS-UEFISCDI, project number PN-III-P4-ID-PCE-2016-0355, within PNCDI III, by the CEEPUS network AT-0063 and the University of Innsbruck. References: [1] Dimitriu, D.G., et al., Plasma Phys. Contr. Fusion 49 (2007) 237-248. [2] Stenzel, R.L., et al., Plasma Sources Sci. Techn. 17 (2008) 035006. [3] Stenzel, R.L., et al., Phys. Plasmas 18 (2011) 012104 and 18 (2011) 012105. [4] Teodorescu-Soare, C.T., et al., Physica Scripta 91 (2016), 034002. [5] Schrittwieser, R.W., et al., Physica Scripta 92 (2017), 044001. [6] Teodorescu-Soare, C.T., et al., Int. J. Mass Spectrom. Ion Proc. 436 (2019), 83-90.

8 Particle modelling of HiPIMS plasma I-07 T. Minea1,*, A. Revel1, C. Costin2 1LPGP, UMR 8578 CNRS, Universite Paris-Sud, Universite Paris-Saclay, 91405 Orsay Cedex, France 2Iasi Plasma Advanced Research Center (IPARC), Faculty of Physics, Alexandru Ioan Cuza University of Iasi, Iasi, Romania *[email protected]

HiPIMS (High Power Impulse Magnetron Sputtering) has known a gain of interest worldwide due to its extraordinary capability to produce improved or unique coatings. However, the plasma development during the pulse and its space and time-dependent properties are still subject of numerous studies, most of them using diagnostic techniques. Recently, the formation of numerous instabilities has been reported, typical for the E~ × B~ plasma devices leading to spoke formation [1-3]. In this communication, we focus on magnetron plasma modelling and particularly on the HiPIMS plasma development during the pulse and the afterglow, as it is revealed by the 2D Particle-in-Cell (PIC) model coupled to Monte Carlo approach for collision treatment. The PIC self-consistency gives as output the pulse current behaviour, depending of the external circuit parameters, and its waveform can be compared to experimental results, using as input the voltage pulse. Moreover, we obtained for the first time the evolution of the electron and ion energy distribution into the plasma and onto the target [4]. Recently, the metal species have been considered as part of the plasma and the estimations of the ionization fraction will be given. In the second part, we present the novel approach called Pseudo-3D PIC, that treats phenomena in the azimuthal direction. The azimuthal component of the electric field can thus be estimated even if it is not fully solved in 3D. The magnetic field used is B~ (r, z), as before in the 2D PIC [2]. The Pseudo-3D model undoubtedly shows plasma oscillations in magnetron with a high frequency (1 to 6 MHz), characterized by a short space scale (≈ mm), compatible with the cyclotron gyration. They were initially assigned to electron cyclotron drift instability [1]. FFT analysis of electron density fluctuations given by the simulation shows the same typical frequencies [2] as the ones measured by coherent Thomson scattering [1]. At a larger (cm) scale, HiPIMS electron density presents a moving density pattern, independent of the individual particle behaviour. The information on the ionization region around the electron azimuthal structures gives the first insights on the possible mechanism responsible for the spokes formation.

References: [1] S. Tsikata and T. Minea, Phys. Rev. Lett. 114 (2015) 185001. [2] A. Revel, T. Minea, and S. Tsikata, Phys. Plasmas 23 (2016) 100701. [3] H. Luo, T. Minea, F. Gao, A. Billard, Plasma Sources Sci. Technol. 27 (2018) 115003. [4] A. Revel, T. Minea, and C. Costin, Plasma Source Sci. and Technol. 27 (2018) 105009.

9 Double layers and oscillatory phenomena in laser ablation I-08 transient plasmas: optical and electrical investigations * C. Focs, a Universit´ede Lille, CNRS, UMR8523 – Physique des Lasers, Atomes et Mol´ecules, F-59000 Lille, France *[email protected]

Development and optimization of a large number of applications in various fields such as nuclear fusion or precision micromachining at nanoscale synthesis of high technological materials depend on understanding the complex processes induced by the interaction of short pulsed lasers with the condensed matter. At high-fluence, this interaction leads to the formation of a transient plasma plume which may exhibit peculiar effects as fragmentation (plume splitting and sharpening), oscillations (in the MHz-GHz frequency range), (multiple) double-layer occurrence, electron and ion acceleration etc. In this frame, we have performed systematic experimental studies on the characterization of plasma plumes generated by laser ablation in various temporal regimes (ns, ps, fs) at fluences up to 1 kJ/cm2 and irradiances up to 1 PW/cm2. Optical (fast gate intensified CCD camera imaging and space–and time–resolved emission spectroscopy) and electrical (mainly Langmuir probe and mass spectrometry) methods have been applied to experimentally investigate the dynamics of the plasma plume and its constituents. A new theoretical method based on a fractal hydrodynamic approach has been proposed to describe the expansion of the plasma plume. Our results provide strong arguments for the occurrence of these peculiar effects in a multiple double-layer scenario intimately linked to the existence of hot and cold electrons in two-electron-temperature (TET) laser ablation plasmas. We present an overview of these studies performed over the last decade [1-7], in close collaboration with colleagues from Iasi (Alexandru Ioan Cuza and Gheorghe Asachi Universities).

Keywords: laser ablation, transient plasma, double layer, fractal

References: [1] Nica, P., et al., Applied Surface Science 481 (2019) 125-132. [2] Nica, P., et al., Physics of Plasmas 24 (2017) 103119. [3] Focsa, C., et al., Applied Surface Science 424 (2017) 299-309. [4] Irimiciuc, S., et al., Journal of Applied Physics 121 (2017) 083301. [5] Nica, P., et al., Europhysics Letters (EPL) 89 (2010) 65001. [6] Ursu, C., et al., Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 267 (2009) 446-450. [7] Gurlui, S., et al., Physical Review E 78 (2008) 026405.

10 Laser and plasma processing of thin ﬁlms and nanostructures for applications in opto-/micro-electronic devices I-09 A. Bercea, C. Constantinescu*, C. Champeaux, F. Dumas-Bouchiat IRCER UMR 7315, CNRS, University of Limoges, 12 rue Atlantis, 87068 Limoges, France *[email protected]

Laser processing of thin films is a powerful tool in material science. Here, Au and Ir thin films are grown by pulsed laser deposition (PLD) on various substrates, such as BK7 glass, c-cut sapphire, or MgO. First, we discuss on surface nanostructuring, created by using a combination of colloidal lithography and PLD. The colloidal lithography process consists in using colloidal masks made of polystyrene microspheres (PS) deposited on a substrate of choice by a modified Langmuir-Blodgett technique. When covered by a thin film using PLD and after the removal of PS, the masks reveal an array of polyhedral nano/micro-patterns exhibiting a quasi-equilateral triangular base (Fischer’s patterns), that can be further laser processed and/or combined with dewetting effects [1, 2]. Such structures are used for exploiting localized surface plasmon resonances (LSPR). The intensity and peak wavelength position are related to the coupling between the size and shape of the resonators (i.e. altitude and thickness) as presented in Figure 1 [3], but also to other factors (environment, distance).

Figure 1: Eﬀect of size and shape on LSPR extinction spectrum, for various metallic structures formed by nanosphere lithography; image reprinted from ref. [3].

Finally, we briefly present and discuss results on Ba2/3Sr1/3TiO3 (BST) films integrated in metal-insulator-metal (MIM) capacitors [4]. Au/BST/Ir and Ir/BST/Ir MIM structures have been fabricated on Ir/MgO single crystal substrates. Upon applying different voltage biases in the 100 MHz–30 GHz domain, depending on the specific polarization of top/bottom electrodes, several conduction mechanisms are highlighted in the respective devices.

Keywords: laser processing, thin ﬁlms, nanostructures, dewetting, materials science

Acknowledgement: This work is partially supported by the H2020 European project “MASTERS” within the M-ERA.NET call (http://www.unilim.fr/h2020_masters).

References: [1] Constantinescu, C. et al, Applied Surface Science 336 (2015) 112-117. [2] Constantinescu, C. et al, Applied Surface Science 374 (2016) 124. [3] Anker, J.N. et al, Nature Materials 7 (2008) 442-453. [4] Ghalem,Canceled A. et al, Journal of Applied Physics On 120 (2016) Last 184101. Minute

Oral Presentations

Electromagnetic model for simulations plasma wall-touching kink and vertical modes in ITER tokamak O-01 C.V. Atanasiu1,*, L.E. Zakharov2, K. Lackner3, M. Hoelzl3 1Institute of Atomic Physics, Bucharest, Romania 2LiWFusion, PO Box 2391, Princeton NJ 08543, USA 3Max Planck Institute for Plasma Physics, Garching b. M., Germany *[email protected]

Due to the necessarily large toroidal currents (15 MA in ITER) the tokamak concept suffers from a fundamental problem of stability. The nonlinear evolution of MHD instabilities leads to a dramatic quench of the plasma current within milliseconds - a major disruption. In ITER tokamak, a limited number of major disruptions will definitively damage the chamber with no possibility to restore the device. The magnetic effects of a disruption is known also as Vertical Displacement Events (VDE) and is associated with the sudden loss of the net Ipl. During fast VDE disruptions, the plasma acquires a contact with the plasma facing material surfaces, generating the edge currents which from the free plasma surface enter the wall surface mostly through the contour of the wetting zone (Figure 1). It is to note that for tokamak plasma disruptions modeling it was necessary to understand how currents ow to the plasma facing surfaces during disruption events [1, 2]. We verified successfully our numerical simulations (a weak formulation with finite elements) with analytical solutions [3].

Figure 1: Eddy, Hiro & Evans currents in Vertical Displacement Evenets.

Keywords: plasma physics, tokamak, MHD, instability Acknowledgement: This work has been partially carried out within the framework of the EURO fusion Consortium and has received funding from the Euratom research and training programme 20142018 under grant agreement no. 633053. The views and opinions expressed herein do not necessarily reﬂect those of the European Commission. References: [1] L.E. Zakharov, et al., Phys. of Plasmas 19 (2012) 055703. [2] L.E. Zakharov, C.V. Atanasiu, et al., Journal of Plasma Physics, 81 (2015) 515810610. [3] C.V. Atanasiu, L.E. Zakharov, Phys. of Plasmas, 20 (2013) 092506.

15 Dynamic generation of shear of the velocity at the L to H O-02 transition F. Spineanu*, M. Vlad, A. Croitoru National Institute for Laser, Plasma and Radiation Physics, Bucharest – Magurele, Romania *ﬂ[email protected]

The transition from L to H mode consists of formation of a narrow layer of sheared rotation at the edge, which acts as a transport barrier by reduction of the linear growth rate of the drift instabilities. The shear of the poloidal velocity is essential. We identify a mechanism that produces and maintains the shear of the velocity rotation in the edge layer where the transport barrier of the H mode is located. This mechanism has not been examined before. The point-dependent number of trapped ions (in a narrow layer close to the last surface) is maximum on the equatorial plane but advancing along the surface at higher poloidal angle θ their number decreases due to the intrinsic geometry of a banana which departs from the magnetic surface. The fast NBI ions leave part of their energy by collisions and produce current which is directed along the magnetic field line. Due to the variation of density of trapped fast NBI along the magnetic line, the momentum transferred by them to the background plasma particles has variation along the line. Then the parallel component of the current has variation along the line. This is a source of vorticity: the time variation of the vorticity (i.e. the shear of the rotation velocity) is the parallel gradient of the parallel current. The mechanism is, according to the first evaluations, more efficient than the Reynolds stress, since it exists beyond the formation of the quasi-laminar sheared flow in the narrow layer at the edge. During the L-H transition, the mechanism accompanies the usual neoclassical polarization effect, which connects the radial velocity of trapped particle with the fast time variation of the radial electric field. Integration of the neoclassical drift-kinetic equation on transitory part of the orbits of NBI ions with both pitch angle and direct momentum transfer collisions, produce an estimation of the flow induced by NBI ions in a narrow layer at the edge. Using the numerical evaluation of the variation of the current along the line we integrate the equation for vorticity (which is the shear of the velocity) with reasonable assumptions on the dissipative terms.

Acknowledgement: This work is supported by the contract C5-04 IFA-CEA and by WPJET1-C.

16 Electron-impact excitation and dissociative recombination of + + molecular cations in cold plasma: application to BeH ,H2 and their isotopomers O-03 F. Iacob1,*, N. Pop2, J. Zs Mezei3, S. Niyonzima4, M.D. EpéeEpée5, O. Motapon6, K. Chakrabarti7, I.F. Schneider8,9 1 Physics Faculty, West University of Timis, oara, Timis, oara, Romania 2 Dept. of Physical Foundations of Engineering, Politehnica University Timis, oara, Romania 3Institute of Nuclear Research of the Hungarian Academy of Sciences, Debrecen, Hungary 4Déptde Physique, Universitédu Burundi, Bujumbura, Burundi 5Dept of Physics, Faculty of Sciences, University of Douala, Douala, Cameroon 6Faculty of Science, University of Maroua, Maroua, Cameroon 7Dept of Mathematics, Scottish Church College, Calcutta, India 8Laboratoire Ondes et Milieux Complexes, CNRS, Universitédu Havre, Le Havre, France 9Laboratoire AiméCotton, CNRS, ENS Cachan and UniversitéParis-Sud, Orsay, France *[email protected]

The detailed collisional-radiative modeling of cold plasmas requires accurate cross sections and rate coeﬃcients of the major elementary processes, in particular of the dissociative recombination, ro-vibrational excitation and dissociative excitation: + + + − + + + − + − AB Ni , vi + e → A + B, AB Nf , vf + e ,A + B + e where N +/v+ stand for the rotational/vibrational quantum numbers of the cation. The Multichannel Quantum Defect Theory (MQDT) [1-3] has been employed in computing cross sections and Maxwell rate coeﬃcients for the above reactions involving the molecular cations BeH+ [4], BeD+ [5] and BeT+ –Figure 1– relevant for the fusion edge plasmas (ITER project). On the other hand, data for + + the processes involving H2 and HD , in order to model the same plasma, but also the excessively cold environments involved in the chemistry of the early Universe, interstellar molecular clouds, supernovae and planetary atmospheres, have been produced.

Figure 1: Dissociative Recombination (DR) and state-to-state Vibrational Excitation (VE)/ Vibrational De-Excitation (VdE) rate coefficients of BeT+ in its ground electronic state. Keywords: cold plasma, dissociative recombination, rate coefficients. References: [1] Schneider, I. F., et al., editors, Proceedings of DR2013, EPJ Web of Conf. (2015) 84. [2] EpéeEpée,MD., et al., MNRAS 455 (2015) 276–281. [3] Motapon, O ., et al., Phys. Rev. A 90 (2014) 012706. [4] Niyonzima, S., et al., Atomic Data and Nuclear Data Tables 115-116 (2017) 287. [5] Niyonzima, S., et al., Plasma Sources Sci. Technol. 27 (2018) 025015.

17 Investigation of direct and resonance contributions to the O-04 electron-impact excitation of neon-like Mo32+ ion C. Iorga1,2,*, V. Stancalie1 1National Institute for Laser, Plasma and Radiation Physics, Atomistilor 409, P. O. Box-36 Magurele-Ilfov, 077125, Romania 2University of Bucharest, Faculty of Physics, Atomistilor 405, CP-MG 11, Magurele-Bucharest, 077125, Romania *iorga.cristian@inﬂpr.ro

Two x-ray lines belonging to the neon-like Mo32+ ion have been measured at JET [1] along the lines emitted from W45+ and W46+ ions. The concentrations for these two elements are comparable and the molybdenum source has yet to be identified, thus further theoretical and experimental investigation is required. In the present study we employ the relativistic-distorted wave [2, 3] and independent-process isolated-resonance approximations [4, 5] in order to determine the direct and resonance contributions to electron-impact excitation of neon-like Mo32+ ion. The model-potential method is used to compute the structure of target states arising from 1s22s22p5nl (n ≤ 7, l ≤ 4) and 1s22s2p6n0l0 (n0 ≤ 5, l0 ≤ 4) configurations. In order to model the resonance excitation process we include 324,860 resonances resulting in partial wave expansions up to J = 29/2. We account for radiation damping via core-transitions and also allow radiative decay to other resonances followed by autoionization cascade. Effective collision strengths are computed for electron temperatures 100 eV ≤ Te ≤ 80 keV assuming a Maxwellian electron energy distribution function. Resonance excitation contributions to the rate coefficients for relevant electric and magnetic multipole transitions at different temperatures are discussed. This work is part of a larger project encompassing the study of forbidden and magnetic-induced electric dipole [6] transitions for diagnostic purposes in fusion related phenomena and astrophysics.

Keywords: atomic structure, distorted-wave approximation, resonance excitation

Acknowledgement: This work has been ﬁnanced by the Ministry of Research and Innovation, Romania, in the frame of Nucleus programme-contract LAPLAS VI 16N/08.02.2019. Partial ﬁnancial support from the Institute of Atomic Physics under project number F01/2016 is also acknowledged.

References: [1] Nakano, T., et al., J. Phys. B: At. Mol. Opt. Phys. 48 (2015) 144023. [2] Gu, M. F., Can. J. Phys 86(5) (2008) 675-689. [3] Iorga, C. and Stancalie, V., ADNDT 115-116 (2017) 1-286. [4] Shen, T.-M., et al., Phys. Rev. A 76 (2007) 022703. [5] Iorga, C. and Stancalie, V., JQSRT 224 (2019) 206-216. [6] Li, J., et al., Phys. Rev. A 88 (2013) 013416.

18 Eﬃcient algorithms for 3D modeling of fusion technology relevant superconductor cables from X-ray tomography data O-05 D. Dumitru*, I. Tiseanu National Institute for Laser, Plasma and Radiation Physics (INFLPR), Magurele-Bucharest *daniel.dumitru@inﬂpr.ro

The superconducting magnets in fusion reactors are based on Cable-in-Conduit-Conductor (CiCC) concept. On exterior, the CiCC cables consist of a relatively thick stainless-steel pipes and in interior is a highly packed twisted multiﬁlament Nb3Sn superconductor and Cu strands. Operation and data acquisition of an X-ray micro-tomography developed at INFLPR are optimized to produce fully 3D high-resolution tomographic reconstruction of relevant CiCC samples. In Matlab environment, eﬃcient algorithms were developed in analogy with photometric analysis to automatically process the tomography data in order to identify and determine the path of the strands inside the CiCC, which is important for the development of models of electrical performances (i.e. AC loses) and of conductor thermal-hydraulics. From the tomogram analysis, various information can be extracted: automatic strands detection and positioning, local and global void fractions (over a relevant length of the cable), twist pitch angle of individual strands. All these parameters have a substantial impact on CCiC performances.

Figure 1: a) 3D strand trajectory reconstruction; b) elliptically shaped individual strand trajectory. Using a ﬁtting procedure, it is possible to catch the real morphology and further on, to convert the reconstructed strand in to solid geometry and to discretize it in ﬁnite element for multiphysics simulations. An example of 3D strand trajectories reconstruction and an individual strand represented in solid geometry is presented in Figure 1a and 1b, respectively. Keywords: CiCC, X-ray microtomography, strand trajectory reconstruction, twist pattern

Acknowledgement: This work was supported by the IFA-CEA-C5-05 project.

References: [1] I. Tiseanu, et al., Fusion Engineering and Design. Vol. 88 (2013) 1613-1618. [2] I. Tiseanu, et al., Fusion Engineering and Design. Vol 98 (2015) 1176-1180.

