1St Nordic Meeting in Physics 16-18 June 2009 Copenhagen

1st Nordic Meeting in Physics 16-18 June 2009 Copenhagen

Arranged by the Danish Physical Society in collaboration with all Nordic Physical Societies

Program

Hosted by DTU Fotonik, Lyngby The 1st Nordic Meeting in Physics has received economic support from Carlsbergfondet, Toyota-fonden, Oticon Fonden and Knud Højgaards Fond.

The meeting has been arranged by the staﬀ at DTU Fotonik.

The Danish Physical Society greatfully acknowledges support from the exhibitors: Casio, Gammadata, Terco, LOT-Oriel Nordic, Pfeiﬀer Vacuum, Lesker Ldt., Metric Industrial, BFI Optilas, Springer, Pearson Education, Ultimate Vacuum, John Wiley, Polyteknisk Boghandel and Matrixmultimedia.

Organizing Committee Nordic Committee Jørgen Schou, Anders Kristensen, Peter Balling Jørgen Schou (DK, Chair), Kalle-Antti Suominen and Britt Boding. (FI), Sveinn Olafsson (IS), Hans Pecseli (NO), Anders Kastberg (SE).

Section committees

AMO (Atomic, Molecular and Optical Physics) Educational Physics Chair: Matti Kaivola (FI). Jan Thomsen (DK), Jan Petter Chair: Ian Bearden (DK). Carl Angell (NO), Ismo Kopo- Hansen (NO), Mats Larsson (SE). nen (FI), Ann-Marie Pendrill (SE). Astrophysics Nanophysics and Nanomaterials Chair: Johannes Andersen (DK). Juri Poutanen (FI), Chair: Ulf Karlsson (SE). Peter Bøggild (DK), Jukka Boris Gudiksen(NO), Sofia Feltzing (SE). Pekola (FI), Kristjan Leosson (IS), Bodil Holst (NO). Biological and Medical Physics Nuclear and Elementary Particle Physics Chair: Mattias Goksör(SE). Lise Arleth (DK), Ilpo Vat- Ian Bearden (DK), Rauno Julin (FI), Dirk Rudolph (SE). tulainen (FI). Plasma Physics Condensed Matter Physics Chair: Hans Pecseli (NO). Jens Juul Rasmussen (DK), Chair: Petriina Paturi (FI). Kim Lefmann (DK), Sven Rami Vainio (FI), Gert Brodin (SE). Stafström(SE). Program

Tuesday 16 June

12:30 Sandwiches and coﬀee 13:00 Opening of conference

13:15 President of Technical University, Lars Pallesen

Plenary talk 13:30 The new holy grail : a quest for a growing correlation length in glass physics Christiane Alba-Simionesco Plenary talk 14:10 Memorization or understanding: are we teaching the right thing? Eric Mazur 14:50 Break and exhibition 15:45 Five topical sessions (AMO, CDM, Nano, PE, Astro). See page 11

17:45 End of sessions 18:00 Dinner After-dinner talk 19:30 (Title to be announced) Dorthe Dahl-Jensen 20:30 Posters I, beer and exhibition

22:00 Buses for hotels and get-together at the Science Caf´e

Wednesday 17 June

Plenary talk 9:00 Exploration of the Ultra-Small and Ultra-Fast Worlds with X-Rays Joachim St¨ohr Plenary talk 9:40 Precision Quantum Metrology and Optical Atomic Clock Jun Ye 10:20 Break and exhibition 10:50 Five topical sessions (Plasma, Bio, Nano, NEP, Astro). See page 13

12:20 Lunch

3 Plenary talk 13:10 Light takes shape: novel photonics for the biomedical sciences Kishan Dholakia Plenary talk 13:50 Complex plasmas - a laboratory for strong correlations Dietmar Block 14:30 Break and exhibition Five topical sessions (AMO, CDM, Nano (2)/Bio (6), PE, Astro). See 15:00 page 15

Plenary talk ESS (European Spallation Source) in Lund: Opportunities for Northern 17:00 Europe Christian Vettier 17:30 Exhibition, Posters II and beer

18:30 Buses for hotels and city center

Thursday 18 June

Plenary talk 9:00 One year of the superconducting pnictides Andrew Boothroyd

9:40 Opening by EPS President

10:00 Break Five topical sessions (AMO (2)/Nano (2), Plasma, Nano, NEP, Astro). See 10:20 page 17

Plenary talk 11:20 The Amazing Diversity of Planetary Systems M. Mayor

12:00 Lunch 13:00 End of meeting - Bus departure for airport and central station

13:30 General Assembly for DFS

14:30 End of DFS General Assembly

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Atomic, Molecular Nanophysics and Condensed matter Physics education Astrophysics and optical physics nanomaterials 15:45-16:15 15:45-16:15 15:45-16:15 15:45-16:15 15:45-16:15 Towards persistent Optical manipulation Electronic ”‘peer The unexpected Quantum transport ﬂow of Bose-Einstein of individual gold and response system”’ used emergence of truth in from classical Condensates in a 2D silver nanoparticles as basis for talking astronomy and molecular dynamics ring trap. and quantum dots physics cosmology Jian-Sheng Wang Martin Zelan Lene Oddershede Carl Angell Bengt Gustafsson 11 16:15-16:45 16:15-16:45 16:15-16:30 Improving Teaching at 16:15-16:45 Rotational cooling of Ultrafast carrier the Basic Physics 16:15-16:30 Subgap resistance of translationally and dynamics in courses to prevent Gravitational lens as a SIS’ Al/AlOx/Al vibrationally cold InGaN/GaN multiple dropping out – standard candle tunnel junctions MgH+ ions quantum wells successes and Danuta Paraﬁcz T. Greibe A. K. Hansen H. P. Porte disappointments Ilkka Hendolin 16:30-16:45 Sub-gap conductance 16:30-16:45 through a spinfull The strongest quantum dot with gravitational lenses in superconducting leads the universe Brian Møller Andersen H. Dahle

Continued on Next Page. . . Atomic, Molecular Nanophysics and Condensed matter Physics education Astrophysics and optical physics nanomaterials 16:45-17:15 16:45-17:00 16:45-17:15 16:45-17:00 In-situ growth of 16:45-17:15 Spontaneously trapped Acceleration – in Efficiency of Brownian two-terminal silicon Early galaxy assembly magnetic flux quanta Student Conceptions motors in dissipative nanowires from locally and evolution: Recent in a quenched niobium and in Mathematics, optical lattices heated cantilevers in progress ring Physics and Life H. Hagman TEM Tommy Wiklind A. V. Gordeeva Ann-Marie Pendrill Christian Kallesøe 17:00-17:15 17:00-17:15 Collective Strong materials and magnetic Coupling with Ion refrigeration at room Coulomb Crystals in temperature. an Optical Cavity Britt Rosendahl Joan Marler Hansen 17:15-17:45 17:15-17:30 17:15-17:30 Conceptualizing 17:15-17:30 17:15-17:30 Unravelling Time-resolved THz Electrons and Photons InP x-ray detector for Cosmic Evolution of non-Markovian waveguide as Quantum Particles 12 nanoscale resolution Submillimeter Galaxies dynamics spectroscopy in Physics Teacher Luisa Ottaviano , Michal Michalowski K.-A. Suominen , David G. Cooke Education Ismo T. Koponen 17:30-17:45 17:30-17:45 Development of 17:30-17:45 Powerful and 17:30-17:45 Integrated Electronics From spin squeezing to Cost-Effective Escape of Lyman α for Readout of High non-Gaussian atomic Elliptical Neutron radiation from young, Frequency quantum states Guide Designs for the dusty galaxies Micro/Nano- Jürgen Appel ESS Peter Laursen Mechanical Resonator Kaspar H Klenø Meng Tang Wednesday 10:50 - 12:20

Nuclear- and Bio- and medical Nanophysics and Plasma physics Astrophysics elementary physics nanomaterials particle physics 10:50-11:05 10:50-11:20 10:50-11:20 Structure of thin-film Osmotically driven Improved Polymer Dye 10:50-11:20 10:50-11:05 oxides from ab initio flows in microchannels Lasers with Emergent complexity Understanding the thermodynamics: and their relation to Multifunctional in soft Yukawa systems Star Formation Rate ultra-thin alumina 13 sugar transport in Photonic Crystal Kristoffer Rypdal Ake˚ Nordlund films on titanium plants Mads Brøkner carbide K˚are Hartvig Jensen , Christiansen J. Rohrer 11:05-11:20 11:05-11:20 Isotropic metal Gamma-ray burst host deposition technique galaxies for metamaterials D. Malesani fabrication R. Malureanu 11:20-11:35 11:20-11:35 11:20-11:35 11:20-11:40 Water Isotope Effect 11:20-11:35 Bulk isotropic The performance of Mass separation by a on the Bilayer Supermassive black negative-index ATLAS Tau trigger in magnetized Properties: A holes in galaxies metamaterial for presence of pileup plasma-sheath-lens Molecular Dynamics Margrethe Wold infrared collisions Eugen Stamate Simulation Study A. Andryieuski P. Jez T. Rog Continued on Next Page. . . Nuclear- and Bio- and medical Nanophysics and Plasma physics Astrophysics elementary physics nanomaterials particle physics 11:35-11:50 11:40-12:00 11:35-11:50 11:35-12:05 Distributed computing Interactions of two X- and gamma-ray 11:35-11:50 Thermal Insensitivity for LHC: interfacing objects in flowing astronomy with Planar Hall effect of Silicon-based AliEn and ARC to plasmas studied by JEM-X and magnetic biosensors Optofluidic Photonic unify the Nordic numerical simulations INTEGRAL Bjarke Dalslet Crystal Cavities resources W. J. Miloch S. Brandt Cameron L. C. Smith Philippe Gros 11:50-12:05 11:50-12:05 11:50-12:20 Dielectric relaxation Thermonuclear X-ray Dark Matter as apple processes in bursts from IGR sized balls, Tunguska, ethanol/water J17473-2721 Sodoma and Gomorra mixtures J. Chenevez Holger B. Nielsen Uffe Moeller , 12:05-12:20 12:05-12:20 12:05-12:20 Using fiber-coupled Towards a Dynamic Study of a 12:00-12:20 organic scintillators to 14 Square-Kilometer Sliding Interface Wear On the nature of the examine linear Optical Telescope: The Process of TiAlN and plasma equilibrium accelerator pulse promise of intensity CrN Multi-Layers by Hanno Essén delivery interferometry X-ray Absorption Anders Ravnsborg Dainis Dravins Inge L Rasmussen Beierholm Wednesday 15:00 - 17:00

Atomic, molecular Astrophysics Physics Education Condensed matter Nano/Bio and optical physics 15:00-15:30 15:00-15:30 MasteringPhysics, 15:00-15:30 15:00-15:30 Ultrafast, Clickers and Peer 15:00-15:15 Stellar structure and Waveguiding time-resolved studies of Instruction: Do ’Isomorphs’ in liquid exoplanet studies in properties of metallic solution-state systems American Solutions state diagrams the Kepler era strips and nanowires with X-rays Work in Danish Nicoletta Gnan 15 Hans Kjeldsen K. Leosson K. Haldrup Universities? I.G. Bearden 15:15-15:30 Generic property for alpha relaxation in 53 viscous liquids Albena I. Nielsen 15:30-16:15 15:30-15:45 15:30-15:45 Sequence and 15:30-15:45 3d models of the Solar 15:30-16:00 Yield stress fluids. To Molecular Simulation Ultra-short-pulse atmosphere – from Teaching laser physics flow or not to flow, Studies of Insertion excitation of matter convection zone to to first-year students that is the question. and Stabilization of Peter Balling corona J. Henningsen Peder Møller Membrane Proteins Viggo H. Hansteen Erik Lindahl Continued on Next Page. . . Atomic, molecular Astrophysics Physics Education Condensed matter Nano/Bio and optical physics 15:45-16:00 15:45-16:00 Exponential 15:45-16:00 Laser-driven electron Distributions of flow Sunspots and Solar acceleration and X-ray event properties in Active Regions production viscous liquid Ake˚ Nordlund G. Genoud dynamics Nicholas P. Bailey , 16:00-16:15 Theoretical Study of 16:00-16:15 16:00-16:30 Multi-Electron Hunting Transiting 16:00-16:15 A course on Transfer Processes in Exoplanets with Fingerprints of random experimental physics Collisions of Fast Kepler and the Nordic flows for the B.Sc. level N∧(6+) and O∧(7+) Optical Telescope B. Mehlig 1) Kim Lefmann Ions with Methane Lars Buchhave J.R. Sabin 16:15-16:45 16:15-16:30 16:15-16:30 16:15-16:30 Novel Applications of 16 An EPR Study of Planetary system Structure and binding Positron Annihilation Cu2+ Doped in survival in stellar of Platonic-like Spectroscopy – Potassium Dihydrogen clusters molecular crystals. Biomaterials and Citrate Single Crystal Melvyn B. Davies Kristian Berland Medical Polymers Z. Yarbasi P. Sane ,

16:30-16:45 16:30-16:45 16:30-16:45 16:30-17:00 Monolithic Evolution of Dynamic On the origin of Guided labworks: femtosecond Yb-fiber Heterogeneity in eccentricities among Redesign as obstacle laser with photonic Ageing Studied Via extrasolar planets dislodgement crystal fibers Micro-PCS Daniel Malmberg Lærke Bang Jacobsen Xiaomin Liu Claudio Maggi 16:45-17:00 16:45-17:00 Low dispersion fiber 16:45-17:00 16:45-17:00 Propagation modes of link for distribution of Solar system like Density functional entropically trapped femtosecond pulses to exoplanet discoveries theory of and extended DNA photonicly-driven with a network of nonequilibrium molecules terahertz emitter and modern 1m telescopes tunneling Morten Bo Mikkelsen detector units Uffe Graae Jorgensen Per Hyldgaard Finn Eichhorn Thursday 10:20 - 11:20

Nuclear- and Nanophysics and AMO/Nano Plasma physics elementary Astrophysics nanomaterials particle physics 10:20-10:40 10:20-10:35 10:20-10:35 10:20-11:10 Fast ion collective Molecular Dynamics 10:20-10:50 Heat capacities of Discussion meeting on Thomson scattering – Simulations of The HIE-ISOLDE freely evaporating cooperation in Nordic present results and Nanocarbon formation project charged water clusters astronomy plans for ITER from Methane K. Riisager 17 A.E.K. Sund´en S.B. Korsholm N. L¨ummen 10:40-11:00 10:35-10:50 First measurement of 10:35-10:50 Femtosecond thermal the ion Bernstein wave Xsense Explosive ionization of large spectrum by means of Detection molecules collective Thomson F. Bosco M. Kjellberg , scattering M. Stejner

10:50-11:05 10:50-11:05 10:50-11:05 Deposition and Coarse-grained 3α break-up of Implantation of simulations of ¡sup¿12¡/sup¿C Size-Selected Co polyphilic molecules resonances Clusters Jacob Judas Kain O. Kirsebom , S. Vukovich Kirkensgaard Continued on Next Page. . . Nuclear- and Nanophysics and AMO/Nano Plasma physics elementary Astrophysics nanomaterials particle physics 11:00-11:20 11:05-11:20 11:05-11:20 Generation and The perfect ﬂuid and Quantifying and 11:05-11:20 characterization of other highlights from pinpointing sources of The MAX-lab tagged huge (kTesla) magnetic the relativistic heavy noise in nanoscale photon facility ﬁelds in laser-produced ion collider experiments L. Isaksson plasmas P. Christiansen Fabian Czerwinski M. Burza 18 Abstracts

19 Index

3α break-up of 12C resonances, 170 Design and characterization of optical surfaces for daylight- 3d models of the Solar atmosphere - from convection zone ing applications, 87 to corona, 50 detached Eclipsing Binary Age Test Synergies, 52 Detection of low frequency electrostatic waves and turbu- Langmuir waves in a colisionless plasma: nonlinear models., lence in the ionospheric E-region by instrumented 192 rockets , 191 Development of Integrated Electronics for Readout of High A course on experimental physics for the B.Sc. level, 181 Frequency Micro/Nano- Mechanical Resonator, 158 A JEM-X catalog of X-ray sources, 54 Dielectric relaxation processes in ethanol/water mixtures, Ablation of dielectric materials with ultra-short laser pulses: 101 Experimental test of a numerical model, 83 Dielectrophoresis Investigations of Human Chromosomes, Acceleration - in Student Conceptions and in Mathematics, 103 Physics and Life, 176 Distributed computing for LHC: interfacing AliEn and ARC Acoustic resonances in helium liquid, 134 to unify the Nordic resources, 173 Amplitude-phase methods for calculating and analyzing scat- DNA traficking: Colliding RNA polymerases, 108 tering states in relativistic and non-relativistic quan- Doubly uniform semiclassical quantization formula for res- tum mechanics., 77 onances, 79 An EPR Study of Cu2+ Doped in Potassium Dihydrogen Dynamic Study of a Sliding Interface Wear Process of TiAlN Citrate Single Crystal, 69 and CrN Multi-Layers by X-ray Absorption, 151 Applications of negative ions in mass spectroscopy, 86 Early galaxy assembly and evolution: Recent progress, 48 Approaching the quantum phase transition of CoCl .2D O, 2 2 Effect of Membrane Viscosity on Endothelial Cell Motility, 139 110 Efficiency of Brownian motors in dissipative optical lattices, Broadband high power THz generation., 78 59 Bulk isotropic negative-index metamaterial for infrared, 146 Electronic ‘peer response system’ used as basis for talking physics, 177 Characterization and control of attosecond pulse trains, 75 Emergent complexity in soft Yukawa systems, 183 Characterizing propagation of femtosecond optical pulses Escape of Lyman α radiation from young, dusty galaxies, in fiber links using frequency-resolved optical gat- 46 ing., 90 ESS (European Spallation Source) in Lund: Opportunities Coarse-grained simulations of polyphilic molecules, 153 for Northern Europe, 30 Collective Strong Coupling with Ion Coulomb Crystals in Evolution of Dynamic Heterogeneity in Ageing Studied Via an Optical Cavity , 61 Micro-PCS, 121 Combined many-body and QED calculations in helium-like Excited by X-rays - modern spectroscopy of the electronic systems, 72 structure, 142 Complex plasmas - a laboratory for strong correlations, 29 Exploration of the Ultra-Small and Ultra-Fast Worlds with Conceptualizing Electrons and Photons as Quantum Parti- X-Rays, 26 cles in Physics Teacher Education, 179 Exponential Distributions of flow event properties in viscous Confinement of fast ions during applied resonant magnetic liquid dynamics, 127 perturbations in TEXTOR using collective Thom- son scattering diagnostic, 190 Fabrication of a microfluidic trap for single cell immobiliza- Controlled manipulation and immobilisation of peptide nanospheres, tion and studies., 111 109 Fast ion collective Thomson scattering - present results and Cosmic Evolution of Submillimeter Galaxies, 45 plans for ITER, 188 Critical scattering in CoO Nanoparticles, 136 Femtosecond thermal ionization of large molecules, 65 Crystallisation of a binary mixture, 132 Field induced quantum phase transition in a high-temperature superconductor, 129 Dark Matter as apple sized balls, Tunguska, Sodoma and Fingerprints of random flows, 118 Gomorra, 167 First measurement of the ion Bernstein wave spectrum by Density functional theory of nonequilibrium tunneling, 131 means of collective Thomson scattering , 187 Deposition and Implantation of Size-Selected Co Clusters, From spin squeezing to non-Gaussian atomic quantum states, 161 62

20 Fully Correlated Wavefunctions for Small Atoms, 74 Magnetic fluctuations in a critically doped cuprate super- Fundamental studies of negative ions, 89 conductor, 133 Mass separation by a magnetized plasma-sheath-lens, 184 Gamma-ray burst host galaxies, 35 materials and magnetic refrigeration at room temperature., Generation and characterization of huge (kTesla) magnetic 120 fields in laser-produced plasmas, 186 Memorization or understanding: are we teaching the right Generic property for alpha relaxation in 53 viscous liquids, thing ?, 24 117 Memory effects and systematic errors in the RL signal from Geometry-Energy Unified Field Theory, 51 fiber coupled Al2O3:C for medical dosimetry, 113 3 3 Gravitational lens as a standard candle, 38 Metastable Mg Spectroscopy of (3s3p) P0,1,2 - (3s4s) S1 Green’s functions and Lanczos’ method for large scale elec- transitions, 84 tronic structure calculations, 135 mm-Wave Technology for the collective Thomson scattering Guided labworks: Redesign as obstacle dislodgement, 182 diagnostic, 195 Modeling flux pinning in thin undoped and BaZrO3-doped Heat capacities of freely evaporating charged water clusters, YBCO films, 140 56 Molecular Dynamics Simulations of Nanocarbon formation High brightness external cavity broad area diode laser bar from Methane, 159 using off-axis spectral beam combining, 73 Monolithic femtosecond Yb-fiber laser with photonic crystal How to calibrate optical tweezers in viscoelastic media, 105, fibers, 68 197 Morphology and solar cell performance of thin-films of polyflu- Hunting Transiting Exoplanets with Kepler and the Nordic orene:fullerene blends, 163, 196 Optical Telescope, 42 Novel Applications of Positron Annihilation Spectroscopy - Biomaterials and Medical Polymers, 99 Ice Sheets, sealevel rise and ice core research, 25 Imaging liquid and biological processes with electron micro- On the nature of the plasma equilibrium, 185 scopes, 106 On the origin of eccentricities among extrasolar planets, 37 Improved Polymer Dye Lasers with Multifunctional Pho- One year of the superconducting pnictides, 31 tonic Crystal, 157 Optical investigations of the mating-type region in fission Improving Teaching at the Basic Physics courses to prevent yeast, 107 dropping out - successes and disappointments, 178 Optical manipulation of individual gold and silver nanopar- In-situ growth of two-terminal silicon nanowires from locally ticles and quantum dots, 155 heated cantilevers in TEM, 148 Optofluid microscope in a microfluidic separation device, Incubational effects in femtosecond laser ablation of metals, 102 76 Optofluidic applications using 1,2-PolyButadine nano-porous Infrared laser sources for rotational cooling of translation- + diblock polymer, 165 ally cold MgH ions, 88 Origin of Remanent Magnetization in Hemo-Ilmenite Inves- InP x-ray detector for nanoscale resolution, 156 tigated With Polarized Neutron Scattering., 137 Interactions of two objects in flowing plasmas studied by Osmotically driven flows in microchannels and their relation numerical simulations, 189 to sugar transport in plants, 97 Investigation of metastable Magnesium atoms, 80 Isolating of cancer markers using a microfluidic device, 115 Physical Changes of Nucleic Acids Induced by Fullerenes: Isomorphs in liquid state diagrams, 128 A Single Molecule Study, 114 Isotropic metal deposition technique for metamaterials fab- Planar Hall effect magnetic biosensors, 95 rication, 160 Planetary system survival in stellar clusters, 44 Powerful and Cost-Effective Elliptical Neutron Guide De- Laser colored stainless steel: Modeling of the colors and signs for the ESS, 125 applications to color pixeling, 71 Precision Quantum Metrology and Optical Atomic Clock, Laser induced non-adiabatic alignment and orientation of 27 quantum-state-selected molecules., 92 Progress report on the Aarhus Micro ion trap Project, 85 Laser-driven electron acceleration and X-ray production, 58 Propagation modes of entropically trapped and extended Laser-induced adiabatic alignment and orientation of molecules, DNA molecules, 98 82 Least square methods accounting for nuisance parameters Quantifying and pinpointing sources of noise in nanoscale for collective Thomson scattering, 193 experiments, 150 Light takes shape: novel photonics for the biomedical sci- Quantum Learning by Measurement and Feedback, 91 ences, 28 Quantum Phase Transition in LiHoF4 Measured by Torque Liquid crystal tunable microfluidic dye lasers, 166 Magnetometer, 143 Long-Range Correlations in Turbulent Fusion Plasmas, 194 Quantum transport from classical molecular dynamics, 124 Low dispersion fiber link for distribution of femtosecond pulses to photonicly-driven terahertz emitter and Respiratory motion of lung tumours in photon radiation detector units , 57 therapy , 104 Low loss structured polymer fiber for terahertz, 81 Rotational cooling of translationally and vibrationally cold Low-energy transfer reactions with 11Be, 174 MgH+ ions, 55

21 Semiclassical solution of the radial Dirac equation, 93 Water Isotope Effect on the Bilayer Properties: A Molecular Sequence and Molecular Simulation Studies of Insertion and Dynamics Simulation Study, 100 Stabilization of Membrane Proteins, 96 Waveguiding properties of metallic strips and nanowires, Solar system like exoplanet discoveries with a network of 154 modern 1m telescopes, 49 Spectroscopy of red giants in cluster NGC1545, 53 X- and gamma-ray astronomy with JEM-X and INTEGRAL, Spontaneously trapped magnetic flux quanta in a quenched 47 niobium ring , 116 Xsense Explosive Detection, 149 Stellar structure and exoplanet studies in the Kepler era, 40 Structure and binding of Platonic-like molecular crystals., Yield stress fluids. To flow or not to flow, that is the ques- 126 tion., 130 Structure of thin-film oxides from ab initio thermodynamics: ultra-thin alumina films on titanium carbide, 152 Sub-gap conductance through a spinfull quantum dot with superconducting leads, 119 Subgap resistance of SIS’ Al/AlOx/Al tunnel junctions, 162 Sunspots and Solar Active Regions, 34 Supermassive black holes in galaxies, 43 Systems-level analysis in microfluidics, 145

Teaching laser physics to first-year students, 180 The Amazing Diversity of Planetary Systems, 32 The HIE-ISOLDE project, 168 The MAX-lab tagged photon facility, 169 The Near-Threshold Pion Production Program at MAX- lab, 175 The new holy grail : a quest for a growing correlation length in glass physics, 23 The perfect fluid and other highlights from the relativistic heavy ion collider, 171 The performance of ATLAS Tau trigger in presence of pileup collisions, 172 The strongest gravitational lenses in the universe, 39 Theoretical analysis of electrokinetic analyte transport in nano-slits, 164 Theoretical analysis of ultrasound resonances in lab-on-a- chip systems, 112 Theoretical Study of Multi-Electron Transfer Processes in Collisions of Fast N(6+) and O(7+) Ions with Methane, 60 Thermal Insensitivity of Silicon-based Optofluidic Photonic Crystal Cavities, 147 Thermonuclear X-ray bursts from IGR J17473-2721, 41 Thin-film detector of x-ray helicity, 144 Time-resolved THz waveguide spectroscopy, 122 Tomography of an atomic Fock state, 70 Towards a Square-Kilometer Optical Telescope: The promise of intensity interferometry, 36 Towards persistent flow of Bose-Einstein Condensates in a 2D ring trap., 66

Ultra-short-pulse excitation of matter, 67 Ultrafast carrier capture in quantum dots, 138 Ultrafast carrier dynamics in InGaN/GaN multiple quantum wells, 123 Ultrafast, time-resolved studies of solution-state systems with X-rays, 63 Understanding the Star Formation Rate, 33 Unravelling non-Markovian dynamics, 64 Using ﬁber-coupled organic scintillators to examine linear accelerator pulse delivery, 94

Virtual vs. real world experiments - validation of McStas components, 141

22 Plenary Speaker

PL1 The new holy grail : a quest for a growing correlation length in glass physics

By Christiane Alba-Simionesco

23 PL2 Memorization or understanding: are we teaching the right thing ?

By Eric Mazur Harvard University, USA Education is more than just transfer of information, yet that is what is mostly done in large introductory courses – instructors present material (even though this material might be readily available in printed form) and for students the main purpose of lectures is to take down as many notes as they can. Few students have the ability, motivation, and discipline to synthesize all the information delivered to them. Yet synthesis is perhaps the most important – and most elusive – aspect of education. I will show how shifting the focus in lectures from delivering information to synthesizing information greatly improves the learning that takes place in the classroom.

24 PL3 Ice Sheets, sealevel rise and ice core research

By Dorthe Dahl-Jensen

25 PL4 Exploration of the Ultra-Small and Ultra-Fast Worlds with X-Rays

By Joachim Stöhr Stanford Synchrotron Radiation Lightsource , Stanford University, Stanford, California, USA While many techniques offer the spatial resolution to image matter on the length scale down to atoms, they fall short in two other key aspects. First, the structural arrangements of interest are often buried below the surface and remain hidden, second, they are not static but dynamic. Therefore time resolved studies are required that are capable of following motions on the natural and operational time scales. The ”natural” time scale refers to the motions of atoms, electrons, and spins in the equilibrium state of the sample while the ”operational” or non-equilibrium time scale determines function and is the key in technological applications. Today’s operational time scales are of the order of 100 picoseconds which are a remarkable factor of 105 longer than the natural time scale of electrons and spins around 1 femtosecond. Hence there is much room for improvements [1,2]. For the investigation of the ultra-small and ultra-fast world, x-rays are uniquely powerful. Since the fundamental interaction that holds matter together is of electromagnetic origin, it is intuitively clear that electromagnetic radiation is a critical tool for the study of material properties. The modern power of x-rays is based on our ability to construct x- ray sources and optics with suitable brightness, wavelength, polarization and time structure. This talk will review some of the latest developments in x-ray science that allow us to see nanostructures and phenomena in a new light. It will cover novel x-ray techniques that allow us to directly image nanoscale structures and their temporal evolution. Both real space microscopy and reciprocal space techniques such as coherent scattering and photon correlation spectroscopy will be discussed. Finally, a brief outlook will be given how our present capabilities will be expanded by the next generation of x-ray sources based on free electron lasers. [1] J. Stöhr and H. C. Siegmann, Magnetism: From Fundamentals to Nanoscale Dynamics, Springer 2006 [2] http://www-ssrl.slac.stanford.edu/aboutssrl/documents/future-x-rays-09.pdf

26 PL5 Precision Quantum Metrology and Optical Atomic Clock

By Jun Ye JILA, National Institute of Standards and Technology and University of Colorado , Boulder, Colorado 80309-0440, USA Quantum state preparation of ultracold matter and precise control of coherent optical fields have allowed accurate measurement of light-matter interactions for applications ranging from precision tests of fundamental physics to quantum information science. Optical frequency combs distribute the state-of-the-art optical phase coherence across the entire visible and infrared parts of the electromagnetic spectrum, leading to direct visualization and measurement of light ripples at precisions below 1 part in 1018. A new light-based atomic clocks has been developed, with ultracold Sr atoms confined in an engineered optical lattice offering unprecedented coherence times for light-matter interactions. The uncertainty of this new clock has reached 1 x 10−16, a factor of 4 below the current Cs primary standard. These developments represent a remarkable convergence of ultracold science, laser technology, and ultrafast science. Further improvements are tantalizing, where quantum correlations and measurement protocols will enable explorations of the next frontiers in precision metrology and quantum information science.