19 On the Penning processes in atmospheric pressure plasma jet in O-06 helium with oxygen impurities 1,* 1 1 2 3 3,4 I. Topal˘a , A.S. Chiper , V. Pohoat, ˘a , I. Mih˘ail˘a , C. Anastassiou , C. Lazarou , G.E. Georghiou3,4 1Iasi Plasma Advanced Research Center (IPARC), Faculty of Physics, Alexandru Ioan Cuza University of Iasi, Iasi 700506, Romania 2Integrated Center of Environmental Science Studies in the North-Eastern Development Region (CERNESIM), Alexandru Ioan Cuza University of Iasi, Iasi 700506, Romania 3ENAL Electromagnetics and Novel Applications Lab, Department of Electrical and Computer Engineering, University of Cyprus, Nicosia, 1678, Cyprus 4FOSS Research Centre for Sustainable Energy, Department of Electrical and Computer Engineering, University of Cyprus, Nicosia, 1678, Cyprus *[email protected]

The last two decades brought many laboratory and clinical results emphasizing that non- thermal plasma jets are promising candidates for direct medical applications, including bacterial decontamination, liquid activation, wound healing and cancer treatment. Our joint team developed experiments and a two dimensional axi-symmetric model [1] in order to better understand the physics of guided streamers and their potential applications in medicine. We discuss in this paper the role of Penning ionization with nitrogen and oxygen molecules in ambient air, on the propagation dynamics and the shape of guided streamers. For example, removing the nitrogen Penning processes from the model (middle line in figure below) modifies significantly the distribution of radiation emitted at 706.5 nm (last line in figure below). Furthermore, we found that the absence of Penning ionization of nitrogen molecules slightly increases the value of the guided streamer velocity.

Figure 1: Experimental and numerical results concerning the time and space evolution of light emitted at 706.5 nm from guided streamers in He+O2 (1000 ppm) plasma jet. The experimental and numerical results on guided streamers launched by He and He/O2 plasma jet devices will give insight on the subsequent medical experiments with healthy and non-healthy cells or living tissues.

Keywords: plasma jet, plasma medicine, ﬂuid model, Penning reactions Acknowledgement: This project has received funding by the EU Horizon 2020 (MSCA-IF 2015) program under grant agreement 703497. References: [1] Lazarou, C., et al., Plasma Sources Science and Technology 27 (2018) 105007.

20 Pulsed Solid-State Lasers for Plasma Diagnostics and Processing O-07 E. Colin*, R. Sade Lumibird, Les Ulis, France *[email protected]

LUMIBIRD (formerly Quantel-Keopsys group), one of the world’s leading specialists in lasers, offers compact industrial high power, pulsed nanosecond lasers, scientific flashlamp pumped lasers, fiber lasers, laser diode stacks, and custom laser solutions for Plasma diagnostics and processing. With 50 years of experience and expertise in 3 key technologies - solid-state lasers, laser diodes and fiber lasers - the group designs, manufactures, and markets high performance lasers for the industrial (manufacturing, LIDAR sensors), scientific (laboratories and universities), medical (ophthalmology) and defense markets. Lumibird expanded its solid state laser portfolio with the release of the new DPSS Merion platform, ideal for Plasma diagnostics and processing. The Merion is designed to be a flexible platform and can be quickly adapted to our customer’s requirements from both scientific and industrial market. All the critical components, such as laser diodes, gain modules, and laser driver electronics are internally manufactured ensuring a full control of the entire process. This new DPSS generation combines the advantages of a compact and powerful laser; from 100 mJ up to 1 Joule, tens of Hz to 500 Hz, the Merion can be equipped with integrated or plug and play harmonic generators down to 266 nm to cover a wide range of applications. The Merion series represents the best solution for high demanding applications like LIDAR, LIBS, material processing. Our customers can use this laser simply as tools that they can install in their system, operate remotely and forget, rather than as complex instruments requiring frequent adjustments and care. Its compact size makes it easy to integrate.

Key features: • High power in a small footprint; • Superior beam proﬁle, up to 500 Hz; • Designed to last; • Diodes warranty: 2 billion shots; • SLM option for narrow bandwidth.

Further information about Merion series are available directly at www.quantel-laser.com or through an authorized Lumibird representative. For more information on this or any other Lumibird product, please contact a customer service representative at:

Histeresis: Address: EVO Business Center Et.1-06, Sos. Pacurari Nr.127 700545, IASI, ROMANIA Phone: +40 766 056 348 E-mail: oﬃ[email protected] WEB: www.histeresis.ro

21 Non-Maxwellian velocity distributions within plasma jets interacting with increasing magnetic ﬁelds: particle-in-cell O-08 simulations G. Voitcu1,*, M. Echim1,2 1Institute of Space Science, Magurele, Romania 2Belgian Institute for Space Aeronomy, Brussels, Belgium *[email protected]

The transport of collisionless plasma jets (or beams, clouds, blobs, streams, plasmoids) across transverse non-uniform magnetic fields is an important research topic that is relevant for both laboratory and space plasmas. In this paper we discuss the microphysics of a non-penetrating plasma jet that is deflected by a tangential discontinuity. For this purpose, we performed three-dimensional electromagnetic particle-in-cell simulations. The setup used here corresponds to a high-speed plasma jet impacting the frontside region of the Earth’s magnetopause, described as a parallel tangential discontinuity. The plasma jet is split into two counterstreaming flows streaming tangential to the discontinuity surface [1]. We focus on the kinetic structure of such a non-penetrating plasma jet. Our numerical simulations reveal the formation of non-gyrotropic (or crescent-shaped) velocity distribution functions for electrons at the edges of the plasma jet [2]. The physical mechanism we propose to explain the formation of such non-Maxwellian velocity distributions is based on finite Larmor radius effects. The combined effect of the gradient-B drift and the remote sensing of large Larmor radius electrons leads to the formation of non-gyrotropic electron velocity distribution functions. Our study provides new insight into the kinetic structure of high-speed plasma jets moving in the vicinity of unidirectional magnetic barriers. Such non-gyrotropic electron velocity distribution functions can indicate the presence of a finite-size plasma jet deflected tangentially near a parallel magnetic discontinuity.

Keywords: space plasma, jets, tangential discontinuity, velocity distribution function, numerical simulations, particle-in-cell

Acknowledgement: The authors acknowledge support from the Romanian Space Agency (ROSA) through the Space Technology and Advanced Research (STAR) Programme under contract 182/2017 (OANA) and also from the Romanian Executive Agency for Higher Education, Research, Develop- ment and Innovation Funding (UEFISCDI) through project VESS/2018. Marius Echim acknowledges support from the Belgian Solar-Terrestrial Centre of Excellence (STCE) in Brussels, Belgium.

References: [1] Voitcu, G., Echim, M., Geophysical Research Letters 44 (2017) 5920-5927. [2] Voitcu, G., Echim, M., Annales Geophysicae 36 (2018) 1521-1535.

22 Hidden drifts, a source of heavy impurity pinch in tokamak plasmas O-09 M. Vlad*, F. Spineanu National Institute of Laser, Plasma and Radiation Physics, Magurele, Romania *madalina.vlad@inﬂpr.ro

Turbulence is a complex nonlinear process that mixes disorder and order. The turbulence in magnetically confined plasmas has a self-organizing character, which consists of the generation of quasi-coherent structures and flows. In addition to that, we have found more subtle effects, namely the hidden drifts (HDs). The HDs are evidenced in the statistics of ion trajectories as organized components of the motion, which appear in the presence of a average velocity Vr and are oriented perpendicular on this direction [1]. They exactly compensate one another and do not yield average displacements of the trajectories. However, the HDs represent a reservoir of direct transport (average velocity or pinch), in the sense that any perturbation of the equilibrium between the positive and negative HD determines an average radial velocity (pinch). We discuss the effects of the HDs in an important process in tokamak plasma physics, the turbulent transport of the heavy impurities. These impurity ions determine large radiation that can strongly affect the energy balance if they accumulate in the core plasma (for the W, which is chosen as the material for plasma facing components in ITER, the maximum accepted concentration is only 10−4). We have shown that a radial pinch velocity VHD can be generated by the combined action of the HDs and of the polarization drift [2]. For the W ions, it is large enough to ensure significant pinches especially in ITG turbulence. Here we study the effects of the collisions of the W impurity ions with plasma electrons. It is an important and necessary analysis for yielding accurate predictions, because the collisional diffusivity of the W ions is much larger than that of plasma ions (with factors larger than 10). The study is based on the decorrelation trajectory method, which was developed for the description of this complex double stochastic process. We have determined VHD and the diffusion coefficient as function of the main parameters of the turbulence and of the W ions, which determine the four dimensionless parameters of the model. The importance of the pinch compared to the diffusive transport is represented by the factor p, which was also evaluated. The main conclusion is that the transport regimes of the W ions are essentially determined by the poloidal rotation velocity and by the decorrelation time of the W ions. These quantities decide the direction of the convective transport, which establishes when the turbulent transport contributes to W accumulation or extraction. The collisions produce the decrease of the amplitude of the pinch velocity without the change of the direction. This is a nonlinear effect that shows an opposite tendency compared to the results of the simplified estimations. The values of p show that the pinch is dominant compared to the diffusive transport for a large range of parameters.

Acknowledgement: This work was supported by the contract C5-04 IFA-CEA.

References: [1] M. Vlad, F. Spineanu, Europhysics Letters (EPL) 124 (2018) 60002. [2] M. Vlad, F. Spineanu, Phys. Plasmas 25 (2018) 092304.

23 O-10 Stochastic transport in strongly turbulent plasmas D.I. Palade*, M. Vlad, F. Spineanu National Institute for Laser Plasma and Radiation Physics, M˘agurele,Romˆania *dragos.palade@inﬂpr.ro

Energy and particle turbulent transport in magnetically confined plasma is one of the important problems in fusion research. In this context, test particle stochastic transport can evaluate the diffusion coefficients, provided that the characteristics of the turbulence are known. Besides, it is a basic ingredient of the Lagrangian methods for determining the evolution of turbulence. The test particle motion is determined by the E × B drift which, being divergence-free, imposes two constrains: a) the invariance of the potential along trajectories and b) the statistical invariance of the Lagrangian velocities. A standard (semi-analytical) method to approximate the turbulent trajectories is the decorrelation trajectory method (DTM) [1]. While it is able to give good qualitative results regarding the transport coefficients and its trajectories obey the first constrain (a), it does not reproduce the statistical invariance of the velocities. Moreover, it predicts average periodic trajectories, which in reality must have a helical character. For these reasons, we explore a series of possible extensions of the method capable to cure, at least partially, its drawbacks: a) Each subensemble defined by DTM is endowed with an internal structure and the trajectory dynamics is studied within the associated phase space employing a Fockker-Planck-like equation. In this way, the trajectories and the average velocity can acquire fluctuations needed for a better representation of the average trajectory. b) Starting from the above kinetic description, hydrodynamic-like models can be constructed for the trajectory or the velocity probability distribution functions. c) We have considered an average velocity Vd superposed on the stochastic component. This determines an average Lagrangian velocity VL that has to be equal to Vd at any time. The result of the DTM gives a smaller VL in the nonlinear regime characterized by trajectory trapping or eddying on the contour lines of the potential. The reason is that the trapped trajectories do not contribute to VL, which is determined only by the fraction of free trajectories. We have shown that the fluctuations neglected in the DTM contribute to a supplementary average velocity Vfr along the free trajectories. The first evaluation of Vfr yielded much improved results that show differences between VL and Vd smaller than 25%.

Keywords: Turbulence, test particle, statistical invariance

References: [1] M. Vlad, F. Spineanu, J.H. Misguich, R. Balescu, Phys. Rev. E 58 (1998) 7359.

24 Interstellar carbonaceous dust analogs obtained in plasma. Morphology and chemical characterization O-11 1,* 2 2,3 1 1 1 I.C. Gerber , I. Mih˘ail˘a , L.V. Soroaga , A.S. Chiper , V. Pohoat, ˘a , I. Topal˘a 1Faculty of Physics, Iasi Plasma Advanced Research Center (IPARC), Alexandru Ioan Cuza University of Iasi, Bd. Carol I No. 11, Iasi, 700506, Romania 2Integrated Center of Environmental Science Studies in the North-Eastern Development Region (CERNESIM), Alexandru Ioan Cuza University of Iasi, Bd. Carol I No. 11, Iasi, 700506, Romania 3Faculty of Chemistry, Alexandru Ioan Cuza University of Iasi, Bd. Carol I No. 11, Iasi, 700506, Romania *[email protected]

As important component of astrophysics, the study of the interstellar medium (ISM) has been achieved by deploying space probes capable of gathering information about its chemical composition and morphology by infrared spectroscopy, mass spectrometry or scanning electron spectroscopy. The ISM, known to be composed mainly of amorphous silicates of carbonaceous materials, contributes to stars, planets and small bodies’ formation, UV and optical radiation scattering and absorption, molecular catalysis, etc. The data collected so far offers insufficient information and experimental and additional theoretical studies that validate the observational data needed as a next step towards understanding the ISM components and their interactions. We employ plasma based techniques, using hydrocarbon gases as a precursor, in order to obtain carbonaceous grains with properties similar to the as the real interstellar/ interplanetary dust, extrapolated from observational data. To this extent, we use three different methods: dielectric barrier discharge [1], radiofrequency discharge and pulsed laser deposition using a carbon target. Although all these methods offer products with similar hydrocarbon absorption features as in the diffuse ISM, measured along the line of sight toward the Galactic center (Sgr A* or Quintuplet Cluster) or to the entire neighboring galaxies, such as IRAS 08572+3915, IRAS 19254–7245, NGC 1068 and NGC 5506, the three carbonaceous materials are significantly different even at macroscopic scale. In this paper, we will focus on discussing the morphological and chemical properties of the three carbon-based products focusing on methods like: infrared absorption spectra (study of spectral signatures of astrophysical relevance, sp2 and sp3 abundances, comparison to observational spectra), SEM imaging (porosity, grain/flake dimensions, deposition particularities) and XPS (carbon signal components, oxygen abundance).CPPA 2019 Keywords: plasma physics, hydrocarbon, dust analogs, interstellar medium, morphology, carbon materials

References: [1] Hodoroaba B., et al., Monthly Notices of the Royal Astronomical Society 481 (2018) 2841- 2850.

Best Oral Presentation Award

25 Multilayered all-oxide plasma coatings for colored glazed solar O-12 thermal collectors * I. Pana , C. Vit, elaru, M. Dinu, N.C. Zoita, A.E. Kiss, M. Braic National Institute of Research and Development for Optoelectronics - INOE 2000, 407 Atomistilor St., 077125 Magurele, Romania *[email protected]

The architectural integration of solar thermal collectors into the building envelope components has attracted an increasing interest over the last years. This is mainly due to the need to offer an aesthetic alternative to the actual dark-bluish or black colors of the commercially available solar collectors. We propose a simple solution for colored glazing by considering colored interference coatings [1,2], by using a stack of dielectric multilayers. Considering the need for large coated surfaces for the envisaged application, in our approach we considered also the use of abundant materials and an economical design of the multilayer. The aim of the present study is to obtain a green-yellow all-oxide multilayer with high solar transmittance (Tsol) comprising only few alternating dielectric layers along with good wear resistance and temperature stability up to 200 ◦C. The multilayer was modeled and then deposited by RF magnetron sputtering technique from TiO2 and SiO2 stoichiometric targets in an Ar/O2 gas mixture. The deposited coatings were analyzed by spectrophotometry, surface profilometry, SEM, X- ray reflectivity and AFM. Low roughness (<1 nm), superior optical properties (Tsol≈ 80.3 %, Rsol≈ 45.4 %) even after thermal tests, along with a hardness to modulus ratio of 0.081 and good scratch resistance up to 13 mN were obtained. Figure 1 shows the similarity of the designed and experimental spectrophotometric curves and the CIE coordinates of the obtained yellowish color. Summarizing, the obtained colored interference filters can be considered a viable solution for rising the architectural attractiveness in terms of the cost-effectiveness, custom color tuning and process reproducibility.

Figure 1: Optical properties of a 7-layer yellow-green SiO2-TiO2 multilayer. Keywords: optical coatings, multilayer design, thermal solar collector, magnetron sputtering Acknowledgement: This work was supported by Romanian Research & Innovation Ministry: Core Project 18N/08.02.2019, and Project PROINSTITUTIO-contract no.19PFE/17.10.2018. References: [1] Schuler, A., et al., Solar Energy 79 (2005) 122-130. [2] O’Hegarty, R., et al., Solar Energy 135 (2016) 408-422.

26 Study of TID propagation parameters using Dynasonde measurements from Wallops Island, VA O-13 C. Negrea* Institute of Space Science, M˘agurele,Romˆania *[email protected]

Travelling Ionospheric Disturbances (TIDs) are often caused by underlying Acoustic Gravity Waves (AGWs). It is generally assumed that the two phenomena share the same set of propagation parameters (frequency, wavevector components, etc) and as such, that TIDs follow the AGW dispersion relation. This study uses Dynasonde electron density and ionospheric tilt measurements from Wallops Island, VA, to investigate TID parameters in a range of ionospheric altitudes during June and November 2015. Spectral analysis is performed on the data at each individual altitude, and the results are used to determine the TID parameters associated with each time interval, altitude and frequency. The height-stratiﬁed statistical distributions of the vertical and horizontal wavelength, propagation direction and phase speed are determined and discussed. For several selected datasets, a procedure is demonstrated to autonomously identify individual wave-packets, based on the variation of the TID parameters over at least one wave period. Finally, for the selected wave packets, the propagation parameters and empirical model results are used to test the agreement with the gravity wave dispersion relation.

Keywords: Dynasonde technique, Spectral analysis of non-uniformly sampled data, TID propagation parameters, Atmospheric gravity waves

27 Cold atmospheric plasma as an associative agent for chemotherapy O-14 of breast cancer C.T. Mihai1,2,*, I. Mih˘ail˘a3, I.C. Gerber4, D. Gherghel2, G. Vochita2, C. Anastassiou5, I. Topal˘a4 1Center for Advanced Research and Development in Experimental Medicine (CEMEX), “Grigore T. Popa” University of Medicine and Pharmacy from Iasi, Iasi, Romania 2NIRDBS/Institute of Biological Research Iasi, Iasi, Romania 3Integrated Center of Environmental Science Studies in the North-Eastern Development Region (CERNESIM), Alexandru Ioan Cuza University of Iasi, Bd. Carol I No. 11, Iasi, 700506, Romania 4Faculty of Physics, Iasi Plasma Advanced Research Center (IPARC), Alexandru Ioan Cuza University of Iasi, Bd. Carol I No. 11, Iasi, 700506, Romania 5ENAL Electromagnetics and Novel Applications Lab, Department of Electrical and Computer Engineering, University of Cyprus, Nicosia, Cyprus *cosmin-teodor.mihai@umﬁasi.ro

Cold atmospheric plasma (CAP) have received growing interest to be used in different anticancer therapeutic approaches [1,2]. Also, plasmas shown the potential to selectively target the cancerous cells, leaving almost unaffected the normal cells, which is a desirable trait for anticancerous agents in order to reduce the deleterious side effects of the current treatment options[3]. Also, the capacity of cold atmospheric plasma to improve the chemotherapy by reducing drug dose or by sensitizing the resistant cancer cell populations is under investigation [4]. In the current work are presented the results obtained on two cancerous cell lines (MCF-7, double negative mammary cancer line, and MDA-MB-231, triple negative mammary cancerous cell line) exposed to cold atmospheric plasma and different doses of camptothecin (CPT, a topoisomerase inhibitor). Different experimental setups were employed in order to investigate the capacity of CAP to improve CPT efficiency on cancerous cell lines and to partially understand the mechanism of action of CAP. Assessment of the impact of combined treatment was determined by cell viability variations and apoptosis development in mammary cancerous cells.