27 PL6 Light takes shape: novel photonics for the biomedical sciences

By Kishan Dholakia

28 PL7 Complex plasmas - a laboratory for strong correlations

By Dietmar Block Since the early days of plasma physics, it is known that plasma is more than a hot gaseous state of matter. The electric charge of the plasma constituents (usually electrons and ions) allows for collective behavior and the time scales of electron and ion dynamics are well separated. Thus, plasmas exhibit a rich variety of phenomena which are unknown to ordinary gases. Especially the spontaneous formation of crystalline structures in plasmas, which contain micrometer size particles (complex plasmas), is surprising and triggered considerable research activities. This contribution reports on the current understanding of the formation of crystalline structures in ﬁnite dust clouds and their dynamical properties. Special attention is paid to the diagnostic challenges to observe a 3D particle arrangement at a kinetic level.

29 PL8 ESS (European Spallation Source) in Lund: Opportunities for Northern Europe

By Christian Vettier

30 PL9 One year of the superconducting pnictides

By Andrew Boothroyd Oxford University, Department of Physics, Clarendon Laboratory, Oxford OX1 3PU, United Kingdom The discovery [1] of a new family of superconductors containing iron pnictide layers with transition temperatures up to 56 K has generated world-wide research activity of such intensity that has not been seen since the early days of the copper oxide superconductors. In this talk I will review what has been learned over the last 12-15 months about the basic physical characteristics of the iron pnictides. I will pay particular attention to their magnetic properties, and I will discuss neutron scattering experiments which provide evidence that magnetic ﬂuctuations could play an important role in the formation of the superconducting state.

31 PL10 The Amazing Diversity of Planetary Systems

By M. Mayor Geneva University, Switzerland Since the discovery of the first planet orbiting another star, in 1995, more than 350 extra-solar planets have been detected. These exoplanets are found orbiting stars with masses from 0.3 to 4 solar-masses, with periods as short as 0.8 days. These early discoveries have revealed an impressive diversity of extrasolar planets, including some with totally unexpected properties: The solar system is clearly not a typical example of planetary systems in the Universe. The observed great diversity of orbital properties has led to a major revision of the physical models for the formation of planetary systems. More than 50 planets have now been seen transiting the disk of their host star. Combining accurate Doppler and light curve observations of such planets opens the possibility to get direct physical information on their internal structure and atmospheric properties. We can anticipate revealing an amazing diversity of internal compositions for low-mass planets in short-period orbits. Several surveys and advanced new instruments are being pursued with the goal to find Earth-like planets. What are the difficulties and chances of success? The search for twins of the Earth is motivated by the ultimate prospect of finding sites with favourable conditions for the development of life.

32 Astrophysics

AP1 Understanding the Star Formation Rate

By Ake˚ Nordlund1 and

Paolo Padoan2

1 Niels Bohr Institute, University of Copenhagen2 University of California, San Diego We have developed a theory that predicts the Star Formation Rate (SFR) in the interstellar medium as a function of key properties such as temperature, density, and turbulent Mach number. The theory has been arrived at by ”looking the horse in the mouth”; i.e. by analyzing computer simulations of supersonic magnetihydrodynamic turbulence in a self-gravitating gas representing the interstellar medium. The supersonic motions create localized strong compressions that become gravitationally unstable and collapse. The collapsing gas, and additional gas that subsequently accretes is collected onto ’sink particles’, and the total rate of conversion of gas into stars is measured. By analyzing the balance of processes involved we have derived an analytical expression for the star formation rate that can be used in larger scale studies of star formation in the ISM, and in studies of galaxy formation.

33 AP2 Sunspots and Solar Active Regions

By Ake˚ Nordlund1 and

Anders Lagerfj¨ard1,2 Fernando Moreno-Insertis2 G¨oranScharmer3 Robert F. Stein4

1 Niels Bohr Institute, Univ. of Copenhagen2 Instituto de Astrof´ısica de Canarias, Tenerife, Spain3 Institute for Solar Physics, Royal Swedish Academy, Stockholm4 Dept. of Physics and Astronomy, Michigan State University The emergence of magnetic fields at the surface of the Sun creates sunspots and solar ’active regions’ – these are excellent sites for developing an understanding of the dynamics of magnetic fields in astrophysical objects, since very detailed observations are available that provide not only high spatial resolution but also unique coverage of the time domain; because of the brightness of the Sun one can achieve high cadence over periods of time that cover many dynamical evolution times. We have successfully modeled the ascent and emergence of structured magnetic field in models of the solar convection zone, and also modeled the structure of sunspots and their penumbra. We use 3-D animation to illustrate the complex hierarchical magnetic field responsible for the emerging structure at the solar surface.

34 AP3 Gamma-ray burst host galaxies

By D. Malesani1 and

J. Hjorth1, J.P.U. Fynbo1, P. Jakobsson2, B. Milvang-Jensen1, P.M. Vreeswijk1, A.O. Jaunsen3

1 Dark Cosmology Centre, Niels Bohr Institute, Copenhagen,2 University of Iceland, Reykjavik,3 Institute of Theoretical Astro- physics, University of Oslo I will report on the ﬁrst results of a large observational program on gamma-ray burst (GRB) host galaxies (PI: Jens Hjorth), completed in 2008. The survey has targeted a carefully selected sample of 71 Swift GRBs. The bursts have been chosen primarily based on their X-ray afterglow detection, in order to avoid biases against dusty or high-redshift objects. The project has several goals. 1) The detection of the hosts through deep photometry. 2) The search for red systems through infrared photometry. 3) The determination of missing redshifts, to increase the completeness in the sample. 4) The search for Ly-alpha emission for all hosts at z > 2. 5) The study of clustering properties of short-duration GRB hosts. The main results of the program include a large host detection rate, the limited presence of red(dened) systems, the derivation of an improved (less biased) redshift distribution, a lower-than-expected Ly-alpha recovery fraction, and clues on the nature of dark GRBs.

35 AP4 Towards a Square-Kilometer Optical Telescope: The promise of intensity interferometry

By Dainis Dravins1 1 Lund Observatory, Box 43, SE-22100 Lund Many stars begin to appear as surface objects for interferometric baselines of hundreds of meters, while kilometric ones are needed for imaging stellar-disk features or for resolving more remote objects. Since atmospheric turbulence makes amplitude/phase interferometry of the Michelson type challenging for such long baselines, kilometric space telescope clusters have been proposed. The complexities of such projects make their realization uncertain but comparable imaging could be realized rather soon by ground-based intensity interferometry, at least for brighter and hotter stars. The method is insensitive to both atmospheric turbulence and to imperfections in telescope optics, but requires large flux collectors, such as being set up as atmospheric Cherenkov telescopes for studying energetic gamma rays. In a larger array, high-speed detectors and digital signal handling enable very many baselines to be synthesized between many pairs of telescopes; in essence, this becomes a digital revival of the technique pioneered by Hanbury Brown & Twiss long ago, now forming an optical software telescope somewhat analogous to equivalents in the radio. Following laboratory work, first test observations with digitally combined optical instruments have now been made with pairs of 12-meter telescopes of the VERITAS array in Arizona. Observing at short wavelengths adds no problems, and similar techniques on future extremely large telescopes could achieve diffraction-limited imaging down to the atmospheric cutoff, achieving a spatial resolution superior to that feasible by adaptive optics operating in the (infra)red. Of particular interest is the planned CTA, Cherenkov Telescope Array, foreseen as an array of perhaps 50 to 80 optical dishes of 10-20 meter size, spread over some square km. In recent community studies, CTA was identified as one of the priority projects in European astronomy for the 2010’s, and its ongoing design study includes also its optimization for stellar intensity interferometry. Its main task of observing atmospheric Cherenkov light will probably be feasible only during dark-Moon periods while the bright time might be made available for interferometry, thus perhaps realizing the first kilometric-scale optical imager.

36 AP5 On the origin of eccentricities among extrasolar planets

By Daniel Malmberg1 and

Melvyn B. Davies1

1 Lund Observatory, Box 43, SE-221 00, Lund, Sweden Most observed extrasolar planets are at least as massive as Jupiter, but have orbits which are much tighter, and often much more eccentric than the orbits of the gas giants in the solar system. We show that some of these extrasolar planets might have formed in planetary systems resembling the solar system, i.e. in systems whith gas giants on initially rather wide and circular orbits. Using numerical simulations we have studied stellar binary systems where one star hosts a planetary systems. We have considered the eﬀect of the stellar companion on the planetary system. We ﬁnd that quite often the companion star will perturb the orbits of the planets, triggering strong planet-planet interactions in the system. These can lead to the ejection of one or several planets, leaving those remaining on much tighter and more eccentric orbits, similar to the orbits of the observed extrasolar planets. The eccentricity distribution of these perturbed systems is similar to that of the observed extrasolar planets with semi-major axes between 1 and 6 au, if they initially consisted of gas giants which all had rather similar masses.

37 AP6 Gravitational lens as a standard candle

By Danuta Paraﬁcz and

Jens Hjorth

DARK Cosmology Centre We will present a theoretical explanation of how strongly lensed quasars can be used as standard candles. We will also show the sensitivity of the theory on cosmological parameters using simulations.

38 AP7 The strongest gravitational lenses in the universe

By H. Dahle1 1 Institute of Theoretical Astrophysics, University of Oslo A new deep imaging survey of galaxy clusters aims to ﬁnd the most powerful gravitational lenses in the large ∼6 Gpc3 volume of the Sloan Digital Sky Survey. So far, this ongoing survey has deeply imaged nearly 500 massive clusters, mostly using the Nordic Optical Telescope, and has revealed some of the most dramatic examples of gravitational lensing ever discovered. Follow-up spectroscopy and imaging at 8-10m class telescopes seek to address whether the dark matter distribution in galaxy clusters is consistent with predictions in the currently favoured ΛCDM cosmological model. Our initial results reveal strongly signiﬁcant discrepancies between model model predictions and observations. In addition, these cluster lenses can be used as ”gravitational telescopes” to study the high-redshift universe.

39 AP8 Stellar structure and exoplanet studies in the Kepler era

By Hans Kjeldsen Institut for Fysik og Astronomi, Aarhus Universitet, Ny Munkegade 120, DK-8000 Aarhus C, Denmark NASA’s Kepler Satellite was successfully launched into space on 6 March 2009. The goal of this mission is ambitious and exciting. Using Kepler we expect to answer a very fundamental question; do planets the size of Earth exist in orbit around other stars? The Kepler Satellite is equipped with a large telescope that will allow observations of 170,000 stars simultaneously and continuously for a period of 3.5 years. Over the course of the mission the Kepler team expects to detect hundreds of planets, estimate the number of planets around diﬀerent types of stars and not only answer the fundamental question concerning the existence of Earth-sized planets but also determine how frequent they are. The Kepler Satellite will not only be able to search for planets around other stars. The measurements from the satellite can also be used to study stars and their interiors. By use of standing sound waves and stellar oscillations the Kepler team will use asteroseismic techniques to probe the core of a large number of stars. This will allow the team to determine the size and age of stars, and to get information about the chemical composition and the rotation of the observed stars. In the present talk I will describe the expected results we foresee throughout the Kepler mission and review this based on the important results obtained by using the the CoRoT satellite which was launched by CNES in December 2006.

40 AP9 Thermonuclear X-ray bursts from IGR J17473-2721

By J. Chenevez1 and

D. Altamirano2, D. Galloway3, E. Kuulkers4, J. in ’t Zand5, E. del Monte6, M. Falanga7

1 DTU Space, Denmark,2 Astronomical Institute, the Netherlands,3 Monash university, Australia,4 ESA/ESAC, Spain,5 SRON, the Netherlands,6 INAF/IASF, Italy,7 CEA, France The X-ray transient source IGR J17473-2721 aka XTE J1747-274 was discovered with INTEGRAL in April 2005 in the Galactic Centre region. This source exhibited a second episode of activity between March and September 2008, which was preceded two days earlier by a thermonuclear X-ray burst. This observation made possible to identify the source as a neutron star in a low-mass X-ray binary. A total of 40 bursts were subsequently observed through the whole outburst period by the X-ray instruments on four diﬀerent satellites. Among the 14 bursts observed by the danish X-ray monitor JEM-X onboard INTEGRAL, one was simultaneously observed by RXTE. Observations results will be presented that allow us to interpret the bursting behaviour of the source in terms of rate and composition of the accreted material from the donor star.

41 AP10 Hunting Transiting Exoplanets with Kepler and the Nordic Optical Telescope

By Lars Buchhave and

Johannes Andersen David Latham

Johannes Andersen: Niels Bohr Institute, Copenhagen University Lars Buchhave: Niels Bohr Institute, Copenhagen University Harvard-Smithsonian Center for Astrophysics David Latham: Harvard-Smithsonian Center for Astrophysics The study of extrasolar planets will remain one of the most vibrant ﬁelds of astronomy for the next several decades. Until direct imaging becomes possible, planets that transit the disk of their host star will be the main source of precise physical data with which to constrain theoretical models of planet formation and evolution. Transiting planets permit an arsenal of exciting follow-up observations such as characterizing the planet’s atmosphere via transmission and emission spectroscopy, ultimately looking for atmospheric biomarkers, transit timing variations to detect other non- transiting planets and spin-orbit alignment observations to constrain formation and migration models. This project focuses on verifying newly-discovered transiting planet candidates from the Kepler space mission (launched March 6, 2009), sorting out false positives and getting spectroscopic orbits for the planets transiting the brightest stars. Work has begun on candidates from the ongoing ground-based photometric survey HATNet using spectroscopic observations from the FIES spectrograph at the Nordic Optical Telescope on La Palma and the TRES spectrograph at the Whipple Observatory.

42 AP11 Supermassive black holes in galaxies

By Margrethe Wold1 and

Gabriela Canalizo2 Mariana Lazarova2 Mark Lacy3

1 University of Oslo2 UC Riverside3 Caltech/Spitzer Science Center Supermassive black holes weighing between a million to a billion solar masses are thought to reside in the centres of most galaxies. They are also thought to be important for how galaxies form and evolve. Most galaxies probably go through a phase in their evolution when the black hole is ”active”, and such active supermassive black holes are known as quasars, or active galactic nuclei. Quasars have therefore become instrumental in our understanding of galaxy evolution. I will discuss the role of supermassive black holes in galaxy formation and how in particular quasars obscured by dust are unique in this respect.

43 AP12 Planetary system survival in stellar clusters

By Melvyn B. Davies and

Daniel Malmberg

Lund Observatory, Box 43, SE-221 00 Lund, Sweden. Many stars are formed in some form of cluster or association. These environments can have a much higher number density of stars than the field of the galaxy. Such crowded places are hostile environments:a large fraction of initially single stars will undergo close encounters with other stars or exchange into binaries. We describe how such close encounters and exchange encounters will affect the properties of a planetarysystem around a single star. We define singletons as single stars which havenever suffered close encounters with other stars or spent time within a binary system. For solar-mass stars we find that the singleton fraction is less than0.9, in other words at least ten percent of solar-like stars have either exchanged into a binary or suffered at least one close encounter. Close encounters or the presence of astellar companion will perturb the planetary system, leading to strong planet- planet interactions, often leaving planets on tighter and more eccentric orbits. Thus, planetary systems which initially resembled our ownsolar system may later more closely resemble the observedextrasolar planetary systems. It may be that planetary systems similar to our own solar system can only survive around singletons.

44 AP13 Cosmic Evolution of Submillimeter Galaxies

By Michal Michalowski Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen Submillimeter galaxies (SMGs) are massive, star-forming galaxies at redshifts ∼2-3. Due to the coarse resolution of submillimeter detectors and the faintness of SMGs in the optical, it was only recently when a signiﬁcant sample of SMGs with spectroscopically measured redshift was compiled using localizations derived from high-resolution radio maps. Therefore there are still open questions regarding their nature and evolution. I will present the results of spectral energy distribution ﬁtting for a sample of 76 SMGs using data from UV to radio. I will characterize their redshift evolution, contribution to the cosmic mass assembly and dominant mechanism of emission. Additionally I will claim that the local far-infrared-radio correlation holds at least up to redshift ∼3.6.

45 AP14 Escape of Lyman α radiation from young, dusty galaxies

By Peter Laursen and

Jesper Sommer-Larsen Anja C. Andersen

Dark Cosmology Centre Niels Bohr Institutet Københavns Universitet The Lyman α emission line (λ = 1216 A)˚ is an extremely powerful diagnostic tool for studying the early (”high- redshift”) Universe. Produced mainly by young stars and gravitational cooling, it may reveal detailed information about the physical properties of young galaxies, including kinematics, star formation history, and luminosity function. However, even in young galaxies there may be a considerable amount of dust, possibly created by supernovae. Whereas the effect of dust on continuum radiation (that which is not Lyman α) is quite well constrained, the fact that Lyman α scatters on neutral hydrogen and thus follows a complicated path makes it difficult to predict. To interpret correctly observations, it is crucial to know how the spectrum is affected and, specifically, how large a fraction (fesc) of the radiation reaches our telescopes. Previous attempts of ascertaining fesc have merely been trying to explain discrepancies between observed and expected Lyman α luminosities.In the presented work, using a combination of high-resolution cosmological hydro- simulations and an adaptively refinable Lyman α radiative transfer code with an advanced model of dust, the effect of dust on various observables is calculated in a more fundamental way. In particular, it is shown that fescdecreases with increasing galactic mass, and that the emission line is highly narrowed.

46 AP15 X- and gamma-ray astronomy with JEM-X and INTEGRAL

By S. Brandt1 and

C. Budtz-Jørgensen1, J. Chenevez1, N. Lund1, N.J. Westergaard1, E. Kuulkers2 A. Hill3

1DTU Space, Denmark2ESA/ESAC, Spain3University of Southampton, UK ESA’s high energy astrophysics mission INTEGRAL was launched in 2002 and has now been in orbit for more than 6 years and is expected to operate at least 3 more years. We report on the INTEGRAL science, with special focus on the results obtained with the X-ray monitor, JEM-X developed by DTU Space. An extensive monitoring program of the Galactic bulge region has been carried out in the X- and gamma-ray range and selected result are reported. This region is highly variable and contains a wide variety of persistent and transient X-ray sources. We report on an outburst of the transient X-ray pulsar GRO J1750-27 and the determination of the orbital parameters and the pulsar spin-up rate. JEM-X has also observed hundreds of thermo-nuclear X-ray bursts and several new X-ray burst sources, like XTE J1739-285, have been discovered. Finally, the prospects for using the extensive INTEGRAL data public base for archival research will be described.

47 AP16 Early galaxy assembly and evolution: Recent progress

By Tommy Wiklind ESA/STScI Our understanding of how and when galaxies form have improved enormously over the last decade. Progress is being made on modeling of how the initial small ﬂuctuation in the matter density evolves into large scale structure. Observational progress have likewise improved and we can now study the galaxy population at a time when the universe was just a few million years old and follow the evolution to the present time. In this talk I will give an overview of where we stand today in our understanding of galaxy formation and evolution, where the models and observations do not agree and what can be done with the next generation instruments like JWST and ALMA.

48 AP17 Solar system like exoplanet discoveries with a network of modern 1m telescopes

By Uﬀe Graae Jorgensen and

Per Kjærgaard Rasmussen, Jørgen Christensen-Dalsgaard, Hans Kjeldsen, Frank Grunddahl, Søren Frandsen, Torben Arentoft

Niels Bohr Institute, Copenhagen University Institute for Physics and Astronomy, Aarhus University

49 AP18 3d models of the Solar atmosphere - from convection zone to corona

By Viggo H. Hansteen1 and

Mats Carlsson1 Boris Gudiksen1

1 Institute of Theoretical Astrophysics, University of Oslo With the advent of massively parallel computers it has ﬁnally become feasible to simulate the solar atmosphere in models that extend from the upper convection zone to the lower corona. These advances come fortuitously at a time when there is a wealth of high quality observational material available. Thus, it is to be hoped that progress can be made in understanding how the magnetic ﬁeld couples the energy reservoir found in solar convection with the dynamic chromosphere and the hot tenuous corona. We will discuss recent models and compare the results derived with high resolution observations made with Hinode and at the Swedish 1-meter Solar Telescope.

50 AP1P Geometry-Energy Uniﬁed Field Theory

By Anacleto Rivera Nivon and

Susana Rivera Cabrera

(Anacleto Rivera Nivón)Independent Researcher (Susana Rivera Cabrera) Universidad AutónomaMetropolitana Azcapotzalco On this work we consider the existence of geometry-energy strings, different from the ones of super string theory or any other gut theory, that supports on a new system of mathematical equations established to describe natural properties and phenomena that take place on those strings, which are considered to form a cosmic tissue base. Such strings experience shrinking and elongations as a result of intrinsic elasticity shift, caused as a reply to some external action, or a reaction on the vicinity of string, which in time is due to a stimuli on the surrounding tissue. The shrinking and elongation on the strings are due to a shift in a variable called symbiosis (σ), a new term introduced to describe the coexistence between properties of that cosmic tissue, such as directed flux, plasma, radiation and mass, which obtain mutual benefits. If local tissue experiments a decrease on symbiosis value, we have a Direct Transformation (elongation on strings), but if there is an increase on symbiosis value, we have an Inverse Transformation (shrinking on strings). In the above mentioned transformations arises the relationship among the Electromagnetic Field and the Gravitational Field, representing them by 3-D surfaces, which shape and state will be a function of its inherent geometry and energy. The concept of space - time is directly correlated to the oscillatory property of the strings on the geometry-energy field. The novelty of this work is an attempt of unifying the macrocosmos with the microcosmos, the unification of the Electromagnetic Field with the Gravitational Field, as well as the strong interactions and weak interactions. These forces are regarded as a result of the correlation between geometry-energy on the strings that generates the dynamics of mass and energy at the Universe. There is a symbiotic relationship between geometry and energy. Properties of the Geometry-Energy Unified Field (GEUF), such as Internat Energy Directed Flux, Ef (σ, r, ρ), Plasma Energy, Ep (σ, r, ρ), Radiation Energy, Er (σ, r, ρ), and Mass Energy, Em (σ, r, ρ), are related in a coherent way; they are interdependent variables. Ef and Ep are elastic properties, while Er and Em are inelastic properties. This proposal enables us to redifine concepts such as electromagnetic oscillations, gravitational oscillations, low temperature plasma and high temperature plasma, velocity and acceleration-deceleration of particles, represented by vector fields, associated with particles generated by the GEUF, and thus let us try to explain the origin of the strings, all of them under a new optic. On the ongoing process of elongation, there is the formation of the Black Holes; and we belief that on the ongoing process of shrinking there is the probable formation of White Holes. This last one is represented mathematically by the Inverse Transformation, while the formation of the Black Holes is represented mathematically by the Direct Transformation. Under this view, detected particles like quarks, gluons, muons and other fundamental particles might suffer a slight change on perception. f p r m (σ) = fe (r, E ,E ,E ,E ) (1) The aim of this work is an attempt to simplify and perhaps to improve comprehension of the properties and phenomena that takes place at the Universe.

51 AP2P detached Eclipsing Binary Age Test Synergies

By Karsten Brogaard1 and

F. Grundahl1 S. Frandsen1 J. V. Clausen2

1 Institute for Physics and Astronomy, Aarhus University2 NBI, University of Copenhagen When multiple detached eclipsing binaries are found in open clusters they can be provide tight constraints to test stellar evolution models. We present here our progress on such a procedure in the old open cluster NGC 6791.

52 AP3P Spectroscopy of red giants in cluster NGC1545

By L. Zacs1 and

A.Laure1, O.Alksnis1, J.Sperauskas2

1 University of Latvia, Latvia2Vilnius University Observatory, Lithuania The results of LTE abundance analysis based on high-resolution spectra are presented for three red giants in the open cluster NGC1545 (log age = 8.448). Radial velocity monitoring using CORAVEL spectrometer was launched to clarify possible binarity of giants. Detailed analysis of atmospheric parameters and chemical composition using method of atmospheric models for more than 20 elements confirmed the membership of two giants (HD27276 and HD27292). The distance to the third star HD27277 = NGC1545 4 seems to be much lower than estimated for NGC1545 (r = 711 pc). The effective temperature for HD27276, HD27277, and HD27292 was found to be between 4300 K and 5100 K in agreement with spectral classification from G8 to K2.5. Calculated gravity, log g from 0.9 to 2.2 (cgs), support the (bright) giant luminosity. The mild deficiency of iron group elements was found, [M] ∼ -0.10 dex. Radial velocity measurements in the 3 years interval do not confirm the binary nature of observed stars.

53 AP4P A JEM-X catalog of X-ray sources

By Niels J. Westergaard National Space Institute, DTU JEM-X is the X-ray monitor on the INTEGRAL mission that has been in orbit - and still is - for more than 6 years. In that period a large fraction of the sky has been covered. In particular the galactic center and its neighborhood has had an exposure of more than 5 Ms. The energy range of JEM-X is 3-35 keV. About 200 sources have been found in the database of publicly available data. The catalog of these sources is presented as well as highlights of selected sources.

54 Atomic, molecular and optical physics (AMO)

AMO1 Rotational cooling of translationally and vibrationally cold MgH+ ions

By A. K. Hansen1 and

K. Højbjerre1, P. S. Skyt1, P. F. Staanum1, M. Drewsen1

Quantop - Danish National Research Foundation Centre for Quantum Optics1 Department of Physics and Astronomy, University of Aarhus We present experimental results demonstrating laser induced cooling of the rotational degree of freedom of translationally and vibrationally cold trapped 24MgH+ ions. 2 + 2 + The 4MgH ions are formed in a linear Paul trap by reaction between laser cooled 4Mg ions and H2 molecules at room temperature. They are sympathetically cooled to a translational temperature below 100 mK by the Coulomb interaction with the remaining laser cooled 24Mg+ ions in a two-component crystal1. After a thermalisation period of a few minutes, the molecular ions’ internal degrees of freedom are brought to equilibrium with the blackbody radiation field. At this point, the molecules will predominantly occupy the vibrational ground state v = 0, while the lowest 10 rotational states J = 0 to J = 9 will be populated significantly. The rotational cooling scheme being applied is the direct scheme proposed in ref. 2. Rotational cooling towards the (v = 0,J = 0) ground state is achieved by the combined action of a lead salt diode laser operating at a wavelength of 6.2 µm driving the transition from the (v = 0,J = 2) level to the (v = 1,J = 1) level, and rotational state redistribution by the blackbody radiation field2. The rotational population distribution is determined by a two-photon resonance enhanced photodissociation spectroscopy method which probes the populations in each rotational state. A cooling effect is evident when comparing the photodissociation spectra taken in the presence and in the absence of the lead salt laser field driving the above mentioned rovibrational transition. Internally cold molecular ions should enable state dependent reaction studies as well as coherent control experiments, even at the single ion level3. 1. Mølhave, K., Drewsen, M. Phys. Rev. A 2002, 62, 011401 2. Vogelius, I. S., Madsen, L. B. and Drewsen, M. Phys. Rev. Lett. 2002, 89, 173003 3. Staanum, P. F., Højbjerre, K., Wester, R. and Drewsen, M. Phys. Rev. Lett. 2008, 100, 243003

55 AMO2 Heat capacities of freely evaporating charged water clusters

By A.E.K. Sund´en1 and

P. Hvelplund2 K. Støchkel2 K. Hansen1

1 Institute of Physics, University of Gothenburg2 Institute of Physics and Astronomy, University of Aarhus + We report on evaporation studies on positively charged water clusters (H (H2O)N ) and negatively charged mixed − clusters (X (H2O)N ) with a small core ion X, in the size range N = 5 ∼ 300. The clusters were produced by corona discharge in ambient air, accelerated to 50 keV and mass selected by an electromagnet. The loss of monomers during the subsequent 3 m free ﬂight was recorded. The average losses are proportional to the clusters’ heat capacities and this allowed the determination of size-dependent heat capacities. For clusters with N < 21 the heat capacities coincide with those of bulk ice, whereas for N > 21 they are intermediate between liquid and solid bulk water values.

56 AMO3 Low dispersion ﬁber link for distribution of femtosecond pulses to photonicly-driven terahertz emitter and detector units

By Finn Eichhorn1 and

Rasmus Kjelsmark Olsson1, Jonas Due Buron2, Peter Uhd Jepsen1

1 DTU Fotonik, Department of Photonics Engineering, Technical University of Denmark2 DTU Nanotech, Department of Micro- and Nanotechnology, Technical University of Denmark We will present our results on a low dispersion fiber link for the distribution of 1550 nm femtosecond pulses to photonicly-driven terahertz (THz) emitter and detector units. The fiber-based solution facilitates a larger flexibility in the positioning of emitter and detector compared to the standard free-space terahertz time-domain spectrometer (THz-TDS) setup. Furthermore, this also opens up for new application areas as multi-element detector/emitter pairs and handheld THz-TDS modules. The propagation of ultrafast laser pulses in optical fibers is modelled by linear propagation effects, including linear attenuation, group velocity dispersion and third-order dispersion, as well as the nonlinear propagation effects, including the Kerr effect, stimulated Raman scattering, and self-steepening. The fiber link is characterized by a frequency optical gating technique (FROG) resolving the intensity and the phase of the transmitted pulse. Standard single-mode fiber displays anomalous dispersion at 1550 nm and the pulses will be stretched to the picosecond range after a few centimetres of fiber. Therefore there is need to employ a dispersion management scheme making use of a combination of anomalous and normal dispersion specialty fiber. This fiber link is capable of delivering near Gaussian pulses with a pulse duration of less than 100 fs over a total length of 5 m of fiber. We will exhibit how the distributed femtosecond pulses drive a full fiber-based THz spectrometer setup.

57 AMO4 Laser-driven electron acceleration and X-ray production

By G. Genoud1 and

M. Burza1 C. Kamperidis1 A. Persson1 S. P. D. Mangles2 S. Kneip2 N. Dover2 F. Wojda3 K. Cassou3 B. Cros3 C.-G. Wahlstr¨om1

1 Department of Physics, Lund University, Lund, Sweden2 Blackett Laboratory, Imperial College, London, United Kingdom3 Laboratoire de Physique des Gaz et des Plasmas (LPGP), UniversitéParis Sud 11, Orsay, France The intensity achievable in a focused laser beam from a multi-terawatt laser can be as high as 1020 W/cm2, corresponding to a peak transverse electric field exceeding 1013 V/m. This extremely high field will accelerate any charged particle in the focus, but because of the oscillating nature of the field, it is not suited for direct acceleration. However, by transferring the laser energy to a plasma, the energy density of this field can create extremely strong and longitudinal electrostatic fields that can be used to accelerate particles in a narrow forward directed cone. The same laser can be used to generate beams of electrons, protons and heavier ions. Electrons are routinely accelerated to hundreds of MeV over acceleration distances of only a few mm, using a principle known as laser plasma wakefield acceleration. The ponderomotive force of an intense femtosecond laser pulse generates a large amplitude plasma wave. This wave can break, trap and accelerate electrons at rates that are more than a thousand times higher than those achieved in accelerators based on conventional technology. These beams have a small angular divergence and a significant charge (about 109 electrons). However, in order to increase the energy of the electrons to the GeV range and above, the interaction length must be increased. With the help of dielectric capillary tubes diffraction effects can be circumvented and plasma waves can be excited over several centimeters. This may soon lead to multi GeV table-top acceleration. One of the future potential applications of these compact plasma accelerators is ultra-short pulse X-ray production. As in an electron storage ring X-rays are generated by means of wiggling a relativistic electron beam, but now the plasma itself plays the role of both accelerator and wiggler - drastically reducing the size. The femtosecond pulse duration delivered by such a source, provides a time resolution from which many applications will benefit.

58 AMO5 Eﬃciency of Brownian motors in dissipative optical lattices

By H. Hagman and

M. Zelan C. M. Dion A. Kastberg

Department of physics, Ume˚aUniversity A dissipative optical lattice is a periodic light shift potential created in the interference patern of laser beams, with a frequency sufficiently close to resonance for ligth scattering to be of importance. This provide an inherent cooling of the atoms, and a dynamic governed by fluctuations. The atoms held in such a lattice have a temperature that is typically small compared to the potential depth of the trapping potential, and they are therefore trapped near the bottom of the potential wells. The fluctuations do however introduce a momentum diffusion, which enables the trapped atoms to overcome the trapping barrier and become untrapped. These untrapped atoms will be subject to dissipation and become trapped again. During these short untrapped sessions, the atom will be free to move around in the optical lattice, which leads to a spatial diffusion of the atoms. We have experimentally realized a Brownian motor, which rectify this diffusion into a deterministic drift. This is done by the use of two state-dependent dissipative optical lattices, with an adjustable relative spatial phase. We have shown that the induced drift is controllable in 3D, by the control of the relative spatial phase. By comparing the size of the induced drifts and the diffusion we should to be able to determine an effective efficiency of the Brownian motor, and by introducing rapid shifts in the relative spatial phase while the atoms are held in the lattice, we hope to be able to induce drifts along predetermined closed paths.

59 AMO6 Theoretical Study of Multi-Electron Transfer Processes in Collisions of Fast N(6+) and O(7+) Ions with Methane

By J.R. Sabin1,2 and

N.L. Guiverra2 E. Teixeira2 B. Hall2 E. Deumens2 Y. Ohrn2

1 Institute for Physics and Chemistry, University of Southern Denmark2 Quantum Theory Project, University of Florida There is considerable current interest in the interaction of fast, highly charged ions with small molecules, as such collisions are important in fields as diverse as radiobiology and astrophysics. Fast ions can both cure and cause cancer while the ions are present in the solar wind and small molecules can be found in comets and planetary atmospheres. Recent experimental studies1,2 by the Debrecen group have shown that although N6+ and O7+ are both hydrogenic, they give quite different fragmentation patterns when colliding with small molecules such as methane or water. We use Electron Nuclear Dynamics to study these collisions theoretically and to determine the origin of the differences. The method is a non-adiabatic application of the time dependent variational principle to a dynamical wavefunction represented in the coherent state representation. The nuclei and electrons are fully coupled. The nuclei, although in principle quantum mechanical, are represented in the narrow width approximation, and so move as if they were classical. This study is focused on the first step of the interaction process, namely the capture of electrons from methane by highly charged ions with energy of the order 1 keV/amu. Calculated cross sections are reported for multiple electron capture, and differences for the two equal velocity projectiles. 1. Z.Juhasz et al., Nucl. Inst. Meth B 267, 326 (2009). 2. Z.Juhasz et al., AIP Conf. Proc. 1080, 118 (2008).

60 AMO7 Collective Strong Coupling with Ion Coulomb Crystals in an Optical Cavity

By Joan Marler and

Aur´elienDantan, Magnus Albert, Peter Herskind, and Michael Drewsen

QUANTOP, Department of Physics and Astronomy, University of Aarhus, Ny Munkegade, bygn. 1520, DK-8000 Aarhus, Denmark Cavity Quantum Electrodynamics (CQED) is a powerful platform for the realization of efficient light-matter quantum interfaces at the single photon level. Laser-cooled, trapped ions offer many attractive features for CQED, namely long coherence and trapping times, low densities and excellent localization. Using a linear rf-Paul ion trap incorporating a high-finesse optical cavity along its axis [1] we have realized such an interface with a cloud of cold ions, cooled to a self-organized Coulomb crystal structure. This allowed us to observe for the first time collective strong coupling between cold ions and a cavity field at the single photon level [2]. This system has now been used to explore other CQED phenomena. We will present recent results of coherent coupling to various transverse modes of a cavity field which take advantage of some of the attractive features of ion Coulomb crystals. First, the high degree of spatial localization of the ions makes it possible to use a string-like Coulomb crystal for precise reconstruction of the spatial profile of the cavity mode by measuring the ion-light coherent coupling. Second, the stationarity and uniform density of large crystals ensures that identical coupling strengths are achieved with higher order modes. These results are promising for cavity mediated cooling, and combined with the long coherence times of ion Coulomb crystals[2], for multi-mode quantum state generation and storage. 1. P. Herskind, A. Dantan, M. B. Langkilde-Lauesen, A. Mortensen, J. L. Sørensen, M. Drewsen, Appl. Phys. B 93, 373 (2008) 2. P. Herskind, A. Dantan, J. P. Marler, M. Albert, M. Drewsen, ”‘Realization of Collective Strong Coupling with Ion Coulomb Crystals in an Optical Cavity”’, submitted.

61 AMO8 From spin squeezing to non-Gaussian atomic quantum states

By J¨urgenAppel1 and

Anne Louchet1, Ulrich Busk Hoﬀ1, Daniel Oblak1, Niels Kjærgaard1, Eugene Polzik1

1 Niels Bohr Institute, Copenhagen, Denmark The collective enhancement of the coupling between light and atomic ensembles provides a mapping of the quadra- ture operators of the light field onto quasi-spin variables of atoms. This enables the demonstation of central building blocks of quantum technology such as entanglement, quantum memory, single-photon generation and teleportation. Recently [1] we presented a light shot noise limited method to perform quantum non-demolition measurements of the atomic state, and thus conditionally prepared an entangled and spin squeezed state of 105 cold dipole trapped Caesium atoms. I will report about our recent progress towards using this dispersive probing method for performing full tomography of the atomi quasi-spin state, in analogy to homodyne detection of light. Applying the DLCZ-scheme [2] we plan to generate and characterize a single atomic excitation as a first step in detecting non-Gaussian collective atomic states. We investigate the effect of our QND probing on the coherence between the atomic states and analyze the effect of phase noise of our microwave oscillator on these measurements. [1] J. Appel et al., Arxiv 0810.3545 (2008) [2] L. M. Duan et al., Nature 414, 413 (2001)

62 AMO9 Ultrafast, time-resolved studies of solution-state systems with X-rays

By K. Haldrup1,2 and

M. Christensen1,3 M. Cammarata1,5 K.S. Kjær1,4 K. Bechgaard1,3 N. Harrit1,3 R. Feidenhans’l1,2 M. Wulﬀ5 M. M. Nielsen1,2

1 Centre for Molecular Movies2 Niels Bohr Institute, KU3 Chemistry Department, KU4 Nanoscience Centre, KU5 ESRF, Grenoble In recent years, several synchrotron beamlines have developed methods to study the structure and dynamics of solution-state systems with the laser-pump/X-ray probe technique. Time resolutions down into the ps regime have been demonstrated, and the systems investigated span the range from small organic molecules, over metal complexes to proteins such as myoglobin. The present work describes a broadly applicable analysis technique developed for the study of metal complexes in solution, a technique that oﬀers direct information on key structural parameters in the investigated systems. The technical details are illustrated with newly published results on the excited-state structure of a square-planar-like platinum compound (”PtPOP*”) and its formation of exciplexes with thallium and silver ions, TlPtPOP* and AgPtPOP*. An outlook towards the possibilities oﬀered by the new X-ray Free Electron Lasers will be also given .

63 AMO10 Unravelling non-Markovian dynamics

By K.-A. Suominen1, and

L. Mazzola1, K. H¨ark¨onen1, S. Maniscalco1, J. Piilo1, B.M. Garraway2

1 Department of Physics and Astronomy, University of Turku, Finland2 Department of Physics and Astronomy, University of Sussex, United Kingdom Unravelling non-Markovian dynamics Quantum systems embedded in passive but structured reservoirs can have non-Markovian dynamics. This can be described under certain conditions with a time-local master equation. The unravelling of this equation can be performed with various techniques. We shall discuss the connection between the time-local master equation, the non-Markovian quantum jump method, and the pseudomode approach. As an example we provide the simple case of two entangled quantum bits coupled to a common non-Markovian reservoir. It turns out that in addition to the usual sudden death of entanglement, one can also see revival of entanglement, or even birth of entanglement if starting from an initial product state. [1] H.-P. Breuer and F. Petruccione, The Theory of Open Quantum Systems (Oxford University Press, Oxford, 2002). [2] J. Piilo, S. Maniscalco, K. Härkönen,and K.-A. Suominen, Phys. Rev. Lett. 100, 180402 (2008); J. Piilo, K. Härkönen,S. Maniscalco, and K.-A. Suominen, arXiv:0902.3609 [quant-ph] (2009). [3] B.M. Garraway and P.L. Knight, Phys. Rev. A 54, 3592 (1996). [4] L. Mazzola, S. Maniscalco, J. Piilo, K.-A. Suominen, and B. M. Garraway, arXiv:0810.1361 [quant-ph] (2008). [5] L. Mazzola, S. Maniscalco, J. Piilo, K.-A. Suominen, and B. M. Garraway, arXiv:0812.3546 [quant-ph], to appear in Phys. Rev. A (2009).

64 AMO11 Femtosecond thermal ionization of large molecules

By M. Kjellberg1, and

O. Johansson2, E.E.B. Campbell2, A.V. Bulgakov3, M. Goto4, K. Hansen1

1Department of Physics, University of Gothenburg, Sweden,2School of Chemistry, Edinburgh University, Scotland,3Institute of Thermophysics, SB RAS, Novosibirsk, Russia4Department of Chemistry, Tokyo Metropolitan University, Japan Photoelectron spectra of polycyclic aromatic hydrocarbons and of fullerenes following femtosecond laser excitation with hν = 1.6 eV have been measured with a velocity mapping electron spectrometer [1,2]. The spectra are well described by Boltzmann distributions, as also observed previously for C60[3,4], albeit with extremely high temperatures, above 104 K. For comparison, the electronic temperatures observed in experiments with nanosecond laser pulses are approximately 4000 K. These results show that the behaviour observed previously for C60 [3,4] are more general and do not result from special properties of this molecule. The observed extreme electron temperatures are qualitatively understood in terms of transient highly excited electron systems. This conclusion is corroborated by additional experiments: For C70 and coronene, ion yields and electron temperatures were measured in experiments where the pulse duration was changed, as well as in pump-probe experiments. Increasing the pulse duration leads to lower apparent electron temperatures due to quenching of the excitation energy in the electronic system to the vibrational lattice. The pump-probe measurement of the C70 ion yield shows a lifetime of the highly excited electronic subsystem which is similar to that of C60, on the order of 200 fs. For anthracene, the smallest molecule in this study, peaks appear in the spectra which correspond to direct above threshold ionization. [1] M. Kjellberg et al., to be published [2] C. Bordas et al., Rev. Sci. Inst. 67 1996 (2257) [3] E. E. B. Campbell et al., Phys. Rev. Lett. 84 (2000) 2128 [4] K. Hansen et al., J. Chem. Phys. 119 (2003) 2513

65 AMO12 Towards persistent ﬂow of Bose-Einstein Condensates in a 2D ring trap.

By Martin Zelan1 and

Sergio Muniz2,3, Anand Ramanathan2,3, Kristian Helmerson2,3, William D. Phillips2,3

1 Department of Physics, Ume˚aUniversity, SE-90187 Ume˚a,Sweden2 Atomic Physics Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8424, USA3 Joint Quantum Institute, NIST and University of Maryland, College Park, Maryland 20742, USA Persistent flow of Bose-Einstein Condensates is an interesting feature of superfluidity. I will present an overview over a ongoing experiment at NIST concerning persistent flow of a sodium BEC in a 2D ring trap. I will discuss the techniques used in order to trap and to condense the atoms in the ring.

66 AMO13 Ultra-short-pulse excitation of matter

By Peter Balling and

Bjarke H. Christensen Jeppe Byskov-Nielsen Christian Smith Mehrnaz Zadeh Kristian Wædegaard Juha-Matti Savolainen Rasmus R. Olofsson

Department of Physics and Astronomy University of Aarhus Ny Munkegade 120 DK-8000 Aarhus C Denmark The excitation of materials by ultrashort laser pulses has significant importance, both in relation to investigations of ultrafast surface dynamics, e.g. chemistry or phase transitions, and in relation to laser-induced material modifications as for instance laser ablation or changing the refractive index in dielectric materials. The underlying physics in the ablation process of metals and dielectric materials is quite dissimilar. Metals are characterized by a large density of quasi-free electrons that may absorb the incoming radiation, and much of the dynamics following excitation by ultrashort laser pulses is captured by advanced thermal models [1]. On the other hand, dielectric materials are often transparent to the light, and typically conduction-band electrons must first be generated by the light to be able to start the ablation process [2]. In the present talk, the excitation of both metals and dielectrics will be discussed. The theoretical modeling of metals in the so-called two-temperature model [3] will be described and compared with analytical approximations valid at low and high excitation [2]. The dielectric materials are described in a multiple-rate-equation model, which was originally proposed by Ref. 4 and was recently extended to include propagation of the light into the material [2]. The results of the models are compared to experimental investigations of a range of materials. In addition, recent examples of applications for material modifications in our group will be briefly described. [1] B. H. Christensen, K. Vestentoft, and P. Balling, Appl. Surf. Sci. 253, 6347 (2007). [2] B. H. Christensen and P. Balling, Phys. Rev. B to be published (2009). [3] S. I. Anisimov, B. L. Kapeliovich, T. L. Perel’man, Sov. Phys. JETP 39, 375 (1974). [4] B. Rethfeld, Phys. Rev. Lett. 92, 187401 (2004).

67 AMO14 Monolithic femtosecond Yb-ﬁber laser with photonic crystal ﬁbers

By Xiaomin Liu and

Jesper Lægsgaard, Dmitry Turchinovich.

DTU Fotonik, Department of Photonics Engineering, Technical University of Denmark We demonstrate a monolithic stable SESAM-modelocked self-starting Yb-fiber laser. A novel PM all-solid photonic bandgap fiber is used for intra-cavity dispersion management. The ex-cavity final pulse compression is performed in a spliced-on PM hollow-core photonic crystal fiber. The laser directly delivers 9 nJ pulses of 275 fs duration with pulse repetition of 26.7MHz.

68 AMO15 An EPR Study of Cu2+ Doped in Potassium Dihydrogen Citrate Single Crystal

By Z. Yarbasi1 and

B. Karabulut2, A. Karabulut1

1 University of Atatürk,Faculty of Science, Physics Department, Erzurum, Turkey2 University of Ondokuzmayis, Faculty of Science, Physics Department, Samsun, Turkey In this study, we have undertaken the resolution and identification of Cu2+ complex EPR spectra in potassium dihydrogen citrate single crystal and powder. It crystallizes in triclinic symmetry. There are two molecules in a unit cell. Cu2+ doped potassium dihydrogen citrate single crystals has been studied at room temperature in three mutually perpendicular planes ( bc*, a*b and c*a*). EPR spectra of Cu2+ doped potassium dihydrogen citrate single crystals yield unexpectedly large number of lines. The positions and spacing of lines are highly dependent on orientations. The angular variation of the EPR spectra has shown that three different Cu2+complexes are located in different chemical environments, and each environment contains one magnetically inequvalent Cu2+sites in distinct orientations. When the transition metal ions are doped in a diamagnetic host lattice as an impurity, they form paramagnetic centers, from which we can get information about the local symmetry. The magnetic structures of the paramagnetic center in the local symmetry and bond shape of the ligands are defined by EPR technique. Using this method, the principal g, and the hyperfine (A) values of potassium dihydrogen citrate single crystals are determined. Both g and A values of three sets of Cu2+ complexes groups are also explained. These values of each site are found to be nearly axial symmetry. The calculated results of the Cu2+ doped in potassium dihydrogen citrate indicate that Cu2+ is substitute entering the lattice with K+ ions. The powder spectrum of Cu2+ doped potassium dihydrogen citrate crystal has shown four perpendicular and parallel lines so we can say that local symmetry is axial symmetry. The EPR data from the powder gives almost the same values on single crystals.

69 AMO1P Tomography of an atomic Fock state

By Anne Louchet1 and

J¨urgenAppel1, Daniel Oblak1, Ulrich Busk Hoﬀ1, Niels Kjærgaard1, Eugene Polzik1

1 Niels Bohr Institute, Copenhagen, Denmark We propose to create and characterize a collective atomic Fock state in an ensemble of cold cesium atoms. A weak pulse of classical light followed by the detection of a single scattered photon prepares the single excitation state, as in the first step of the DLCZ protocol [1]. A resonant π/2 microwave pulse then rotates the collective Bloch vector to the equatorial plane of the Bloch sphere, where it can be completely characterized using quantum state tomography. The Fock state’s Bloch vector is then rotated around its own axis with the help of another microwave pulse, 90 degrees phase-shifted from the first one. A large number of population difference measurements for different rotation angles give access to the projection of the Wigner quasi-probability distribution along different directions, and allow complete state reconstruction. The population difference will be measured by detecting the state dependent phase shift of two off-resonant laser beams using our Mach-Zehnder interferometer [2]. [1] L.-M. Duan, et al. Nature 414, 413-418 (2001) [2] J. Appel, et al. arXiv:0810.3545

70 AMO2P Laser colored stainless steel: Modeling of the colors and applications to color pixeling

By Anni Lehmuskero1 and

Jouni Hiltunen2 Ville Kontturi1 Markku Kuittinen1

1 University of Joensuu, Department of Physics and Mathematics, P.O. Box 111, FI-80101, Finland2University of Joensuu, InFotonics Center Joensuu, P.O. Box 111, FI-80101, Finland Colored surfaces were obtained by heating stainless steel substrates with pulsed fiber YLP laser. The laser was attached to f160 f-theta optics and beam expander to control the quality of the laser spot. In this work we present a model for the colors. We also consider the process application for color pixeling. The colors on the surface after the laser processing originate from the thin film interference in the oxide films that are formed by laser-assisted chemical reactions with air. Different colors are obtained by varying the laser parameters and thus varying the thickness of the oxide. However, as we take a microscopic view of the colored sample, it can be concluded that the color seen by naked eye is actually an effective average spectrum of different colored pixels on the surface. Thus, this kind of laser oxidizing can be used as a pixel technique resulting into durable and aesthetic surfaces. The effective spectra of the samples were measured with a spectral camera over the wavelength range 420-720 nm by 10 nm steps. The microscopic spectra, it is the spectrum of each pixel, were measured with a spectral camera through an optical microscope. Also an elementary analysis was made for the samples with energy dispersive X-ray spectroscopy (EDS). Furthermore, the samples were cut and the thickness of the oxide layers were determined from the cross spectral images taken with scanning electron microscope (SEM). The model that was used for the microscopic spectra consisted of a Cr2O3 or Fe2O3 thin film on stainless steel. We tried different thicknesses of oxide layers and noticed soon that only Cr2O3 produced matching spectra with the measured ones.

71 AMO3P Combined many-body and QED calculations in helium-like systems

By Daniel Hedendahl and

Sten Salomonson Ingvar Lindgren

Department of Physics, University of Gothenburg, Sweden Helium-like systems constitutes an interesting and challenging field for high precision physics with bright future possibilities due to the construction of the new Fair facility at GSI. The recent accurate experimental results achieved for Si+12 by the group of Myers [1] proclaim the importance of theoretical calculations that combines relativistic, QED and electron correlation effects. For Si+12 the closest theoretical result, a combination of relativistic many-body perturbation theory, Plante et al. [2], and QED calculations, Drake [3], is not able to match the accuracy of the experimental result. Other theoretical results, Artemyev et al. [4], where the QED corrections are complete to the order of (Zα)4 atomic units, are impressive, but they are still far from matching the new experimental accuracy for Si+12 [1]. This is mainly due to that the combined effects of electron correlation and QED are not treated in a complete way. From the covariant-evolution-operator method [5] we have developed a relativistically covariant many-body procedure, where relativistic, QED and electron correlation effects are treated on the same footing. With a systematic procedure similar to the atomic coupled-cluster approach, which has been used by our group for a long time, we are able to evaluate QED effects with correlated relativistic wave functions. The first numerical implementation of the procedure shows that the effect of electron correlation on first-order QED for He-like ions in the moderate Z region dominates heavily over second-order QED-effects. The progress in the development at our laboratory is at present focused to complete the full non-radiative effect of one retarded photon with correlated wave functions for helium-like ions. First to be implemented to the ground state, but also in the near future to the fine-structure separations of the 1s2p-state for comparison with the above considered experimental results. [1] T. R. DeVore, D. N. Crosby and E. G. Myers, Phys. Rev. Lett. 100, 243001 (2008). [2] D. R. Plante, W. R. Johnson and J. Sapirstein, Phys. Rev. A 49, 3519 (1994). [3] G. W. F. Drake, Can. J. Phys. 66, 586 (1988). [4] A. N. Artemyev et al., Phys. Rev. A 71, 062104 (2005). [5] I. Lindgren, S. Salomonson and B. Asén,Physics˚ Report 389, 161 (2004).

72 AMO4P High brightness external cavity broad area diode laser bar using oﬀ-axis spectral beam combining

By Deepak Vijayakumar and

Ole Bjarlin Jensen and Birgitte Thestrup

Department of Photonics Engineering, Technical University of Denmark, Frederiksborgvej 399, DK-4000 Roskilde, Denmark

73 AMO5P Fully Correlated Wavefunctions for Small Atoms

By Frank E. Harris Department of Physics, University of Utah, Salt Lake City, UT, USA, and Quantum Theory Project, University of Florida, PO Box 118435, Gainesville, FL, USA Accurate wavefunctions are extremely valuable for gaining understanding of quantum systems; independent-particle descriptions are inherently inadequate for this purpose due to their inability to take proper account of electron correlation. We consider here the use of fully correlated wavefunctions, i.e. formulations in which all the interparticle distances occur explicitly. The most widely-used approach of this kind has been that originated for the He atom by Hylleraas, who appended powers of the inter-electron distance to an orbital description of the electron-nuclear distribution. An alternative, which we consider here, is to include all the interparticle distances in an exponential form; such a wavefunction can be termed fully exponentially correlated. Once all the interparticle distances of a few- body system have been introduced into the wavefunction in an equivalent fashion, there is no longer a simplification achievable by assuming any of the particles to have infinite mass (so-called adiabatic systems), and a fully exponentially correlated wavefunction is seen to be suitable for nonadiabatic systems, and in particular for exotic quasiatoms such − + − − + − + − + − − as Ps (the e e e system), Ps2 (e e e e ), or mesonic systems, e.g. µ e e . For three-body systems, fully exponentially correlated wavefunctions are fairly easy to work with. However, for four-body systems, the situation is far more complex. The basic integrals for four-body fully exponentially correlated wavefunctions were evaluated by Fromm and Hill in 1986. However, mathematical complexities in the evaluations introduced computational difficulties and unexplained behavior that we now discuss and elucidate. This understanding permits us to obtain compact, but rather accurate wavefunctions for the Li ground state. Supported by U.S. National Science Foundation Grants PHY-0601758 and DMR-0325553.

74 AMO6P Characterization and control of attosecond pulse trains

By J. Marcus Dahlstr¨omand

J. M. Dahlstrom1, T. Fordell1, E. Mansten1, T. Ruchon1,2, X. He1, R. Rakowski1, M. Gisselbrecht1,3, K. Klunder1, M. Swoboda1, A. L’Huillier1, J. Mauritsson1

1 Department of Physics, Lund University, P.O. Box 118, SE-221 00 Lund, Sweden2 CEA-Saclay, DSM, Service des Photons, Atomes et Molcules, 91191 Gif sur Yvette, France3 CNRS-Universite Paris Sud, UMR8624, LIXAM, Bat. 350, 91405, Orsay, France Attosecond pulse trains (APTs) are created when intense infrared (IR) laser pulses interact with a gas of atoms or molecules [1]. The characteristics of the attosecond pulses depend both on the quantum-mechanical single atom dynamics as well as on macroscopic effects due to propagation in the nonlinear medium. On this poster we present a comparion of two different characterization techniques: the Reconstruction of Attosecond Bursts by Interference of Two-photon Transitions (RABITT) [1] and a two-color in-situ method [2], that uses a weak perturbation of high-order harmonic generation (HHG) by the second harmonic (blue) of the fundamental laser field. Both techniques aim to characterize the average attosecond pulse structure in an APT. Using the Strong Field Approximation (SFA) [3], the Fourier components of the HHG dipole can be approximated and the effect of the blue field can be understood. It turns out that the-blue field induces a change in the quasiclassical electron trajectories in opposite ways for adjacent half- cycles of the fundamantal. This change leads to an interferometric control over the high-order harmonic emission and a signal in the even harmonics which is related to the chirp of the attosecond pulses. We observe that the interferometric structure becomes more complicated as the relative intensity is increased. The interferences from ajacent half-cycles are eventually washed out since the tunneling probability in one half-cycle of the fundamental starts to dominate over the other [4]. In this regime we observe how the quasiclassical trajectories are strongly shaped by the blue field [5]. References [1] P. M. Paul et al., Science 292, 1689 (2001). [2] N. Dudovich et al., Nature Phys. 2, 781 (2006). [3] M. Lewenstein, P. Salieres, and A. L’Huillier, Phys. Rev. A 52, 4747 (1995). [4] J. Mauritsson et al., Phys. Rev. Lett. 97, 013001 (2006). [5] E. Mansten et al., New. J. Phys. 10 No.8, 083041 (2008).

75 AMO7P Incubational eﬀects in femtosecond laser ablation of metals

By Juha-Matti Savolainen1 and

Kristian Juncher Wædegaard1 Jeppe Byskov-Nielsen1 Peter Balling1

1 University of Aarhus, Department of Physics and Astronomy, Aarhus C, 8000, Denmark

76 AMO8P Amplitude-phase methods for calculating and analyzing scattering states in relativistic and non-relativistic quantum mechanics.

By K. -E. Thylwe KTH-Mechanics, Royal Institute of Technology, SE-10044 Stockholm, (Sverige) Sweden Amplitude-phase methods were introduced long ago by Milne (bound states) and Wheeler (scattering states) in the 1930’s. The methods calculate almost constant amplitude functions in ’no time’, together with phase functions that increase almost linearly at ’the same’ time. From amplitudes and phases one constructs the interesting physical quantities, like phase shifts, S-matrix pole positions, residues, etc., with very high precision. One reason that allows extreme accuracies of computations is that the calculated quantities can be obtained as being almost constant (for amplitudes) or monotonically increasing (for phases). The basic equations are ’non-linear’ in the amplitude functions and, therefore, the solutions depend on the boundary conditions that must be chosen with some care. Until very recently amplitude-phase methods were applied only in regions of decoupled atomic (and nuclear) radial wave equations. Recent formulations of the amplitude-phase approach to (radial) wave equations have dealt with coupled radial (Schr¨odinger/Dirac)equations with scattering boundary conditions. Some numerical results for relativistic (Dirac) phase shifts, non-relativistic 2-state Regge pole positions and residues are presented, relevant for electron/atom/molecule scattering physics.

77 AMO9P Broadband high power THz generation.

By K. Iwaszczuk and

D. G. Cooke P. Uhd Jepsen

DTU Fotonik - Department of Photonics Engineering, Technical University of Denmark, Ørsteds Plads 343, DK 2800 Kongens Lyngby, Denmark We have studied terahertz generation by optical rectification, which is a difference frequency mixing process and occurs in media with large second order susceptibility. For ultrashort laser pulses (fs pulses from Ti:sapphire laser) that have large bandwidth, the frequency components are differenced with each other to produce bandwidth from 0 to several THz. The generated terahertz pulse is the envelope of the optical pulse. Phase matching between the optical and terahertz beams plays crucial role for efficient optical rectification. Matching between group velocity and the terahertz phase velocity in some nonorganic crystals like ZnTe or GaP can be achieved in a collinear configuration. We have investigated THz generation in a new organic crystal: N-benzyl-2-methyl-4-nitroaniline (BNA). Comparison to commonly used ZnTe shows that BNA is a promising material for wideband, efficient, and strong THz-wave generation. Nonlinear coefficients of ZnTe or BNA are still much smaller than high dielectric ferroelectrics such as lithium niobate (LiNbO3). However for those materials velocity matching of the terahertz phonon-polariton wave cannot be achieved collinearly. To reach phase matching in LiNbO3 we have studied tilting of the pump pulse front by using diffraction grating.