Keywords: breast cancerous cells, chemotherapy, viability, apoptosis

Acknowledgement: This work was partially supported by the internal research grant ﬁnanced by University of Medicine and Pharmacy “Grigore T. Popa” from Iasi by research contract nr. 27504 / 20.12.2018.

References: [1] Dubuc, A., et al., Therapeutic Advances in Medical Oncology, 10 (2018) 1-12. [2] Chauvin, J., et al., Scientiﬁc Reports 9 (2019) 4866. [3] Wang, M., et al., PloS one, 8 (2013) e73741. [4] Zhu, W., et al., Scientiﬁc Reports, 6 (2016) 21974.

28 Surface dielectric barrier discharge micro-plasma in humid air at atmospheric pressure O-15 1 1 2 1,* A. Dascalu , V. Pohoat, ˘a , K. Shimizu , L. Sirghi 1Iasi Plasma Advanced Research Center (IPARC), Faculty of Physics, Alexandru Ioan Cuza University of Iasi, Iasi 700506, Romania 2Organization for Innovation and Social Collaboration, Shizuoka University, 3-5-1, Nakaku, Johoku, Hamamatsu, Shizuoka 432-8561, Japan *[email protected]

The surface dielectric barrier discharge (SDBD) plasma is a handy and low-cost plasma source that is scalable from small devices used in laboratory research or medical applications to large industrial applications [1]. In our group, we have studied the capability of SDBD micro-plasma generated in atmospheric air by small devices to treat water for either removal of organic chemical pollutants [2] or for activate water [3]. In these experiments, SDBD plasma generates primary reactive oxygen and nitrogen species in gas phase, which in contact with water produce secondary reactive species that oxidize and mineralize the organic molecules in contaminated water. Generated in clean water, these species confer upon it special properties useful for applications in medicine and agriculture. However, we found that the SDBD plasma enhances evaporation of water and, thus, raise the humidity of air in the treatment chamber with bad consequences on the efficiency of the treatment. To investigate this effect, in the present work we use FTIR absorption spectroscopy measurements to fallow the time evolution of molecular species in gaseous phase during discharge and post-discharge. Figure 1:a) illustrates the effect of air humidity on ozone production, which is 3 times smaller in humid environment. The humidity has strong effect on the discharge current, the intensity of discharge during formation of individual plasma filaments being much smaller in humid environment (Figure 1:b).

Figure 1: Eﬀect of air humidity on a) ozone production and b) discharge current. Keywords: atmospheric pressure micro plasma, surface dielectric barrier discharge, ozone production. FTIR absorption spectroscopy References: [1] Shimizu, K., Blajan, M., Kuwabara, T., IEEE Trans. Ind. 47 (2011) 2351–2358. [2] Dascalu, A, et al, Plasma Medicine 4 (2017) 395. [3] Dascalu, A., Besleaga, A., Shimizu, K., Sirghi, L., Recent Advances in Technology Research and Education. Proceedings of the 17th International Conference on Global Research and Education Inter-Academia – 2018, Laukaitis, Giedrius (Ed.) Springer Nature Switzerland (2019) AG 97-104.

29 O-16 Magnum-PSI plasma parameters mapping by electrical probes 1,* 2 3 1 3 3 C. Costin , I. Mih˘ail˘a , H. van der Meiden , V. Anit, a , S. Brons , J.M.W. Vernimmen , J. Scholten3 1Iasi Plasma Advanced Research Center (IPARC), Faculty of Physics, Alexandru Ioan Cuza University of Iasi, Iasi, Romania 2Integrated Center of Environmental Science Studies in the North-Eastern Development Region (CERNESIM), Alexandru Ioan Cuza University of Iasi, Iasi, Romania 3DIFFER - Dutch Institute for Fundamental Energy Research, De Zaale 20, 5612 AJ Eindhoven, the Netherlands *[email protected]

Magnum-PSI is a magnetically confined linear plasma facility designed to study fusion-relevant plasma-surface interactions. In 2016, Magnum-PSI has been upgraded with a superconducting magnet capable to provide magnetic fields up to 2.5 T [1]. The present work reports on the electrical diagnostic of Magnum-PSI by a multi-probe system, aiming to improve the knowledge and control of plasma parameters. The target of Magnum-PSI was replaced by a multi-probe system consisting of 64 probes positioned in a 2D square matrix (8×8), with a linear resolution of 4 mm in each direction [2]. The probes (W wires of 0.89 mm diameter and 0.9 mm length) are flush mounted with a W front plate (disc of 0.9 mm thickness and 85 mm diameter). The electrical signals were measured with a National Instruments data acquisition system, at a maximum acquisition frequency of 1 MHz. Two-dimensional spatial distributions, in cross section of the plasma column, of the floating potential and ion saturation current were measured at the target surface for different discharge conditions (discharge currents from 80 A to 150 A, magnetic fields from 0.2 T to 0.8 T, different hydrogen flows). The center of the plasma column is characterized by the most negative local floating potential (which is more negative than the floating potential of the target) and by the highest ion saturation current. The floating potential is more negative at lower discharge currents and at higher magnetic fields. The ion saturation current increases with both discharge current and magnetic field. Radial distributions of the current flowing to the target were registered for different bias of the target, allowing to estimate the charged particle (ions and electrons) fluxes. The ion-to-electron flux ratio to the target can be controlled by the target bias, as well as the discharge current and the magnetic field.

Keywords: multi-probe diagnostics, linear plasma generators, fusion-related plasma

Acknowledgement: We acknowledge the support of the Magnum-PSI Facility Team at DIFFER. DIFFER is part of the Netherlands Organisation for Scientiﬁc Research-Institutes (NWO-I). This work has been carried out within the framework of the EUROfusion Consortium and has been received funding from the European Union’s Horizon 2020 research innovation programme under grant agreement number 633053 and also from the Romanian National Education Minister under contract 2/23.02.2016. The reviews and opinion expressed herein do not necessarily reﬂect those of the European Commission.

References: [1] H.J.N. van Eck et al, IEEE Trans. Appl. Supercond. 28 (2018) 4203305. [2] C. Costin et al, Plasma Sources Sci. Technol. 24 (2015) 015014.

30 Posters Topic 1 Fundamental processes in plasmas, modelling and simulation.

Transient inward helical orbits and heavy impurity accumulation in tokamak P1-01 A. Croitoru1,2,*, F. Spineanu1, M. Vlad1 11National Institute for Plasma, Laser and Radiation Physics, Magurele Bucharest, Romania 2Faculty of Physics, University of Bucharest, Magurele, Romania *[email protected]

The neoclassical explanation of the process of accumulation of heavy impurities in the center of tokamak is here supplemented with alternative mechanisms. Essentially a helical orbit connecting the edge and the central region of the plasma can be created by a combination of rotation and swirl fluid motion. Plasma has a behavior similar to a fluid and supports advection of the heavy ion impurities toward the center. This occurs transiently at the transition between the L and the H mode of confinement, since large poloidal and toroidal rotations are involved. These rotations are combined with vorticity concentration on the axis and make possible inward transport. We explain how the poloidal rotation (sustained by radial electric field at the transition and by Stringer mechanism [1, 2] in stationary states) is combined with small but systematic radial displacements due to local vortical perturbations (a baroclinic effect). Even in the presence of the up-down symmetry there is a small non-compensation due to the periodic modification of the origin of the orbit in circular poloidal rotation. It is sufficient to induce inward average flow. This explains the observed global rise of the density in the center (impurities and background gas ions) at the transition.

Keywords: plasma physics, impurities, tokamak, Stringer mechanism

Acknowledgement: This work was supported by the contract C5-04 IFA-CEA and by WPJET1-C

References: [1] A.B. Hassam, J.F. Drake, Phys. Fluids B (1993) 5-11. [2] T.E.Stringer, Phys. Rev. Lett. 22-50 (1969) 770-774.

33 Nonlinear dynamics of non-concentric multiple double layers as a P1-02 source of low-temperature plasma instabilities D.G. Dimitriu1,*, S.A. Irimiciuc2, M. Agop3 1Faculty of Physics, Alexandru Ioan Cuza University, Iasi, Romania 2National Institute for Laser, Plasma and Radiation Physics, Bucharest, Romania 3Physics Department, Faculty of Machine Manufacturing and Industrial Management, “Gheorghe Asachi” Technical University, Iasi, Romania *[email protected]

When a low-temperature plasma is locally driven far from equilibrium by applying a positive potential to an immersed electrode, a complex space-charge structure appears in front of it, in form of simple or multiple double layers. If the electrode is large or asymmetric (for example rectangular or ring shapes), the complex structure takes the form of a network of fireballs (known also as non-concentric multiple double layer), almost uniformly distributed on its surface [1,2]. For high values of the potential applied to the electrode, the structure passes into a dynamic state, consisting of periodic disruptions and re-aggregations of the double layers existing at the border of each of the individual fireballs. Bunches of charged particles (electrons and positive ions) are periodically released into plasma simultaneously with the disruptions of the double layers, triggering plasma instabilities or leading to chaotic states of plasma [2,3]. If the individual dynamics of the fireballs composing the multiple structure are correlated, the instability manifests as complex strong oscillations of the plasma parameters (plasma potential and density, discharge current). Contrarily, if these dynamics are uncorrelated, different scenarios of transition to chaos are developing, leading to chaotic states of the plasma system. Here, experimental results are presented, emphasizing both correlated and uncorrelated dynamics of a non-concentric multiple double layers developed in front of a rectangular electrode immersed into a hollow-cathode discharge plasma. The dynamics of the multiple structure was investigated by recording and analyzing the time series of the current collected by the electrode. When the dynamics are correlated, the current displays bunches of oscillations in mutual relationship with the number of fireballs (up to six experimentally recorded) generated in front of the electrode. If the individual dynamics of the fireballs are uncorrelated, a scenario of transition to chaos through intermittency was evidenced. A theoretical model was developed in the frame of Scale Relativity Theory [4], able to describe the generation and dynamics of the non-concentric multiple double layer in front of the electrode.

Keywords: multiple double layer, ﬁreball, instability, intermittency, chaos

Acknowledgement: This work was supported by a grant of the Ministry of Research and Innova- tion, CNCS-UEFISCDI, project number PN-III-P4-ID-PCE-2016-0355, within PNCDI III.

References: [1] Ivan, L. M., et al., IEEE Trans. Plasma Sci. 33 (2005) 544-545. [2] Agop, M., et al., Phys. Scripta 87 (2013) 045501. [3] Dimitriu, D. G. And Agop, M, Chaos in Plasma Physics, in Handbook of Applications of Chaos Theory, edited by Skiadas, C. H. And Skiadas, C., CRC Press, Taylor & Francis Group, Boca Raton, FL, 2016. [4] Nottale, L., Scale Relativity and Fractal Space-Time: A New Approach to Unifying Relativity and Quantum Mechanics, Imperial College Press, London, 2011.

34 High–β plasmas: from space observations to lab experiments P1-03 M Lazar1,2,* 1Centre for Mathematical Plasma Astrophysics, KU Leuven, Belgium 2Theoretical Physics IV, Ruhr-University Bochum, Germany *[email protected]

The multitude of spacecraft missions provide valuable direct in–situ measurements of the space plasma dynamics, which, however, do not guarantee understanding of the physical processes governing the observations. Recent studies outline multiple benefits from lab experiments with increasing capabilities in reproducing, in particular, high–β conditions from space plasmas, e.g., solar wind or planetary magnetospheres. Experiments are repetitive and therefore able to ensure re-examination of the same conditions, reproducing measurements and facilitating analysis of the results. Discussed here are a series of observations in space plasmas which have gained valuable understanding from lab experiments (e.g., Large Experiment on Instabilities and Anisotropies – LEIA at UCLA, or Auburn Linear Experiment for Instability Studies - ALEXIS at Auburn University). These observations reveal the ability of self-organization of the non-thermal plasmas by mechanisms involving wave-turbulence and fluctuations, and their interactions with plasma particles. In the hot and rarefied plasmas from space binary particle collisions may be inefficient, but deviations from thermal equilibrium, e.g., kinetic anisotropies, appear to be controlled and constrained by the self-generated instabilities. The anisotropic particles are scattered by the enhanced fluctuations, leading to their diffusion and relaxation in velocity space. Constraining effects of the self-generated low-frequency Alfvenic fluctuations have been confirmed in lab experiments, providing valuable insights on the wave-particle interactions. An important component of high–β plasmas are the energetic, or suprathermal particles with energies up 1 KeV, and here it is shown that these populations are widely involved in interactions with plasma waves and fluctuations. Thus, suprathermals are generated (and entertained) by various mechanisms of acceleration like Landau or cyclotron damping of resonant waves and fluctuations, but suprathermals also trigger and stimulate the anisotropy driven instabilities and, implicitly, the relaxation of plasma particles. Observations from space plasmas are contrasted with relevant results from lab experiments.

Keywords: High–β plasmas, kinetic anisotropy, instabilities, wave ﬂuctuations

References: [1] G.G. Howes, Phys. Plasmas 25 (2018) 055501. [2] V. Pierrard and M. Lazar, Sol. Phys. 267 (2010) 153. [3] Lazar et al., Phys. Plasmas 25 (2018) 022902.

Canceled On Last Minute

35 Turbulence in planetary plasmas, at the interface with the solar P1-04 wind: Observations and Techniques M. Echim1,2,*, P. Kovacs3, N. Dwivedi4, E. Yordanova5, E. Teodorescu1, C. Munteanu1 1Institute of Space Science, Magurele, Romania 2Royal Belgian Institute for Space Aeronomy, Brussels, Belgium 3Hungarian Geological Survey, Budapest, Hungary 4Space Research Center of the Austrian Academy of Sciences, Graz, Austria 5Swedish Institute for Space Physics, Uppsala, Sweden *[email protected]

Solar terrestrial plasmas investigated by fleets of spacecraft are a genuine plasma turbulence laboratory. We present analysis results of data recorded in the magnetosheaths of two planets: Venus, with no intrinsic magnetic field, and the Earth. Data are provided by the European Space Agency spacecraft Venus Express and Cluster. Venus magnetosheath exhibit rather robust statistical evidence for inertial range scaling while such an evidence lacks for the Earth; both planets exhibit statistically significant breaks but for rather different scales. In terms of propagation and compressibility, the fluctuations exhibit a more regular pattern for Venus magnetosheath possibly explained by coexistence of Alfven ion cyclotron and mirror modes. Nevertheless in the case of the Earth magnetosheath there is some evidence for the Alfvenic fluctuations. Similarities and differences between the two planets are probably related to the role of the bow-shock that has different scale, strength and dynamics for Venus and respectively the Earth.

Keywords: space plasma, turbulence, complexity, magnetosheath, anisotropy, spectral analysis

Acknowledgement: The author M.E. acknowledges support from the Romanian Space Agency (ROSA) through the Space Technology and Advanced Research (STAR) Programme under contract 182/2017 (OANA), from the Romanian Executive Agency for Higher Education, Research, Develop- ment and Innovation Funding (UEFISCDI) through project VESS/2018, as well as from the Belgian Solar-Terrestrial Centre of Excellence (STCE) in Brussels, Belgium. The authors E.T. and C.M. acknowledge support from the Romanian Space Agency (ROSA) through the Space Technology and Advanced Research (STAR) Programme under contract 122/2017 (ODYN).

36 Minimum entropy production in the process of ﬁreball formation P1-05 S. Popescu, D.G. Dimitriu* Faculty of Physics, Alexandru Ioan Cuza University, Iasi, Romania *[email protected]

Fireballs are self-organized space-charge structures confined by an electric double layer, which appear in front of the anode of an electrical gas discharge as a consequence of driving the plasma away from the thermodynamic equilibrium [1,2]. They act as internal sources of particles and energy, being related to a negative differential resistance, which amplifies the discharge current. The double layer ensures the stability of the fireball by accelerating thermal electrons from plasma to energies high enough to produce new electrons and ions through ionization collisions with neutrals, necessary to compensate the loss of charged particles due to recombination and diffusion [3,4]. In this way, a part of thermal energy (disordered) of the charged particles is transformed into electrical potential energy (ordered) of the structure. In this contribution, a new mathematical model for the plasma fireball formation is presented, which describes the energy transformation during the evolution of the plasma system and, also, the entropy variation during the self-assembling of the fireball in front of the discharge anode. The non-equilibrium phase transition that takes place at the formation of the fireball minimizes the free energy of the system, representing its reaction to the external constraints. The obtained results indicate that the fireball assembling takes place according to the Prigogine’s theorem of the minimum entropy production [5].

Keywords: ﬁreball, double layer, entropy, self-organization

Acknowledgement: This work was supported by a grant of the Ministry of Research and Innova- tion, CNCS-UEFISCDI, project number PN-III-P4-ID-PCE-2016-0355, within PNCDI III.

References: [1] Sanduloviciu, M and Lozneanu, E., Plasma Phys. Control. Fusion 28 (1986) 585-595. [2] Popescu, S., Europhys. Lett. 73 (2006) 190-196. [3] Stenzel, R. L., et al., Plasma Sources Sci. Technol. 17 (2008) 035006. [4] Stenzel, R. L., et al., Plasma Sources Sci. Technol. 21 (2012) 015012. [5] Kondepudi, D. and Prigogine I., Modern Thermodynamics: From Heat Engines to Dissipative Structures, Wiley, New York, 1998.

Posters Topic 2 Plasma diagnostics. Gas discharge physics, dusty plasma, plasma sources and reactors at low and atmospheric pressure. Laser plasmas.

Time-space evolution of pulsed dielectric barrier discharge in presence of ﬁber-based woven substrate P2-01 I.C. Gerber, I. Topal˘a,G. Borcia* Faculty of Physics, Iasi Plasma Advanced Research Center (IPARC), Alexandru Ioan Cuza University of Iasi, Bd. Carol I No. 11, Iasi, 700506, Romania *[email protected]

Dielectric barrier discharges (DBD) are broadly used as technical solutions to obtain nonthermal plasmas at atmospheric pressure. Specific advantages are present when DBDs are used for materials processing: the short treatment duration, the operation at room temperature, no vacuum equipment, flexibility and various geometrical shapes, working gas mixtures, operational parameters and scale- up capabilities. Taking into account all these, DBDs represent a suitable technology for treating textiles, as they can be easily integrated with continuous processing lines. Nonetheless, since DBD is characterized by the presence of at least one insulating layer in contact with the discharge and the dielectric is the key for proper working regime, the presence of a supplementary dielectric layer may shift the behavior of the discharge and the plasma parameters. More, fiber-based woven textiles are heterogeneous structures, from mechanical, electrical and chemical point of view, with particular 3D nature resulting from interlacement of yarns, influencing, thus, the plasma gas flow between the electrodes, the dielectric constant and the ionization efficiency in the discharge. Taking this into account, we investigate here the time–space evolution of a pulsed atmospheric– pressure DBD, in presence of fiber–based woven textile, as a function of the woven structural characteristics. Six types of commercial polyester woven (PES), raw material, are selected as substrate, with different yarn thickness and weaving density. Helium is used as working gas, as allowing a good control of the homogeneous diffuse discharge regime, and the results will be further exploited for DBD operation in atmospheric air. The DBD parameters were monitored using high voltage and electric current probes. The waveforms were recorded simultaneously with images of the discharge between the electrodes, using ICCD fast imaging technique, monitoring thus the time–space behavior of the ionization front. The current waveforms demonstrate the presence of two temporally distinct discharges, so-called primary and secondary discharge, respectively, associated to the HV rising and falling slope, where the primary discharge waveform shows multiple discharges regime instead of the single discharge, depending on the substrate (Figure 1).