78 AMO10P Doubly uniform semiclassical quantization formula for resonances

By Karl-Erik Thylwe1 and

Irina Jakusjina Linnaeus2

1KTH-Mechanics, Royal Institute of Technology, 10044 Stockholm, Sweden2Dalarna University College, 78188 Borl¨ange,Sweden

79 AMO11P Investigation of metastable Magnesium atoms

By K´ariGunnarsson1 and

Kasper T. Therkildsen1 Brian B. Jensen1 Anders Brusch1 Ming He1 Morten H. Madsen1 Jan W. Thomsen1

1 University of Copenhagen We present recent results on two different experiements that are used to investigate the metastable states of Mg24. 3 One experiment uses a three level ladder system to load ultra cold atoms into the metastable P2 state. The Mg 1 1 atoms are trapped using a Magneto-Optical-Trap (MOT) on the S0 → P1 transition using frequency doubled light 1 1 at 285 nm, a 881 nm laser is then used to excite the P1 → D2 transition, which in turn leaks down to the metastable 3 3 P2 state. The P2 atoms are magnetically trapped and investigated for the first time. 3 The second experiment populates the P2 state using a beam line that is collided with electrons from a tungsten filament in order to excite them to the metastable states. The fast travelling atomic beam is cooled down using a 3 3 3 Zeeman slower with laser light at the 383 nm P2 → D3 transition. The aim of the experiment is to trap the P2 atoms 3 3 in a MOT, on the P2 → D3 transition, which has a significantly lower Doppler temperature than the traditionally 1 1 used S0 → P1 transition MOT.

80 AMO12P Low loss structured polymer ﬁber for terahertz

By Kristian Nielsen1 and

Aurele J. L. Adam3 Paul C. M. Planken3 Henrik K. Rasmussen2 Peter Uhd Jepsen1 Ole Bang1

1 DTU Fotonik, Technical University of Denmark, Ørsteds Plads, byg. 343, DK-2800 Kgs. Lyngby2 DTU Mek, Technical University of Denmark, Ørsteds Plads, byg. 343, DK-2800 Kgs. Lyngby3 Delft University of technology, Faculty of Applied Physics, Department of Imaging Science and Technology, Lorentzweg 1, 2628 CJ Delft, the Netherlands We report on the properties of the first THz polymer photonic crystal fiber (PCF) made of Topas cyclic olefin copolymers (COC). Topas has previously been used for microstructured optical fiber but to our knowledge this is the first time Topas has been used for THz fiber. The reason for using Topas is that it has exceptionally low loss and flat dispersion in the THz range. We report on the propagation loss and on the dispersion of the THz Topas PCF. The properties of the fiber have also been modeled numerically using the full vectorial software package COMSOL. From these numerical calculations the dispersion of the fiber has been calculated. The calculated dispersion profile is compared to the measured dispersion and shows excellent agrement. The mode profile of the fibers is also characterized experimentally by using near-field electro-optic sampling. Cutback measurements were made on the fiber. From these measurements the broadband loss was found. The broadband loss is defined as the total attenuation of the integrated electric field squared. The Broadband loss is found to be 0.4 +/-0.06 dB/cm corresponding to a absorption coefficient of 0.09 cm−1. This value is lower than the measured bulk loss of the Topas of 0.15 cm−1.

81 AMO13P Laser-induced adiabatic alignment and orientation of molecules

By Line Kalhøj and

Soﬁe Louise Kragh, Lotte Holmegaard, Jonas Lerche Hansen, Jochen Maurer, Jens H. Nielsen, Iftach Nevo, Henrik Stapelfeldt.

Department of Chemistry, Aarhus University

82 AMO14P Ablation of dielectric materials with ultra-short laser pulses: Experimental test of a numerical model

By M.N. Zadeh1 and

B.H.Christensen2 P.Balling1

1 Dept. of Physics and Astronomy, University of Aarhus2 Tribology Centre, Danish Technological Institute

83 3 AMO15P Metastable Mg Spectroscopy of (3s3p) P0,1,2 - 3 (3s4s) S1 transitions

By Ming He and

Kasper T. Therkildsen, Brian B. Jensen, Anders Brusch, Kari Gunnarsson, Morten H. Madsen, and Jan W. Thomsen

Niels Bohr Institute, Copenhagen University, Universitetsparken 5, DK-2100 Copenhagen We present a laser operating at 517 nm for our Magnesium laser cooling and atomic clock project. A two- stage Yb-doped fiber amplifier (YDFA) system generates more than 1.5 W of 1034 nm light when seeded with a 15 mW diode laser. Using a periodically poled lithium niobate (PPLN) crystal, we obtained more than 40 mW of 517 nm output power by single pass frequency doubling. In addition, we report new measurements of the isotope 3 3 24 25 26 shifts of the (3s3p) P0,1,2 - (3s4s) S1 Mg I transitions for the stable isotopes Mg (I=0), Mg (I=5/2) and Mg 25 3 3 (I=0). Futhermore the Mg S1 hyperfine coeffcient A( S1) = (−321.6 ± 1.5) MHz is extracted and found to be in 3 excellent agreement with state-of-the-art theoretical predictions giving A( S1) = -325 MHz. Compared to previous measurements, the data presented in this work is improved up to a factor of ten.

84 AMO16P Progress report on the Aarhus Micro ion trap Project

By Otto Nielsen and

Gregers Poulsen, Yevhen Miroshnychenko, Richard Hendricks, David Grant, Michael Drewsen.

QUANTOP - Danish National Research Foundation’s Center for Quantum Optics Department of Physics and Astronomy Uni- versity of Aarhus Bygning 1520 Ny Munkegade DK-8000 Aarhus C Denmark As part of our involvement in the EU MICROTRAP project, we have designed, manufactured and assembled a micro-scale ion trap with integrated optical fibers. These prealigned fibers will allow delivering cooling laser light to single ions. Therefore, such a trap will not require any direct optical access for laser cooling. All the parts for the trap have been made in our institute [1]. In our group we have developed a technique to manufacture lensed optical fibers. The electrodes and the spacers were laser cut in the collaboration with the group of P. Balling. The trap is now installed in an ultra high vacuum chamber, which includes an ablation oven for all-optical loading of the trap [2]. The next steps on the project are to demonstrate the operation of the micro-trap and the cooling of ions using fiber delivered light.

85 AMO17P Applications of negative ions in mass spectroscopy

By P. Klason1 and

P. Andersson1, A. O. Lindahl1, J. Rohl´en1, O. Frostner2, Y. Liu3, C. C. Havener3, and D. Hanstorp1

1 Department of Physics, University of Gothenburg, 412 96 Gothenburg, Sweden 2 Faculty of Physics, University of Vienna, A-1090 Wien, Austria 3 Physics Division, Oak Ridge National laboratory, P.O. Box 2008, Oak Ridge, Tennesee 37831-6368, USA Accelerator Mass Spectroscopy (AMS) is used in many different fields, such as physics, chemistry, biology and medicine, to distinguish atoms or molecules with different masses from each other. One of the most well known applications of AMS is age determination of biological samples, where the abundance of 14C in the sample is measured. AMS is able to detect trace elements at typical abundances well below 10−12. One major challenge in AMS is to separate different isobars from each other. For light ions there are various techniques available for such energy loss in matter, but for heavy ions these methods are normally not applicable. As shown by Berkovits et al. [1, 2] it is possible to achieve suppression of an interfering isobar in a tandem accelerator using selective laser photodetachment. The experiments by Berkovits, however, showed a suppression factor far from practical use in AMS applications. A solution to this problem has been proposed Liu et al. by means of a linear gas filled rf quadrupole in which the ions are decelerated and cooled [3]. As a consequence, the interaction time between photons and ions is prolonged by up to three orders of magnitude. A laser propagating collinearly with the ion beam in the ion guide can then give an efficient photodetachment due to the long interaction time. We present the results of an experiment where we examine the suppression on a Co− ions in a beam of Ni− using a Nd:YAG fundamental (1064 nm) as the photodetachment laser. Furthermore, we have investigated if laser photodetachment spectroscopy of negative ions can be used as an isobar selective filter for the astrophysical interesting radionuclide 182Hf. In this case the stable isobar 182W gives a strong interfering background. We present experiments using a pulsed Nd:YAG laser on the most promising hafnium negative − − − ions for AMS, i.e. the HfF5 [4]. Studies of the photodetachment cross section for WF5 and HfF5 was preformed at several laser wavelengths. A lower energy limit is presented for which laser photodetachment can be used as a selective − suppression filter of WF5 in AMS. References: [1] D. Berkovits et al. Nucl. Instr. and Meth. in Phys. Res. A 281 (1989) 663. [2] D. Berkovits et al. Nucl. Instr. and Meth. in Phys. Res. B 52 (1990) 378. [3] Y Liu et al. Nucl. Instr. and Meth. B 255 (2007) 416. [4] C. Vockenhuber et al. Nucl. Instr. and Meth. in Phys. Res. B 223-224 (2004) 823.

86 AMO18P Design and characterization of optical surfaces for daylighting applications

By Peter Barkholt Muller1 and June Holm Rasmussen1 and

Anders Kristensen1 Morten Bo Lindholm Mikkelsen1 Elin Sønderg˚ard2 Alban Letailleur2

1 DTU Nanotech - Department of Micro- and Nanotechnology, Technical University of Denmark, DK-2800 Lyngby, Denmark2 Laboratoire Surface du Verre et Interface, Saint-Gobain, 93303 Aubervilliers Cedex, France Various benefits such as power savings and better indoor climate can be achieved by extending the use of daylighting applications. The long time goal is to use nano and micro gratings in window glass to redirect and spread sunlight. The different parameters of the gratings are varied. The period of the structure range from 500 nm to 3000 nm. The height range from 1000 nm to 2000 nm. The fill factor range from 10 % to 70 %. The diffraction pattern is measured with a linear CMOS sensor which scans a 180 degree range. Three different wavelengths within the visible spectrum are used and their superposition is used to predict the effect of the grating on sunlight. Chirped binary gratings are characterized to determine whether the changing period leads to an angular shift in the intensity distribution. Simulations are made to optimize gratings for coupling light into the non-zeroth orders.

87 AMO19P Infrared laser sources for rotational cooling of translationally cold MgH+ ions

By Peter S. Skyt and

Simon B. Kristensen Anders K. Hansen Klaus Højbjerre Peter F. Staanum Michael Drewsen

Department of Physics and Astronomy University of Aarhus Molecular ions confined in an iontrap can be cooled to sub-Kelvin translational temperature through the Coulomb interaction with co-trapped laser cooled atomic ions. Such cold molecular ions are applied in a variety of experiments, e.g., chemical reaction and photodissociation studies [1,2]. At room temperature, many diatomic molecular ions are predominantly found in the vibrational ground state; by bringing also the rotational degree of freedom to the ground state unprecedented quantum-state specific studies will become feasible. Rotational cooling can be obtained by optical pumping on ro-vibrational transitions using infrared laser sources [3,4]. Here we present two such infrared diode laser systems, which operate near 6200 nm and 1650 nm, respectively, and describe their application in rotational cooling of MgH+ ions [5]. The laser system near 6200 nm is based on a liquid-nitrogen cooled PbSe diode laser with 0.5 mW output power. The laser wavelength is tunable by change of the diode injection current and the diode temperature. Absolute frequency measurements are performed by absorption spectroscopy on ammonia as well as water vapor, while a relative frequency calibration is obtained using a solid germanium Fabry-Perot etalon. With these tools at hand, the relevant transition frequency of 1608.96 cm−1 can be reached and rotational cooling observed [5]. Further manipulation of the rotational quantum state distribution can be obtained by employing an additional laser source near 1650 nm. For this purpose an external cavity InP diode laser with diffraction grating feedback has been built. The laser is tunable over ∼50 nm and the output power is ∼15 mW. [1] P. F. Staanum et al., Phys. Rev. Lett. 100, 243003 (2008) [2] K. Højbjerre et al., Phys. Rev. A 77, 030702(R) (2008) [3] I. S. Vogelius et al., Phys. Rev. Lett. 89, 173003 (2002) [4] I. S. Vogelius et al., Phys Rev. A 70, 053412 (2004) [5] K. Højbjerre et al., to appear in New J. Phys.

88 AMO20P Fundamental studies of negative ions

By Pontus Andersson and

Dag Hanstorp, Peter Klason, Anton O Lindahl, Johan Rohl´en

Göteborgs Universitet, Institutionen förfysik Fundamental studies of negative ions Pontus Andersson, Dag Hanstorp, Peter Klason, Anton O Lindahl, Johan Rohlén Department of Physics, University of Gothenburg, SE412 96 Gothenburg, Sweden Negative ions are fragile quantum systems with binding energies typically one order of magnitude smaller than the corresponding ionization potentials[1]. They are ideal systems for studying electron correlation, since this effect is more prominent in negative ions than in atoms or positive ions. The fundamental properties of theses ions are also important for the understanding of many phenomena in nature. Negative hydrogen ions are governing the opacity in the infrared part of spectrum in the suns atmosphere, and the first negative ions have just recently been detected in dense interstellar clouds [2]. Negative ions also play a major role in the d-layer of the atmosphere where they balance the charge of the positive ions to the same extent as the free electrons. There are also technological applications where a thorough understanding of negative ions is essential. Most importantly, negative ions are used in mass spectroscopy, both in the injection stage of tandem accelerators used in AMS and as the primary ion beam in Secondary Ionization Mass Spectrometry (SIMS). Atomic negative ions have been studied at the University of Gothenburg since the late 1980’ies [3]. The ions are studied by laser photodetachment in a collinear ion-laser-beam spectrometer. Ions are produced in a cesium sputter negative ion source, extracted and accelerated to an energy of typically 6 keV. The ion beam is mass selected by a 90 ◦ sector magnet with a mass resolution of typically 600. After mass selection the beam is bent into the interaction region by an electrostatic quadrupole deflector. The overlap between laser- and ion-beam is defined by two 3 mm apertures placed 60 cm apart. After the interaction the ion beam is turned into a Faraday cup, whereas neutrals produced in the photodetachment process are detected and counted by a neutral particle detector and a computer based acquisition system. The laser light is produced with two Optical Parametric Oscillators (OPO) with a combined tuning range of 220 to 5000 nm. This setup has been used to investigate the structure of several atomic negative ions. In this work we will present the laser photodetachment threshold spectroscopy measurements of the electron affinity of phosphorus and tungsten. The Electron affinities was found to be 746.68(6) and 816.486(70) meV respectively. In the phosphorous case the fine structure splitting of the ground state was measured as well and yielded a splitting of 22.48(7) and 32.73 (7) meV 3 3 3 above the P2 ground state for the P1 and P0 states respectively. For Tungsten we conclude through careful mass analysis that the nonzero background found beneath the ground state threshold must originate from a previously unobserved excited state. As a third example we present the first observation of a predicted [4] excited state in Pt−. The setup is currently upgraded with a position sensitive detector that will allow state selective detection of the neutral particles. Using this detector, high lying doubly excited states in negative ions will be investigated A detailed study of the Wannier law is also planned using the new detector. References [1] T. Andersen, H. K. Haugen and H. Hotop, J. Phys . Chem. Ref. Data, 28, 1511 [2] S. Brünken et al. Astrophys. Journ. 664, L43-L46 [3] D. Hanstorp, C. Bengtsson and D. J. Larson, Phys. Rev. A, 40, 670 [4] J. Thøgersen, M. Scheer, L. D. Steele, and H. K. Haugen, Phys. Rev. A, 76, 2870

89 AMO21P Characterizing propagation of femtosecond optical pulses in ﬁber links using frequency-resolved optical gating.

By R.K. Olsson1 and

F. Eichhorn1, P.U.Jepsen1

1 DTU Fotonik, Department of Photonics Engineering, Technical University of Denmark Fiber links consisting of dispersion compensating fiber (DCF), fiber optic splitters and standard single mode fiber can be used to distribute femtosecond pulses to several locations with only little distortion. We show how frequency- resolved optical gating (FROG) can be used to characterize pulse distortion in a fiber link designed for 1550 nm input pulses with a pulse width of around 100 fs. The FROG technique allow a complete characterization of the pulse intensity and phase. The fiber link is optimized in order to get the shortest possible pulses at the output. The results are compared to numerical simulations of the pulse propagation based on a nonlinear Schrödingerequation (NLSE) which includes the effects of group velocity dispersion, self-phase modulation, higher order dispersion, stimulated Raman scattering and self-steepening. 1. Dudley, J.M. et al. Characterizing Pulse Propagation in Optical Fibers around 1550 nm Using Frequency- Resolved Optical Gating. Optical Fiber Technology 4, 237-265(1998).

90 AMO22P Quantum Learning by Measurement and Feedback

By S. Gammelmark and

K. Mølmer

Lundbeck Foundation Theoretical Center for Quantum System Research, Department of Physics and Astronomy, University of Aarhus We investigate an approach to quantum computing in which quantum gate strengths are parametrized by quantum degrees of freedom. The capability of the quantum computer to perform desired tasks is monitored by measurements of the output and gradually improved by successive feedback modiﬁcations of the coupling strength parameters. Our proposal uses only information available in an experimental implementation and is demonstrated with simulations on search and factoring algorithms.

91 AMO23P Laser induced non-adiabatic alignment and orientation of quantum-state-selected molecules.

By Soﬁe Louise Kragh and

Line Kalhøj, Lotte Holmegaard, Jonas Lerche Hansen, Jochen Maurer, Jens H. Nielsen, Iftach Nevo, Henrik Stapelfeldt

92 AMO24P Semiclassical solution of the radial Dirac equation

By Staﬀan Linnaeus1 and

Karl-Erik Thylwe2

1Dalarna University College, 78188 Borl¨ange,Sweden2KTH-Mechanics, Royal Institute of Technology, 10044 Stockholm, Sweden

93 Bio- and medical physics

BF1 Using ﬁber-coupled organic scintillators to examine linear accelerator pulse delivery

By Anders Ravnsborg Beierholm and

Claus Erik Andersen Lars Ren´eLindvold

Radiation Research Department, Risø National Laboratory for Sustainable Energy, Technical University of Denmark, DK-4000 Roskilde Organic plastic scintillators coupled to light-guiding optical fibers were largely introduced in 1992 as a method for performing real-time dose rate measurements during radiotherapy of cancer [1]. Radiation-induced luminescence and Cerenkov light generated in the optical fiber itself has since prevented the method from being used on a routine clinical basis. However, an approach called chromatic removal has been shown to remove this so-called stem effect successfully, ensuring a better dose rate estimate [2]. For most organic scintillators, the scintillation process occurs in the order of nanoseconds. Using fast data acquisition, organic scintillators can therefore be used to measure individual microsecond-duration pulses of high energy x-rays from a medical linear accelerator. In this way, the scintillator probes can be used to investigate the impact of dose delivery discrepancies on patient treatment. For instance, transients in dose delivery occurring shortly after the radiation beam has been turned on can be investigated on a per-pulse timescale using fast dose rate measurements. We report on fiber-coupled organic scintillator measurements performed on Varian Clinac medical linear accelerators at the Copenhagen University Hospital, delivering high energy electron and photon beams. The scintillator measurements are compared with measurements performed using standard ionization chambers as well as monitoring of accelerator target current [3]. [1] S. A. Beddar et al., Phys. Med. Biol. 37, 1883-1900. [2] L. Archambault et al., Med. Phys. 33, 128-135. [3] K. L. Lam et al., Med. Phys. 25, 334-338.

94 BF2 Planar Hall eﬀect magnetic biosensors

By Bjarke Dalslet and

Christian Danvad Damsgaard , Mikkel Fougt Hansen

DTU Nanotech Magnetic biosensors for lab-on-a-chip systemts rely on the indirect detection of the presence of biomolecules via the detection of magnetic beads attached to the biomolecules. Across the world different sensor principles are being applied: spin valves, tunnel and giant magnetoresistance sensors, etc. At DTU Nanotech, we are investigating magnetic biosensors based on the planar Hall effect. The planar Hall effect utilizes anisotropic magnetoresistance in a Hall measuring geometry. Two biodetection schemes are investigated: (1) A surface based sandwich assay, where the biomolecules of interest act as highly specific glue between biocoated magnetic beads and the biocoated sensor surface. The presence of magnetic beads on the sensor is detected as a change in the magnetic field acting on the sensor. (2) A volume based assay in an alternating magnetic field, where changes in the rotation resonance frequency of the magnetic beads when biomolecules attach to them, are monitored in the sensor signal. In the presentation, the principle of planar Hall effect sensors will be described and the two detection schemes will be introduced. We will present recent results of our work and an outlook on applications.

95 BF3 Sequence and Molecular Simulation Studies of Insertion and Stabilization of Membrane Proteins

By Erik Lindahl Center for Biomembrane Research Stockholm University, Sweden Membrane proteins constitute one of the most fascinating classes of biological macromolecules. In a typical genome, roughly 30% of the genes code for proteins associated with membranes, but since these proteins are present on the cell surface they are of extremely high importance for pharmaceutical applications. Over half of currently available drugs target membrane proteins, and in terms of market value it is close to 80%. Due to difficulties in overexpression and crystallization there are still only a couple of hundred membrane protein structures known, and for this reason computational modeling of membrane proteins has received a lot of attention.While most transmembrane segments in proteins are clearly hydrophobic, there are a number of exceptions where marginally stable or even hydrophilic segments appear in the hydrophobic region. Many of these are critically important, for instance the S4 segments of voltage- gated ion channels. There has been significant debate between experimental results that claim insertion for these is quite cheap, and theoretical calculations claiming it is prohibitively expensive. At CBR, we use a fairly wide range of combined methods to study these systems, ranging from bioinformatics through modeling and molecular simulations all the way to in vitro experiments. I will discuss these methods and talk about recent work where we have shown that the hydrophobicity values derived from experimental insertion is amazingly efficient at predicting insertion, how this can be used to understand (and predict) helix-helix interactions in membranes, and finally how we have been able to use molecular simulation methods to reconcile previously inconsistent experimental and theoretical results.

96 BF4 Osmotically driven ﬂows in microchannels and their relation to sugar transport in plants

By K˚areHartvig Jensen1, and

Tomas Bohr2, Henrik Bruus1

1 Center for Fluid Dynamics, Department of Micro- and Nanotechnology, Technical University of Denmark, DTU Nanotech Building 345 East, DK-2800 Kongens Lyngby2 Center for Fluid Dynamics, Department of Physics, Technical University of Denmark, Building 309, DK-2800 Kongens Lyngby Osmotically driven flows in microchannels are studied experimentally and theoretically. The propagation of a front of sugar solutions has been measured using dye and particle tracking in 0.20 mm wide and 0.05, 0.10 and 0.20 mm high polymer-based microchannels. Each of these microchannels was separated by a semipermeable membrane from a reservoir containing pure water. We find that the sugar front travels with constant speed, and that this speed is proportional to the concentration of the sugar solution and inversely proportional to the depth of the channel. The theoretical predictions agree well with the measurements. Our motivation for studying osmotically driven flows are, that these are believed to be responsible for the translo- cation of sugar in plants. Also, we suggest that our channel design can be used as the driving mechanism in integrated micropumps with no movable parts.

97 BF5 Propagation modes of entropically trapped and extended DNA molecules

By Morten Bo Mikkelsen1 and

Walter Reisner1,2, Henrik Flyvbjerg1, Anders Kristensen1

1 DTU Nanotech - Department of Micro- and Nanotechnology, Technical University of Denmark, DK-2800 Lyngby, Denmark2 Department of Physics, Brown University, Providence, Rhode Island 02912, USA Nanoconfinement is a powerful tool for controlling polymer conformation and dynamics in lab-on-a-chip type devices for the analysis of DNA and other biomolecules. We present a new device concept that combines confinement-based extension of DNA with the entropic trapping principle, leading to qualitatively new physics and applications. The device consists of a 50 nm slit channel with an array of transverse 150 nm by 100 nm grooves, where the transport of DNA molecules perpendicular to the groove axis is investigated under pressure driven buffer flow. At low flow velocities the DNA remains trapped and extended in the nanogrooves while buffer circulates through the slit, enabling physical mapping of the DNA while performing real time buffer exchanges. For flow velocities above a molecular weight dependent escape threshold, we show that the molecule transport through the slit channel randomly alternates between two modes of propagation: A stepwise groove-to-groove hopping, which we refer to as the ’sidewinder’ state, because of its resemblance with the mode of propagation of the snake of that name, and a state of continuous tumbling across groves, which we refer to as the ’tumbleweed’ state. In this state grooves give rise to an effective friction, like potholes would for tumbleweed. The observed length-dependence of the molecule’s velocity may lead to a novel separation methodology.

98 BF6 Novel Applications of Positron Annihilation Spectroscopy - Biomaterials and Medical Polymers

By P. Sane1, and

F. Tuomisto1, E. Salonen1, I. Vattulainen1,2, J. Holopainen3

1 Department of Applied Physics, Helsinki University of Technology, Finland,2Department of Physics, Tampere University of Technology, Finland,3Department of Ophthalmology, University of Helsinki; Helsinki Biophysics & Biomembrane Group, Institute of Biomedicine, University of Helsinki, Finland Positron annihilation spectroscopy (PALS) is an efficient tool to study atomic scale defects in semiconductors [1] and routinely used to study the void sizes in polymer materials [2]. In crystalline solids, the positron lifetime and the Doppler broadening of the positron-electron annihilation radiation can be used to determine the sizes, concentrations and chemical environments of vacancy defects, hence giving the possibility to study, e.g., their energy levels or their thermal behavior. Polymer studies are common around the world, mostly in the field of physical chemistry e.g. characterization of glass transition temperature and changes in void sizes occurring in different phases. Applying PAS to study biomaterials is uncommon and until recent years mostly unheard of, even though preliminary studies were performed in early 1980’s [3]. Through the increased understanding of the biomolecular materials, results from PAS experiments can now be compared with simulations and further analysis/confirmation of the results is possible. In biomolecular material, a thermalized positron forms a meta-stable bound state, Positronium (Ps), with an electron from the material. An o-Ps-atom can be applied as a probe, due to the Ps lifetime in the material being strongly affected by the free volume characteristics of the probed material. PAS-results convincingly show the viability of PAS to study the void sizes in e.g. lipid bilayers and further developments are underway to create analytical tools to accurately quantify the lifetime results to e.g. free volume pocket radii. Our studies combines the experimental results achieved with PALS and atomistic MD simulations. In this work we present results obtained in DPPC, POPC and Sphingomyelin-lipids. As well as studying manufactured lipids with PALS, also in vivo studies of organic biomaterial are possible, such as studying the changes in internal free volume/dynamics of a mammalian lens and the lipid membranes separated from lenses [5]. [1] F. Tuomisto et al, Phys. Rev. Lett. 93 (2004) 055505 [2] O. E. Mogensen, Positron annihilation in Chemistry (Springer-Verlag, Heidelberg, 1995) [3] Y.Y. Wang et al., J. Am. Chem. Soc. 105 7272-7276 (1983) [4] P. Sane et al, J. Phys. Chem. B. 113 1810-1812 (2009) [5] P. Sane et al, ”‘Temperature induced phase transition in-situ in porcine lens”’ subm. BioPhys. J. 24.1.2009

99 BF7 Water Isotope Eﬀect on the Bilayer Properties: A Molecular Dynamics Simulation Study

By T. Rog1 and

K. Murzyn2, J. Milhaud3, M. Karttunen4, M. Pasenkiewicz-Gierula2

1 Department of Physics, Tampere University of Technology, Tampere, Finland2 Department of Biophysics, Faculty of Bio- chemistry, Biophysics and Biotechnology, Jagiellonian University, Krakow, Poland3 Laboratoire de Biophysique Moleculaire, Cellulaire et Tissulaire, UFR SMBH Universite Paris 13, Paris, France4 Department of Applied Mathematics, The UniVersity of Western Ontario, London, Ontario, Canada

Physicochemical properties of heavy water (D2O) differ to some extent from those of normal water. Substituting D2O for H2O has been shown to affect the structural and dynamic properties of proteins, but studies of its effects on lipid bilayers are scarce. In this paper, the atomic level molecular dynamics (MD) simulation method was used to determine the effects of this substitution on the properties of a dipalmitoylphosphatidylcholine (DPPC) bilayer and its hydrating water. MD simulations of two DPPC bilayers, one fully hydrated with H2O and the other with D2O, were carried out for over 50 ns. For H2O, the simple point charge (SPC) model was used, and for D2O, the extended SPC-HW model was employed. Analyses of the simulation trajectories indicate that several properties of the membrane core and the membrane/water interface are affected by replacing H2O by D2O. However, the time-averaged properties, such as membrane compactness, acyl chain order, and numbers of PC-water H (D)-bonds and PC-PC water bridges, are much less affected than time-resolved properties. In particular, the lifetimes of these interactions are much longer for D2O molecules than for H2O ones. These longer lifetimes results in a slightly better ordering of the D2O molecules and average self- diffusion, which is 50% slower compared with the H2O molecules. This large isotope effect has been assigned to the repercussions of the longer lived D-bonding to DPPC headgroups insofar as all water molecules sense the presence of the DPPC bilayer.