Figure 1: Examples for the primary and secondary discharge current waveform. The woven represents a patterned dielectric layer, with insulating and conducting regions, due to polymeric ﬁbers and gas “cells” inside the woven, respectively, which modiﬁes the discharge power and energy. More, our results suggest the possibility to use heterogeneous multi-layer polymer-air dielectric structures as dielectric layers to increase the stability of atmospheric-pressure discharges. Keywords: barrier discharge, atmospheric-pressure, heterogeneous dielectric layer

41 P2-02 Preliminary Characterization of a Plasma Driven Shock Tube D. Bivolaru*, G. Papadopoulos Innoveering, LLC, Ronkonkoma, New York, USA *[email protected]

The development of small scale plasma driven shock tube at atmospheric conditions is described in this work as a new tool for dynamic characterization of sensors used in high speed aerodynamics applications. The technique [1] uses a high energy pulsed plasma discharge (≈ 40 J/pulse) initiated in a quartz tube to generate a shock wave that travels downstream of the tube (Figure 1). The repetition rate and the energy release are controllable resulting in a robust operation. In a closed circuit, the system generates a burst of pressure waves of decaying amplitudes and speeds lasting in the tube for more than 300 ms. The main shock wave, traveling more than 60 tube diameters, arrives at the test section at a speed of about 425 m/s. A maximum pressure increase of about 40 kPa is obtained from the main wave within the ﬁrst 10 µs of the pulse. The instrumentation consists of electro-optical and spectroscopic techniques, as well as, sound and high speed pressure sensing elements.

Figure 1: Image of the plasma driven shock tube arrangement, the measured pressure wave and the first reflection from the end wall (blue) and the optical detection signal of the shock wave (green). Figure 2 shows two spectra of the integrated plasma luminosity collected from a parallel direction (p-spectra (black)) and, respectively, from a perpendicular direction (s-spectra (red)) relative to the plasma flow direction. The spectra are integrated for 4 milliseconds starting at about 100 µs after the plasma initiation. The p-spectra contain mainly the species of N, O and Cu ions with a high content in the red and near IR spectral bands. The s-spectra, are dominated almost exclusively by the singly ionized Cu ions in the green band at about 510 nm.

Figure 2: Spectra of the plasma flow obtained from a perpendicular direction near the discharge region (red) compared with the spectra obtained from a collinear direction (black). This study demonstrates that the plasma driven shock tube is a useful tool for investigating high speed plasma flows and offers a new environment for the characterization of sensors in terms of dynamic response and calibration. Future work will include the development of new designs and theoretical models for the discharge elements and the dynamics of the plasma region to closely relate the measurable plasma properties to the high speed flow properties.

Keywords: DC discharge plasma, optical emission spectroscopy, shock tube, shock wave Acknowledgement: This work was supported by the Department of Energy, Oﬃce of Science, Oﬃce of Basic Energy Sciences, under Award Number DE-SC0018708. References: [1] V. Josephson, J. Appl. Phys. 29 (1958) 30-32.

42 Stretching and compression of double plasma vortex P2-03 * A. Scurtu , D. Ticos, , E. Constantin, C.M. Ticos, National Institute for Laser, Plasma and Radiation Physics, Bucharest-Magurele, Romania *[email protected]

The interest for complex plasmas is increasing due to the multiple applications [1] they are targeting (astrophysics, plasma fusion, industry etc). In this paper we report a Kelvin-Helmhotz instability obtained in a laboratory plasma. Micrometric particles with a diameter of 14.45 µm immersed in RF plasma behave like probes that collect electrons and ions. We obtain a crystal under low pressure (250 mT in CO2) that levitate between two electrodes. The electric power fed into the discharge is 2 W. The particles are illuminated by a He-Ne laser beam passed through a cylindrical lens. The particularity of this crystal is the presence of two symmetrical vortexes in the crystal extremities. In Figure 1 we can see the two phases of the crystal, in the middle zone the particles are static and in the extremities the particles move continuously in ellipsoidal shapes. After introducing more gas (CO2) into the vacuum chamber at constant speed through the gas valve, we observe a collective displacement of the particles in the crystal in the direction of gas ﬂow. Crystal shift also involves a change of his shape, especially at the level of the two vortexes. One vortex was stretched and the other was compressed. The presence of vortex in dusty plasma is a great opportunity to investigate turbulent ﬂow and instabilities. In the community of dusty plasma physics there are several ideas to explain the nature of vortexes, from non-conservative force [2] to gradient temperature [3] between the two electrodes or the fact that the gradient of dust-charge is not parallel to non-electrostatic force (gravitational force and ion drag force) [4].

Figure 1: Dusty plasma with vortexes obtained at 250 mT and 2 W. Keywords: plasma physics, dusty plasma. Acknowledgement: This work was supported by the by Romanian Space Agency (ROSA) under contract DUSTEXSPACE nr. 123 Competition C3- 2016 and PN 18 13 01 01 References: [1] Merlino R., Plasma Physics Applied (2006) 73–110. [2] Akdim M., et al., Phys. Rev. E 67 (2003) 056405. [3] Shimizu S., et al., J. Geophys. Res.: Atmos. 115 (2010) D18205. [4] Fortov V., et al., J. Exp. Theor. Phys. 96 (2003) 704.

43 Particle Tracking Velocimetry of Plasma Crystal Rotation Induced P2-04 by Electron Beams * D. Ticos, , A. Scurtu, E. Constantin, C. M. Ticos, National Institute of Research and Development for Lasers, Plasma and Radiation Physics, Magurele, Romania *dorina.toader@inﬂpr.ro

Rotation of plasma crystals induced by the torque exerted by an electron beam slightly oﬀ–axis was investigated. The crystal was made of melamine formaldehyde microparticles with a diameter 11.8 µm and was levitated in a radiofrequency discharge at 13.56 MHz. A beam of electrons with energies from 8 to 14 keV determined the rotation of the whole crystal. Depending on the energy and beam frequency the crystal rotated with variable speed and kept its hexagonal symmetry. However, above a threshold, the symmetry was broken and the crystal lost its particle arrangement. The particle tracking velocimetry (PTV) technique was used to determine the individual trajectories of the microparticles and their velocities.

Figure 1: Rotation of two plasma crystals: a) a crystal with 10 particles under the inﬂuence of a 9 KeV electron beam pulsed at 53 Hz; b) a crystal with 43 particles irradiated by a 10 keV electron beam pulsed at 46 Hz.

Keywords: plasma physics, electron beam, PTV, dusty plasma

Acknowledgement: This work was supported by the Nucleu Laplas and Star DustExpSpace ﬁnanced by ROSA

References: [1] Yan Feng, J. Goree, Bin Liu, Phys. Rev. E. 86 (2012) 056403. [2] V.Nosenko, J. Goree, Phys. Rev. Lett. 93 (2004) 155004-1. [3] S.A. Khrapak, G.E. Morﬁll, Phys. Rev. E. 69 (2004) 066411. [4] M. Mulsow, M. Himpel, A. Melzer, Phys. Plasmas 24 (2017) 123704.

44 Ion propulsion based on microwave vaporization and ionization of the metal wires P2-05 C.P. Lungu1, M. Mogildea2, G. Mogildea2, C.M. Achim (Popa)1, C. Porosnicu1, P. Dinca1, B. Butoi1, O. Pompilian1, C. Staicu1, P. Chiru1 1National Institute for Lasers, Plasma and Radiation Physics, M˘agurele,Romania 2Institute of Space Science, Bucharest-Magurele, Romania

Ion propulsion is an emerging technology to be used in space propulsion, already proved on NASA’s missions. Usual thrusters work by using an electrical charge to accelerate ions from xenon fuel. Instead of xenon we propose the use metallic wires. A 2.45 GHz frequency, 800 W microwave power generator (MPG) and a cylindrical cavity having the TM011 propagation mode produces ions by vaporization and ionization of metallic wires made on Pb, Zn, In, W, Ni. The image of plasma produced in Pb vapors is shown in Figure 1. We investigated the dependence between the metal quantity which is vaporized and ionized by the microwave ﬁeld and the microwave power. We evaporated 0.5 mm in diameter metallic wires in a cylindrical cavity and buﬀer gases as air and nitrogen at normal atmospheric pressure. The electron temperature of gas and metallic plasma produced during experiments was estimated using the ratio of atomic emission lines acquired by a high resolution optical multichannel analyzer/spectrometer followed by Boltzmann plot. The electron temperature was estimated between 41.000 K and 43.000 K in the case of plasma ignited in Pb vapors, and about 15.000 K in the case of plasma ignited in In vapors. Optimum operating parameters were found in the range of 750–800 W microwave power in the case of Pb and 600–650 W in the case of In.

Figure 1: Image of plasma ignited in Pb vapors. MPG - Microwave power generator.

Keywords: microwave power, metallic plasma, plasma characterization

45 Mass spectrometry investigation during magnetron sputtering of P2-06 PTFE S.D. Stoica*, B. Mitu**, V. S˘atulu,G. Dinescu National Institute for Laser, Plasma and Radiation Physics, Magurele, 077125, Romania *daniel.stoica@inﬁm.ro**mitub@inﬁm.ro

Polytetrafluorethylene (PTFE) is among the most known materials used for obtaining super- hydrophobic and anti-sticking surfaces, while presenting high chemical resistance, electrical stability, excellent mechanical properties, for a wide range of temperature and humidity. We previously reported on the use of PTFE (Polytetrafluoroethylene) targets for RF magnetron sputtering deposition of thin films [1]. In this contribution, we focus on the investigation of the plasma processes contributing to the deposition process. Specifically, the content of species with long life, such as atoms and molecules on fundamental states and molecular radicals, and their energy distributions, were monitored by mass spectrometry [2, 3]. The discharge was generated in Ar (50 sccm), using RF (13.56 MHz) power values in the range 50–100 W. The mass spectrometer head was mounted in front of the magnetron gun, at a distance of 8 cm from the target. A typical mass spectra of neutral species is presented in Figure 1, illustrating besides the Ar related peaks at 20 a.m.u and 40 a.m.u. the presence of CF2 (50 a.m.u.) and CF3 (69 a.m.u.) radicals.

Figure 1: Mass spectra of neutral species present in the PTFE magnetron plasma at 80 W The results evidenced the behavior of the neutral and positive ions as function of the RF power, as well as their energy distribution function, giving insight into the magnetron sputtering deposition process of polymers.

Keywords: mass spectrometry, magnetron sputtering, polytetraﬂuoroethylene (PTFE) Acknowledgement: This work was supported by the Romanian Ministry of Research and Innova- tion, by Nucleus-Programme of INFLPR, project nr. 19150101. References: [1] V. Satulu, B. Mitu, V.A. Altynov, N.E. Lizunov, L. Kravets, G. Dinescu, Thin Solid Films 630 (2017) 92-99. [2] B. Mitu, V. Satulu, G. Dinescu, Rom. Journ. Phys. 56 P (2011) 120–125. [3] S. Vizireanu, S.D. Stoica, C. Luculescu, L.C. Nistor, B. Mitu, G. Dinescu, Plasma Sources Sci. Technol.19 (2010) 034016.

46 Vacuum Ultra-Violet irradiance measurements of an atmospheric pressure AC high voltage driven plasma jet P2-07 A.V. Nastuta1,*, T. Gerling2, P. Holtz2 1Biomedical Science Department, Faculty of Medical Bioengineering, ‘Grigore T. Popa’ University of Medicine and Pharmacy Iasi, Iasi, Romania 2Leibniz Institute for Plasma Science and Technology (INP Greifswald), Greifswald, Germany *[email protected]

Atmospheric pressure plasma sources are rapidly gaining importance as tools for material worldwide processing, since they are easy to use, technologically simple and environmentally friendly. Applications of these plasmas include: surface modification and deposition, plasma-based synthesis of biomedical surfaces, decontamination and sterilization, oncotherapy and wound healing. Depending on the application the plasma source must be tuned as to fulfill the application requirements. This is why it is important to characterize and monitor plasma sources from electrical and optical point of view. Vacuum ultra violet spectroscopy (VUV) is a powerful technique that can reveal information about plasma excited species with high energy (up to 10 eV), in the 100–300 nm domain. These high energetic plasma species are of great importance for plasma applications. In this report an dielectric barrier atmospheric pressure plasma source (appj), running in helium and argon, is characterized by means of electrical diagnosis, optical emission and vacuum-ultraviolet spectroscopy. We used He and Ar as working gases, at a flow rate of 2 slm. The applied voltage on the discharge electrodes was around 10 kVpp, at 18 kHz, and 10 W mean power. The optical characterization of plasma source revealed a homogeneous discharge, both in He and Ar. The global emission spectra, in the 200–900 nm range contains beside working gas lines (He or Ar) also lines and bands corresponding to atmospheric pressure impurities such as: NOγ , OH + radicals, N2,N2 , O. We further on investigated the emmission spectra in the 110–200 nm range using a VUV scanning monocromator (Acton Research Corporation, VM 505 + Thorn -EMI 9635 QB detector). In this spectral range the followings were identified: the lines of atomic hydrogen (121.5 nm), oxygen (130.5 nm) and nitrogen (149.5 nm and 174.5 nm), providing powerful VUV radiation with energies from 7 to 9.5 eV. For the Ar appj we observed also the 126 nm Ar excimer. The complete characterization of this He/Ar appj source is beyond the scope of this paper. Nevertheless, furthermore experiment should be made, like electrical field charcterization, surface charge production, ultra-fast photography, in order to have the hole understanding of the plasma source.

Keywords: plasma physics, vacuum-ultraviolet spectroscopy

Acknowledgement: This work was supported by the UEFISCDI, PNCDI III, project PN-III-P1- 1.1-MC-2017-1098, and by ‘Grigore T. Popa’ University of Medicine and Pharmacy Iasi under the project ’Young Researcher Internal Grant’, no. 30339/28.12.2017.

47 Experimental study of an atmospheric pressure piezoelectric P2-08 plasma jet J. Orejas1, C. Muja1, C. Tendero2, F. Pigache3, Ph. Guillot1,* 1DPHE, Universitéde Toulouse, INU Champollion, Albi, France 2CIRIMAT, Universitéde Toulouse, UPS, INP, CNRS, Toulouse, France 3Laplace, Universitéde Toulouse, UPS, INP, CNRS, Toulouse, France *[email protected]

In this work, an argon plasma jet generated at atmospheric pressure from a piezoelectric transformer is presented. The objective is to characterize this plasma source under fixed operating conditions (gas / argon, gas flow / 1 L.min-1, distance between the source exit and the target / 1.5 cm) and to assess its biocidal potential. Optical spectrometry was used to identify optical emissions from the carrier gas and the reactive species. ICCD camera imaging was used to give the 2D distribution of argon and nitrogen within the plasma jet. We will focuss on the spatial distribution of the biocidal effect of the jet was assessed using B. subtilis spores inoculated on stainless steel carriers. And these results will be completed by the variation of the conductive carriers’ temperature during the plasma treatment. The experiments have been made on a dry target.

Figure 1: Experimental setup and conditions, operating resonant frequency ≈ 55 kHz, input voltage 1.5 V, argon gas, flow rate / 1 L.min-1, stainless steel target, distance (source exit/target) 1.5 cm. The experimental setup is represented Figure 1. An optical spectrometer (HR2000+, Ocean Optics) coupled to an optical fiber was used to identify the optical emissions of the carrier gas and of the reactive species. An ICCD camera (PIMAX-2K-RB, Pearson Instruments) gave the 2D distribution of the total plasma emission (without filter) and of argon and nitrogen within the plasma jet (with filters). For target temperature measurements under plasma exposure, a K type thermocouple, 1.5mm diameter, stainless steel, based on an insulated hot junction to reduce electrical interference, has been used. In order to evaluate the biocidal effect of the plasma source, stainless steel carriers were inoculated with spores of Bacillus subtilis (ATCC 6633). After plasma treatment the spores were recovered in sterile PSB containing 0.1 % detergent. The number of viable cells were estimated using the plate counting method on tryptic soy agar after 24 hours of incubation.

Keywords: piezoelectric, plasma diagnostic, temperature, sporocidal eﬀect

48 Posters Topic 3 Plasma material processing. Surface treatments, thin ﬁlm deposition, plasma assisted nano-fabrication techniques.

Structural characterization of Au-incorporated tungsten trioxide used for improving gas sensing P3-01 I. Tirca, M. Jigau, M. Osiac* Univerty of Craiova, Faculty of Science, Craiova, 200585, Romania *m [email protected]

Tungsten trioxide (WO3), an important n-type metal oxide semiconductor was intensively studied due to physical and chemical proprieties in the field of gas sensors. In order to improve gas sensitivity and selectivity, noble metals like Au is incorporated in metal oxides structures [1-4]. The aim of this works is to prepare WO3 and Au-incorporated WO3 thin films as sensing layers of resistive sensors using Pulsed Laser Deposition (PLD) technique at various parameters. Pure and Au doped targets were irradiated using a pulsed laser with a frequency of 10 Hz, pulse width of 7 ns and energy 30 mJ. The wavelengths used to irradiate the targets were 213 and 266 nm. The oxygen pressure in the range of 75-250 mTorr shows the nanowire growth on the substrate. The substrate temperature during deposition was 600 ◦C. The concentration of Au in the substrate was around 2% at. The samples obtained were examined by SEM coupled with EDS, XRD and Raman spectroscopy. It was shown that the effect of the pressure higher than 75 mTorr presents the nanowire growing on the surface. The results obtained demonstrate that Au can be used as a dopant to improve the response of the gas sensor.

Keywords: pulsed laser deposition, tungsten trioxide, gas sensing

Acknowledgement: This work was supported by the project PCCDI-15.

References: [1] Srivastava,V. et al., Sensors and Actuators B 46 (2008) 133. [2] Ionescu, R. et al., Sensors and Actuators B 104 (2005) 132. [3] Tao,W.H. et. al., Sensors and Actuators B 81 (2002) 237. [4] Marquis, B.T. et al., Sensors and Actuators B 77 (2001) 100.

51 On the erosion of Tungsten surfaces exposed to an atmospheric P3-02 pressure microdischarge V. M˘ar˘ascu1,*, C. Stancu1, A. Bonciu1,2, V. S˘atulu1, G. Dinescu1,** 1National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor Street, 077125 Bucharest – Magurele, Romania 2Faculty of Physics, University of Bucharest, 405 Atomistilor, 077125 Bucharest - Magurele, Romania *valentina.marascu@inﬁm.ro, **dinescug@inﬁm.ro

Tungsten represents a material of wide scientific and technological interest, due to its usage as inner wall in the future ITER tokamak [1], performance as electrodes in plasma generation devices, and because its nanostructured oxides are promising for developing new gas sensors [2], photocatalysis cells, and for many other applications. Therefore, the behavior of tungsten surfaces in presence of discharges, in respect to erosion, nanostructuration, chemical stability, is an intensive subject of study [3]. In this work we discuss the erosion process caused by the interaction of an atmospheric pressure microplasma with W surfaces, for various gases and input RF power values. In this line we have used an atmospheric pressure microplasma channel generated in a radiofrequency discharge (13.56 MHz), which was anchored at the W electrode surface [4]. We have used Argon and Helium as working gases, a time exposure of 30 minutes and an input power in the range of 20 W – 100 W. The Scanning Electron Microscopy used to analyze the electrodes surface indicated the presence of erosion zones. The OES diagnostic of the constricted plasma channel confirmed the erosion process by showing the presence of W spectral lines in the discharge. The erosion is influenced by the working gas, Ar leading to a higher erosion grade, comparing to He. Nanostructures were observed at the electrode surface, near the erosion zone. Also, nano- and microparticles, exhibiting a large variety of shapes and sizes were collected on Si substrates, depending on the experimental conditions. XPS analyses indicated that the collected W particles were partially oxidized. The presented results are relevant for fusion technology and nanotechnology.

Keywords: tungsten surfaces, plasma erosion, microplasma

Acknowledgement: This work was partially carried out in the frame of IFA-CEA project C5-07. Also, it has been partially carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014-2018 and 2019-2020 under grant agreement No 633053.

References: [1] Grisolia, C., et al, Journal of Nuclear Materials 463 (2015) 885–888. [2] Palla-Papavlu, A., et al, J. Phys. D: Appl. Phys. 49 (2016) 205101. [3] Ueda, Y,. et al, Fusion Engineering and Design 89 (2014) 901–906. [4] Marascu, V., et al, Plasma Processes and Polymers, (2018) e1700091.

52 Silicon based coatings for composite membranes with tunable wettability properties P3-03 V. S˘atulu1, B. Mitu1,*, L. Kravets2, G. Dinescu1 1National Institute for Lasers, Plasma and Radiation Physics, PO Box MG-36, 077125 Magurele Bucharest, Romania 2Joint Institute for Nuclear Research, Flerov Laboratory of Nuclear Reactions, Joliot-Curie Str. 6, 141980 Dubna, Russia *mitub@inﬁm.ro

Hydrophobic/hydrophilic composite membranes have received considerable attention for their potential applications in various separation processes, such as pervaporation, reverse osmosis, gas separation, micro- and nano- filtration and membrane distillation [1,2]. In particular, membrane distillation is a promising technology for water filtration, water desalination, metal salts removal and pharmaceutical products purification [3]. In this work we describe the synthesis and characterization of silicon-based composite membranes with hydrophobic/hydrophilic sides. In this context, polyethylene terephthalate track etched membranes (PET-TM) were used as porous substrates. By using plasma enhanced chemical vapor deposition (PECVD) method with hexam- ethyldisiloxane (HMDSO) precursor, they were coated with hydrophobic SiOC thin films on one side and with super hydrophilic SiOx layers on the other side. The morphological properties of the silicon-based composites membrane surfaces were studied by Scanning Electron Microscopy (SEM) technique. The chemical composition and bonding of hydrophobic/hydrophilic thin films composite membranes were revealed through X-ray Photoelectron Spectroscopy (XPS) investigations. The hydrophobic/hydrophilic character of each sides of the resulted composite membranes was proved by static water contact angle measurements. The separation performances of the hydrophobic/hydrophilic composite membranes were evaluated by means of air gap membrane distillation home-made set-up. The results indicate that such porous hydrophobic/hydrophilic composite membranes with high wettability difference between the upstream and downstream sides are suitable for desalting highly saline waters by means of direct membrane distillation technology [4].

Keywords: PET-TM, composite membranes, silicon-based coatings, membrane distillation

Acknowledgement: This work has been performed under the cooperation agreement between JINR Dubna and NILPRP, protocol no. 4648-5-17/21, theme 04-5-1131-2017/2021. Funding from the NILPRP Nucleus Programme number: PN 19150101/2019 is gratefully acknowledged.

References: [1] Alkhudhiri A., Darwish N., Hilal N., Desalination 287 (2012) 2-18 [2] Satulu V., Mitu B., Altynov V.A., Lizunov N.E., Kravets L., Dinescu G., Thin Solid Films 630 (2017) 92-99 [3] Qtaishat M., Rana D., Khayet M., Matsuura T., J. Membr. Sci. 327 (2009) 264-273 [4] Tompkins B.D., Dennison J.M., Fisher E.R., J. Membr. Sci. 428 (2013) 576-588

53 Surface properties of polymers treated by air P3-04 atmospheric-pressure discharge E. Birleanu, I. Mih˘ail˘a,I. Topal˘a,G. Borcia* Faculty of Physics, Iasi Plasma Advanced Research Center (IPARC), Alexandru Ioan Cuza University of Iasi, Bd. Carol I No. 11, Iasi, 700506, Romania *[email protected]

Plasma is a complex source of energy for surface modification of polymers. It contains many short lived and long lived components, such as excited and ionized particles, photons, radicals. All these species are involved in induce chemical processes, both in the plasma volume and at interfaces with solid surfaces. Among the various applications of plasma, DBDs in air that run at atmospheric pressure represent a convenient, reliable and economic alternative for surface processing of polymers, also allowing for integration in continuous on-line processing. Recognizing the above, this work provides an investigation on the surface modification of polymers treated by an air atmospheric-pressure dielectric barrier discharge (DBD), under conditions simulating continuous processing. Here, aromatic-structure polymers are selected, as polystyrene (PS), polyethylene -terephthalate (PET) and polysulfone (PSU), known to exhibit enhanced mechanic characteristics and chemical stability, related to intrinsic rigidity and chemical inertness of the aromatic ring, in comparison to aliphatic polymers, as polyethylene (PE), in order to assess the plasma exposure effects on various structures. The selected polymers are offering variety of chemical structure, functional groups, degree of oxidation in terms of intrinsically structurally bonded oxygen in their structures, crystallinity and surface polarity, in order to analyze the different forms of alteration to the polymer surface, as removal of the weak cohesion layer or other contamination present at the surface, introduction of new chemical functionalities or adding such to those already present. The surface of the polymers, before and after treatment, is analysed by contact angle, X-ray photoelectron spectroscopy (XPS) and solvent absorption. The dynamics and stability of modified surfaces of the surface is assessed by monitoring the ageing of samples, to evaluate the loss of polarity and possibly the mechanisms related to it. The surface modification is found to be largely dependent on the surface oxidation, also providing uniform and markedly stable surface properties over the entire area of the test surfaces exposed to the discharge at various transit speeds. Nonetheless, the tested polymers behave differently, depending on their chemical structure. Both, the plasma modified surface properties and the ageing behaviour, are influenced by the chemical structure of the polymer and the initial oxygen content. Compared to the aliphatic-structure polymers, the modification of the surface adhesion and polarity was found to be more efficient for the aromatic polymers. The limiting level of modification attainable and the factors controlling are involved in restrain- ing the ageing process, as a necessary condition for polymer operational stability.

Keywords: DBD, atmospheric-pressure, polymers, oxidation, stability

54 Morphology and structural investigations of graphene / graphite nanowalls grown by capacitively coupled RF-PECVD at various substrate temperatures P3-05 O.-G. Simionescu1,2,*, A. Avram1, R. Popa1, O. Tutunaru1, C. Pachiu1, G. Dinescu2,3 1National Institute for Research and Development in Microtechnologies, 126A Erou Iancu Nicolae Street, Voluntari city, Ilfov county, 077190, Romania; 2Faculty of Physics, University of Bucharest, 405 Atomistilor Street, Magurele City, Ilfov county, 077125, Romania 3National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor Street, Magurele city, Ilfov county, 077125, Romania *[email protected]

The growth of graphene/graphite nanowalls (GNW), more commonly referred to as carbon nanowalls (CNW), has been studied through various methods over the years, such as: direct current (DC) plasma-enhanced chemical vapour deposition (PECVD), electron cyclotron resonance CVD (ECR-CVD), microwave PECVD (MW-PECVD) and radiofrequency PECVD (RF-PECVD). As it is well known, substrate temperature is a key factor in obtaining sp2 hybridized carbon (C) thin films of different morphologies, as it plays a major role in the C atoms surface diffusion. In this work we investigate the influence of substrate temperature on the structure and morphology of capacitively coupled RF-PECVD grown GNW. The deposition is made in argon (Ar) plasma using methane (CH4) as a precursor and varying the temperature within a range of 700–900◦C. A parallel plate reactor was used, with the precursor injected through the top electrode, while the substrate was placed on the lower grounded electrode. Raman spectroscopy and Scanning Electron Microscopy (SEM) were used to check for changes in the thin films structure and morphology as a function of substrate temperature. The difference in size and width can be observed from the SEM micrographs and the Raman spectra provides us with the ID/IG ratio which we use to calculate the lateral crystallite size (La) according to [1]. Electrical conductivity was also investigated, to determine the correlation between electrical properties and nanowall morphology. At a higher substrate temperature, the greater surface energy causes more nucleation sites/seeds to arise which results in denser, more compact carbon thin films. The morphological and structural changes can be seen in the electrical conductivity as well.

Keywords: carbon nanowalls, plasma deposition, vertical graphene, carbon nanomaterials

Acknowledgement: This work was supported by the project PN-III-P1-1.2-PCCDI-2017-0619 “Nanostructured carbon based materials for advanced industrial applications” (NANOCARBON+).

References: [1] Can¸cadoL.G., Takai K., and Enoki T., Appl. Phys. Lett. 88 (2006) 163106.

55 Conduction anisotropy in carbon nanowall layers obtained by P3-06 a low-pressure plasma jet 1,2,* 1,** 1 1,2 2 2 1,2 B.I. Bit, ˘a , S. Vizireanu , S.D. Stoica , S.A. Yehia , A. Radu , S. Iftimie , G. Dinescu 1National Institute for Laser, Plasma and Radiation Physics, Magurele, 077125, Romania 2University of Bucharest, Faculty of Physics, Magurele, 077125, Romania *bogdan.bita@inﬂpr.ro; **s vizi@inﬁm.ro

Carbon nanowalls (CNW, vertical graphenes) consisting of inter-connected vertical carbon sheets built from small graphene domains with their c-axis parallel tot the substrate are promising materials for new electrical devices. Nevertheless, their electrical properties are not sufficiently known [1]. In this study we studied the behavior of the load carriers in plasma deposited CNW. The carbon layers were grown by Plasma Enhanced Chemical Vapor Deposition by injecting H2, and C2H2 (acetylene) in an Ar radiofrequency plasma jet [2]. SEM and Raman techniques were used to characterize the material. A special electrical cell was designed, consisting of a three-layer sandwich built on silicon wafer, having as base a Pt electrode, in the middle the CNW layer, and on top, as upper electrode, a gold disc. The upper gold electrode was deposited by magnetron sputtering at angled incidence (30 degrees to vertical) thus preventing the deep penetration of the metal in the pores of the CNW layer, thus preventing the short-circuit with the Pt electrode. The I-V curves were measured directly between the Pt and Au, across the CNW layer, without and with a magnetic field applied parallel to the substrate (in plane with the c-axis of the sheets). The measurements, revealed us the type of conduction and the mobility of carriers along, and perpendicular on the carbon sheets. The results indicated for CNW a semiconductor of p-type, whose conductivities parallel and perpendicular to the sheets planes are different.

Keywords: PECVD, Hall Eﬀect, CNW

Acknowledgement: This work was supported by a grant of the Romanian Ministery of Research and Innovation, CCCDI - UEFISCDI, in the frame of Nucleus Programme INFLPR/2019 and project number PN-III-P1-1.2-PCCDI-2017-0637/ 33 PCCDI-MultiMonD2 within PNCDI III.

References: [1] Vizireanu, S., et al., Plasma Sources Science and Technology, 19 (2010), 034016. [2] Acosta Gentoiu M, et al., Journal of Nanomaterials, (2017) 1374973.

56 Atmospheric pressure plasma treatment of surfaces for cleaning and modiﬁcation P3-07 1,2 1,3 1,* 1 1 1 1 M. Zarif , S.A. Yehia , S. Vizireanu , V. S˘atulu , V. M˘ar˘ascu , B.I. Bit, ˘a , G. Dinescu 1National Institute for Lasers, Plasma and Radiation Physics, 77125, Magurele – Bucharest, Romania 2Faculty of Engineering in Foreign Languages, University “Politehnica” of Bucharest, Bucharest, Romania 3Faculty of Physics, University of Bucharest, 77125, Magurele – Bucharest, Romania *s vizi@inﬁm.ro

Plasma sources working in open air could be easily adapted to specific applications (etching, cleaning, activation and thin film deposition, etc.) [1, 2]. Beside the common advantages of plasma treatments, the processing at atmospheric pressure involves low costs, easiness in handling samples with complex geometry and the opportunity to be used in industrial production lines. In particular, the plasma sources are used for cleaning of textiles, polymers, ceramics, glass, metals and waste water decontamination. The disadvantages of the classical cleaning (usually toxic substances) could be avoided by using atmospheric pressure plasma treatments. In this contribution we report plasma treatments applied on stainless steel and silicon for cleaning and surface modification. For cleaning, the samples were prepared by coating the substrates with polyamide, amorphous carbon, diamond-like carbon or vertical graphene layers. The samples were treated with a radiofrequency plasma jet/torch (13.56 MHz) in various regions by scanning the surface. The gas type (Ar, N2), flow rate (1000–20000 sccm), power (100–300 W), the distance between the plasma source and the sample and the number of scans were changed. The untreated and plasma treated surfaces were analyzed by optical microscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), profilometry and contact angle measurements. The experiments showed that the cleaning is very effective, being observed even after a few scans. The optimal conditions for removal of the deposited layers were identified. Additionally, the treatments were tested for nitridation and oxidation of the stainless-steel supports. The XPS results indicated the introduction of nitrogen and oxygen in the substrates. The results are relevant for increasing the lifetime of the tools in injection molding of plastics.

Keywords: atmospheric pressure plasma, surface cleaning, surface treatment

Acknowledgement: This work was supported by a grant of the Romanian Minister of Research and Innovation, CCCDI - UEFISCDI, project number PN-III-P1-1.2-PCCDI-2017-0387 / 80 PCCDI, within PNCDI III, and project INFLPR Nucleu/2019.

References: [1] Stancu, C., et al., Fusion Engineering and Design 103 (2016) 38-44. [2] Dinescu, G., et al., Pure and Applied Chemistry 80 (2008) 1919-1930.

57 Effect of nitrogen content on physical and mechanical properties of P3-08 tungsten films deposited by CMSII F. Baiasu, M. Gherendi*, E. Grigore National Institute for Lasers, Plasma and Radiation Physics, Magurele, Romania *mihaela@infim.ro

Transition metal nitrides represent a class of materials with outstanding characteristics concerning mechanical properties (microhardness, Young’s modulus), chemical stability, high melting point and conductivity. Representative for this class of materials is titanium nitride, a compound that attracted a large scientific and technological interest for a long period of time. A different situation is in the case of tungsten nitride. The first studies on this compound were focused on its use in the field of electronic applications or diffusion barriers. However a number of studies were related to mechanical application as standalone coatings or in combination with other elements (Si, Ti etc). In this paper tungsten films with various nitrogen content, intended for use as hard coatings were deposited by Combined Magnetron Sputtering and Ion Implantation (CMSII) method. A study was performed to assess the correlations between relevant deposition parameters (nitrogen flow rate) and physical and mechanical properties of the films. Structural and chemical characterizations were performed by X-ray diffraction (XRD) and Glow Discharge Optical Emission Spectrometry (GDOES), respectively. The morphology of the films was characterized by Scanning Electron Microscopy (SEM), while mechanical properties were evaluated by microhardness measurements and wear resistance investigations using a pin-on-disc tribometer. The thickness of the deposited layers was ˆınthe range of 12–14 µm. The films were polycrystalline and, in the case of the films with small nitrogen concentration (below 3 at.%), no WNx phase was observed, nitrogen atoms being dissolved in W lattice. GDOES results show relatively uniform concentration profiles of N2 ˆınall films. It was found that, with increasing nitrogen content, the hardness of the films increases, while the size of the crystalline grains decreases significantly. As far it concern the microhardness, a value of 2230 HV0.05 was measured for the film with 2.5 at.%. nitrogen content.

Keywords: plasma physics and applications, high power pulsed magnetron sputtering, materials science.

58 Wearing and friction properties of octadecyltrichlorosilane layers deposited by chemical vapour deposition on plasma activated silica surfaces P3-09 * S. Teodoroﬀ-Onesim, A. Bes, leag˘a,L. Sirghi Plasma Advanced Research Center (IPARC), Faculty of Physics, Alexandru Ioan Cuza University of Iasi, Blvd. Carol I nr. 11, Iasi 700506, Romania *[email protected]

Octadecyltrichlorosilane (OTS) coatings are commonly used in electronic industry as electric insulator layers and for fabrication of anti stiction surfaces in micro electro mechanical systems (MEMS). In the present work, we investigate the wearing and friction properties of OTS coatings obtained by silanization of hydroxylated silicon surfaces of atomic force microscopy (AFM) probes and samples. As AFM samples, we used polished N-type Si<100> wafers with a native silica layer on top. Before silanization, the surfaces of silicon samples were activated by negative glow plasma of a luminescent discharge in humid air, process that cleaned and hydroxylated the surfaces. To reduce the surface contamination during the whole process, the plasma surface activation and OTS deposition were performed in the same reactor. After the OTS depositions, the samples were baked in air at 100 ◦C for 24 hours. Then, the AFM probes and samples were kept in low vacuum until use in wearing and friction experiments. The geometry of OTS coated tip was investigated by analysis of AFM topography images of sharp edges (curvature radius < 5 nm) of a silicon grating (TGG 1 from Mikromasch). Figure 1 presents results of wearing and friction investigation of OTS coating on silicon wafer.

Figure 1: a) Wearing track and b) friction force recorded during 1000 wearing cycles performed with a silicon AFM tip on OTS coated silicon wafer. The surface of OTS coatings on silicon wafers is very smooth (RMS roughness of 0.19 nm). To investigate the wearing properties of this surface, a sharp silicon AFM tip (curvature radius of 17 nm) was moved forwards and backwards in 1000 cycles along a path on the surface with length of one micron under a normal load of 50 nN. Then, the topography of resulted wearing track has been investigated by scanning the surface in contact mode with the same AFM tip. The depth of the resulted wearing track was around 0.8 nm. Because of the surface wearing, the friction force recorded during wearing experiments decreased by about 20% during the ﬁrst 200 wearing cycles and remained constant afterwards. The decrease of friction force, in spite of the increase of contact area in the wearing track, can be attributed to a decrease of the energy loss associated to the process of AFM tip brushing OTS molecules during cyclic movements. Keywords: silica surface functionalization, silanization, plasma activated surface, wearing References: [1] Zhuang, Y. X., et al., J. of Microelectromechanical Systems, 16 (2007) 1451.