100 BF8 Dielectric relaxation processes in ethanol/water mixtures

By Uﬀe Moeller1, and

Jacob Riis Folkenberg2, Koichiro Tanaka3,4, Peter Uhd Jepsen1

1 DTU Fotonik, Technical University of Denmark, Oersteds Plads, DK-2800 Kongens Lyngby, Denmark,2 FOSS Analytical A/S, Slangerupgade 69, DK-3400 Hillerød, Denmark,3 Department of Physics, Graduate School of Science, Kyoto Univer- sity, Kitashirakawa, Sakyo-ku, Kyoto 606-8502, Japan,4 Institute for Integrated Cell-Material Sciences, Kyoto University, Yoshidakonoe-cho, Sakyo-ku, Kyoto 606-8501, Japan The dielectric properties of neat water and ethanol have been extensively studied [1-3] due to their importance in various scientific contexts. Alcohol/water mixtures are recognized as the simplest prototype of biomolecules and micelle forming systems and have been subject to a number of studies. Alcohol interacts with water through hydrogen bonding and therefore it influences the dielectric relaxation properties of water when added. We use attenuated total reflection terahertz time-domain spectroscopy [3] to characterize the dielectric relaxation processes of 10 different ethanol/water mixtures at 25◦C with ethanol molar fractions from 0-100%. Combined with previously published data [4] these measurements cover the frequency range from 100 MHz to 2.5 THz (1 THz = 1012 Hz). We show that a model containing three Debye relaxation terms and an intermolecular stretching vibration term can be used to describe the dielectric relaxation behaviour of ethanol/water mixtures. We find strong correlation between the extracted relaxation time constants and other important physical properties of the mixtures such as the mixing enthalpy. [1] C. Rønne and S. Keiding, J. Mol. Liquids 101, 199 (2002) [2] J. T. Kindt and C. A. Schmuttenmaer, J. Phys. Chem., 100, 10373-10379 (1996) [3] H. Yada, M. Nagai, and K. Tanaka, Chem. Phys. Lett., 464, 166-170 (2008) [4] T. Sato and R. Buchner, J. Phys. Chem. A, 108, 5007-515 (2004)

101 BF1P Optoﬂuid microscope in a microﬂuidic separation device

By A. L. Vig and

R.T.Nielsen E.Jensen A.Kristensen

DTU Nanotech - Department og Micro and Nanotechnology

102 BF2P Dielectrophoresis Investigations of Human Chromosomes

By Casper Hyttel Clausen1 and

Sonia Buckley2, Maria Dimaki, and Winnie Svendsen1

1 Department of Micro- and Nanotechnology, Technical University of Denmark, Kgs. Lyngby, Denmark2 School of Physics, Trinity College Dublin, College Green, Dublin 2, Ireland In this work we present an investigation of the electrical properties of polyamine buffer prepared chromosomes, (condensed chromosomes, elliptical shaped). The electrical properties are measured using electrophoresis, dielectrophoresis, and electrical force microscopy. As chromosomes are on the order of a few ”µ”’s in size the techniques used for this investigation are scanning probe microscopy methods and electrical microfluidic systems. The investigation shows that despite the fact, that it is difficult to distinction between the different chromosomes, they show small variations in electrical properties which can be used for characterization and sorting. There seems to be a good agreement between theory and experimental results, when the data obtained from scanning probe microscopy are used in combination with the data from (di)electrophoresis. An estimation of the dialectical constant and conductivity of the chromosomes will be presented.

103 BF3P Respiratory motion of lung tumours in photon radiation therapy

By Ditte E Nygaard, and

Gitte F Persson, Lena Specht, Stine S Korreman.

Dept. of Radiation Oncology, Rigshospitalet, Copenhagen, Denmark Background and Purpose In radiation therapy, computed tomography (CT) scans are used for individualized treatment planning and radiation dose calculation. In radiation therapy of lung cancer it is of major concern that lung tumours undergo breathing related motion. Breathing related motion of lung tumours during conventional CT acquisition can cause artefacts impacting the imaged tumour configuration and position, and thereby lead to a risk of systematic error in the radiation treatment. Due to breathing related tumour motion, large radiation fields are often used as a standard to ensure tumour control. However, the motion pattern of a lung tumour can change during a treatment session, and the baseline of the motion pattern can furthermore change between treatment sessions. This can lead to random as well as systematic error in the radiation treatment. To improve the radiation treatment of lung cancer, the breathing related tumour motion must be considered and taken into account. Four-dimensional (4D) breathing correlated CT scans can be used to reduce breathing related artefacts. In a 4DCT scan the images are over-sampled and divided into a number of bins each related to a different phase of the breathing cycle, thereby creating images of the tumour configuration and position throughout the breathing cycle. By using the bin of a 4DCT scan best representing the time-weighted mean position of the tumour (the midventilation bin - MidV) for treatment planning, the systematic error during treatment can be reduced. In this study the breathing related tumour motion for five lung cancer patients are characterized. Furthermore, two different methods for identifying the MidV bin are evaluated. Methods 4DCT scans (ten bins) were acquired for five patients with low stage lung cancer. Before CT acquisition the patients had a fiducial marker implanted in the tumour to represent the tumour position accurately in x-ray images. The position of the marker was measured in each bin based on the centre of volume of the marker. The MidV bins were selected by two different methods based on (1) Displacement of the marker in all three directions and (2) Diaphragm motion in the cranio-caudal (CC) direction, respectively. The accuracy of both methods was defined as the distance between the marker in the selected MidV bin and the time-weighted mean position of the marker. Results The mean peak-to-peak displacement of the tumour (based on displacement of the marker) was 2.1 ± 1.1 mm (range: 0.5-3.2) in the left-right (LR) direction, 3.4 ± 1.8 mm (range: 1.2-5.9) in the anterior-posterior (AP) direction and 7.2 ± 9.6 mm (range: 0.4-24) in the CC direction. The tumour with the largest displacement in the CC direction was located in the lower part of the lung, where the other tumours were located in the upper part. The accuracy in selecting the MidV bin was 1.0±0.5mm for method (1) (mostly owing to hysteresis) and 1.5±0.9mm for method (2). Conclusion Tumor motion due to breathing was greatest in the CC direction. Furthermore, in the CC direction the tumour motion was significantly greater for the tumor located in the lower part of the lung compared to the tumours in the upper part. However, before decision of a motion management strategy in clinical practice, tumour motion for a higher number of patients must be evaluated, as well as the day-to-day variation in baseline for the tumour motion. The absolute difference between the accuracy of the two methods for selecting the MidV bin was small and the clinical consequences by choosing one over the other would be minor.

104 BF4P How to calibrate optical tweezers in viscoelastic media

By Kirstine Berg-Sørensen1 and

Mario Fischer1 Andrew C Richardson2 S. Nader S. Reihani3 Lene Oddershede2

1 Department of Physics, Technical University of Denmark, Kgs Lyngby, Denmark2 Niels Bohr Institute, University of Copen- hagen, Denmark3 Institute for Advanced Studies in Basic Science, Zanjan, Iran

105 BF5P Imaging liquid and biological processes with electron microscopes

By Kristian Mølhave and

Eric Jensen, Christian Fink Elkjær, Jakob Lyager Rasmussen, Torben Michael Hansen, Ashley Roberts, Peter Bøggild

DTU Nanotech, 345ø-154, Technical University of Denmark Liquid processes are fundamental in nature and industrial production. New capabilities for imaging these essential processes in electron microscopes with high spatial resolution are becoming available. Since electron microscopes require a vacuum for the electron beam, liquids have previously been studied mainly as cryogenically frozen samples or in environmental electron microscopes at reduce pressure and temperature. Recently developed systems [1, 2] now allow electron microscopes to be used to image liquids under ambient conditions enclosed behind thin electron transparent membranes. We are developing a microfluidic chip system with membrane windows that provides detailed scanning (SEM) and soon transmission electron microscope (TEM) images of processes in liquid samples under controlled environmental conditions. We are currently testing them on studies of electrochemical processes. The membrane chips systems also allows us to work with standard fixed and stained biological samples, such as adherent cells on the membrane. We can then perform 3D slice-and-view imaging with FIB-SEM. We use a focused ion beam to cut slices of material away and then image with an electron microscope to provide images with a resolution of about 10-20 nm in three dimensions when cutting sequential slices off the sample. 1. Thiberge, S., et al., PNAS, 2004. 101(10): p. 3346-3351. 2. Jonge, N.d., et al., PNAS, 2009. 106(7): p. 2159-2164.

106 BF6P Optical investigations of the mating-type region in ﬁssion yeast

By M.D. Jord¨o1, and

G. Thon2, L.B. Oddershede1

1 Niels Bohr Institute, University of Copenhagen2 Department of biology, University of Copenhagen

107 BF7P DNA traﬁcking: Colliding RNA polymerases

By Mette Eriksen1 and

Liselotte Jauﬀred1 Lene Oddershede1

The Niels Bohr Institute1

108 BF8P Controlled manipulation and immobilisation of peptide nanospheres

By Nikolaj Christiansen and

Jaime Castillo Winnie Svendsen

DTU-Nanotech, Department of Micro and Nanotechnology, Technical University of Denmark, Lyngby Denmark In this we are working with controlled manipulation and immobilisation of self-assembled peptide nanospheres (SAPNS). The SAPNS are manipulated using dielectrophoresis (DEP) by changing amplitude and frequency of the applied potential. For this purpose micro-patterned electrode is made using photo lithography and lift-oﬀ techniques on both silicon dioxide layers and Pyrex wafers. The immobilised SAPNS are evaluated using SEM and AFM. The conductivity of the immobilised SAPNS is found using I-V characterisation. Current measurements show that it is possible to immobilise the peptide nanospheres using DEP. A later part of the project involves manipulating the SAPNS using magnetic properties. For this to succeed it’s necessary to make the SAPNS magnetic. This is intended done in two ways, either by attaching magnetic beads or by adding a metal to the SAPNS. This work will show a way to integrate biological nanostructures into bio-nanoassemblies with concrete applications.

109 BF9P Eﬀect of Membrane Viscosity on Endothelial Cell Motility

By Ninna S. Rossen1 and

Christine Selhuber-Unkel1 Anker J. Hansen2 Lene B. Oddershedde1

1 The Niels Bohr Institute, University of Copenhagen, Denmark2 Novo Nordisk A/S, 2760 M˚aløv,Denmark

110 BF10P Fabrication of a microﬂuidic trap for single cell immobilization and studies.

By Peter Jensen Paluszewski1 and

Jacob Moresco Lange1 Pranjul Jaykumar Shah1 Winnie Svendsen1

1 DTU Nanotech - Department of Micro and Nanotechnology, Technical University of Denmark, DK-DK - 2800 Kongens Lyngby, Denmark Controlling and analyzing single cells in microfluidic systems (Lab-on-a-chip devices) is intensively studied as automation and low sample consumption are important issues to address for optimization of bio/medical analysis and diagnosis. Additionally some types of analysis are only applicable on single cells. Optical trapping or dielectrophoresis are methods often used in positioning of single cells, but a suitable design of a microfluidic system can achieve this using only the flow properties of the system. This minimizes external structures (e.g. electrodes or optics) for positioning of cells. A microfluidic structure designed to trap single cells was fabricated in polydimethylsiloxane (PDMS) using molds made by UV-lithography on SU-8 polymer. The structure and a milled polymethylmethacrylate (PMMA) lid with in- and outlets were assembled to a working device. The structure design uses a principle, where the main flow path passes through one of many narrow traps smaller in width than the cell size. Upon cell trapping, the flow is blocked and the main flow path switches to the next trap structure. Part of the flow will still pass around the cells, providing the possibility of supplying cell sustaining media or chemicals for cell analysis or lysis. The final device was tested for successful trapping with beads and cells, with the possibility of further cell analysis, either on living cells in the trap or after lysing.

111 BF11P Theoretical analysis of ultrasound resonances in lab-on-a-chip systems

By Rune Barnkob and

Henrik Bruus

Department of Micro- and Nanotechnology, Technical University of Denmark The use of ultrasound standing waves for particle manipulation and separation has received renewed interest and widespread use in the past decade since its application in the emerging field microfluidics. In many silicon-based separation devices the so-called acoustic radiation force is utilized by establishing transverse half-wavelength pressure modes in microchannels containing aqueous solutions of the particles to be separated. In the present theoretical work we study the acoustic resonances in such microchannels. We show that the localization of acoustic energy in the active channels can be optimized by choosing the width of the channel in the right proportion relative to the width of the surrounding silicon chip. This analysis provides a simple but important design tool, in particular for design of high throughput chips with many parallel channels. In addition we study how the position of the piezo-actuators on the chip influences the acoustic resonances in the microchannels. In particular, for each position of the actuator, we analyze the total acoustic energy in the system as a function of the driving frequency, the radiative energy loss to the surroundings, and the viscous energy dissipation in the liquid.

112 BF12P Memory eﬀects and systematic errors in the RL signal from ﬁber coupled Al2O3:C for medical dosimetry

By S.M.S. Damkjær Radiation Research Department, Risø National Laboratory for Sustainable Energy Technical University of Denmark - DTU We have developed an optical dosimetry system to perform real-time in vivo dose verification for radiotherapy. The detector of the system is a crystal of carbon-doped aluminum oxide (Al2O3:C) which is highly sensitive to ionizing radiation. The crystal offers two types of luminescence signals: A radioluminescence (RL) signal emitted during irradiation which is proportional to the dose rate and an optically stimulated luminescence (OSL) signal proportional to the total absorbed dose. To guide the light from and to the detector it is attached to a 10-15 m long fibre cable. The RL and OSL signals generally provide measurements with a reproducibility of about 0.5 to 2 % (one standard deviation). However, we have observed that the variability of such measurements is not always random: the result of one dose measurement is not completely independent of the previous irradiations and optical stimulations of the system. Essentially, this indicates that the system has a memory (probably related to deep traps) which cannot be reset completely during the OSL. The memory effect therefore is a potential source of systematic errors and to our knowledge this type of effect has not previously been reported for the RL signal of Al2O3:C. The present poster assesses the magnitude of this problem using data obtained in the laboratory using more than 1000 repeated measurements of two Al2O3:C crystals irradiated with 50 kV x-rays in the range from 0 to 4 Gy. The measurements were performed in cycles of irradiation and subsequent optical stimulation under a range of conditions including randomization of irradiation doses.

113 BF13P Physical Changes of Nucleic Acids Induced by Fullerenes: A Single Molecule Study

By Shahid Aftab Mir1 and

Fabian Czerwinski2 Lene B. Oddershede3

1 The Niels Bohr Institute, University of Copenhagen2 The Niels Bohr Institute, University of Copenhagen3 The Niels Bohr Institute, University of Copenhagen

114 BF14P Isolating of cancer markers using a microﬂuidic device

By Simon Levinsen1 and

Winnie Svendsen1 Maria Dimaki1 Jacob Moresco Lange1

1 DTU Nanotech, Technical University of Denmark In this work we present a method for isolating cancer markers in blood using a microfluidic device. Targeted markers are lumphocytes which surface proteins are altered due to the present of tumour cells in the body. For isolating the specific lumphocytes a microfluidic H-filter combined with dielectrophorecis (DEP) is used. The DEP force shifts the flow of the lumphocytes making it possible to collect these in a separate outlet. For optimizing the H-filter Comsol simulation are used in order to increase the DEP forces cells experience. To find operational frequencies for isolating targeted cells, experiments were preformed on specialized chips for determents of cross-over frequencies between positive and negative DEP forces. This work contributes to the fabrication of a total on chip analys system for cancer diagnosing.

115 Condensed matter physics

FF1 Spontaneously trapped magnetic ﬂux quanta in a quenched niobium ring

By A. V. Gordeeva1 and

M. R. K. Jensen1, M. Aaroe1, P.N. Dmitriev2 and J. Mygind1

1 Department of Physics, B309, Technical University of Denmark, DK-2800 Lyngby, Denmark 2 Kotelnikov’ Institute of Radio Engineering and Electronics, Russian Academy of Science, Mokhovaya 11, Building 7, 125009, Moscow, Russia The spontaneous trapping of flux in a niobium ring cooled though the normal-superconducting transition is investigated. The ring is carefully shielded from external magnetic fields and loosely coupled to a high-Tc SQUID used as a magnetometer. The statistical distribution of the number of fluxons trapped per cooling cycle is measured as a function of quench time (cooling rate). Results are compared to the Kibble-Zurek predictions of the formation of topological defects when a symmetry is spontaneously broken in a phase transition.

116 FF2 Generic property for alpha relaxation in 53 viscous liquids

By Albena I. Nielsen1 and

Tage Christensen1 Bo Jakobsen1 Kristine Niss1 Niels Boye Olsen1 Ranko Richert2 Jeppe C. Dyre1

1 DNRF centre “Glass and Time,” IMFUFA, Department of Sciences, Roskilde University, Postbox 260, DK-4000 Roskilde, Denmark2 Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85387-1604, USA The results from analysis of dielectric relaxation data for 53 organic glass-forming liquids (compiled from different groups and supplemented by new measurements) will be presented. The main quantity of interest is the “minimum slope” of the alpha dielectric loss plotted as a function of frequency in a log-log plot, i.e., the numerically largest slope above the loss peak frequency. The data consisting of 347 spectra for 53 liquids show prevalence of minimum slopes close to -1/2, corresponding to approximate squareroot(time) dependence of the dielectric relaxation function at short times. The paper studies possible correlations between minimum slopes and: Temperature (quantified via the loss-peak frequency); How well an inverse power law fits data above the loss peak; Degree of time-temperature superposition; Loss-peak half width; Deviation from non-Arrhenius behavior; Loss strength. For the first three points we find correlations that show a special status of liquids with minimum slopes close to -1/2. For the last three points only fairly insignificant correlations are found, with the exception of large-loss liquids that have minimum slopes that are numerically significantly larger than 1/2 and half loss peak widths that are significantly smaller than those of most other liquids. We conclude that – excluding large-loss liquids – approximate relaxation appears to be a generic property of the alpha relaxation of organic glass formers.

117 FF3 Fingerprints of random ﬂows

By B. Mehlig1 and

V. Bezuglyy2, M. Wilkinson2

1Department of Physics, University of Gothenburg, Sweden 2Department of Mathematics & Computing, The Open University, England Suspensions of small anisotropic particles, termed ”‘rheoscopic fluids”’, are used for flow visualisation. By illu- minating the fluid with light of three different colours, it is possible to determine Poincaréindices for vector fields formed by the longest axis of the particles. Because this vector field is non-oriented, half-integer Poincare indices are possible, and are observed experimentally. An exact solution for the direction vector appears to preclude the existence of topological singularities. However, we show that upon averaging over the random initial orientations of particles, singularities with half-integer Poincare index appear. We describe their normal forms. The talk is based on: M. Wilkinson, V. Bezuglyy, and B. Mehlig, arXiv:0809.3120

118 FF4 Sub-gap conductance through a spinfull quantum dot with superconducting leads

By Brian Møller Andersen1 and

Jens Paaske1 Karsten Flensberg1

1 Niels Bohr Institute, University of Copenhagen A number of recent experiments have measured the voltage driven current through a quantum dot with superconducting leads. By changing the gate voltage of the dot, several unusual properties of the sub-gap current have been revealed. For example, when the dot is occupied by an odd number of electrons, the cotunneling conductance exhibits regions of negative differential conductance as well as significant weight redistributions among the multiple Andreev scattering resonances. We have calculated the sub-gap cotunneling current within a general Hamiltonian approach, allowing us to treat the even occupied (spinless) dot exactly, and the odd occupied (spinfull) dot perturbatively. In the latter case, we present calculations of unusual sub-gap current and relate these finding to the experiments.

119 FF5 materials and magnetic refrigeration at room temperature.

By Britt Rosendahl Hansen Fuel Cells and Solid State Chemistry Division, Risø DTU The talk is intended as a general introduction to magnetic refrigeration at room temperature. When a magnetic field is applied to a material at a temperature that is close to a magnetic phase transition, the material may heat up or cool down depending on the nature of the transition. This effect, known as the magnetocaloric effect, may be used in a cooling cycle and could therefore be utilized for refrigeration. The obtainable advantages of a magnetic refrigeration setup when compared to the vapor compression systems in use today are higher efficiency and lower noise. In addition, a cooling system based on magnetic refrigeration would be more environmentally friendly. However, several problems need to be resolved if magnetic refrigeration is to be a viable alternative. One challenge is finding and optimizing the magnetocaloric material that constitutes the refrigerant. In the talk I will show how the magnetocaloric effect is a consequence of conservation of entropy as a magnetic field is applied or removed adiabatically. From a temperature versus entropy diagram of the cooling cycle we find two important material-dependent quantities: the magnetic entropy change, Delta SM , and the adiabatic temperature change, Delta Tad. I will talk about what these quantities mean for magnetic refrigeration, how they depend on the nature and order of the magnetic transition and how we determine them experimentally. Other relevant properties such as e.g. the heat capacity, cp, of the magnetocaloric material will also be touched upon.

120 FF6 Evolution of Dynamic Heterogeneity in Ageing Studied Via Micro-PCS

By Claudio Maggi1 and

Roberto Di Leonardo2 Giancarlo Ruocco2,3 Jeppe C. Dyre1

1 DNRF Centre ’Glass and Time’, IMFUFA, Dept. of Sciences, Roskilde University, DK-4000, Denmark.2 Research center ”‘Soft”’, INFM-CNR, c/o Dept. of Physics, ”‘Sapienza”’ University of Rome, Italy.3 Dept. of Physics, ”‘Sapienza”’ University of Rome, Piazzale Aldo Moro 5, I-00185, Rome, Italy. Non-equilibrium dynamics and dynamic heterogeneity are distinctive features of complex disordered systems. We develop a new technique (micro-PCS) that can measure directly the dynamic heterogeneity for colloidal suspensions of nano-particles. In our experiment we combine heterodyne and homodyne dynamic light scattering within micron-sized scattering volumes to reveal a growing dynamic heterogeneity in an aging solution of Laponite. The behavior of this dynamical correlation length is compared with exact prediction for critical coarsening. These results suggest a new possibility for the direct measurement of dynamic heterogeneities even in molecular liquids provided that the radiation is focused to nano-sized volumes.

121 FF7 Time-resolved THz waveguide spectroscopy

By David G. Cooke and

Peter Uhd Jepsen

DTU Fotonik, Technical University of Denmark Time-resolved THz spectroscopy is a powerful tool to investigate photoconductivity dynamics in a wide variety of materials with sub-picosecond resolution, all without applying contacts to the material. This technique uses coherently detected and broadband pulses of far-infrared light, known as THz pulses, as a probe pulse following photoexcitation of a material with a femtosecond optical pulse. In the usual geometry, the THz pulse probes the sample in free space by normal incidence transmission. We have devised a new technique for performing these measurements on materials embedded inside a parallel plate waveguide, termed time-resolved THz waveguide spectroscopy. The interaction of the THz radiation with the sample is then enhanced by travelling along the material over lengths of cm’s instead of through it where the length can be nm’s. We highlight the performance of this technique by examining photocarriers induced in Si and show a spin-oﬀ technique where we can use the photocarriers to control the propagation of the THz pulse within the waveguide.

122 FF8 Ultrafast carrier dynamics in InGaN/GaN multiple quantum wells

By H. P. Porte and

D. G. Cooke P. Uhd Jepsen D. Turchinovich

DTU Fotonik - Department of Photonics Engineering, Technical University of Denmark, Ørsteds Plads 343, DK 2800 Kongens Lyngby, Denmark Large strain-induced built-in piezoelectric fields in InGaN/GaN quantum wells lead to modifications of the electronic and optical properties, due to the quantum confined Stark effect. This piezoelectric field will lead to a decrease in the effective bandgap and a decrease in the absorption coefficient and recombination rate. The samples consist of 10 InGaN MQWs with thickness of 1.8, 2.7 and 3.6 nm, between 7.2 nm GaN barriers. We excite the carriers only into the InGaN quantum wells. Due to the built-in piezoelectric field, the electrons and holes are spatially separated, which leads to screening of the built-in piezoelectric field. We have performed time-integrated photoluminescence experiments to show the increase in the effective bandgap as the carriers screen the piezoelectric field. To study the effects on the recombination rate, we use time-resolved terahertz spectroscopy, where the terahertz beam acts as a probe for the induced conductivity. A nonexponential carrier density decay is observed, caused by the restoration of the built-in piezoelectric field, as the carriers recombine. Furthermore, we measured the THz conductivity by time-resolving the THz probe. The combination of a suppressed dc-conductivity with a negative imaginary part of the conductivity demonstrates a clearly nonmetallic behavior of the carriers. We attribute this to either carrier localization at the interface between the quantum wells and the barriers or the creation of excitons.

123 FF9 Quantum transport from classical molecular dynamics

By Jian-Sheng Wang Center for Computational Science and Engineering and Department of Physics, National University of Singapore, Singapore 117542 Traditional molecular dynamics, since it is based on classical mechanics produces only classical results. We show that it is possible to simulate quantum thermal and electronic transport using a form of molecular dynamics subject to Langevin heat baths with correlated noises. The noise spectra and the memory kernel are derived by analyzing the effect of the leads of junction system quantum-mechanically. It is shown that quantum ballistic transport can be reproduced for linear systems, and nonlinear effect can be understood as a quasi-classical approximation to the quantum problems. Results for 1D lattice chain model and graphene nano-ribbons heat transport will be reported. Refs. J.-S. Wang, Phys. Rev. Lett. 99, 160601 (2007); J. T. Lüand J.-S. Wang, J. Phys.: Condens. Matter, 21, 025503 (2009).

124 FF10 Powerful and Cost-Eﬀective Elliptical Neutron Guide Designs for the ESS

By Kaspar H Klenø1,2,5 and

Kim Lefmann1,2, Peter K Willendrup2, Peter B¨oni3, Emmanuel Farhi4

1Niels Bohr Institute, University of Copenhagen,2Risø, Technical University of Denmark,3Physik-Department E21, Technische UniversitätMünchen,4Institut Laue-Langevin5ESS-Scandinavia, University of Lund, Sweden We present advanced designs for long neutron guides, intended for use with the Long Pulse Target Station (LPTS) at the European Spallation Source. These designs have been optimized with computer simulations, using the McStas software package. Modern supermirror coatings can reach critical angles of reflection as high as 6 times the critical angle of Ni (m = 6). However, the high costs of such coatings impedes their use for long neutron guides. We show that careful design analysis can reap the benefit of high quality coating, while keeping the cost down. Put in quantitative terms, this means that we can achieve the same performance with a non-uniform distribution of supermirror coatings (1 ¡ m ¡6) as with a uniform distribution, at less than 1/10th of the costs. Alternatively, keeping the price fixed at the value for a uniform distribution of supermirror m = 2, it is possible to increase the neutron flux at the sample position by a factor of 3. Guide designs have been optimized by maximizing a cost function which takes both instrument price and neutron flux into account. The proposed guide designs have been benchmarked with more conventional guide configurations. Furthermore, we have explored methods suitable for use with advanced guide designs, that can block direct line of sight between the neutron source and the target position.

125 FF11 Structure and binding of Platonic-like molecular crystals.

By Kristian Berland and

Per Hyldgaard

Chalmers, MC2, Bionanosystems Van-der Waals density functional theory (vdW-DFT) includes the long range dispersion-forces in a fully ab-initio manner, and thus extends the range of DFT to sparse matter. The performance of the functional is evaluated for the crystal structure of the platonic-like molecules Hexamine, Cubane and Dodecahedrane. The results compares well with with experiments, but is dependent on the speciﬁc choice of GGA-exchange. The highly idealized structures enable straightforward comparison with the often-used asymptotic account of the van-der Waals forces. The nature of the binding is shown to diﬀer in the two cases, indicating that the asymptotic-account does not give the correct physical description neither at relevant binding separations nor at intermediate ranges.

126 FF12 Exponential Distributions of ﬂow event properties in viscous liquid dynamics

By Nicholas P. Bailey1, and

Thomas B. Schrøder1, Jeppe C. Dyre1,

1 Roskilde University We study the statistics of flow events in the inherent dynamics in supercooled two- and three-dimensional binary Lennard-Jones liquids. The inherent dynamics are defined by minimizing the potential energy of configurations in the real dynamics to find a local minimum, which is the associated inherent state; a flow event is a change of inherent state. Distributions of changes of the collective quantities energy, pressure and shear stress become exponential at low temperatures, as does that of the event “size” S, the sum of squares of the individual particle displacements. The S-distribution controls the others, in that the other distributions are Gaussian for fixed S; the exponential distribution of S then gives rise to the other exponential distributions. The distribution of S itself can be traced to exponential tails in the distributions of (1) single particle displacements d, involving a Lindemann-like length dL and (2) the number of active particles (i.e. those with d > dL). Results of barrier height calculations will also be presented. These also exhibit an exponential distribution.

127 FF13 Isomorphs in liquid state diagrams

By Nicoletta Gnan and

Thomas B. Schrøder and Jeppe Dyre

DNRF centre “Glass and Time,” IMFUFA, Department of Sciences, Roskilde University, Postbox 260, DK-4000 Roskilde, Denmark It was recently shown that van der Waals type liquids have a hidden approximate scale invariance that does provide important ”global” information about the system from knowledge of virial and potential energy second-order moments at one state point. It was very briefly argued that such systems (which include the standard Lennard-Jones liquids and ...) have curves in the state diagram along which the entire collection of equilibrium states and their probabilities to a very good approximation are “isomorphic.” The present work starts by postulating the existence of “isomorphs”, i.e. curves in which all the state points have equivalent configurations. We then deduce several isomorph properties that are compared to computer simulations of binary Lennard-Jones systems. The simulations confirm the existence of (approximate) isomorphs.

128 FF14 Field induced quantum phase transition in a high-temperature superconductor

By Niels Bech Christensen1,2 and

Johan Chang1 Christof Niedermayer1 Kim Lefmann3 H. M. Rønnow4 D. F. McMorrow5 A. Schneidewind6 P. Link6 A. Hiess7 M. Boehm7 R. Mottl1 S. Pailhes1 N. Momono8 M. Oda8 M. Ido8 J. Mesot1

1 Laboratory for Neutron Scattering, ETH Zurich and PSI Villigen, Schweiz2 Materials Research Department, Risø National Laboratory for Sustainable Energy, Denmark3 Nano-Science Center, Niels Bohr Institute, Denmark4 Laboratory for Quantum Magnetism, EPFL Lausanne, Schweiz5 London Centre for Nanotechnology and Department of Physics and Astronomy, Univer- sity College London, UK6 Forschungsneutronenquelle Heinz Meier-Leibnitz, TU Munchen, Germany7 Institut Laue-Langevin, Grenoble, France8 Department of Physics, Hokkaido University, Sapporo, Japan. We have used neutron scattering to study the magnetic ﬁeld-dependence of the gap to excitations in the high- temperature superconductor La1.855Sr0.145CuO4. As expected for a quantum phase transition, the gap closes continuously and vanishes at the ﬁeld required to induce long range magnetic order.

129 FF15 Yield stress fluids. To flow or not to flow, that is the question.

By Peder Møller1,2 and

Abdoulaye Fall3 M.A.J. Michels4 Steph´aneRodts5 Daniel Bonn2,3

1 The Niels Bohr Institute, University of Copenhagen2 Laboratoire de Physique Statistique, Ecole Normale Supérieure, Paris3 The van der Waals-Zeeman Institute, University of Amsterdam4 Group Polymer Physics, Eindhoven University of Technology5 Navier Institute, University of Eastern Paris Many materials do not flow unless the stress on them exceeds some critical value. This critical stress is called the ’yield stress’ and such materials ’yield stress fluids’. Examples include: mayonnaise, and foodstuffs in general, toothpastes, engine greases, crude oils, muds, soils etc. In spite of these examples being ubiquitous and important, yield stress fluids are ill understood. It is even hard just to measure the yield stress of a given material reproducibly! Here I’ll show how yield stress fluids can be understood qualitatively, and demonstrate how most (if not all) of the reported difficulties disappear when yield stress fluids are divided into two subgroups and appropriate measurement protocols used. Further I’ll show how a simple physical model quantitatively explains the flow behavior of a particularly ’difficult’ yield stress fluid, and explains the common but poorly understood phenomenon of shear banding, where a material flows freely in one part, and remains solid in another - in spite of all conditions being identical for both parts! Finally I will present the recent discovery of ’overaging’ in yield stress fluids. This closes a decade-old discussion on whether yield stress fluids flow VERY slowly below the yield stress or not at all.