59 Chemical vapour deposition of octadecyltrichlorosilane on plasma P3-10 activated silica surfaces * A. Bes, leag˘a, S. Teodoroﬀ-Onesim, L. Sirghi Plasma Advanced Research Center (IPARC), Faculty of Physics, Alexandru Ioan Cuza University of Iasi, Blvd. Carol I nr. 11, Iasi 700506, Romania *[email protected]

Deposition of octadecyltrichlorosilane (OTS) layers is commonly used in electronic industry and in various applications that require modiﬁcation of silicon surfaces as in biosensors, micro electro mechanical systems, actuators or atomic force microscopy. Usually, OTS functionalization of silica surfaces is based on wet chemistry technique comprising self-assembled monolayers (SAMs) deposition of OTS on silica surfaces that were previously activated (cleaned and hydroxylated) in piranha solution. However, this technique may yield inhomogeneous depositions characterized by formation of nanoscopic OTS particulate aggregates on the functionalized surfaces due to polymerization of OTS molecules on water contaminated surfaces. However, it has been found that presence of certain amount of water on activated silica surfaces plays a key role in SAMs depositions of OTS [1]. In this work we use low-pressure plasma of a glow discharge in air and water vapor to clean and hydroxylate silicon surfaces fallowed by chemical vapor deposition (CVD) of OTS in the same reactor chamber. We have found that adding an additional fabrication step between plasma surface activation and CVD consisting in intentional introduction of certain amount of water vapor in the deposition chamber is beneﬁcial to OTS depositions. There is an optimum in the amount of water introduced into the deposition chamber, introduction of too much water leading in formation of particulate aggregates of OTS, while introduction of a too small quantity of water results in formation of ill-covered OTS surfaces. Figure 1 shows AFM topography images of OTS covered silicon obtained when the amount of water introduced in the deposition chamber was a) optimum and b) too much. The amount of water introduced in the deposition chamber was controlled by the water vapor pressure, which was varied between 0.8 and 10 Torr.

Figure 1: Topography images OTS covered silicon obtained when the amount of water introduced in the deposition chamber was a) optimum and b) too much. Keywords: surface functionalization, low-pressure plasma, humid air plasma, OTS chemical vapor deposition References: [1] Myung, M., Sung, G., Jonathan Kluth, R., Maboudian, J. Vac. Sci. Technol. A 17 (1999) 540.

60 The use of HiPIMS for DLC deposition of micrometer thick coatings P3-11 1,* 1 1 1 1 2 3 C. Vit, elaru , A.E. Kiss , A.C. Parau , M. Dinu , L.R. Constantin , A. Sobetkii , T. Kubart 1National Institute of Research and Development for Optoelectronics - INOE 2000, 409 Atomistilor St., Magurele-Bucharest, P.O.Box MG 05, Romania 2SC MGM STAR CONSTRUCT SRL, 7 Pancota St, Bucharest 022773, Romania 3Department of Engineering Sciences, The Angstr¨omLaboratory,˚ Uppsala University, P.O. Box 534, SE-751 21 Uppsala, Sweden *[email protected]

The High Power Impulse Magnetron Sputtering (HiPIMS) technique has gained a lot of interest in the last decades [1], being implemented in an increasing number of applications. Many types of target materials and gas compositions were used to obtain a wide variety of coatings [2]. Carbon sputtering is a particularly challenging task, due to relatively low ionization degree, low sputtering rate and the occurrence of micro arcs under high power regimes [3]. This contribution deals with the development of HIPIMS process for the deposition of DLC coatings by sputtering of a graphite target. The development is focused on the increase of peak current and corresponding ionized flux to the substrate [4]. This task is performed by tuning some key parameters of the discharge, each dedicated to control one or more issues related to carbon sputtering. In that respect, peak voltage was used to finely tune the power input to the target and the sputtering regime, pulse duration was used to reduce the number of arc events and increase the maximum peak power, gas composition (Ar/Ne/C2H2 mixtures) was used to increase the electron temperature, the ionization degree and correspondingly the maximum achieved current. Moreover, addition of C2H2 is shown to increase the deposition rate by a factor of two, without significantly affecting the coatings overall properties. The DLC coatings in the micrometer thickness range were deposited both on Si and on 304L steel substrates. The stability of the coatings was ensured by using a thin Ti interlayer to improve the adhesion between the DLC coating and the substrate. Nanoindentation hardness adjustable in the range from 15 to 30 GPa was obtained. The friction coefficient under dry environment was around 0.01, typical for hard carbon coatings, with wear rates tested against sapphire ball in the range of 0.5−1 × 10−6 mm3N-1m-1.

Keywords: HiPIMS, diamond like carbon, hard coatings

Acknowledgement: This work was supported by M-ERA Net project TANDEM through the Romanian Ministry of Research and Innovation, UEFISCDI, project No 56,57/2016, PROINSTI- TUTIO Project contract no. 19PFE/17.10.2018, National Core Project 18N/08.02.2019.

References: [1] Sarakinos K., et al, Surfac & Coatings Technology 204 (2010) 1661-1684. [2] Yuan Y., et al. Plasma Sci. Technol 20 (2018) 065501. [3] Lattemann M. Diamond & Related Materials 20 (2011) 68–74. [4] Vitelaru C. et. Al. J.Phys. D: Appl. Phys. 52 (2018) 165201.

61 CNW/WO3 hybrid nanostructures obtained by plasma assisted P3-12 thermal evaporation 1,2,* 1 1 1,2 1 3 1,2 L.G. Carpen , T. Acsente , S. Vizireanu , B.I. Bit, ˘a , V. S˘atulu , E. Matei , G. Dinescu 1National Institute for Lasers, Plasma and Radiation Physics, Magurele, Romania 2University of Bucharest, Faculty of Physics, Magurele, Romania 3National Institute for Materials Physics, Magurele, Romania *lavinia.carpen@inﬁm.ro; tomy@inﬁm.ro

Hybrid nanostructures consisting of carbon nanowalls (CNW) decorated with tungsten oxide (WO3) have been successfully synthesized using plasma assisted thermal evaporation. These were prepared using a horizontal furnace tube that allow simultaneous plasma ignition and heating. The material to be evaporated was placed in the center of the furnace heating region (800 ◦C), while in the extremity of the furnace hot zone (at 500 ◦C, 400 ◦C, and 300 ◦C) were placed three silicon substrates deposited (coated) with CNW [1]. Firstly, the W nanoparticles (WNPs, obtained by magnetron sputtering combined with gas aggregation [2]) were oxidized in a mixture of Ar/O2 at a temperature of 800 ◦C for 2 hours. A dynamic process of WNPs oxidation followed by the oxide evaporation takes place; subsequent condensation of the oxide vapors on the CNW substrates lead to their decoration. In the second type of experiments, the oxidized WNPs were used as evaporation source material; these processes were performed in Ar ﬂow, with and without plasma. The samples were characterized by SEM and XPS measurements. XPS investigations reveal the presence of WO3 on the top CNW leading to hybrid nanostructures. SEM images reveal that the decoration process depends strongly on the substrate temperature. Thus, in the absence of plasma, either in Ar or ◦ ◦ Ar/O2, the decoration process was most eﬃcient for 400 C (see Figure 1 a), while at 500 C the CNW substrate degradation was observed. At 300 ◦C is hardly to observe any decoration of the CNWs.

◦ ◦ Figure 1: SEM images of the CNW decorated with WO3: a) at 400 C in Ar/O2; b) 500 C in Ar plasma. In contrast, the CNW decoration process performed in Ar plasma was eﬀective for all working temperatures. In this situation, the WO3 nanoparticles totally cover the CNW walls and the dimension of the decoration grains increases with the substrate temperature. This novel nanostructured material has potential for photocatalysis and gas sensing applications. Keywords: tungsten nanoparticles, carbon nanowalls, plasma assisted decoration Acknowledgement: We acknowledge the ﬁnancial support in the frame of the projects: EUROfu- sion Consortium WPEDU-RO and CCCDI – UEFISCDI project PCCDI 46/2018 within PNCDI III INFLPR 4N/2018, MALASENT References: [1] Vizireanu, S., et al., Plasma Sources Science and Technology 19 (2010) 034016. [2] Acsente, T., et al., The European Physical Journal D 69 6 (2015) 161.

62 Chitosan-based patches obtained by atmospheric pressure dielectric barrier discharge plasma treatment P3-13 B. Mitu1,*, S. Iorgoaia1, C. Chiﬁriuc2, C.M. Saviuc2, G. Dinescu1 1National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor, Magurele 077125 Romania 2University of Bucharest, Faculty of Biology, 60101, Bucharest Romania *mitub@inﬁm.ro

Chitosan is a polysaccharide commercially produced by deacetylation of chitin (extracted from crustaceans). It is well known for its properties like biocompatibility and biodegradability [1]. By presenting an intrinsic antimicrobial effect, this natural polymer is extensively studied for its applications, either alone or in combination with other components, as Ag, for the treatment of epithelial infections, as well as for the stimulation of wound healing [2]. In the present work, we investigate the effect of atmospheric pressure plasma for the treatment of non-woven polyester textiles, in order to induce plasma grafting of chitosan and chitosan – Ag nanocomposites. A linear plasma source based on dielectric barrier discharge configuration working in radiofrequency (13.56 MHz) at 100 W in a continuous argon flow of 3000 sccm was used for scanning the textile surface in order to induce superhydrophilic behavior. Chitosan solutions, with or without Ag nanoparticles inclusion (30 nm diameter, concentration in the range 1–5 %), were afterwards grafted onto the surface and a similar plasma treatment was performed in order to enhance adhesion and stabilize active components onto the surface. The morphological characteristics of the chitosan-based patches were investigated by means of Scanning Electron Microscopy (SEM) while the chemical composition of the obtained materials was evaluated by X–ray Photoelectron Spectroscopy (XPS). The antifouling activity was tested against the Gram negative Escherichia coli, Gram positive Staphylococcus aureus as well as the fungal Candida albicans strains, using a culture-based, quantitative assay of viable cells included in biofilms harvested after 24 h, 48 h and 72 h of incubation. The effect of the total chitosan loading and Ag NP concentration is discussed.

Keywords: chitosan, Ag nanoparticles, dielectric barrier discharge

Acknowledgement: This work was supported by a grant of the Romanian Ministry of Research and Innovation, CCCDI – UEFISCDI, project number PN-III-P1-1.2-PCCDI-2017-0728, within PNCDI III and by Nucleus-Programme, project nr. 19150101.

References: [1] Kim S.-K., et al., Carbohydrate Polymers 62 (2005) 357–368. [2] Latif U., et al., Int. J. Polym. Mat. Polym. Biomat. 64 (2015) 448-458.

63 P3-14 Carbon-based thin ﬁlms for high-power laser applications L. Dinc˘a1,2,*, B. Diaconescu1, V. S˘atulu3, V. M˘ar˘ascu3, C. Gheorghiu1, B. Mitu3 1IFIN-HH / ELI-NP, M˘agurele,Romania 2’Politehnica’ University of Bucharest, Bucharest, Romania 3INFLPR, M˘agurele, Romania *[email protected]

Interaction between high-power lasers (HPL) and targets presents a new method to accelerate positive ions and electrons at high kinetic energies. Solid targets can generate high density beams of accelerated particles, much higher than classical electromagnetic methods. Using thin solid films as targets, charged particles can be accelerated even at ultra-relativistic energies [1]. Because thin film target is destroyed after one HPL interaction, it is needed to use a structure which is designed as an array of free-standing zones of thin film separated by non-free-standing zones (which have substrate support). In this work, thin carbonic films were fabricated and characterized. Plasma enhanced chemical vapor deposition (PE-CVD) was used to grow films on substrates, with different precursor gaseous mixtures. Hydrogen content of precursor mixture had an important role in sp3 and sp2 carbon concentration of the grown films [2]. The suitability of these films for using as targets for HPL with λ = 800 nm was assessed by: atomic force microscopy and optical profilometry for roughness determination; contact profilometry for thickness; X–ray photoelectron spectroscopy for quantitative analysis of carbon allotropes from 3 film. For the samples grown using CH4+H2 precursor mixture (C:H=1:9), sp carbon concentration was 45.5 %, that meaning 2.15 times more than for the samples grown in CH4+Ar. Roughness values were found well below λ/10 limit, for all samples.

Keywords: high-power laser, target, carbonic ﬁlm

Acknowledgement: This work was supported by the Plasma Processes, Materials and Surfaces Group from INFLPR and by the Target Laboratory from ELI-NP.

References: [1] Bulanov, S. S., et al., Physics of Plasmas 19 (2012) 093112. [2] Bachmann, P. K., et al., Diamond and Related Materials, 1 (1991) 1-12.

64 Plasma dry etching, a critical step in SiC device technology. Physico-chemical mechanisms, and applications P3-15 M. Lazar1,*, J. B´eal1, F. Marty2, A. Rumyantseva1 1Light, nanomaterials, nanotechnologies (L2n), CNRS, University of Technology of Troyes, France 2ESYCOM, CNRS, ESIEE-Paris, France *[email protected]

Silicon Carbide (SiC) is a wide bandgap semiconductor material, intensively studied in the last decades in an attempt to substitute the silicon (Si) based semiconductors and improve their properties in power device electronics. The new generation of SiC-based power electronics for hybrid and full-electric auto-motives are expected to have a higher efficiency, but nevertheless to be lighter and compacter [1]. Many advantages of SiC come from the intrinsic physical properties, which are adequate to a high critical electric field strength, and an excellent thermal stability and conductivity. Also, a high hardness, resistance to corrosion and to radiation damage, qualities that make SiC a promising candidate for a wide variety of applications, especially for the use under critical conditions, e.g., sensors for drilling, for spacecraft techniques, or wastewater monitoring. Recently, a new interest has been manifested for its potential in quantum technology, due to the so-called room temperature luminescent defects, also known as color centers, which are atomic defects in the lattice of SiC crystals that can emit photons with unique spectral signatures. In the fabrication of these electronic devices on SiC, an important role is played by the plasma- based dry etching as wet approaches are not conceivable due to the SiC chemical inertness and the strong bonding between Si and C in SiC. Typically, fluorinated plasmas are used in ICP (Inductively Coupled Plasma) or RIE (Reactive Ion Etching) reactors to adapt SiC surfaces (eliminating areas of high electric field strength in power devices), to create color centers resonators (by localizing them in submicron pillar structures) or roughening SiC in order to increase the active detection surfaces for the different sensors and to extract light with an optimized optical index. Figure 1 presents examples of SiC surface processed with SF6/O2 plasma ICP with deep trenches required by the different geometries of power and nanophotonic devices as well as a ”spontaneous” growth of ”Black-SiC”.

Figure 1: Scanning electron microscopy images of SiC surfaces processed with ICP SF6/O2 plasma

Details will presented about the physical and chemical mechanisms involved during the ﬂuori- nated plasma etching of SiC, the obtained structures and applications. Keywords: SiC etching, ICP, ﬂuorinated plasma References: [1] Beaurenaut, L., Power Electronics Europe 3 (2018) 22. Canceled On Last Minute

65 Plasma modification of vertically graphene for energy P3-16 storage 1,* 1 1 1 2 3 1 S. Vizireanu , S.D. Stoica , B.I. Bit, ˘a , A. Trefilov , A. Achour , M. Iordoc , G. Dinescu 1National Institute for Lasers, Plasma and Radiation Physics, 77125, Magurele – Bucharest, Romania 2LISE Laboratory, Research Centre in Physics of Matter and Radiation (PMR), University of Namur, BE-5000 Namur, Belgium 3A National Institute for Research and Development in Electrical Engineering, ICPE-Advanced Researches, 313 Splaiul Unirii, 030138, Bucharest-3, Romania *s vizi@infim.ro

Micro-supercapacitors attracted considerable attention, because represent the future of the new generation of energy storage and conversion devices. Various nanomaterials are usually used as high-performance electrodes for electrochemical reactions. In particular, vertically graphene layers or carbon nanowalls (CNW) present special interest in fabrication of nanostructured electrodes, due to their unique properties like high active surface, high electrical conductivity, mechanical and chemical stability. In this study we present some routes for enhancement of the efficiency of electrodes based on vertically oriented graphene. The graphene layers were obtained by using low pressure RF plasma jet from Ar/H2/C2H2 on various substrates (silicon wafers, Pt electrodes on Si or carbon paper). The layers were further processed by plasma functionalization in nitrogen, coating with ZnO layers by pulsed laser deposition [1], decoration with Ag, Pt nanoparticles by magnetron sputtering [2], with RuO2 nanoparticles by electrodeposition [3], and covered with conducting polypyrole (Ppy) polymer by RF-PECVD. The morphology, composition and structures of the as- made and the modified materials were intensively studied. The electrochemical performances of these hybrid nanomaterials and nanocomposites were tested by cyclic voltammetry, and electrochemical impedance spectroscopy (EIS). After plasma functionalization of CNW, we observed a significant enhancement of their electrochemical activity. Under optimized conditions, the CNW-ZnO hybrid electrode exhibits a high current density of 0.2 mA/cm2 and areal capacitance of 4.3 mF/cm2, and high life time (over 26000 cycles in mild electrolyte of 1M KCl). Also, these types of electrodes based on vertical graphene, obtained after decoration of CNW with ruthenium, deliver specific capacitance in excess of 1000 mF/cm2 [3]. The last results show that the electrodes obtained by decoration with Pt nanoparticle of CNWs/PPy composite lead to highest capacitance of 4500 mF/cm2. Such composite CNWs/PPy/Pt layers deposited on carbon paper support, used in GDL fuel cells, show very good power performance comparable to industrial quality membrane assemblies.

Keywords: plasma functionalization, energy storasge, nanoparticles, supercapacitors

Acknowledgement: This work was supported by a grants of the Romanian Ministery of Re- search and Innovation, CCCDI - UEFISCDI, in the frame of Nucleus Programme INFLPR/2019, PN-III-P1-1.2-PCCDI-2017-0387 /80 PCCDI EMERG2Ind and PN-III-P1-1.2-PCCDI-2017-0172/ PCCDI-15/2018-TESTES, within PNCDI III.

References: [1] Guerra A., Vizireanu S., et al, Applied Surface Science 481 (2019) 926-932. [2] Stoica, SD; Vizireanu, S; et al, Plasma Chem. and Plasma Process. 38 (2018) 695-706. [3] Dinh, TM; Achour, A; Vizireanu, et al, Nano Energy 10 (2014) 288-294.

66 Indium oxide thin films by pulsed electron beam deposition: growth and plasma investigation P3-17 F. Gherendi*, N.B. Mandache, M. Nistor** National Institute for Lasers, Plasma and Radiation Physics (NILPRP), Plasma Physics and Nuclear Fusion Laboratory, P.O.Box MG-32, 077125, Bucharest-Magurele, Romania *floring@infim.ro ** mnistor@infim.ro

Transparent conducting thin films are intensively studied for applications in transparent electronics. Among them, undoped and doped indium oxide (In2O3) shows high conductivity and high optical transmittance that make this material still one of the most used transparent conducting oxides for a wide variety of applications. Indium oxide thin films were grown by pulsed electron beam deposition method (PED) on c-cut sapphire single crystal substrates under oxygen gas at different substrate temperatures [1]. PED has features in common with pulsed laser deposition for the deposition of thin films but uses a pulsed electron beam instead of a laser beam for ablating of a target. A slight difference in oxygen pressure during the PED growth (from 2×10-2 to 1.3×10-2 mbar) had strong effects on the electrical and optical film properties, without evidencing large differences in the crystalline structure and film stoichiometry. Therefore, epitaxial In2O3 thin films having bixbyite crystalline phase were grown on single crystal substrates at substrate temperatures higher than 200 ◦C. Under a slight change in oxygen pressure, the electrical properties of indium oxide thin films changed from a non-degenerate semiconductor behaviour (at 2×10-2 mbar) to a degenerate one (at 1.3×10-2 mbar), while for all films the optical transparency had high values ( 80%) in the visible spectral range. In order to understand these pressure effects, the ablation plasma plume obtained at the interaction of the pulsed electron beam with the In2O3 target was investigated by a Langmuir ion probe placed in the substrate position. A correlation established between the film composition, crystallization, electrical, optical properties and kinetic energies of the plasma species and plasma parameters will be discussed.

Keywords: plasma physics, materials science, thin ﬁlm deposition, pulsed electron beam ablation

Acknowledgement: This work was supported by the project 16N/08.02.2019.

References: [1] Nistor M., Gherendi F., Perri`ereJ., Mater. Sci. Semicond. Process. 88 (2018) 45.

67 Fabrics with electromagnetic shielding properties achieved by P3-18 magnetron sputtering deposition A.A. Ardeleanu1, C. Stancu1, L. Surdu2, E. Visileanu2, I-R. R˘adulescu2, M. B˘adic3, C. Morari3, B. Mitu1,* 1INFLPR, M˘agurele-Bucharest, Romania 2INCDTP, Bucharest, Romania 3ICPE-CA, Bucharest, Romania *mitub@inﬁm.ro

Electromagnetic shielding achieved by flexible materials has gained an increased significance in today’s radiation polluted environment [1]. One of the modern approaches for obtaining electromagnetic textile shields with good surface electrical conductivity is represented by the deposition of metallic thin films onto the fabrics. The use of magnetron sputtering technique insures some advantages, e.g. improved reflections of the fabric once metallic coatings are deposited on both sides of the fabric, as well as light weight and good flexibility due to nanoscale thickness of layers [2]. In the present work, cotton and polyester fabrics with various structural parameters, such as yarn finesses, fabric density, and specific mass were used as samples to be coated. Magnetron sputtering technique was utilized for the deposition of Cu layers with various thicknesses, either on one side or on both sides of the fabrics, in order to insure good conductivity of the fabric. In addition, fabric samples with inserted conductive yarns of silver and stainless steel were considered as substrates, as well. The modifications induced by the Cu coatings to the yarns thickness and the fabrics specific mass, as well as the total amount of Cu present in the coated textile materials were determined. Electromagnetic shielding tests were performed on the copper coated samples by means of a TEM cell, according to the ASTM ES07 standard. The fabrics with inserted conductive yarns coated with magnetron sputtering copper layers presented a shielding effectiveness between 20 and 34 dB in the frequency range from 0.1–1000 MHz. It results from the combined shielding effectiveness of the fabrics with inserted conductive yarns of 10–12 dB, on one hand, and the presence of the plasma-deposited copper layers on both sides of the fabrics, on the other hand, which add an improvement of shielding of 10–15 dB.

Keywords: magnetron sputtering, Cu layers, electromagnetic shielding, fabrics

Acknowledgement: This work was supported by Manunet project C28/2018 TexEMFiRe.

References: [1] Schwab A., Kuerner W., Electromagnetic compatibility, Chapter 6 – Electromagnetic shielding, Editura AGIR, 2013 [2] Ziaja J., Jaroszewski M. - EMI shielding using composite materials with plasma layers, InTechOpen, March 2011

68 Copolymerized ﬁlms under atmospheric pressure plasma conditions P3-19 1,* 1 2 3 1 V. Chiriac , I. Topal˘a , L. Curecheriu , M. Dobromir , N. Dumitras, cu 1Iasi Plasma Advanced Research Center (IPARC), Faculty of Physics, Alexandru Ioan Cuza University of Iasi, Blvd. Carol I nr. 11, Romania 2Dielectrics, Ferroelectrics & Multiferroics Group, Department of Physics, Alexandru Ioan Cuza University of Iasi, 11 Bv. Carol I, 700506, Iasi, Romania 3Research Department, Faculty of Physics, Alexandru Ioan Cuza University of Iasi, Blvd. Carol I nr. 11, Romania *[email protected]

The copolymerization is a chemical reaction between two or more different monomers getting polymeric films with various physic-chemical properties, usually different as characteristics of each polymer. By a precise control of each component and its ratio, also by use diverse methods and conditions of copolymerization, it can change the properties of final product. For example, using hydrophilic/hydrophobic monomers with different ratio of functional groups it can prepare polymer films with different wettabilities and pH responsiveness, or combinations of ethylene and propylene monomers, each of these giving a semi-crystalline polymer, but the copolymer exhibiting elastomeric properties [1, 2]. The copolymerized films can be prepare by various ways including conventional chemistry, plasma at low and atmospheric pressure, RF plasma etc., methods which are capable to combine the initial monomers into new and unexpected properties of final products. Our research is intended to tailor hybrid structures for specific interactions and functional devices. For this aim it used a combination of two monomers, respectively thiophene (Th) and ethylene glycol (EG), taking into account explicit characteristics of each final polymer, i.e., the PTh as a nondegradable and PEG as a water-soluble polymer. An atmospheric pressure plasma in a plan-plan geometry, working in a mixture of helium plasma and monomer vapors is used as chemical reactor. During the polymerization reactions the plasma parameters were monitored by electrical and optical signals keeping similar conditions of deposition, respectively voltage, frequency, flow rates of gases and duration. The copolymerized films are characterized by contact angle measurements (CA) for wettability evaluation and time stability, XPS for chemical composition, morphology by AFM/SEM, absorbtion by UV-Vis, crystallinity by XRD and dielectric properties by Impedance Spectroscopy (IS). Thus, chemistry of the films showed a well accordance with the chemical formula of monomers and presence of functional groups based on oxygen confirmed/attested oxidation processes during the film deposition on the substrate. At interaction with water the films of pP(Th+EG) developed a heterogeneous morphology, from nano to macro scale, probably due to a self-assembly process of PEG macromolecular domains in water solution. These PTh/PEG films could be used for potential applications, as porous substrates for selective functional groups deposition, including bioconjugation via PEG (PEGylation) or in optoelectronics. Our technique based on plasma was selected taking into account particular advantages, for example the possibility to use versatile experimental set-ups, efficiency, precise control of polymeric film thickness and lesser costs comparing with another methods

Keywords: plasma at atmospheric pressure, copolymerizated ﬁlms characteristics

References: [1] Iqbal Muzammil et al.,Plasma Processes and Polymers 14 (2017) 1-10. [2] D. Mantione et al., Polymers 9 (2017) 354-375. [3] B. X. Valderrama-Garc´ıaet al., Molecules 21 (2016) 172-190.

69 Enhanced optical and mechanical properties of silicon dioxide thin P3-20 ﬁlms deposited by reactive HiPIMS V. Tiron1,*, I.-L. Velicu2, A. Ceban2, D. Cristea3, G. Bulai4, D. Munteanu3 1Research Department, Faculty of Physics, Alexandru Ioan Cuza University of Iasi, Iasi 700506, Romania 2Faculty of Physics, Alexandru Ioan Cuza University of Iasi, Iasi 700506, Romania 3Faculty of Materials Science and Engineering, Department of Materials Science, Transilvania University, Brasov 500068, Romania 4Integrated Center of Environmental Science Studies in the North-Eastern Development Region (CERNESIM), Alexandru Ioan Cuza University of Iasi, Iasi 700506, Romania *[email protected]

The High Power Impulse Magnetron Sputtering (HiPIMS) technology is currently revolutionizing the coating industry, combining all the advantages of the common coating technologies and methods currently existing on the market. Thanks to a high ionization degree of sputtered species, HiPIMS brought great advantages and opened new perspectives in the area of magnetron sputtering technologies. Unfortunately, many of the technologically attractive thin films are compound films and the reactive magnetron deposition process still needs strategies to increase the deposition rate, to eliminate or reduce as much as possible the hysteresis behaviour and to stabilize the transition zone between the metallic and compound modes. Recently, the reactive HiPIMS (R-HiPIMS) process has been closely investigated, showing great potential in reducing or eliminating hysteresis effects, higher deposition rate and more stable deposition processes. Due to their excellent electrical, mechanical, optical and chemical properties, silicon oxide films have been widely used in semi-conductor, microelectronics and optoelectronics field as passivation or antireflection layers. Deposition of high-quality silicon dioxide (SiO2) thin films with enhanced not only mechanical, but also optical properties is a real challenge. The aim of this paper is to grow silicon dioxide thin films by R-HiPIMS with enhanced optical and mechanical properties to be used as antireflection coatings. Transparent SiO2 thin films, with thickness of approximately 300 nm, were deposited by R-HiPIMS on flexible and rigid substrates. During the deposition processes, a typical set of discharge parameters, consisting of a target voltage amplitude of -700 V, a pulse duration of 3 µm and a substrate-to-target distance of 7 cm was fixed. The Si target was sputtered in argon (mass flow rate of 50 sccm) and O2 (mass flow rate of 5 sccm) atmosphere, under a total pressure of 1 Pa. Topological, structural, optical and mechanical properties were investigated using atomic force microscopy (AFM), X-ray diffraction (XRD), UV-Vis-NIR spectroscopy, optical microscopy, nanoindentation, scratch and bending tests. The obtained coatings exhibit dense amorphous to nanocrystalline structure, very low surface roughness, high hardness, good wear-resistance, fracture toughness, strain resistance and adhesion to the substrate. The average optical reflectance measured in the spectral range of 190–1100 nm is less than 1%.

Keywords: HiPIMS, silicon dioxide, antireﬂection coating, mechanical durability

70 Synthesis and characterization of ZnO-loaded TiO2 nanotube array layers for enhanced photocatalytic application P3-21 1,* 2 2 3 2 2 M. Dobromir , C.T. Teodorescu-Soare , R. Apetrei , G. Stoian , V. Pohoat, ˘a , D. Luca 1Department of Research, Faculty of Physics, Alexandru Ioan Cuza University of Iasi, 11, Carol I Blvd., 700506 Iasi, Romania 2Faculty of Physics, Alexandru Ioan Cuza University of Iasi, 11, Carol I Blvd., 700506 Iasi, Romania 3National Institute of Research and Development for Technical Physics, 47, Dimitrie Mangeron Blvd., 700050 Iasi, Romania *[email protected]

TiO2 is a highly photocatalytic oxide semiconductor material, which, activated by UV light, can be used for pollutant degradation in low-cost, environment-friendly applications. Large area of the catalyst/organic pollutant interface is a key factor to improve the degradation rate and efficiency. This requirement is fulfilled by both nanopowders and uni- or bi-dimensional structures. Nanotube structures feature particularly both large area/volume ratio and faster electron transport, as well as low recombination rate of charge carriers, which enable increased photocatalytic efficiency and durability [1]. The addition of ZnO nanoparticles on the nanotube surface may results in the formation of semiconductor heterojunctions, lead to supplementary spatial separation of electron-hole pairs and to reduced recombination rate [2]. TiO2 nanotube arrays were grown in this study at the surface of Ti metal foils by anodization under a constant voltage of 30 V. For this purpose, we used a diode-type electrochemical cell (using a Pt cathode), with organic electrolyte containing fluorine to prepare titania layers of nanotubes with average diameter of 88 nm, 1.6 µm long, for an anodization time of 3 hrs. Non-contiguous ZnO thin films were then sputter-deposited on top of TiO2 nanotube arrays, at room temperature. The sputtering source was a reactive RF magnetron discharge, using a 2” dia. Zn cathode target, running in a 5:1 Ar/O2 gas mixture, at the total pressure of 2.7 Pa. ZnO thin films with thickness values of 50 nm, 110 nm and 170 nm were prepared for deposition times of 30, 60 and 90 minutes, respectively. The structure, morphology and elemental composition of ZnO-loaded crystal-grade TiO2 nanotube array layers were investigated by XRD, SEM, XPS and EDS techniques, respectively. The samples contained a mixture of anatase and rutile TiO2 nanodomains, with anatase weight percent- age decreasing from 68 wt.% in reference bare TiO2 sample to 57 wt.% in the layer sample with the highest ZnO coverage. The XPS data showed the signatures of Ti 2p, Zn 2p XPS and O 1s core levels, as well as the C 1s signal of adventitious carbon. As resulted from the deconvolution of the high-resolution XPS spectra the Ti2+, Ti3+ and Ti4+ and Zn2+ oxidation states coexist in the loaded nanotube samples. Degradation tests were performed to derive the specific degradation rates of methylene blue pollutant by the investigated samples. Contact angle measurements were, additionally, performed to indirectly monitor the (extended) photoactivation duration, associated with the presence of TiO2/ZnO heterojunctions.

Keywords: TiO2 nanotube arrays, ZnO thin ﬁlms, RF magnetron sputtering

References: [1] Regonini, D., et al., Materials Science and Engineering R 74 (2013) 377-406. [2] Xiujuan, L., et al., Journal of Molecular Structure 1148 (2017) 347-355.

71 Properties of multilayer coatings obtained by pulsed laser P3-22 deposition V. Ion*, N.D. Scarisoreanu, A. Andrei, A. Bonciu, M. Dinescu National Institute for Laser, Plasma and Radiation Physics, Magurele, Bucharest, Romania *valentin.ion@inﬂpr.ro

Microwave antenna developed for space industry must be able to operate in harsh environments where the radiation dose and temperature gradients are high. In order to protect these electronic devices, various coating techniques and materials were developed. Pulsed laser deposition (PLD) coatings allow the deposition of diﬀerent materials on the microwave antenna for shielding it from the outer space harsh conditions. In this work we report the obtaining of multilayer structures for electronic devices protection in space environments. For this purpose, the heterostructures of Al2O3/Y:ZrO2 were deposited by PLD on coplanar antenna. The microwave antenna was obtained by photolithography technique on alumina and high resistive Si substrate. The frequency response of antenna was measured before and after deposition of heterostructures. The thicknesses of layers were calculated by spectroscopic ellipsometry (SE) and the crystalline and morphologic properties of the coatings were studied by X-ray diﬀraction, atomic force microscopy (AFM) and by scanning electron microscopy (SEM). The chemical evaluation of the Al2O3/YSZ heterostructures was performed using energy dispersive X-ray spectroscopy (EDAX). The penetration depths of proton and alpha particles into heterostructures have been simulated using the SRIM (stopping and range of ions in matter) code.

Keywords: multilayer coating, PLD, AFM, XRD, spectroscopic ellipsometry

Acknowledgement:This work was supported by a grant of the Ministry of National Education and Scientiﬁc Research, RDI Programe for Space Technology and Avanced Research - STAR, project number 168/20.07.2017.

72 Characterization of chlorinated polythiophene ﬁlms obtained under the plasma conditions P3-23 1 2,* 3 4 2 I. Mih˘ail˘a , V. Chiriac , V. Tiron , L. Curecheriu , N. Dumitras, cu 1Integrated Center of Environmental Science Studies in the North-Eastern Development Region (CERNESIM), Alexandru Ioan Cuza University of Iasi, Bd. Carol I No. 11, Iasi, 700506, Romania 2Iasi Plasma Advanced Research Center (IPARC), Faculty of Physics, Alexandru Ioan Cuza University of Iasi, Bd. Carol I No. 11, Iasi, 700506, Romania 3Research Department, Faculty of Physics, Alexandru Ioan Cuza University of Iasi, Iasi 700506, Romania 4Dielectrics, Ferroelectrics & Multiferroics Group, Department of Physics, Alexandru Ioan Cuza University of Iasi, Bd. Carol I No. 11, Iasi, 700506, Romania *[email protected]

Usually, the polymeric films are characterized by a very low electrical conductivity and various methods (chemical, electrochemical, vapour deposition, plasma) are used to modify this dielectric behaviour. In our experiments, thin films with a lower optical band gap than the polythiophene were obtained by polymerisation of thiophene mixture with various source of negatively charged ions (FeCl3, CuCl2 and CHCl3-trichloromethane) using a low-cost technique based on atmospheric pressure plasma. The thin films were characterized by ATR-FTIR, contact angle measurements, UV-VIS, XPS, IS, XRD and profilometry (for surface topography and roughness) techniques. The dielectric properties of the thin films were analysed in a frequency range of 1-106 Hz aiming to correlate the dielectric response with the slow or fast events of molecular chains and with relaxation processes, too. The contribution of the above chloride ions (as electron donors) to the semiconducting behaviour of the thin films can be estimated by the optical band gap energy (Eg). Using the measured optical absorption spectra of thin films and the Tauc’s equation

(αhν)1/n = B (hν − Eg) ,

(αhν)1/n as function of photon energy hν is plotted (Tauc’s plot). By extrapolating the linear portion of the dependence above mentioned to zero, the Eg is estimated. In the Tauc’s equation, α is coefficient of absorption, B a constant (the band tailing parameter), h Planck’s constant and n a constant related to the density of states distribution (1/2, 3/2, 2 and 3), available for direct allowed, direct forbidden, indirect allowed, and indirect forbidden transitions. The Tauc’s equation is an accepted approximation for amorphous and thin films with Eg above 1 eV and α larger than 104 cm-1, conditions that are met by our samples. The thickness of the films and its homogeneity onto the substrate of glass is also analysed. Additionally, Tauc analysis can offer the possibility to study type of electronic transitions in the sample, as well as estimations on extinction coefficient and refractive index. Possible errors due to films thickness measurements, presence of defects, inhomogeneous deposition and how affect the Eg values are also discussed. The results showed that a mixture of thiophene and trichloromethane (1:1) can be the most convenient solution to obtain thin films with lower optical band gap energy that in the case of polythiophene films. A subsequent sample exposure at chloride vapours shows an reduction of Eg with 28%. Preliminary results suggest that optimization of thiophene monomer / trichloromethane ratio may be an important parameter for improvement the semiconductor character of the samples.

Keywords: Chlorinated plasma polymers based on thiophene, Tauc’method and band gap energy

References: [1] Santosh K. Suram, et al., Am. Chem. Soc., ACS Comb. Sci. 18 (2016) 673. [2] Shujahadeen B. Aziz et al., Nanomaterials (Basel) 9 (2019) 216.

73 Modiﬁcation of elasticity modulus and work of adhesion of PDMS surface by treatment in negative glow plasma of a luminescent P3-24 discharge in argon at low pressure G. Tifui, S. Teodoroﬀ-Onesim, L. Sirghi* Iasi Plasma Advanced Research Center (IPARC), Faculty of Physics, Alexandru Ioan Cuza University of Iasi, Iasi 700506, Romania *[email protected]

Polydimethylsiloxane (PDMS) is an elastomer material often used for fabrication of nano- or micro- structured surfaces for biosensors, microfluid devices or functional surfaces inspired by nature [1]. PDMS with elastic modulus ranged from several tens of kPa to a few MPa can be obtained by using various values for polymer/curing agent mixing ratio, curing temperature and curing time. All these parameters control the number of linking sites between PDMS monomers, which greatly affect friction, adhesion and elasticity of the material. In some applications, the PDMS surface is treated by plasma to increase surface energy (adhesion) [2]. In the present work we study the effect of plasma treatment on the elastic modulus and surface adhesion of PDMS. The PDMS samples were obtained by curing PDMS mixed with curing agent in ratio of 10/1 for 24 hours at 60 ◦C. The samples were cut in pieces (1 cm×1 cm) from a mold of PDMS slab (thickness of about 1 mm) and treated by negative glow plasma of a d.c. glow discharge in Ar at low pressure (0.2 Torr). Details of plasma reactor and plasma treatment were published elsewhere [3]. The elastic modulus, E, and work of adhesion, γ, were determined by atomic force microscopy (AFM) indentation experiments with commercial silicon AFM probes (NSG 30 from Mikromasch). The force-displacement curves recorded during unloading were fit with a theoretical model that allow for computation of E and γ [3]. Figure 1 shows an example of the effect of plasma treatment on force-displacement curves and the corresponding values of these parameters.