130 FF16 Density functional theory of nonequilibrium tunneling

By Per Hyldgaard Institute of Microtechnology and Nanoscience, MC2 Chalmers University of Technology Goteborg SE-41296 Sweden Standard approaches for materials-speciﬁc characterizations of nonequilibrium tunneling combine ground-state density-functional theory (DFT) calculations of eﬀective (single-particle) scattering potentials with a Landauer-type formalism. The approaches generally ignore actual many-body scattering and they lack a formal variational basis. This work formulates an exact Lippmann-Schwinger collision DFT for steady-state tunneling transport with full electron- electron interaction. Dyson equations express the variational forms of the noninteracting and interacting many-body T matrices in terms of universal density functionals.

131 FF17 Crystallisation of a binary mixture

By Ulf R. Pedersen1 and

Thomas B. Schrøder1 Jeppe C. Dyre1 Peter Harrowell2

1 DNRF Center “Glass and Time”, IMFUFA, Dept. of Sciences, Systems and Model, Roskilde University, Denmark2 School of Chemistry, University of Sydney, Sydney, Australia

132 FF1P Magnetic ﬂuctuations in a critically doped cuprate superconductor

By A. Rømer1 and

K. Lefmann1,3 J. Chang2 L. M¨achler2 N. B. Christensen2,3 H.M. Rønnow4 J. Gavilano2 Ch. Niedermayer2 A. Schneidewind5 P. Link6 N. Momono7 Joel Mesot2

1 Nanoscience center, The Niels Bohr Institute, University of Copenhagen, Denmark2 Laboratory of Neutron Scattering , ETHZ and Paul Scherrer Institute, Villigen, Switzerland3 Materials Research Division, Risø DTU, Technical University of Denmark, Denmark4 Laboratory for Quantum Magnetism, EPFL, Lausanne, Switzerland5 Institut fürFestkörperphysik (IFP), Technis- che UniversitätDresden, D-01062 Dresden, Germany6 Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II), Technische UniversitätMünchen,85747 Garching, Germany7 Department of Physics, Hokkaido University, Sapporo 060-0810, Japan Coexistence of superconductivity and incommensurate (IC) magnetic order in high-temperature superconductors has been a subject of intense debate throughout the last two decades and it has become evident that the two phases are strongly related, but their precise interrelation remains an open question. In La1.88Sr0.12CuO4 (LSCO) static IC order exists within the superconducting phase and the magnetic order parameter falls off monotonically with temperature until it breaks down in the normal phase[1]. An applied magnetic field enhances the elastic scattering signal significantly [1,2]. In this work we have studied the field and temperature dependence of the magnetic IC fluctuations by inelastic neutron scattering. Fluctuations are observed for temperatures both below and above the superconducting transition temperature, Tc=27 K. This shows that IC fluctuations are present within the superconducting phase and persists even after the breakdown of superconductivity. The scattering signal peaks at a temperature exceeding Tc, but decreases rapidly above a certain threshold temperature. This threshold temperature increases with the fluctuation energy. At low temperatures we observe a suppressed signal strength for small energy transfers of about 0.5 meV . At temperatures significantly below Tc the signal strength increases markedly. We observe no effect on the inelastic signal or it’s temperature dependence when applying a magnetic field of 10 T. This is in sharp contrast with the pronounced field effect on the elastic scattering in this sample and the inelastic signal in other samples [1,2,3,4,5]. [1] R. Gilardi et al. SINQ report I/04 S-14 (2004) [2] J. Chang et al., Phys. Rev B 78, 104525 (2008) [3] J. Chang et al., Phys. Rev. Lett. 98, 077004 (2007) [4] B. Khaykovich et al., Phys. Rev. B 71, 220502(R) (2005) [5] J. Chang et al: arXiv:0902.1191

133 FF2P Acoustic resonances in helium liquid

By A. Salmela1 and

J. Tuoriniemi1

1 Helsinki University of Technology, Low Temperature Laboratory Helium has two isotopes, fermionic 3-He and bosonic 4-He, which are chemically the same, but at low temperatures their properties diverge dramatically, because of the different quantum statistics they obey. Helium has the lowest boiling point of all natural substances, 4.2 K for 4-He and 3.2 K for 3-He, and both isotopes remain liquid to absolute zero temperature at saturated vapor pressure. Both isotopes also turn into superfluids: at saturated vapor pressure the transition temperatures are 2.17 K for 4-He and 1 mK for 3-He. In addition to the usual first sound there exists second acoustic mode in superfluids. Second sound is not a pressure wave, but rather an entropy wave, where the normal and superfluid components move with opposite phases. At temperatures from 2 to 0.1 K the velocity of second sound in mixtures of isotopes ranges from below 10 to 40 m/s depending on pressure, concentration and temperature. For pure 4-He second sound velocity increases from zero to over 40 m/s before becoming meaningless at approximately 0.7 K temperature because of vanishingly small normal fluid fraction. For the first sound, which exists in liquid at all temperatures, the sound velocity varies from 180 to 240 m/s. We have probed these fluids using immersed quartz tuning fork resonators, which have the basic tuning fork shape with two tines, and the dimensions at millimeter range. They are excited and detected piezoelectrically and have the primary vibration mode at 32 kHz and a higher harmonic at about 200 kHz frequency. At certain conditions, when a dimension in the experimental volume matches the wavelength of an acoustic mode, the resonator couples strongly to the liquid by exciting a resonant standing wave, and a sharp dissipation maximum is observed. Most measurements of second sound were performed at the temperature range from 2.17 to 1.5 K at 32 kHz frequency. We observe several such resonances in pure superfluid 4-He as well as in mixtures with varied concentrations. We also observed first sound resonances at 200 kHz frequency in the liquid phase at temperature range from 4.2 K to 1.5 K. One possible application of these distinct features is an accurate temperature reference. This was demonstrated by an experiment where helium mixture was cooled from 2 to 0.1 K. In this temperature range a multitude of acoustic resonances are seen.

134 FF3P Green’s functions and Lanczos’ method for large scale electronic structure calculations

By Elisa Londero Department of Applied Physics Chalmers University of Technology Goteborg SE-41296 Sweden Large scale electronic structure calculations within Density Functional Theory are rapidly approaching the point where the N3 scaling becomes the time-limiting factor, leaving systems with thousands of atoms out of reach for conventional schemes. The method described here is based on the computation of selected elements of the real space Green’s function and on the recursive method. Neither the density nor the energy are calculated through the Kohn-Sham orbitals and this makes the computational workload required scale linearly with the volume of the system. Some of the problems which still hinder the achievement of this goal are discussed and in particular a solution based on the interpolation of the recursive coeﬃcients is presented. Some tests on simple systems like a harmonic oscillator and a double well potential are shown.

135 FF4P Critical scattering in CoO Nanoparticles

By Elisabeth Therese Ulrikkeholm and

Jonas O. Birk1 Niels Bech Christensen2,3 Thierry Straessle3 Sebastian Busch4 Tobias Unruh4 Cathrine Frandsen5 Jari i Hjøllum3 Kim Lefmann1

1 Nano Science Center, Niels Bohr Institute2 Laboratory of neutron scattering, Paul Scherrer Institute3 Risoe National Labora- tory for Sustainable Energy, Risoe DTU4 FRM II, Technischen UniversitätMünchen5 DTU Fysik CoO is an antiferromagnetic material, that has a classical type 1 structure. Earlier investigations have showed that the particles can be well described by a 3-D Ising model [1]. Recent investigations of CoO nanoparticles down to 10 nm size show the same type of order as in bulk. Studies of the magnetic correlation length show interesting nano size- effects.[2] We have seen that the correlation length converges against an upper limit around the critical temperature, Tn=289 K. This cut-off corresponds to a correlation length much smaller than the particle size, a surprising result. We have used time of flight spectroscopy to study and compare the quasielastic response of bulk particles to that of 30 nm and 20 nm nanoparticles. The measurements on the 20 nm particles have been made at FOCUS at PSI and the measurements on the 30 nm particles and the bulk particles have been made on TOFTOF, FRM-II. We can clearly see the critical scattering between 225K and 380K. The signal is quasielastic, and has a width in q of 0.2 A˚−1 which is too broad to correspond to the particle size. The width in energy of the quasielastic signal is of the order of 2-3 meV, for both bulk particles and nanoparticles. Recent measurements on magnetic excitations in bulk CoO, have shown Ising like spin waves between 20 and 35 meV [3], so our quasielastic signal are not of the spin wave type. We can conclude, that our signal is paramagnetic scattering. We will present analysis of the nanosize contributoin to the paramagnetic scattering. [1] M. D. Rechtin and B. L. Averbach, Physical Review, Vol. 26 number 24 [2] J. O. Birk et al, Kritiske faseovergange i CoO nanopartikler studeret med neutronspredning [3] K. Tomiyasu and S. Itoh, Journal of Physical Society of Japan vol.75, 084708, (2006)

136 FF5P Origin of Remanent Magnetization in Hemo-Ilmenite Investigated With Polarized Neutron Scattering.

By Erik Brok1 and

Kim Lefmann1, Luise Theil Kuhn2, Suzanne McEnroe3, Peter Robinson3, Bertrand Roessli4, Richard J. Harrison5

1 Nano Science Center, Niels Bohr Institute, København Ø, Denmark.2 Risø National Laboratory for Sustainable Energy, Technical University of Denmark, Roskilde, Denmark.3 Geological Survey of Norway, Trondheim, Norway.4 Paul Scherrer Institut, Villigen, Switzerland.5 Department of Earth Sciences, University of Cambridge, Cambridge, United Kingdom.

Remanent magnetism in rocks containing hematite (Fe2O3) - ilmenite (FeTiO3) lamellae has been identified as an important contribution to magnetic anomalies on the Earth. These exsolved rhombohedral oxides of ilmenite with hematite lamellae, ”hemo-ilmenite”, have a high natural remanent magnetization (NRM) that cannot be explained solely due to a spin canted moment in the hematite lamellae. At room temperature hematite is canted- antiferromagnetic and ilmenite is paramagnetic. To explain the high NRM it has been proposed 1 that the remanent magnetization stems from uncompensated spins in the contact layers between hematite lamellae and the ilmenite host giving a net ferrimagnetic contribution to the magnetization. Large exchange bias (> 1T ) in similar samples has been measured at low temperature and is interpreted as a verification of that the remanent magnetization stems from contact layers between lamellae {2}{3}{4}. Here we use spin polarized neutron scattering to determine spin directions in the crystal and the response of the magnetic moments to applied magnetic fields of 0.05 -2 T. This method, together with polarized small angle neutron scattering, enable us to determine whether the magnetism originates from the contact layers between lamellae. The polarized neutron scattering experiment was performed on the TASP instrument at the Paul Scherrer Institute in Switzerland and from the data we obtain the spin directions in the crystal. We find that the magnetization of the sample perpendicular to the applied field increases with the field. The data indicates two possible populations of lamellae with moments pointing at an angle of 30◦ and 60◦ to the applied field respectively (0◦ would indicate a purely lamellar moment, 90◦ a purely canted moment). The results show that the remanent magnetization has components both perpendicular and parallel to the sublattice magnetization with components in the two directions of roughly the same size. This could be explained by a vector sum of a lamellar moment and a canted moment. However this experiment cannot completely rule out that the NRM originates purely from canted hematite moments with a unknown spin anisotropy, keeping the spins from aligning with the field. The data shows that the NRM does not come from a purely lamellar moment, nor a pure canted moment. In the presentation we will elaborate on alternative explanations for the NRM.

137 FF6P Ultrafast carrier capture in quantum dots

By J. K. Jensen and

D. G. Cooke P. U. Jepsen

DTU Fotonik We try to determine the carrier capture and escape time in InAs/GaAs quantum dots by using time-resolved terahertz spectroscopy. The samples are pumped with either 800 nm light, exciting carriers into the GaAs barriers, detecting the capture time or by 1030 nm light, exciting carriers into the QDs, to detect the escape time. Other effects also occur e.g. bulk recombination or surface recombination. Multi-exponential fits to the decay curves of the differential THz-transmission are used to determine the different carrier dynamics in the sample.

138 FF7P Approaching the quantum phase transition of CoCl2.2D2O

By Jacob Larsen1 and

Sonja Rosenlund Hansen1 Kim Lefmann1 Sara H. Eisenhardt1 Niels B. Christensen1,3,5 Henrik M. Rønnow2 Klaus Habicht4

1Nano Science Center Niels Bohr Institute (NBI), Denmark.2Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzer- land, 3Laboratory for Neutron Scattering, ETHZ & PSI, Switzerland.4The Helmholtz Centre Berlin for Materials and Energy, Germany5Risø-DTU, Denmark An increasing interest in quantum criticality calls for experimental investigations of quantum phase transitions (QPT’s). The one-dimensional Ising model in a transverse magnetic field is the simplest example of such a phenomenon. A QPT occurs at effectively zero temperature when the thermal fluctuations are negligible compared to the quantum fluctuations, which may be tuned by some non-thermal parameter, like in this case applied magnetic field. Theoretically, QPT’s offer the challenging and exciting possiblility of studying the classical-quantum mapping when calculating the behavior of the energy spectrum with respect to the applied magnetic field. We here present an experimental study of the energy spectrum of the quasi one-dimensional Ising ferromagnet CoCl2.2D2O in an applied magnetic field, and a comparison to theoretical results. The monoclinic crystal CoCl2.2D2O is well known as a quasi one-dimensional Ising system and a promising candidate of quantum criticality. When a magnetic field is applied along the easy axis the system undergoes a second order QPT at a measured critical field Hc = 16.2 T, from antiferromagnetic ordering of ferromagnetic spin chains to a paramagnetic state. We hope to determine how well CoCl2.2D2O fits the pure Ising picture by measuring the HT phase diagram. We have utilized both elastic and inelastic neutron scattering, in applied fields up to 15T, to search for evidence of a antiferromagnetic QPT in CoCl2.2D2O. Elastic scattering reveals how the magnetization behave near the critical point, hence how the spin ordering disappears in high field, wheares inelastic scattering measures the field-dependence of the Ising-like gap in the excitation spectrum of the applied magnetic field. We have obtained precursory evidence of the QPT through a decreasing energy gap and an abrupt change in antiferromagnetic magnetization, without yet reaching the critical field.

139 FF8P Modeling ﬂux pinning in thin undoped and BaZrO3-doped YBCO ﬁlms

By P. Paturi1 and

M. Irjala1,2 H. Huhtinen1 A. B. Abrahamsen3

1 Wihuri Physical Laboratory, Department of Physics and Astronomy, University of Turku, Finland2 Graduate School of Ma- terials Research, Turku, Finland3 Materials Research Division, Risø National Laboratory for sustainable energy, Technical University of Denmark, Roskilde, Denmark

140 FF9P Virtual vs. real world experiments - validation of McStas components

By Peter Willendrup1 and

Linda Udby1,3 Emmanuel Farhi2 Erik Knudsen1 Kim Lefmann3

1 RISØ DTU, Frederiksborgvej 399, DK-4000 Roskilde2 Institut Laue-Langevin (ILL), 6 rue J. Horowitz, BP 156, 38042 Grenoble Cedex 9,France3 Niels Bohr Institute (NBI), Universitetsparken 5, DK-2100 Copenhagen, Denmark In neutron scattering, McStas is becoming an important tool for optimising instrumentation, performing virtual experiments, and data analysis purposes. To allow relevant comparison of virtual and real world experimental data, all included component models must undergo testing and validation to ensure the best possible agreement. This poster presents two recent comparative studies of experiments and virtual experiments, used for validation of McStas components.

141 FF10P Excited by X-rays - modern spectroscopy of the electronic structure

By S. Galambosi1, and

J.A. Soininen1, A. Sakko1, T. Pylkkänen2, S. Huotari2, M. Knaapila3, K. Hämäläinen1

1 Department of Physics, University of Helsinki, Finland2 European Synchrotron Radiation Facility, Grenoble, France3 Depart- ment of Physics, Institute for Energy Technology, Norway With the advent of modern synchrotron radiation sources inelastic X-ray scattering (IXS) has emerged as a poweful method for probing the electronic structure of matter. IXS is partially complementary to other well established techniques such as optical spectroscopy, X-ray absorption or electron energy loss spectroscopy. However, the combination of hard X-rays together with a scattering geometry opens up unique ways to probe the electronic structure. The electronic excitation spectra can be accessed over a large energy regime. Both valence excitations at a few electronvolts as well as core electron excitations having energy thresholds of several hundred eVs can readily be studied. During the scattering process, the X-ray photon transfers also some momentum to the electron system. By controlling the amount of momentum transferred one can select the weight of dipole allowed versus higher order transitions in the measured spectrum. Additionally, in crystalline materials one can study speciﬁc features of the band structure, such as an indirect band gap, simply by choosing appropriate energy and momentum transfers in the experiment. In this work we present results from recent IXS based studies on electronic excitations. We show that this versatile technique can be applied to a wide range of materials from liquids to polymers and hard condensed matter. Moreover, we demonstrate how this method gives access to unique information on the electronic structure.

142 FF11P Quantum Phase Transition in LiHoF4 Measured by Torque Magnetometer

By Sara H. Eisenhardt 1 and

Kim Lefmann 1, Finn Berg Rasmussen 1, Kristian Mølhave 3, Jonas Hauptmann 1, Henrik Rønnow 2

1 Nano-Science Center, Niels Bohr Institute (NBI), University of Copenhagen, Denmark 2 Laboratory for Quantum Mag- netism, Ecole Polytechnique F´ed´erale de Lausanne (EPFL), Switzerland 3 Department of Micro and Nanotechnology, Technical University of Denmark, (DTU), Denmark

The dipolar coupled Ho ions in LiHoF4 is a close-to-ideal realization of the simple Ising spin model. Therefore this system undergoes a quantum phase transition (QPT) in a transverse magnetic field. QPT takes place when thermal fluctuations are negligible compared to quantum fluctations, i.e. temperatures close to 0 K. Litterature reports extensive AC-susceptibility and neutron scattering results, showing that full criticallity is complicated by hyperfine interactions. However to date no direct magnetization measurements have been performed. We present measurements of the LiHoF4 QPT using a torque magnetometer. Measurements were performed in a dilution refrigerator using a 7 T magnet. This enabled us to make field and temperature dependent measurements, thus mapping the QPT as a function of temperature and transverse field. It has been observed that the nuclear spins prohibit a perfect QPT in LiHoF4.

143 FF12P Thin-ﬁlm detector of x-ray helicity

By Sigrid Sandberg and

Pieter Kuiper

VäxjöUniversity, Växjö,Sweden We have calculated the intensity difference between left- and right-polarized soft x-rays, when reflected from a magnetically ordered Fe/Co multilayer. The aim with this study was to find out if it is possible to investigate magnetic domains by measuring the circular dichroism from the reflected x-rays. The study was made with a software program, developed by Alessandro Mirone, which builds a model of a multilayer stack according to some input parameters and ranges. We particularly looked at energies around the Fe L2,3 edge, and varied the numbers of layers and the layer thicknesses. The results show a notable difference between the intensity of the reflected left- and right-polarized x-rays, depending on the number of stack repetitions and layer thicknesses. The figure of merit indicates that circular dichroism would be a possible method for examining magnetic domains.

144 FF13P Systems-level analysis in microﬂuidics

By Søren Vedel1 and

Laurits Højgaard Olesen2, Henrik Bruus1

1 Department of Micro- and Nanotechnology, Technical University of Denmark2 Device Research and Technology, Novo Nordisk A/S Lumped-parameter modeling of microfluidic systems is a simple yet effective tool. The method is based on the lin- earity of the governing Stokes equation, and for steady state systems it has repeatedly been validated by experiments. Perfunctory use of transient extensions to the steady-state approach is in widespread use within the field, although no experimental proof has been presented. Using pulsatile (harmonically oscillating) pressure and flowrate, we extend the validity of this lumped-parameter approach for systems-level analysis to also include dynamic, transient effects such as inertia and compliance. A pressure source has been developed for the experimental generation of the pulsatile conditions, which operates in the range 0.03-800 Hz, while still delivering characteristic volumes of order microliter. By use of this pressure source, the motion of an air-bubble trapped in a water-filled tube has been studied, and good agreement was found between the results of a systems-level lumped-parameter model and the recorded bubble motion.

145 Nanophysics and nanomaterials

NA1 Bulk isotropic negative-index metamaterial for infrared

By A. Andryieuski1 and

R. Malureanu1 A.V. Lavrinenko1

DTU Fotonik, Technical University of Denmark, Denmark Negative-index metamaterials (NIMs) are artificially structured materials exhibiting both negative electric permittivity and magnetic permeability over some frequency range. They propose great opportunities to control the light and to create such devices as invisibility cloaks, superresolution lenses, nanocouplers etc. Nowadays there is a lack of the isotropic negative-index material designs for infrared and optical wavelength. We present the nested structures approach to design isotropic NIM in which the negative permeability part is embedded into the negative permittivity part. We also present a design of NIM working at telecommunication wavelengths and showing n = -1 and figure of merit higher than 2. The effective properties are obtained from numerical simulations for 1-5 layers of metamaterial and show fine convergence with the number of layers. We describe the physical behaviour of NIM and its constituent parts and prove its isotropy. The time-domain simulations of the wave propagation through 20 NIM layers prove its negative refractive index behaviour. The designed structure is a promising building block for construction of an isotropic negative-index material. The proposed nested strucutres approach is useful for designing isotropic metamaterials.

146 NA2 Thermal Insensitivity of Silicon-based Optoﬂuidic Photonic Crystal Cavities

By Cameron L. C. Smith and

Christian Karnutsch2 Alexandra Graham2 Tom Lee2 Snjezana Tomljenovic-Hanic2 Ross McPhedran2 Benjamin J. Eggleton2 Liam O’Faolain3 Thomas F. Krauss3 Sanshui Xiao4 N. Asger Mortensen4

1 Department of nano- and microtechnology, Technical University of Denmark2 Centre for Ultrahigh-bandwidth Devices for Optical Systems (CUDOS), University of Sydney3 School of Physics and Astronomy, University of St. Andrews4 Department of Photonics Engineering, Technical University of Denmark Optofluidics is a burgeoning field of research interest, combining the favourable properties of microfluidics with nanophotonics for increased functionality [1]. Photonic crystals (PhCs), which are periodic (nano)structures that may control the propagation of light, have enjoyed integration with microfluidic elements that utilise liquid flow to alter their optical properties [2, 3]. In particular, PhC cavities may have their properties altered [4, 5] in a reconfigurable scheme by the repeatable addition or removal of liquid [6]. PhC cavities have much to offer optofluidic approaches due to the potential high liquid-light interaction and their wavelength-scale dimensions, allowing for compact and high-resolution sensor devices [7]. In this paper we present a study on the temperature-dependence of optofluidic PhC cavities. We analytically determine the conditions to realise a temperature-insensitive optofluidic PhC cavity, which may be achieved by introducing a liquid of opposite-signed thermo-optic coefficient to the host PhC material. We experimentally investigate the optical characteristics of such a device as a function of temperature, using a planar silicon-based PhC (∂n/∂T = +2.0 × 10−4K−1) infiltrated with an immersion oil (∂n/∂T = −3.1 × 10−4K−1). We show a resonance that remains stable at 1404.9 ± 0.2 nm in the temperature range of 25◦C to 65◦C. Applications range from high-accuracy sensor systems for chemical and biomedical applications, to micro-lasers, optical filters and switches. [1] C. Monat, Nature Photonics 1, (2007). [2] P. S. Nunes, Optics Letters 33, (2008). [3] D. Erickson, Optics Letters 31, (2006). [4] S. Tomljenovic-Hanic, Optics Express 14 (25), (2006). [5] C. L. C. Smith, Applied Physics Letters, 91, (2007). [6] C. L. C. Smith, Optics Express 16 (20), (2008). [7] U. Bog, Optics Letters 33 (19), (2008).

147 NA3 In-situ growth of two-terminal silicon nanowires from locally heated cantilevers in TEM

By Christian Kallesøe1 and

Kristian Mølhave1 Cheng-Yen Wen2 Frances Ross2 Peter Bøggild1

1 DTU Nanotech, Department of Micro- and Nanotechnology, Technical University of Denmark2 IBM, T. J. Watson Research Center, Yorktown Heights Resistively heated crystalline silicon cantilevers extending over the edge of a chip offer excellent control of local growth of nanowires, without heating the entire micro-system. Besides being CMOS compatible, the cantilevers also have a rapid temperature cycling, and furthermore the freestanding cantilevers are suitable for in-situ studies of nanowire growth inside a TEM, offering the possibility of applying electrical fields to direct the growth and growing bridging wires between cantilevers thereby making two-terminal in-situ electrical measurements of nanowires possible. We have used such cantilever loops to study the growth of nanowires in-situ in UHVTEM. Epitaxial growth was observed from the crystalline cantilevers and the rapid temperature cycling ensured a very fast reaction time when crystallizing or melting the catalytic particle. The silicon wires were grown towards a cold cantilever loop, thereby forming bridging nanowires and the nanowire contact was seen to depend on the the gold eutectic particle which crystallizes when hitting the cold cantilever. Furthermore various two-terminal measurements were performed on the bridging silicon nanowires in-situ in UHV.

148 NA4 Xsense Explosive Detection

By F. Bosco1 and

M.S. Schmidt1 G. Blagoi1 J.K. Olsen1 A. Boisen1

1 Department of Micro- and Nano Technology, Technical University of Denmark This project is a four year program supported financially by NABIT enabling hiring of 5 Ph.D. students and 2 post docs. The goal is to realize a portable reliable sensing device, to detect explosive vapors in air with a ppb sensitivity. The sensing device should comprise four different sensing principles. Having independent sensors will improve both sensitivity and selectivity. The different methods of sensing are cantilever based, calorimetric, colorimetric and surface enhanced Raman spectroscopy sensing. The four individual sensors will be integrated in a portable device, where the results from each sensor are analyzed and combined using signal processing for reliable results. The activities are coordinated by an advisory board comprising military and other institution that could benefit from the developed technologies. Industry partners are also a part of the project, to help mature the technologies for real life use.

149 NA5 Quantifying and pinpointing sources of noise in nanoscale experiments

By Fabian Czerwinski and

Andrew C. Richardson Lene B. Oddershede

Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, 2100 Copenhagen, Denmark Nanoscale experiments enable real-time observations of biophysical systems. They have developed to key experiments towards an understanding of mechanics and dynamics at the single-molecule level. For example, optical trapping techniques have evolved to the point where quantitative force measurements on biological systems can be performed down into the femtonewton range. Biological and solid-state nanopores can be used to detect conformational states of individual DNA molecules. As, on the one hand new generations of setups constantly improve the obtained resolution, on the other hand, the pinpointing and elimination of noise sources become increasingly important. Allan-variance analysis is ideally suited to this task. Therefore, adjacent time series are recorded and the variations between observation intervals are calculated. Here, we provide a comprehensive toolbox consisting of: a reliable data-streaming acquisition software that allows for storing long adjacent time series (∼30min), even with high sampling frequencies (> 100 kHz); an analysis software (Matlab- based) with calculation times of only a few seconds; and fitting scripts to extract parameters of noise and drift sources. Furthermore, the validity and robustness of Allan-variance analysis is demonstrated in data obtained from our optical-tweezers setup. Therein laboratory-specific noise sources had been detected and eliminated. We show how our toolbox can be applied to position-time traces of optically trapped spheres. For any setup, this enables a determination of: the optimal calibration interval, suitable settings for update rates in force-feedback loops, and variations due to the geometrical constraints of the sample chamber. In addition, we perform the same kind of analysis to measurements of the ionic current through solid-state nanopores with a diameter down to 3nm. Acquisition parameters were optimized. Individual steps for the production of nanopores could be reviewed critically. Allan-variance analysis might evolve as a standard tool enabling reliable comparison of various nanoscale setups. In fact, the precise quantification of noise and drift sources strengthens the reliability of currently used methods. In particular, this is very relevant in high precision experiments with individual biomolecules.

150 NA6 Dynamic Study of a Sliding Interface Wear Process of TiAlN and CrN Multi-Layers by X-ray Absorption

By Inge L Rasmussen1 and

M. Guibert2, J.-M. Martin2, M. Belin2, N. J. Mikkelsen3, H. C. Pedersen1, R. Feidenhans’l4 and J. Schou1

1 Department of Photonics Engineering, Risø Campus, Technical University of Denmark, DK - 4000 Roskilde, Denmark 2 Laboratoire de Tribologie et Dynamique des Systèmes,CNRS UMR 5512, Ecole Centrale de Lyon, F - 69134 Ecully, France 3 CemeCon A/S, DK - 8230 Abyhøj,˚ Denmark 4 Niels Bohr Institute, University of Copenhagen, DK- 2100 Kbh Ø, Denmark Wear of surfaces is a complicated sequence of dynamic processes, which occurs not only on the coating surface, but also throughout the coated layer and at the interfaces. The induced degradation may lead to structural changes in crystallinity, to amorphization and also to possible tribochemical reactions at the interface. The basic physical and chemical processes on the nano-scale are, however, not yet known fully. Thus, the work presented here is a contribution to the knowledge of the area. The main objectives of this dynamical investigation are to show that real time and in-situ tribology studies of hard coatings by SR are possible and that the tribological wear of a multi-layer system can be monitored with an embedded CrN marker layer. This was achieved by keeping the SR energy on the chromium K-edge energy (close to 6 keV), while a drop in absorption was monitored. The absorption drop indicates the marker layer is worn off and thus the wear process finished. The measurements of the wear during the sliding interface wear experiments were performed in-situ, with a special portable tribo-meter designed and build at Laboratory of Tribologi and System Dynamics, Ecole Centrale de Lyon in France. The contact under investigation (TiAlN/CrN/TiAlN (2000nm/1000nm/2000nm) multi-layer system) was exposed to a reciprocating sliding motion under a normal load. Simultaneously, the contact zone was submitted to a direct, focused and monochromatic SR photon beam. In this way we have studied the effects of tribological wear process of TiAlN and CrN on vitreous carbon.