Figure 1: Force-displacement curves recorded during loading (upwards arrows) and unloading (downwards arrows) parts of indentation on PDMS surface before and after plasma treatment. In conclusion, plasma treatment determines a strong increase of of E and γ even for short treatment time (20 s). This is an eﬀect of a drastic increase of density of linking sites on the PDMS surface. Keywords: low-pressure plasma, plasma surface treatment, polydimethylsiloxane, nano indentation, surface elasticity, work of adhesion References: [1] Xue, L., et al., Langmuir 32 (2016) 2428. [2] Ruiz, A., et al., Biomaterials 29 (2008) 4766. [3] Sirghi, L.; Rossi, F. Nanotechnology 20 (2009) 365702

74 Posters Topic 4 Plasma Chemistry. Plasma applications in environment management, biology, medicine and agriculture.

Atmospheric pressure plasma jet submerged in liquid for dyes decomposition P4-01 1,2 1,3 1,2 1,2 1,* 1 S.A. Yehia , M. Zarif , L.G. Carpen , B.I. Bit, ˘a , S. Vizireanu , G. Dinescu 1National Institute for Lasers, Plasma and Radiation Physics, 77125, Magurele – Bucharest, Romania 2Faculty of Physics, University of Bucharest, 77125, Magurele – Bucharest, Romania 3Faculty of Engineering in Foreign Languages, University “Politehnica” of Bucharest, Bucharest, Romania *s vizi@inﬁm.ro

The decontamination of polluted waters has been accomplished over the time by chemical methods [1] or by filtration [2]. Chemical decontamination involves major disadvantages due to the use of strong chemicals whose variety depends on the diversity of compounds to be removed. In addition, the use of these substances, despite their effect on decontamination, can have on long time adverse effects on humans and the environment. Filtration may have the disadvantage of having low efficiency in the removal of specific pollutants and microorganisms. Recently, water treatment using atmospheric pressure plasma sources [3] is considered an innovative method involving a low decontamination time with low environmental effects and low costs related to its efficiency. In this contribution we report the applicability of DBD (dielectric barrier) atmospheric pressure plasma jet with annular electrodes for the decontamination of methylene blue solutions (C16H18ClN3S). We tested various configurations of the DBD filamentary plasma sources, all of them working in continuous argon flow and sustained by radiofrequency power supply (RF/13.56 MHz). In order to identify optimal conditions for decontamination several parameters were varied: the discharge tube diameters (6, 10 mm), the gas flow rate (1000-20000 sccm), the working power (50-200 W) and electrodes position. We also monitored the decontamination time of the methylene blue solution for each parameter variation and implicitly the configuration. For the analysis of these plasma source configurations, noninvasive optical emission spectroscopy (OES) investigation was made both through air and in liquid discharge. The decomposition process was also monitored by UV-VIS absorption spectroscopy. The key parameters for obtaining the maximum speed decontamination of dyes were identified as being the tube diameter and the injected power in the discharge.

Keywords: plasma in liquid, plasma decontamination, atmospheric pressure plasma

Acknowledgement: This work was supported by a grant of the Romanian Ministery of Research and Innovation, CCCDICPPA - UEFISCDI, in 2019the frame of Nucleus Programme INFLPR/2019 and project number PN-III-P1-1.2-PCCDI-2017-0637/ 33 PCCDI-MultiMonD2 within PNCDI III.

References: [1] H¨ulya Olmez,¨ Ursula Kretzschmar, LWT - Food Sci.and Tech. 42 (2009) 686–693. [2] Nikolay Voutchkov, Desalination 261 (2010) 354–364. [3] E.C. Stancu, D. Piroi, M. Magureanu, G. Dinescu, 20th International Symposium on Plasma Chemistry (ISPC 20), Philadelphia, USA, 2011 Best Poster Award

77 P4-02 Removal of organic dyes by air atmospheric pressure plasma 1,* 2 1 1 A.L. Breab˘an , I. Mih˘ail˘a , V. Pohoat, ˘a , I. Topal˘a 1Faculty of Physics, Iasi Plasma Advanced Research Center (IPARC), Alexandru Ioan Cuza University of Iasi, Bd. Carol I No. 11, Iasi, 700506, Romania 2Integrated Center of Environmental Science Studies in the North-Eastern Development Region (CERNESIM), Alexandru Ioan Cuza University of Iasi, Bd. Carol I No. 11, Iasi, 700506, Romania *[email protected]

Plasma cleaning of solid surfaces is a technical approach widely used in industries such as semiconductor processing, metallurgy, food packing, dentistry and medical technologies, these being only some of the most important areas. Contaminants removal by using atmospheric pressure plasma is a multi-step process that consists in simultaneous generation of multiple oxygen and nitrogen active species, their synergic interaction with the contaminated surface and ultimately the removal of the contaminants from the surface. We discuss here results concerning the removal of thin organic dyes films (Coomassie Brilliant Blue G 250 and Rhodamine 6 G) on glass substrates, using an air atmospheric pressure dielectric barrier discharge (DBD) that produces a non-thermal filamentary plasma. The thin films of organic dyes were prepared on glass slides by spin coating and they were subsequently exposed to the DBD plasma for a total of 60 minutes each. The DBD electrode assembly was connected to an AC power supply that provides a quasi-sinusoidal high voltage wave, with 50 Hz frequency of 18 kV peak-to-peak voltage. Statistical analysis of current peaks over multiple periods allows the access to peak values and average values of discharge current, together with the assessment of distribution shape. Light absorption measurements in the 380–900 nm range were performed on the plasma exposed thin films using Thermo Scientific - Evolution 300 UV-VIS spectrometer. From these spectra an exponential decrease in the thickness of the contaminant dye layer was confirmed. Furthermore based on the CIE 1931 standard we were able to reconstruct the color level variation of the treated thin films in relation to the treatment time, these results being in good agreement with the previous stated decrease in thickness. Emission spectra of the DBD were recorded using Triax 550 Horiba Jobin Yvon spectrometer in the range of 250–900 nm and a further analysis on this spectra indicates the presence of excited N2 molecules on various ro-vibrational levels. The rotational temperature of the gas inside the gap was found to be close to room temperature, as it was returned from the N2 band profile at 337.13 nm simulation the using Massive OES software [1,2] and the comparison with the acquired spectra.

Keywords: air plasma, dye removal, electrical and optical diagnosis

References: [1] Vor´aˇc,J., et al., Plasma Sources Science and Technology, 26 (2017) 025010. [2] Vor´aˇc,J.et al., Journal of Physics D: Applied Physics, 50 (2017) 294002 .

78 Enhanced biocompatibility properties of poly(ethylene terephthalate) foils after AC He DBD plasma jet exposure P4-03 1,* 1 2 2 2 A.V. Nastuta , M. Butnaru , V. Pohoat, ˘a , V. Tiron , I. Topal˘a 1Biomedical Science Department, Faculty of Medical Bioengineering, ‘Grigore T. Popa’ University of Medicine and Pharmacy Iasi, Iasi, Romania 2Iasi Plasma Advanced Research Center (IPARC), Faculty of Physics, Alexandru Ioan Cuza University of Iasi, Iasi 700506, Romania *[email protected]

Polymers are important nowadays in many fields such us: bio-medicine, food or textile industry. A convenient method for customizing polymer surface properties is the usage of non-thermal, atmospheric pressure plasma discharges. Present study relies on the direct usage of an atmospheric pressure AC He plasma source, based on a cylindrical dielectric barrier discharge, for enhancing the biocompatibility properties of poly(ethylene terephthalate) (PET) foils. Plasma source was characterized by electrical and optical diagnosis methods. We used a 2 slm He flow through the discharge tube and applied a 12 kVpp AC voltage on the discharge electrodes, at 48 kHz, keeping a gap of 5 mm between the discharge tube and the sample. Commercial PET foils (100 µm thick), carefully cleaned with distilled water and ethyl alcohol prior to experiments, were plasma exposed for 60 s. Atomic force microscopy, static contact angle method and ATR-FTIR spectroscopy were used for polymer characterization. The biocompatibility of pristine and plasma treated PET samples was tested using Albino rabbit primary fibroblast cells. The cells were cultured for 24 h, 48 h and 72 h on the PET foils, the cell viability being assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The polymeric samples were also studied for cellular adhesion. Giemsa and Calcein-AM dyes (Sigma Aldrich) were used for cell staining. The characterization of plasma source revealed a 50 W mean power discharge, which has in the global emission spectrum beside He lines also lines and bands corresponding to reactive species + such as: OH radicals, N2,N2 , O. The polymer characterization revealed good surface properties after plasma exposure: increased roughness, water work of adhesion, as well as surface oxidation. No cytotoxic effect of the untreated/treated PET was observed. Increased cell adhesion was found on the treated samples in respect to the untreated and control ones. These experimental findings, proven by the good correlation of the obtained results from plasma diagnosis, surface characterization, along with cell viability and adhesion tests, underline the usage of plasma sources in polymer processing for biocompatibility purposes.

Keywords: plasma physics, biomaterials, plasma medicine

Acknowledgement: This work was supported by the ‘Grigore T. Popa’ University of Medicine and Pharmacy Iasi under the project ’Young Researcher Internal Grant’, no. 30339/28.12.2017.

79 Black pepper (Pipper nigrum) decontamination using low pressure P4-04 plasma C. Muja*, A. Kais, T. Maho, L. Th`erese,Ph. Guillot** DPHE, Universit´ede Toulouse, INU Champollion, Albi, France *[email protected] **[email protected]

Spices play an important role as flavoring agents and are used all around the world. However, a matter of concern related to these products is contamination by potential pathogenic agents such as bacteria and fungi. These agents may cause foodborne diseases, and they can alter the food product organoleptic and nutritional properties. Non-thermal plasma is an alternative to current decontamination methods thanks to the relatively high reactive species and other biocidal agents. In this study, the bactericidal efficacy of a plasma treatment using a coaxial microwave plasma source was assessed. The second objective of this study was to evaluate the impact of the plasma decontamination treatment on physical and organoleptic characteristics of peppercorns. The plasma source (Aura-wave) conception was based on electronic cyclotron resonance in order to sustain the plasma in the low pressure range (10-4 mbar - 10-1 mbar). The experimental set-up consisted of a 40 liters vacuum chamber in which the biological substrate (described below) positioned at a fixed distance. A 2.45 GHz solid-state generator (SAIREM SAS) was used as power feeding to generate the plasma from synthetic air.

Figure 1: Experimental setup for sample treatment from microwave air discharge.

The preliminary study showed that plasma exposure for 60 minutes of black peppercorns generates 1log reduction of the naturally present aerobic mesophilic flora. Furthermore, the bactericidal effect of the plasma source was evaluated using samples artificially contaminated with B. subtilis (ATC6633) endospores. Finally, the peppercorn color change, water content, pigment content and piperine content were assessed in order to evaluate the effect of plasma treatment on the pepper characteristics.

Keywords: low pressure plasma, food decontamination, spices

80 An atmospheric plasma source for seed treatment and biological decontamination P4-05 C. Muja1, M. Soulier1, Ph. Guillot1,*, P. Belenguer2,** 1DPHE, Universit´ede Toulouse, INU Champollion, Albi, France 2Laplace, Universit´ede Toulouse, UPS, INP, CNRS, Toulouse, France *[email protected] **[email protected]

Atmospheric plasma treatment can affect growth and physiology of plants. Some recent works on seeds shown modifications of the surface properties and stimulation of seed germination. A plasma exposure can also have biocidal or fungicidal effects on seeds. In this preliminary work, an atmospheric multiple points plasma source has been developed. The source is composed by thousands of points arranged in concentric circles. The diameter is approximately 90 mm. The power supply is a DC one generating 35 kV and 1 mA (max values). The voltage is applied to the multiple points. The ground is connected to the substrate (conductive grid). The plasma is generated in ambient air between the multiple points and the conductive grid. The experimental set-up is presented on Figure 1. For plasma treatment, the samples could be placed on the grid (direct treatment) or under the grid (indirect treatment using the ionic wind generated by the discharge.

Figure 1: Atmospheric plasma source used for the sample treatment.

First, the current characterization as a function of voltage was performed to characterize the plasma source. Next spatial optical emission distribution measurements were performed with an optical spectrometer (HR2000+, Ocean Optics) from the emission spectra for the main observed species. In a preliminary work, this source was used to evaluate the plasma eﬀect on diﬀerent seed properties and seed germination. The seeds were directly in contact with the plasma or exposed to the ionic wind generated by the multiple discharges.

Keywords: Atmospheric plasma, DC discharge, seed treatment, decontamination

Posters Topic 5 Fusion plasma physics and technology.

Enhanced XRF method applied on fusion plasma high Z materials integrated in marker lamellae P5-01 M. Lungu1,*, C. Dobrea1,3, I. Porosnicu1,2, A. Sima1,3, I. Tiseanu1 1National Institute for Laser, Plasma and Radiation Physics, Bucharest, Romania 2Faculty of Physics, University of Bucharest, Magurele, Romania 3Technical University of Cluj-Napoca, Faculty of Science and Material Engineering, Cluj-Napoca, Romania *mihail.lungu@inﬂpr.ro

The thickness of the coating of a specially designed marker lamella that was exposed to the fusion plasma environment can provide crucial and relevant information into defining a state of the art material solution to be implemented as plasma facing component. Generally, marker lamellae are fabricated in multilayer configurations that integrate high Z materials as tungsten [1, 2]. By studying different configuration samples as multilayer alloys and compounds, the material migration that occurs in the form of erosion, transport, deposition and re-erosion can be interpreted in order to provide valuable information that would take the research community a step closer into understanding and mitigating the plasma-wall interactions [1]. In this work, non-destructive X-ray fluorescence method were applied for sample thickness characterizations on marker lamellae. In order to provide calibrated thickness results, the X-ray fluorescence-based methods have to be calibrated. Therefore, several calibration protocols were applied in relation to the investigated sample configuration. Thus, Low Energy X-ray fluorescence (macro-XRF) method that was developed at the NILPRP in the X-ray Microtomography Laboratory was enhanced based on several protocols based on Monte Carlo simulations and sample based measurements. In the current work, different erosion-resistant functional coatings applied as fusion plasma related lamellae, in form of alternative multilayers of W and Mo depositions on W substrate, were successfully investigated. Investigations regarding W thickness distributions were conducted as line profiles. Briefly, the W line profile results were compared with similar samples investigated by means of RBS method [3]. Based on the comparisons, methodology validation was conducted, thus enhanced XRF techniques proved to be a reliable candidate as non-invasive investigation tool.

Keywords: fusion plasma, thin coatings, marker lamellae, X-ray ﬂuorescence, Monte Carlo

Acknowledgement: This work was supported by the National Authority for Research and Inno- vation in the frame of Nucleus program - contract 16N /08.02.2019.

References: [1] Coenen, J. W., et al., Nuclear Materials and Energy 12 (2017) 307-312. [2] Kaufmann, M., Neu, R., Fusion Engineering and Design 82 (2007) 521-527. [3] Rubel, Marek et al. “Overview of erosion-deposition diagnostic tools for the ITER-Like Wall in the JET tokamak.” (2013).

85 Collisions between electrons and molecular cations at extreme P5-02 energy N. Pop1,*, F. Iacob2, R. Bogdan3, J. Zs Mezei4, S. Niyonzima5, M.D. EpéeEpée6, O. Motapon7, K. Chakrabarti8, V. Laporta9, I.F. Schneider10,11 1 Dept. of Physical Foundations of Engineering, Politehnica University Timis, oara, Romania 2 Physics Faculty, West University of Timis, oara, Timis, oara, Romania 3Department of Computer and Information Technology, Politehnica University of Timisoara, Timisoara, Romania 4Instititute of Nuclear Research of the Hungarian Academy of Sciences, Debrecen, Hungary 5Déptde Physique, Universitédu Burundi, Bujumbura, Burundi 6Dept of Physics, Faculty of Sciences, University of Douala, Douala, Cameroon 7Faculty of Science, University of Maroua, Maroua, Cameroon 8Dept of Mathematics, Scottish Church College, Calcutta, India 9 P.Las.M.I. lab, Nanotec, CNR, Bari, Italy 10Laboratoire Ondes et Milieux Complexes, CNRS, Universitédu Havre, Le Havre, France 11Laboratoire AiméCotton, CNRS, ENS Cachan and UniversitéParis-Sud, Orsay, France *[email protected]

In this work, we will focus on peculiar aspects of the approach of electron/molecular cation collisions [1], based on the Multichannel Quantum Defect Theory (MQDT). Cross sections and rate coefficients for very low – below .5 eV - energy have been obtained for reactions induced on + + + + + HD and H2 , and for very high – above 3 eV – energy for BeH , BeD , BeT . At total energy below the 3rd–4th vibrational level, rotational interactions induce an increase of about one order of magnitude of the cross section [2, 3] – the effect on the Maxwell rate coefficient is shown in Figure 1 – whereas above the dissociation limit of the electronic ground state ion, dissociative excitation competes strongly with dissociative recombination and vibrational excitation [4-7]. These data are useful in magnetic confinement fusion edge plasma modelling and spectroscopy, in devices with beryllium based main chamber materials, such as ITER and JET, and operating with the deuterium-tritium fuel mix.

+ + + Figure 1: Dissociative recombination Maxwell rate coefficients of H2 (Ni =0 vi = 0), for direct and total (direct and indirect) processes. Keywords: fusion edge plasma, dissociative recombination, rate coefficients References: [1] Iacob, F., et al. , communication at this conference. [2] Motapon, O ., et al., Phys. Rev. A 90 (2014) 012706. [3] EpéeEpée,M. D., et al., MNRAS 455 (2015) 276–281. [4] Niyonzima, S., et al., Atomic Data and Nuclear Data Tables 115-116 (2017) 287. [5] Niyonzima, S., et al., Plasma Sources Sci. Technol. 27 (2018) 025015. [6] Chakrabarti, K., et al., Phys. Rev. A 87 (2013) 0227021. [7] Laporta V., et al., Plasma Sources Sci. Technol. 59 (2017) 045008.

86 Momentum transfer from fast particles to the H-mode plasma layer P5-03 C. Dumitrescu, D.I. Palade*, F. Spineanu National Institute for Laser Plasma and Radiation Physics, M˘agurele,Romˆania *dragos.palade@inﬂpr.ro

The fast particles in tokamak can originate from Neutral Beam Injection (NBI) or from fusion reactions (alpha particles). Due to the high energy many of the fast ions created deep inside plasma are lost from plasma since the neoclassical drift is very large. Some of the fast ions from NBI remain inside with the outermost half of the banana orbit traversing the narrow layer close to the plasma edge where the rotation is able to generate a transport barrier. We have implemented a computer code to calculate the effect of collisions on the distribution function of the fast ions. The code calculates the solution of the Fokker Planck equation with given source (from NBI) with consideration of the pitch angle scattering which provides the velocity space fluxes. We explore the space of parameters for which reliable results are to be expected (taken into account the approximations). We calculate the amount of momentum transferred by the fast ions that are trapped on large bananas into the H-mode layer. This should be the first step in the calculation of the parallel current sustained by the fast ions.

Keywords: Tokamak, NBI, H-mode