151 NA7 Structure of thin-ﬁlm oxides from ab initio thermodynamics: ultra-thin alumina ﬁlms on titanium carbide

By J. Rohrer1 and

C. Ruberto1,2 P. Hyldgaard1

1 Department of Microtechnology and Nanoscience - MC2, BioNano Systems Laboratory, Chalmers University of Technology, SE-412 96 Göteborg.2 Department of Applied Physics, Materials and Surface Theory Group, Chalmers University of Technology, SE-412 96 Göteborg. We present a strategy to efficiently search for atomic structures of thin-film oxides with first-principle density functional theory (DFT) calculations embedded into a general thermodynamics framework (ab initio thermodynamics). Ultra-thin alumina on TiC(111) serves as a model system to illustrate the structure-search strategy. At the heart of the search method is the complexity of stable and metastable oxide atomic structures (here: α- and κ-Al2O3). These bulk structures possess a number of different structural elements or motifs (e.g. different coordinations of Al ions and different stacking of O planes) that can be used to generate a network of initial films. Subjecting these films to relaxations calculated and implemented in DFT produce a set of thin-film candidate structures that we can order both by DFT and by ab initio thermodynamics. Our analysis of the most favored thin- film candidates shows that a range of new structural motifs (different from those of most common metastable alumina) characterize the nucleation of ultra-thin films. We find that the stoichiometric composition, and thus the structure, critically depends on environmental conditions during film growth. Typical CVD (chemical vapor deposition) growth conditions ensures nucleation of strongly binding structures.

152 NA8 Coarse-grained simulations of polyphilic molecules

By Jacob Judas Kain Kirkensgaard1 and

Lilliana de Campo2 Kell Mortensen1 Stephen Hyde2

1 Dept. of Basic Sciences and Environment, Faculty of Life Sciences, Copenhagen University2 Dept. of Applied Mathematics, Research School of Physical Sciences, Australian National University Coarse-grained simulations of polyphilic molecules We are exploring a novel class of three-arm molecules, ABC star-architecture ’polyphiles’ both experimentally and theoretically. Polyphiles are intermediate molecular-weight oligomers containing hydrophilic, oleophilic and fluorophilic moieties attached to a common junction. These molecules resemble amphiphiles, in that they can self-assemble in solution, with an additional fluorocarbon moiety that is designed to be essentially immiscible with the other two moieties. Here we present results from coarse-grained bead simulations of such molecules. A number of topologically complex liquid crystalline mesostructures arise that can be related to the better-known bicontinuous mesophases of lyotropic amphiphilic systems. The simulations reveal 3D self-assemblies whose structural variations follow those expected assuming a simple steric molecular packing model as a function of star polyphile splay and relative volumes of each arm in the polyphile. The splay of each arm, characterised by the 3D wedge-shape emanating from the core of each molecule to its exterior induces torsion of the interfaces along the triple lines, whereas differences in the relative volumes of arms induces curvature of the triple lines. Several distinct mesostructures are described, characterised by their micro-domain topologies, which are unknown in simpler amphiphilic systems, but resemble in some respects bicontinuous mesophases. These three- (or more) arm polyphilic systems offer an interesting extension to the better- known self-assembly of (two-arm) amphiphiles in solution.

153 NA9 Waveguiding properties of metallic strips and nanowires

By K. Leosson1, and

M.C. Gather1, T. Rosenzveig1, P.G. Hermannsson1, A. Boltasseva2

1 Dept. of Physics, Science Institute, University of Iceland2 DTU Fotonik, Technical University of Denmark Interest in the optics of metal-dielectric structures has been growing rapidly over the past years in the hope that the unique properties of surface plasmon polaritons confined to the metal-dielectric interface can be further utilized in sensing, surface-enhanced fluorescence and Raman scattering, sub-wavelength optics and compact photonic devices. In the talk, we will review recent progress in the fabrication of metallic waveguides for visible and near-infrared wavelengths, consisting of strips or nanowires embedded in a dielectric matrix. Such structures support coupled surface- plasmon modes that exhibit weaker confinement but propagate over considerably longer distances than surface plasmon polaritons on a single interface. In particular, we will address insertion losses and polarization dependence of long- range supermodes and their interaction with dye-doped or fluorescent cladding materials. We will also demonstrate how plasmonic nanowire waveguides have been used to construct a simple and compact thermo-optic variable optical attenuator with a high extinction ratio, operating at telecom wavelengths.

154 NA10 Optical manipulation of individual gold and silver nanoparticles and quantum dots

By Lene Oddershede1 and

Liselotte Jauﬀred1 Christine Selhuber-Unkel1 Poul M. Bendix1

1 Niels Bohr Institute Through improvements, e.g. canceling spherical aberrations [1], we significantly increased the performance of a single beam optical trap thus allowing trapping of individual nanoparticles in three dimensions by a single laser trap using very low laser powers. Using a 1064 nm laser gold nano-spheres with diameters 18 to 250 nm [2] as well as gold nano-rods with thicknesses down to 8 nm and aspect ratios between 1.7 and 5.6 [3] were individually optically trapped in three dimensions, and optical forces of tenths of pico-Newton easily applied. The gold nano-rods aligned with the electrical field, this property making the rods excellent as nano-rotators in single molecule experiments. In contrast to gold nanoparticles, which are known to quench fluorescence, silver nanoparticles enhance fluorescence, and silver spheres with diameters down to 18 nm were also easily individually optically manipulated [4]. Hence, silver nanoparticles are obvious choices as handles for experiments where a clear fluorescent signal is desirable. Even individual quantum dots have been proven individually trapped [5]. Their narrow emission bands combined with a very low degree of photo-bleaching make quantum dots superior as markers or donors in the study of, e.g., single molecule systems. Also, the trapping spring constant carries information about the interaction between the electrical field and the quantum dot, thus allowing a calculation of physical characteristics of the quantum dot such as the polarizability of an individual colloidal quantum dot. A further advantage is that two photon absorption is very efficient, hence, only a single laser is needed in a setup which allows both for visualization, manipulation, and force measurements. [1] Reihani & Oddershede, Optics Letters vol.32, p.1998, 2007 [2] Hansen, Bhatia, Harrit & Oddershede, Nano Letters vol. 5 p.1937, 2005 [3] Selhuber-Unkel, Zins, Sönnichsen & Oddershede, Nano Letters vol. 8 p. 2998, 2008 [4] Bosanac, Aabo, Bendix & Oddershede, Nano Letters vol. 8 p.1486, 2008 [5] Jauffred, Richardson & Oddershede, Nano Letters, vol.8, p.3376, 2008

155 NA11 InP x-ray detector for nanoscale resolution

By Luisa Ottaviano1, and

Ulrik Lund Olsen2, Kresten Yvind1, Søren Schmidt2, Henning Friis Poulsen2

1 DTU Fotonik, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark2 Risø DTU, Technical University of Denmark, DK-4000 Roskilde, Denmark In this work we present the design and fabrication of a strip electrode detector for x-rays with a spatial resolution of 100nm or below. The x-ray absorbing media is a 2 µm thick InP p-i-n doped diode structure where the p side consists of a thin Zn-doped InGaAs layer and the n side is a Si-doped InP layer. InP is a III-V direct band gap material with the K-edge located at 28keV, which makes InP very suitable for 30-50keV x-rays detection. The large band gap of 1.35eV implies that the x-ray detector possibly could work at room temperature with a low noise performance. The detector is meant for single photon detection, which allows a resolution higher than the electrode pitch. The position of the absorption event is determined by the carrier distribution at the metal electrodes through centre-of-mass algorithms. Simulations demonstrate that with this detector design, and in the absence of noise, the spatial resolution should be in the range of 30-100nm for 36keV photons. This enables a non destructive 3D imaging of nanometer features with lensless x-ray labsources. To fabricate the detector we used well known cleanroom techniques demonstrating that it is possible to integrate the III-V device into silicon CMOS technology.

156 NA12 Improved Polymer Dye Lasers with Multifunctional Photonic Crystal

By Mads Brøkner Christiansen1 and

Sanshui Xiao2 Niels Asger Mortensen2 Anders Kristensen1

1 DTU Nanotech, Technical University of Denmark2 DTU Fotonik, Technical University of Denmark We present optically pumped hybrid polymer band edge lasers with a rectangular lattice providing laser feedback and also increasing the amount of pump light being absorbed. The lasers are defined in a thin film of photo-definable Ormocore hybrid polymer. doped with the laser dye Pyrromethene 597. They are 375 nm thick slab waveguides with a rectangular lattice of 100 nm deep air holes imprinted into the surface. The short lattice constant (a) is always 200 nm, while the long lattice constant (b) is varied from 351 nm to 360 nm. A compact frequency doubled Nd:YAG laser (532 nm, 5 ns pulses) is used to pump the lasers from above the chip. At a certain resonance angle, depending on the b lattice contant, light is coupled into the chip plane. When the laser is pumped at the resonance angle the threshold drops to 470 nJ/mm2, far below typical values for optically pumped dye lasers, and the output intensity increases more than two orders of magnitude. The lasers are fabricated in parallel on a 10 cm diameter wafer by combined nanoimprint and photolithography (CNP). CNP relies on a UV transparent quartz nanoimprint stamp with an integrated metal shadow mask. In the CNP process the photonic crystal is formed by mechanical deformation (imprinting) while the larger features are defined by UV exposure through the combined mask/mold. Our results demonstrate that by careful design of the photonic crystal two optical functionalities can be combined at two different wavelengths in the same material. With their low thresholds and simple operation the lasers presented here provide an attractive way of integrating tuneable light sources into polymer lab-on-a-chip systems.

157 NA13 Development of Integrated Electronics for Readout of High Frequency Micro/Nano- Mechanical Resonator

By Meng Tang1 and

Jan Hales1 Alberto Cagliani1 Zachary Davis1

1 DTU nanotech, Technical University of Denmark Micro sized bulk type resonators have been quickly developed through the recent years for applications in the electronics industry for cheap, low power and integreatable alternative to both passive and active components. Fur- thermore, this type of bulk type resonators can also be applicable for bio/chemical sensors, due to the minute size and mass of the resonators. Small amount of absorbed mass can be detected. The main principle is that: the Micro/nano electro-mechanical system (MEMS) is vibrating at its resonant frequency and any mass absorbed or deposited on the surface induces a frequency shift due to a mass change. In order to achieve readout and facilitate a high mass resolution, an Integrated Circuit(IC) module is required to amplify small current signals from the resonator and increase the frequency resolution. The most commonly used method is the traditional feedback scheme such as oscillator or PLL (phase locked loop). The main principle is to conduct a feedback loop for self exciting the whole system. However, because of its inherent phase and gain sensitivity to resonator loss, and the nonlinearity of the loop, it doesn’t work well with disk resonator which has a large motional resistance. An alternative is called pulse mode. The main principle is to excite the resonator with a high quality pulse signal whose power spectrum is all over the whole frequency range of interest. The output impulse response of the resonator is recorded and then all the harmonic information is easily obtained by Fourier transform. It is very simple, quick and able to get a full understanding of the signal. Furthermore, the parasitic capacitance, which is the main factor to deviate the resonant frequency, can be eliminated since there is no AC signal in the pulse mode measurement. Meanwhile, the Q(quality)-factor can be acquired directly from the decay curve. Therefore, more electro-mechanical properties can be investigated. There are different types of pulse signals can be utilized to excite the resonator, such as sine-burst, square, triangle, monocycle Gaussian function and so on. After examining their frequency spectrums, the last one is best for its broad and flat band. As a first test, a PCB based circuit with commercial devices is used to generator a very short pulse (pulse width in nano seconds). In the future, our aim is to design the pulse generator and integrate it with the MEMS device. Micro sized bulk type resonators have been quickly developed through the recent years for applications in the electronics industry for cheap, low power and integreatable alternative to both passive and active components. Fur- thermore, this type of bulk type resonators can also be applicable for bio/chemical sensors, due to the minute size and mass of the resonators. Small amount of absorbed mass can be detected. The main principle is that: the Micro/nano electro-mechanical system (MEMS) is vibrating at its resonant frequency and any mass absorbed or deposited on the surface induces a frequency shift due to a mass change. In order to achieve readout and facilitate a high mass resolution, an Integrated Circuit(IC) module is required to amplify small current signals from the resonator and increase the frequency resolution. The most commonly used method is the traditional feedback scheme such as oscillator or PLL (phase locked loop). The main principle is to conduct a feedback loop for self exciting the whole system. However, because of its inherent phase and gain sensitivity to resonator loss, and the nonlinearity of the loop, it doesn’t work well with disk resonator which has a large motional resistance. An alternative is called pulse mode. The main principle is to excite the resonator with a high quality pulse signal whose power spectrum is all over the whole frequency range of interest. The output impulse response of the resonator is recorded and then all the harmonic information is easily obtained by Fourier transform. It is very simple, quick and able to get a full understanding of the signal. Furthermore, the parasitic capacitance, which is the main factor to deviate the resonant frequency, can be eliminated since there is no AC signal in the pulse mode measurement. Meanwhile, the Q(quality)-factor can be acquired directly from the decay curve. Therefore, more electro-mechanical properties can be investigated. There are different types of pulse signals can be utilized to excite the resonator, such as sine-burst, square, triangle, monocycle Gaussian function and so on. After examining their frequency spectrums, the last one is best for its broad and flat band. As a first test, a PCB based circuit with commercial devices is used to generator a very short pulse (pulse width in nano seconds). In the future, our aim is to design the pulse generator and integrate it with the MEMS device.

158 NA14 Molecular Dynamics Simulations of Nanocarbon formation from Methane

By N. Lümmen1 1 Department of Physics and Technology, University of Bergen, Norway The initial phase of aggregation of carbon nanoparticles after thermal decomposition of methane mixed with other hydrocarbon precursors was simulated by molecular dynamics simulations. A reactive force field (ReaxFF) based on bond order was used to model the interactions between the hydrocarbon molecules. It is able to account for the different types of bonding in different structures and the change of partial charges with molecule geometry, for example. The growth of hydrocarbon molecules in systems of partially decomposed methane was investigated at different temperatures and system densities for up to 4 nanoseconds. The influence of additional acetylene as seed molecule for further growth was also studied. An increasing number of different types of molecules with increasing temperature and system density was found. We also studied the aggregation of particles from single carbon molecules distributed in an atmosphere of molecular hydrogen. Different seed molecules like benzene and pyrene were added to study their influence on the speed of particle growth and the structure formation compared to systems without such seed molecules. Formation of small hydrocarbons, catenation and ring formation in large aggregates were observed. This research project is a cooperation between the University of Bergen’s Department of Physics and Technology and Carbontech Holding AS and is funded by the Research Council of Norway’s NANOMAT-programme.

159 NA15 Isotropic metal deposition technique for metamaterials fabrication

By R. Malureanu1 and

A. Andryieuski1 A. Lavrinenko1

1 DTU Fotonik, Danish Technical University, Kgs. Lyngby, Denmark One of the main challenges in obtaining 3D structures is the difficulty of depositing metallic layers in three dimensions. Due to the impossibility of using classic metal deposition techniques for attaining this goal, efforts have been focused on non-standard ones. The first report showing metal layer deposition on 3D structures was published recently [1] and uses plasma enhanced chemical vapor deposition (PECVD) technique. Apart from the complexity of the parameter space such technique has, the needed substances and their reaction products are highly toxic. Also, such technique needs high temperature, so additional steps to prevent the structure from being damaged in these conditions have to be taken. Our approach is simpler and is based on depositing metallic layers from solution, the so-called electroless technique. This approach allows not only an easier way to control the parameters space, but it also takes place at room temperature without complex equipment. The base idea behind the electroless technique is to obtain a diluted metallic compound that will easily be reduced to the constituent metal on the surface of interest. For the first tests we used a combination of silver-ammonia complex and formaldehyde where the formaldehyde acts as the reducing agent [2]. When adding formaldehyde to the diluted silver complex, the solution changes form transparent to mud-like coloured showing the presence of both silver and silver oxide products. After some time, the silver oxide is reduced to silver and the solution becomes transparent again showing the end of the formaldehyde reaction. At this point the silver compound is completely reduced and silver can be observed both on the surface of interest and, as particles, in solution. Usually the desired layer thickness is obtained before this point and the sample can be removed from solution before the occurrence of big silver particles. Still, extra care has to be taken either to prevent the surface of interest from been reached by the particles, or to reduce the silver particle formation by using ultrasound baths [2]. Such particles by attaching on the growing layer intensively deteriorate the layers’ quality. The intrinsic isotropy of the electroless approach makes it a perfect candidate to be employed in covering complex structures with thin metallic layers. The tests presented are the very first ones that have been performed on a flat surface for better measuring of the deposition characteristics. Uniform layers with average thickness of about 60nm on a fairly big (tens of square microns) surface were obtained. Further progress on these tests will be presented during the conference. [1] M. Rill et. al., Nature Materials, 7, pp. 543 - 546 (2008). [2] G. Ling, J. He, L. Huang, J. of. Mat. Sci., 39, pp. 2955 - 2957 (2004).

160 NA16 Deposition and Implantation of Size-Selected Co Clusters

By Sasa Vuckovic and

Vladimir N. Popok

Department of Physics, University of Gothenburg, Gothenburg, Sweden. Mastering and designing of nanostructured materials is of great interest for both research and industry. Size reduction effects on the electronic, optical, magnetic and other properties and the enhanced role of the interfaces in the nanometric systems are key parameters that can to some extent be modified and controlled to meet the technological requirements or perform certain functions. With cluster ion beams it is easy to manipulate the agglomerates of atoms, to control cluster size, and energy. For many practical applications size-controlled clusters need to be deposited on the surface but it is also important to make them stationary on the surface. Clusters can be immobilised on surface by using so-called pinning regime. Pinning occurs when cluster kinetic energy is high enough to create a defect on substrate surface thus the cluster become bind to this defect that suppresses surface diffusion of the deposited nanoparticles. Cobalt clusters were produced by laser ablation cluster source using the second harmonic (532 nm) of Nd:YAG laser [1]. This cluster source is attached to an already existing apparatus [2] where the positively charged clusters can + be manipulated and deposited on a surface. Size selected Con cluster ions with different energies were used for deposition/implantation on/in graphite in ultra high vacuum. It was found that impact of clusters with relatively high kinetic energies (20-200 eV/atom) courses formation of radiation damaged areas. By reducing the energy to about 10 eV/atom one can approach pinning of size-selected clusters. The transition from implantation to pinning with a decrease of impact energy was confirmed by etching experiments showing that depth of the damage introduced by the cluster collisions is reduced to the very top atomic plane of graphite. The etching experiments allowed also to find a dependence of depth of the radiation damage on cluster kinetic energy and size that is of importance for practical applications of cluster beams for shallow implantation.

161 NA17 Subgap resistance of SIS’ Al/AlOx/Al tunnel junctions

By T. Greibe1 and

E. Olsson2, S. Nik2, T. Bauch1, C. Wilson1, P. Delsing1

1Quantum Device Physics Laboratory, Microtechnology and Nanoscience, MC2, Chalmers University of Technology, Gothenburg, Sweden2Department of Applied Physics, Chalmers University of Technology, Gothen- burg, Sweden 1 Al/AlOx/Al tunnel junctions are key elements in superconductor electronics, e.g. qubits, cooper-pair transistors and tunable microwave resonators 2, as well as in spintronic devices. It is well-known that the leakage current of the tunnel junctions plays a severe role in the devices; it induces decoherence in the qubits and cooper-pair transistors, it lowers the tunability of the microwave resonators. Motivated by understanding and reducing the leakage of Josephson junctions, the subgap resistance has been studied thoroughly in all-Al tunnel junctions in the sub- 100mK regime. The junctions are fabricated with a large variety in oxidation -pressures and -times. The tunnel junctions are e-beam patterned to have sizes between 0.03 - 0.12 µm2 and fabricated by double-angle technique with in-situ thermally growth of aluminum oxide. The oxidation dose (in units T orr · s) has been varied over three orders of magnitude. The Al leads of the junctions are of substantial difference in thickness leading to a large difference in the superconducting gap in the two leads, thus forming an all-Al SIN junction when a high parallel magnetic field is applied. In this way, the subgap resistance of the tunnel junctions has been characterised while avoiding resonances in the subgap regime of the junctions 3. We map out the normal- and subgap resistance of the junctions versus the oxidation dose and present fabrication techniques to increase the subgap resistance at a constant normal resistance. Also, we present Al evaporation rate dependency and temperature dependency of the subgap resistance. We have furthermore investigated selected junctions using high resolution analytical transmission electron microscopy, in order to compare their microstructural appearance, such as barrier width and homogeneity, with their leakage behaviour. 1 A. M. Savin, M. Meschke, J. P. Pekola, Y. A. Pashkin, T. F. Li, H. Im, J. S. Tsai, Applied Physics Letters 91, 063512 (2007). 2 M. Sandberg, C. M. Wilson, F. Persson, T. Bauch, G. Johansson, V. Shumeiko, T. Duty, P. Delsing, Applied Physics Letters 92, 203501 (2008) 3 T. Greibe, T. Bauch, C. Wilson, P. Delsing, to be published in Journal of Physics: Conference Series

162 NA1P Morphology and solar cell performance of thin-ﬁlms of polyﬂuorene:fullerene blends

By Ellen Moons1 and

Krister Svensson1, Jan van Stam1, Ana Sofia Anselmo1, Lars Lindgren2, Mats Andersson2, Jakub Rysz3, Andrzej Budkowski3, Andrzej Bernasik4, Ulrich Hörmann5, Julia Wagner5, Andreas Opitz5, Wolfgang Brütting5.

1 Karlstad University, SE-65188 Karlstad, Sweden;2 Chalmers University of Technology, SE-412 96 Göteborg, Sweden;3 Jagiel- lonian University, 30-057 Kraków,Poland;4 AGH - University of Science and Technology, 30-059 Kraków,Poland;5 University of Augsburg, D-86135 Augsburg, Germany. Polymer solar cells are a promising inexpensive alternative to inorganic ones, however efficiency and long-term stability need to be improved. Conversion efficiency is closely linked to the processes involved in the generation, the transport and the collection of charge carriers within the active layer of solar devices, which are directly influenced by the morphology of the layer. In our research project, we focus on morphological issues in thin-films spin-coated from blends of low-bandgap polyfluorenes and a fullerene derivative (PCBM). Film morphology is manipulated through (a) choice of solvent and spin-coating conditions; (b) control of surface energy of the substrate; and (c) use of specifically tailored molecules aimed at promoting vertical versus lateral structures. Characterization of the thin-film topography is performed through Atomic Force Microscopy (AFM), and the in- depth organization of the blend components through dynamic Secondary Ion Mass Spectrometry (dSIMS). Solar cell devices are fabricated to correlate device performance and film morphology. Previous studies have shown multilayer-structured films of polyfluorene:fullerene blends to form spontaneously under specific conditions, which improved solar cell performance [1, 2]. The mechanisms leading to these results can be rationalized with thermodynamic and kinetic models of nucleation and phase separation [3]. Recently an increased tendency for self-stratification was found in a series of films prepared from PCBM blended with polyfluorene copolymers that had been especially synthesized with a varying fraction of a phenolic monomer for enhanced polymer-fullerene interaction. References [1] Björström,C.M. et al J. Phys.:Condens. Matter 2005, 17, L529-L534; [2] BjörströmSvanström,C.M. Thin films of polyfluorene/fullerene blends Ph.D diss., Karlstad University Studies, 2007:43; [3] Nilsson, S. et al Macromol. 2007, 40, 8291-8301.

163 NA2P Theoretical analysis of electrokinetic analyte transport in nano-slits

By M.B. Andersen and

H. Bruus

Technical University of Denmark Using numerics and experiments we study the concentration of a tracer dye (BODIPY) dissolved in an electrolyte (phosphate buffer) driven through a lab-on-a-chip nanoslit channel (0.5 um by 250 um by 9000 um) by elec- troosmosis. We analyze how the concentration drops across an un-baised center electrode (of Pt) as a function of the external voltage (50 V - 150 V) driving the flow. Furthermore, we study the impact of varying the equilibrium concentrations of tracer dye and electrolyte salt (1 uM - 10 mM). Our numerical results agree with the experimental observations as we see: (i) a concentration drop in the dye across the un-biased electrode, (ii) the drop increases with increasing applied voltage, (iii) the drop is affected by the concentration of buffer and dye, and (iv) high concentration enrichment of dye on the un-biased electrode. Furthermore, we use our numerical results to give insight into the dynamics of the concentration drop phenomenon.

164 NA3P Optoﬂuidic applications using 1,2-PolyButadine nano-porous diblock polymer

By Nimi Gopalakrishnan and

Anders Kristensen

1NSE Optoﬂuidics, DTU Nanotech,DTU,Denmark2Department of Chemical and Biochemical Engieerning,Denmark3DTU Nan- otech West,RISØ, Denmark

165 NA4P Liquid crystal tunable microﬂuidic dye lasers

By Thomas Buß1 and

Mads Brøkner Christiansen1 Anders Kristensen1 Cameron L. C. Smith1

1 DTU Nanotech, Technical University of Denmark In this poster a liquid crystal tunable microfluidic dye laser is presented. Possible applications of this device are compact light sources for microscale integration to optofluidic sensing in lab-on-a-chip systems. The poster presents design, fabrication by combined nanoimprint and photolithography and measurements of laser emission. Furthermore, the physics of transition from random to ordered lasing when the liquid crystal molecules are reoriented is discussed. The laser resonator consists of a rectangular lattice photonic crystal to provide feedback and facilitate coupling of pump light. A liquid crystal layer is used to tune the refractive index of the photonic crystal surrounding by electric field induced molecular reorientation. This change in refractive index shifts the band structure of the photonic crystal and thereby allows tuning of its resonant wavelength. Simulation of the band structure is done by two-dimensional numerical solutions of the eigenvalue formulation of Maxwell’s equations in frequency domain. The finite extend of the laser is taken into account by using effective indices determined for slab waveguides. These simulations suggest a possible tuning range of 20 nm, using 5CB, a common room-temperature nematic phase liquid crystal. The laser dye used is Pyrromethene 597 which is pumped by a frequency doubled Nd:YAG laser, emitting nanosecond pulses at a low repetition rate.

166 Nuclear and elementary particle physics

NF1 Dark Matter as apple sized balls, Tunguska, Sodoma and Gomorra

By Holger B. Nielsen and

Colin D. Friggatt

Niels Bohr Institute, University of Copenhagen We propose the possibility that dark matter could be balls of some human scale size and from time to time fall down on earth. As details in our model we can achieve a way of having such balls produced at a time when the universe were of an age of the order of a quarter of a second and there occured a transition from one type of vacuum to another one. The remarkable thing is that we can achieve this scenario inside the pure standard model provided though that we are allowed to to finetune the coupling constants to some extend. In fact we claim that the top-quark mass matches the value to which we need it finetuned. We are looking forward to seeing bound states of of the order of twelve top quarks being produced in the LHC, and have found some statistically insufficient evidence for their production in the Tevatron.

167 NF2 The HIE-ISOLDE project

By K. Riisager and on behalf of the ISOLDE collaboration

Department of Physics and Astronomy University of Aarhus Several major new radioactive beam facilities are being constructed or planned currently, including RIBF in Japan, FAIR in Germany and FRIB in the US. As recognized by NuPECC and ESFRI, upgrades of the existing ISOL facilities are needed to bridge the technological gap to the ambitious EURISOL facility, to be constructed around 2020. I shall review HIE-ISOLDE, the upgrade program at CERNs ISOLDE facility (the leading ISOL facility in terms of the variety of radioactive beams produced) and present the ﬁrst results. Upgrades of the beam quality are already on the way and eﬀorts are presently concentrated on the energy upgrade of post-accelerated beams. The third large component is an upgrade of the target and ion source region to be able to handle the increased beam intensity that will be provided by the new injector LINAC4, being constructed at CERN at the moment.

168 NF3 The MAX-lab tagged photon facility

By L. Isaksson1 1 Lund University, MAX-lab The tagged photon facility at MAX-lab in Lund, Sweden has recently been upgraded to higher energy. The present facility consists of a ∼200 MeV linac followed by a pulse stretcher ring. The extracted electron beam (∼50% duty factor) is used to generate a bremsstrahlung beam and photons are tagged by a choice of two tagging spectrometers, optimized for diﬀerent energy regions. The tagged photon range may presently be chosen between 15 MeV and 185 MeV. The energy resolution is typically ∼0.5 MeV and the tagged intensity is ∼ 106MeV −1s−1. The available energy may increase somewhat in the near future. The initial experimental programme includes Compton scattering on deuterium using very large NaI detectors, (γ,π+) measurements using both solid-state and scintillator set-ups, and tests of electromagnetic calorimeter elements for the PANDA detector. Initial tests have been performed on total absorption cross-section measurements on 4He, using an active target, and on 6,7Li. A linearly polarized photon beam from coherent bremsstrahlung is being commissioned. The MAX-lab tagged photon facility will be presented and an overview of the present experimental programme given.

169 NF4 3α break-up of 12C resonances

By O. Kirsebom1, and

H. O. U. Fynbo1, S. Hyldegaard1, K. Riisager1, B. Jonson2, T. Nilsson2, G. Nyman2, M. Alcorta3, M. J. B. Borge3, M. Cubero3, R. Dominguez3, M. Madurga3, A. Maira3, A. Perea3, O. Tengblad3, M. Turrion3, G. Garcia4, A. Munoz4, D. Obradors4, B. Fulton5

1 Institut for Fysik og Astronomi, Aarhus Universitet, Aarhus, Denmark2 Fundamental Physics, Chalmers University of Tech- nology, Goteborg, Sweden3 Instituto de Estructura de la Materia, CSIC, Madrid, Spain4 CMAM, Universidad Autonoma de Madrid, Cantoblanco, Spain5 Department of Physics, University of York, Heslington, UK We use the Dalitz plot to study the decay of 12C resonances into three α particles. The requirement of a symmetric 3α final state together with conservation of spin, parity and isospin forces the density to vanish in certain regions of the Dalitz plot, hence inducing general structures that do not in any way depend on the details of the interactions at work. The implications of this understanding is two-fold. First, the observed density of the Dalitz plot can be used to determine or at least impose constraints on the spin and parity of the decaying 12C resonance. Second, once the inevitable structures due to symmetries have been identified the remaining structures in the Dalitz plot can be understood as resulting from the dynamical interactions at play, thus allowing for an understanding of the decay mechanism. In this contribution I present experimental Dalitz plots extracted from complete kinematics studies of the 10B(3He,pααα) and 11B(3He,dααα) reactions. I show how our measurements allow us to determine the spin and parity of 12C states whose quantum numbers were hitherto unknown. Finally, I compare the measured Dalitz distributions to theoretical calculations and discuss the implications for our understanding of the decay mechanism, in particular the validity of a sequential model that assumes the decay to proceed through the broad short-lived 2+ resonance in 8Be. In rare cases the break-up into three α particles is preceded by the emission of a γ ray. I will explain how such events are identified and present the γ ray branching ratios extracted from the present work, some of which have never been measured before. I shall also explore the close connection between these γ transitions and the β decays of 12B and 12N.

170 NF5 The perfect ﬂuid and other highlights from the relativistic heavy ion collider

By P. Christiansen1 1 Lund University, Lund, Sweden The relativistic heavy ion collider (RHIC) began operation in 2000 and since then the four experiments: PHENIX, STAR, BRAHMS, and PHOBOS, have continuously provided new exciting results in the search for the hottest matter in the universe: the Quark Gluon Plasma (QGP). In my talk I would like to focus on a few of the highlights from RHIC that shows why we believe that a new phase of matter is formed: the energy density and the fluid behavior of the matter created in the collisions, and its ability to quench jets leaving behind shock wave like remnants at lower momenta. Finally I will talk about the quark like degrees of freedom observed in both the fluid observables and in the different suppression patterns for baryons and mesons at intermediate transverse momenta. I will throughout the talk outline what results from LHC will be able to tell us more about these signals to show how even a short heavy ion run at the end of 2010 can provide much insight into many of the open questions.

171 NF6 The performance of ATLAS Tau trigger in presence of pileup collisions

By P. Jez and on behalf of ATLAS collaboration

Niels Bohr Institute, Copenhagen Many models, among them light SM Higgs, SUSY Higgs at large tan β and various other SUSY models, predict an abundant production of taus with respect to other leptons. At the energy scale of the LHC, the identification of tau leptons, in particular in the hadronic decay mode, will pose a very challenging task due to an overwhelming QCD background. Nevertheless, exploiting the hadronic decays of the tau lepton allows for an increased signal efficiency by at least a factor of two in many cases, and provides an independent control sample to disentangle leptonic tau decays from prompt electrons and muons. Equipped with excellent tracking and calorimetry, the ATLAS experiment has developed tau identification tools capable of working at the trigger level. I will present the main hadronic tau decay features exploited by the tau trigger algorithms. These include strategies to suppress low multiplicity, low-energy jets contributions and the actual tau trigger chain. The emphasis is given to the effect of multiple interactions per bunch crossing (”‘pileup”’) on the performance of the ATLAS tau trigger. Multivariate analysis techniques are employed in order to determine best combination of cuts for a given range of pileup interactions.

172 NF7 Distributed computing for LHC: interfacing AliEn and ARC to unify the Nordic resources

By Philippe Gros Lund University ALICE, A Large Ion Collider Experiment, is an LHC experiment dedicated to the study of heavy ions collisions. These collisions produce a very large number of tracks, and therefore a lot of computing power is required to process this massive amount of data. That is why a job distribution system is required to access resources all over the world. This is the purpose the new technology that is the grid. The interoperabilty of different middlewares (grid job distribution softwares) is one of the main challenges in grid computing today. Different communities have over time developed several softwares, and they now need to work together to allow access to larger pools of resources. For example, ALICE has developed AliEn, and NorduGrid (a Nordic organisation) has created ARC. The Nordic countries pledged computing and storage resources to the LHC experiments as a single Nordic regional centre (Tier1). The unification of the storage has already been completed. The job distribution should be performed using the ARC middleware. However, currently the ALICE computing resources are in the form of 7 independent sites running the ALICE middleware AliEn. The work presented uses ARC to distribute ALICE jobs from one single AliEn entry point to all the Nordic sites. The talk explains the two different job submission techniques of ARC and AliEn, based respectively on the push and pull models. It will present the challenges of an interoperation solution between the two softwares. In particular, the question of software installation on the grid will be discussed. Finally, the strategy, status, and plans of the interface development will be shown.

173 NF1P Low-energy transfer reactions with 11Be

By Jacob Johansen and on behalf of the ISOLDE collaboration

Department of physics and astronomy, Aarhus University, Aarhus The transfer reaction experiment was done in 2005 at the REX-ISOLDE facility using a 11Be beam with a beam energy at 2.25 MeV/u. With this energy we were able to populate the four bound states in 12Be. The set-up of the experiment was similar to the one used earlier for studying reactions with a 9Li beam and it consists of two 32x32 dsssd’s in forward direction. We were able to detect protons, deuterons, tritons, α-particles and 6He. This corresponds to the production of 12Be, 10Be and 9Li while 6He may come from α+6He breakup of 10Be excited states. The results of the experiment will be presented as well as future plans for experiments with transfer reactions using a 11Be beam.

174 NF2P The Near-Threshold Pion Production Program at MAX-lab

By Jason Brudvik MAX-lab, Lund University Near-threshold pion photoproduction is an elementary process involving an explicit rearrangement of the quarks in the nucleon. It is thus a direct probe of the quark structure of the nucleon. At energies below the Delta resonance, pion photoproduction also provides a stringent test of chiral symmetry as a result of accurate predictions from chiral eﬀective ﬁeld theory. Precision sub-Delta measurements of the angular distribution and the total cross section for pion photoproduction are thus of fundamental importance. Surprisingly, aside from the ( g + p → p + π0) channel which has been thoroughly studied at MAMI-B and SAL, few data exist in this crucial near-threshold region. MAX-lab in Sweden is the one photonuclear facility worldwide whose energy range is perfectly tuned to such experiments. As such, a comprehensive program of near-threshold pion photoproduction experiments has recently been initiated. These experiments include measurements of the angular distribution for pi+ photoproduction in the p-wave energy region for both the proton and heavier targets and the total cross section for pi- photoproduction close to threshold using a deuterium target. In this poster, an overview of the pion photoproduction program at MAX-lab will be presented. This overview will include preliminary results from commissioning runs for the previously mentioned experiments together with a look at future plans.

175 Physics education

UU1 Acceleration - in Student Conceptions and in Mathematics, Physics and Life

By Ann-Marie Pendrill Department of Physics, University of Gothenburg, SE 412 96 Goteborg, Sweden Acceleration, unlike velocity, is absolute in Newtonian mechanics. It is accompanied by force according to Newton’s laws, and can be measured from within an accelerated system, without the need for an external reference. If the accelerating body is our own, we can feel the acceleration throughout the body. Acceleration in its full vector capacity is very much part of everyday life. This experience, which is part of the excitement in most amusement rides, is rarely utilized in textbooks. Students often fail to make the connection between free-body diagrams and forces acting on their body. In this paper, we present excerpts from interviews and group discussions on acceleration in swings and in circular amusement rides. We also present results of diagnoses of large groups of ﬁrst-year engineering students who were asked to draw free-body diagrams for these situations. These students have a good understanding of force concepts, as indicated by entrance scores around 80% on the force concept inventory (FCI). Still, they were often confused about the relation between force and acceleration. The everyday use of acceleration as increase of speed make many students uncertain about what happens e.g. in the bottom of the swing where the speed is maximum. Although the centripetal force may be drawn correctly, it sometimes appears to be seen as a force in its own right - not as a resultant of the real interactions: the force of gravity and the force from the ride acting on the rider. In many responses, the normal force has the ”normal” size, cancelling the weight, mg, rather than the size needed to give the proper resultant centripetal force. The results indicate a need for more situations where students conceptions are challenged, and where the students are encouraged to connect their physical description with a mathematical description.

176 UU2 Electronic ”‘peer response system”’ used as basis for talking physics

By Carl Angell and

Ellen K. Henriksen

Department of physics. University of Oslo The teaching approaches employed in many university physics courses have been described as rigid, traditionalistic and not very effective. At the Department of Physics, University of Oslo, a teaching approach utilising an electronic ”‘peer response system”’ (PRS) was introduced in an introductory mechanics course with the aim of fostering students’ active involvement with the subject matter, promoting individual and group learning processes, and providing instant feedback to individual students as well as the instructor regarding the state of students’ understanding. A range of quantitative and qualitative data was collected. Data from the PRS system software was utilised to investigate students’ responses, a questionnaire was administered to students, and semi-structured interviews during the semester were conducted with students and the lecturer. A follow up study focused on students’ discussion before they made their final click. The PRS system was constructively used and functioned as a positive and useful element in teaching and learning mechanics. The PRS system also provided a form of communication between lecturer and students that is often very weak in traditional courses. Thus, the system has potential to contribute to better learning through interactive engagement and to help students to choose fruitful approaches to enhance their learning. Indeed, through discussions about PRS-questions the students get experience with expressing their own understanding in a scientific language, and help them to use physics concepts and to talk physics as a physicist.

177 UU3 Improving Teaching at the Basic Physics courses to prevent dropping out - successes and disappointments

By Ilkka Hendolin and

Szabolcs Galambosi

Department of Physics, University of Helsinki, Finland The number of students studying physics in high school has continuously decreased in Finland during the last decade. At the same time the competition between different branches of science for students with good skills in physics has intensified. This situation is quickly leading towards a lack of talented physics students. The reform of the basic physics courses at the Department of Physics, University of Helsinki has been initiated in order to enhance students’ commitment to their studies. Changes are necessary because nearly half of the physics majors drop out during their first year. The guidelines for the development are based on various successful teaching methods developed by physics education research groups around the world. As the most important reform, interactive engagement methods (PE, ILD etc.) have been implemented at the first year courses. In addition to this, homework problems are also being renewed. The aim is to enhance students’ cognitive effort in problem solving and thereby motivation to study. Most importantly the teacher students leading tutorial sessions are mentored more carefully than before. The laboratory works associated with the courses have also been renovated thoroughly, emphasising qualitative understanding instead of quantitative measurements and rigorous data analysis. Most of the methods mentioned above were implemented for the first time during the academic year 2008-2009. There was instant improvement evident in student feedback, signalling improved motivation and satisfaction. The atmosphere at the lectures as well as the activity of the students has improved greatly and lecture participation is better than before. The drop-out percentages, however, have remained the same. The situation is puzzling and controversial. Obviously the key factors in dropping or continuing studies are else than just the quality of teaching. Recognising these factors will be emphasised in the future.

178 UU4 Conceptualizing Electrons and Photons as Quantum Particles in Physics Teacher Education

By Ismo T. Koponen Department of Physics, University of Helsinki, Finland Learning about the nature of quantum entities - meaning foremost electrons and photons as quantum entities - and conceptualizing this new class of entities is notoriously diﬃcult for most students. It is well known that learning results and resulting conceptual understanding are often very poor. Recent research on students’ conceptions on quantum objects and entities shows that the conceptions are more or less simple extensions of classical pictures or simple agglomerations of classical particle and wave pictures. One reason for this is that classical models are persistent and prevalent mental images and very little advancement happens during further teaching. This seems to be the situation equally well in upper secondary level instruction and university level instruction In an attempt to improve the learning results, the basic question is how university level teaching in the teacher education should approach the topic of the quantum entities, their nature and the conceptualization of this new class of entities, so that it provides a suitable background for teachers to teach the topic at school level. The question is of particular importance in teacher education, because teachers need to make use of already learned classical physics as a starting point for learning. In this report, we describe an instructional approach which, designed to support qualitative understanding of the quantum nature of electrons and photons and which systematically emphasises the conceptualisation based on notion of quantum states and changes in quantum states due to interaction events. In addition, the approach allows to by pay proper attention to the continuity of concept formation process and to the physically correct use of classical analogies throughout learning. We give evidence that such an approach may help student teachers’ conceptualisation process greatly and the learning results are improved.

179 UU5 Teaching laser physics to ﬁrst-year students

By J. Henningsen1 and

B. Friis Johannsen2

1Niels Bohr Institute, University of Copenhagen2 Department of Science Education, University of Copenhagen It is generally recognized that hands-on activities play an important role in the teaching of physics. Experimental skill in itself is a valuable qualification, and experiments can act as a motivating factor by emphasizing that physics is actually dealing with the real world. The standard approach to introduction of experiments in the curriculum is to construct lab exercises which illustrate elements of the theory that has been covered in the lectures. However, as a rule lectures and exercises take place in different environments, temporally separated, and with different teachers, all of which tend to loosen the connection. We describe an approach to teaching laser physics to first-year students that implies full integration of theoretical and experimental aspects. Taking experiments as the starting point, theory is introduced gradually as needed, and the line of experiments is designed with the aim of ensuring adequate coverage of the topic. The approach has been subject to a preliminary test, and student’s assessment of the approach is presented. Further, the advantages and the didactical rationale for this type of teaching and learning approach is discussed, and possible barriers, identified from interviews with this year’s first-year student cohort, are pointed out.

180 UU6 A course on experimental physics for the B.Sc. level

By Kim Lefmann and

Ian Bearden

Niels Bohr Institute University of Copenhagen We present the plans for a course on experimental physics, to appear on 2nd year of the B.Sc. studies at Univ. Copenhagen. The course will differ from usual experimental teaching in many ways. In addition to conducting experiments themselves, students will learn about different types of experiments, planning an experimental project, theory and practice of data analysis, and the very role of experiments in physics. During the course, the students will hear about experiments in many different fields, e.g. astronomy, geophysics, CERN, and nanoscience. The course will be 7.5 ECTS like other curriculum courses, and exams will be in the form of an article-like report and a conference-like oral presentation. The aim with this course is to strengthen the knowledge about and the motivation for experiments in the Copenhagen physics education.

181 UU1P Guided labworks: Redesign as obstacle dislodgement

By Lærke Bang Jacobsen IMFUFA, NSM, RUC This study investigates why upper secondary physics teachers continuously run laboratory works as a strongly teacher guided activity when research studies long have showed poor learning outcomes conceptually, procedurally and epistemologically. Framed in the model of the process of design and evaluation of a teaching/learning task - developed in the Labwork in Science Education project - effectiveness of a task is viewed two-ways: The first level describes to which extend the students do what they are intended to do, and the second level describes to which extend the students learn what they are intended to learn. A study of the laboratory works of three upper secondary physics teachers at different schools showed how teachers only acknowledge the first level of effectiveness, offering good results for guided activities. The teachers do not operate on the second level of effectiveness, since they are lacking explicit objectives for specific laboratory tasks. The teachers’ design and redesign process converges towards a dislodgment of student obstacles for smooth student performances during task work. Concluding, teachers see no reason to change their guided praxis, since it offers a high degree of effectiveness, though, in the eyes of researchers guided tasks lack realisation of relevant learning outcomes.

182 Plasma physics

PP1 Emergent complexity in soft Yukawa systems

By Kristoffer Rypdal - Critical fluctuations, anomalous transport, and vortical flows are observed in experiments and molecular dynamics simulations of soft, two-dimensional dusty plasma clusters. The grains interact via static Yukawa forces, and are subject to stochastic heating and dissipation from neutrals. We observe emergence of leptokurtic probability distributions of grain displacements, development of humps in the distributions on multiples of the mean inter-particle distance, anomalous transport, and transitions from leptokurtic towards Gaussian displacement distributions on longer time scales. The latter is a signature of intermittency, here interpreted as a transition from bursty transport associated with hopping on intermediate time scales to vortical flows on longer time scales. We analyze experimental data and simulations of a two-dimensional many-body system, of two-dimensional chaotic fluid flow, and two different avalanche models, all subject to random forcing at small scales. A scale-free vortex cascade is apparent from structure functions as well as spatio-temporal avalanche analysis. We find similar scaling exponents for the experiment, the many-body simulation, and the fluid simulation, indicating some common dynamical features. Thus we conclude that the dust monolayer dynamics can be viewed as turbulent as well as avalanching, but a fluid model is a better representation of the dust dynamics for these particular experiments than the avalanche models considered.

183 PP2 Mass separation by a magnetized plasma-sheath-lens

By Eugen Stamate Risoe DTU, Technical University of Denmark Reactive plasmas are state-of-the-art in micro and nano-electronic technologies such as etching, ashing, sputtering, deposition, oxidation, passivation or implantation and also play an essential role in fabrication of various nanostructures (nanotubes, nanowalls or nanodots) and in biomedical and biochemical technologies for enhanced biocompatibility, sterilization and bacterial inactivation. Most of these technologies are based on radical-assisted ion-induced surface- modification in which positive or negative ions accumulate energy in a space charge layer, named sheath, and then strike the surface modifying its properties in a desirable way. Plasma-sheath-lens is a three-dimensional potential distribution of customized shape, formed by the positive or negative space charge surrounding a plasma-immersed biased electrode- insulator interface. Two focusing effects, named the discrete and modal focusing have been associated with this type of electrostatic structures formed in plasma and several applications including sheath thickness evaluation, negative ion detection and extraction of positive or negative ion beams of high current densities have been developed. A non- magnetized plasma-sheath-lens act as a kinetic energy separator, but it is not mass sensitive. However, a magnetized plasma-sheath-lens exhibits mass separation in the sense that ion trajectories depend on the mass, so that ions of different mass will impact the electrode at different locations on the biased electrode surface. The mass spectrum can be measured as the radial distribution of the ion current density over the plasma-sheath-lens electrode. Relevant fluid and particles simulations of the magnetized plasma-sheath-lens structures and ion trajectories within them are presented for different plasma parameters and magnetic filed configurations. Practical aspects linked to the development of a new type of mass spectrometers are also investigated.

184 PP3 On the nature of the plasma equilibrium

By Hanno Essén Department of Mechanics KTH, Stockholm, Sweden It is normally assumed that the currents and magnetic fields of plasmas are driven by non-equilibrium processes, the plasma equilibrium being assumed given by the usual Maxwell-Boltzmann distribution taking into account kinetic energy and the Coulomb interactions. A more exact theory should also include magnetic interactions, but may presumably neglect radiation. The usual terminology is then that one is dealing with a relativistic plasma since the magnetic interaction is of the order of the square of v/c. The long range nature of the interaction and the large number of particles in a macroscopic plasma can, however, make this term quite large even for modest particle speeds. Therefore the prediction from ordinary Maxwell-Boltzmann theory is probably wrong. To prove this one needs an accurate phase-space energy, a Hamiltonian, for the plasma, that includes the magnetic interaction energy. Some progress in our search for this entity will be reported. Our conclusion is that even an equilibrium plasma tends to develop currents and magnetic fields.

185 PP4 Generation and characterization of huge (kTesla) magnetic ﬁelds in laser-produced plasmas

By M. Burza1 and

A. Gopal2 G. Genoud1 O. Lundh1 S. Minardi2 I. Tzianaki2 A. Persson1 C.-G. Wahlstr¨om1

1 Lund Laser Center (LLC), Department of Physics, Lund University, Sweden2 Technological Education Institute-Crete, Greece During laser - solid target experiments at the Lund High Power Facility, magnetic fields up to 40 kilo Tesla have been measured inside plasmas produced when ultra intense, 35 fs, 30 TW, laser pulses strike a solid target [1]. These fields exist in high - density plasmas and are therefore highly confined in space and time. Self generated optical harmonics up to the fifths order are used to probe these fields. As the harmonics originate from the critical density surface of the laser - produced plasma, they are inherently superimposed with the short lived fields, both spatially and temporally [2]. In the presence of a magnetic field the plasma is birefringent and/or optically active depending on the propagation direction of the electromagnetic wave. The harmonics as a probe are subjected to both these effects. Initially the self generated harmonics have the same polarisation state as the incident laser. As they propagate out through the magnetised plasma the polarisation state will be altered. Thus an analysis of the polarisation state of the transmitted harmonic radiation provides information about both the strength and the orientation of the magnetic fields inside the plasma. Depending on the probe wavelength and plasma density, a certain polarisation state will even be incapable of traversing the plasma when the magnetic field strength exceeds a given value. Although a probe continuum would reveal a distinct cut-off frequency, where the plasma index of refraction approaches zero, the cut-off for discrete harmonics serves as a rough but direct diagnostic with encoded information about the magnitude of the magnetic field strengths experienced by the photons [3]. The experimental set-up and preliminary results will be presented. References [1] A. Gopal et al., manuscript in preparation [2] A.Gopal et al, Phys. Plasmas 15 122701 (2008) [3] M. Tatarakis et al., Nature, 415, 280 2002

186 PP5 First measurement of the ion Bernstein wave spectrum by means of collective Thomson scattering

By M. Stejner1 and

S.B. Korsholm1 H. Bindslev1 V. Furtula1 F. Leipold1 F. Meo1 P.K. Michelsen1 D. Moseev1 S.K. Nielsen1 M. Salewski1

1 Risø National Laboratory for Sustainable Energy, Technical University of Denmark Collective Thomson scattering of microwaves on plasma fluctuations is a versatile diagnostic tool which is sensitive to a range of plasma parameters of interest to future fusion experiments. When the scattering geometry is such, that the resolved fluctuation wave vector is nearly perpendicular to the magnetic field the scattered spectrum is strongly modulated by ion Bernstein waves. The Bernstein waves appear in the scattered spectrum at every harmonic of the ion cyclotron frequency. Their damping depends on finite Larmor radius effects, and the spectrum will thus be sensitive to the mass, charge and density of any ion present in the plasma. Measurement of the ion Bernstein spectrum is therefore of significant interest as a diagnostic tool to determine the isotope content of fusion plasmas in future experiments such as ITER. We present the first measurements of the ion Bernstein spectrum by means of collective Thomson scattering in a tokamak plasma. The measurements were performed on the TEXTOR tokamak, and we show that the spectrum has the expected dependence on isotope content. The spectrum is further shown to agree well with fully electromagnetic numerical simulations of Thomson scattering, which open the possibility of forward modelling and inference of the isotope content.

187 PP6 Fast ion collective Thomson scattering - present results and plans for ITER

By S.B. Korsholm and

H. Bindslev, V. Furtula, F. Meo, P.K. Michelsen, D. Moseev, S.K. Nielsen, F. Leipold, M. Salewski, M. Stejner

Risø National Laboratory for Sustainable Energy, Technical University of Denmark Moving towards the era of burning fusion plasmas, a better knowledge of the physics of highly energetic particles, such as the 3.5 MeV fusion born alpha particles, becomes necessary. Diagnosing the fast ions in a fusion plasma is a challenging task, but the technique of collective Thomson scattering (CTS) provides the possibility of revealing the velocity distribution of the conﬁned fast ions along a given direction - resolved both in time and space. Recently, the ITER baseline design has been expanded to include a fast ion CTS diagnostic. The design of this diagnostic was provided by the CTS group at Risø DTU building on the experiences and expertise gained from the group’s construction and current operation of the CTS diagnostic systems on the tokamaks TEXTOR and ASDEX Upgrade. This contribution will introduce the technique of CTS, give an overview of the current diagnostic systems and results, and present the expectations for the ITER CTS diagnostic.

188 PP7 Interactions of two objects in ﬂowing plasmas studied by numerical simulations

By W. J. Miloch1 and

H. L. P´ecseli2, J. Trulsen1

1 Institute of Theoretical Astrophysics, University of Oslo, N-0315 Oslo, Norway2 Department of Physics, University of Oslo, N-0316 Oslo, Norway The interactions between two insulating spherical objects in a supersonic plasma flow are studied by particle-in-cell numerical methods. The objects immersed in plasma are usually negatively charged. Studies of interactions between such objects are important for the understanding of structures and dynamics of plasmas comprising for example many dust grains [1]. In such systems, the alignment of grains in the direction of the flow has been predicted and observed [2,3]. Theoretical descriptions of a two-grain system are difficult, and numerical simulations have to be used to address this nonlinear problem in a self-consistent way. We study interactions between two insulating objects with different alignments with respect to the flows and different relative positions. We find that the spatial variations of the charge distribution and the plasma potential strongly depend on the objects positions. For the case of two spheres aligned perpendicular to the plasma flow, a single wake and a region of enhanced ion density can be observed behind the objects, provided that the distance between them is small [4]. For an object placed behind another one, the resulting wake is not a linear superposition of two individual wakes and the characteristic features, such as ion focusing, can be destroyed due to shadowing. We discuss electrostatic and ion drag forces acting on the objects in the context of their dynamics. Our numerical simulations are carried out in two and three spatial dimensions with ions and electrons treated as individual particles. We employ two corresponding particle-in-cell numerical codes. [1] S. V. Vladimirov, K. Ostrikov, and A. A. Samarian, Physics and applications of complex plasmas, Imperial College, London, 2005. [2] S. V. Vladimirov, S. A. Maiorov and N. F. Cramer, Phys. Rev. E, 67, 016407 (2003). [3] A. Melzer et. al., Phys. Rev. E., 54, R46 (1996). [4] W. J. Miloch, S. V. Vladimirov, H. L. Pécseliand J. Trulsen, Phys. Plasmas, 16, 023703 (2009).

189 PP1P Conﬁnement of fast ions during applied resonant magnetic perturbations in TEXTOR using collective Thomson scattering diagnostic

By D. Moseev1, and

S.B. Korsholm1, M. Stejner1, S.K. Nielsen1, M. Salewski1, F. Meo1, H. Bindslev1, F. Leipold1, P. K. Michelsen1, V. Furtula1, O. Schmitz2, A.Buerger3, M. Kantor3, E. Westerhof3, P. Woskov4

1 Association EURATOM-Risø DTU, National Laboratory for Sustainable Energy, Technical University of Denmark, P.O. Box 49, DK-4000 Roskilde, Denmark2 Institute for Energy Research - Plasma Physics, Forschungszentrum Juelich, Association EURATOM-FZJ, Trilateral Euregio Cluster, 52425 Juelich, Germany3 FOM-Institute for plasma Physics Rijnhuizen, Associa- tion EURATOM-FOM, Trilateral Euregio Cluster, Nieuwegein, The Netherlands, www.rijnhuizen.nl4 MIT Plasma Science and Fusion Center, Cambridge, MA 02139 Fast ion physics has a crucial importance for thermonuclea fusion because confined energetic particles are mainl responsible for heating the plasma. Additionally they are a source of free energy for instabilities. Meanwhile, one of the biggest challenges for large tokamaks (especially ITER) is control or complete elimination of edge localized modes (ELM). One of the most successful approaches is applying externally created resonant magnetic perturbations (RMP) onthe equilibrium field. Recent RMP experiments on DIII-D and other devices have shown complete elimination of ELMs. This makes the technique very promising, but at the same time little is known about the effects of RMP operation on confined fast ions.Collective Thomson scattering (CTS) diagnostic is a sensitive instrument for temporally and spatially resolved measurements of the 1D fast ion velocity distribution function. Probe radiation is launched into the plasma and are scattered on plasma fluctuations. The scattered signal is detected by a multi-channel radiometer. A CTS diagnostic is installed on TEXTOR, while it is also equipped with a dynamic ergodic divertor (DED) which can be used to produce RMPs.This set of experimental tools provides a unique opportunity to study the influence of RMP on fast ion behaviour. Here we discuss fast ion measurements which have been done in the core and the ergodic regions of the plasma with different resolved pitch angles, running DED at different currents. Slowing-down effects are used to investigate how fast-ion confinement is affected by enhanced radial transport induced by the RMP.

190 PP2P Detection of low frequency electrostatic waves and turbulence in the ionospheric E-region by instrumented rockets

By H. Sato1, and

H. L. P´ecseli1, J. Trulsen2

1University of Oslo, Department of Physics, Box 1048 Blindern, N-0316 Oslo, Norway,2 University of Oslo, Institute of Theo- retical Astrophysics, Box 1029 Blindern, N-0315 Oslo, Norway Data from density fluctuations as well as fluctuating potential-differences between four probes are available. The direction and speed of propagation of the waves were obtained. The observations are consistent with expectations for the saturated turbulent stage of electrostatic Farley-Buneman waves excited when a steady state electric field component perpendicular to the geomagnetic field exceeds a certain threshold value, so that the relative Hall-drift between the electron and ion components becomes larger than the ion-acoustic speed. This particular type of instability is interesting also because it gives a direct coupling between the large scale electric field imposed in the polar-cap ionosphere and the small scale dynamics. This coupling does not involve the intermediate scales. For these electrostatic waves we can use the electric field vector (being parallel to the wave-vector) as an indicator for the instantaneous direction of propagation. For the long-wave component (wavelengths much longer than the probe separations) we make a statistical analysis of the time and altitude variation of the directions of propagation, obtaining indications for a strong intermittency of these variations.

191 PP3P Langmuir waves in a colisionless plasma: nonlinear models.

By M. I. Ulriksen1 and

H.L.P´ecseli1

1 Department of Physics, University of Oslo, Norway Waves are an inherent property of plasmas. They are important for explaining phenomena in various ﬁelds such as ionospheric physics, astrophysics and industrial plasmas [1]. Most of these phenomena can be addressed using the ﬂuid plasma model, in which only the macroscopic plasma properties are considered. One of the most fundamental plasma waves is the Langmuir wave. A generalized model for the Langmuir waves that also includes ion dynamics is referred to as the Zakharov- Kuznetsov model [2]. In this work we present a systematic generalization of the Langmuir waves in unmagnetized plasmas. We start with the linear analysis for homogeneous plasma, the problem is further generalized by including nonhomogenous plasma and nonlinear wave phenomena. Finally we present the techniques for generalization of the Zakharov-Kuznetsov model by including the Landau damping, with the reference problem of a three wave interaction. Our analytical studies are supported by numerical analysis. [1] D. G. Swanson, Plasma Waves, CRC Press, 2003. [2] B. K. Shivamoggi, Introduction to Nonlinear Fluid-Plasma Waves, Kluwer AP, Dortrecht, 1988.

192 PP4P Least square methods accounting for nuisance parameters for collective Thomson scattering

By M. Salewski and

H. Bindslev V. Furtula S.B. Korsholm F. Leipold F. Meo P.K. Michelsen D. Moseev S.K. Nielsen M. Stejner

Risø National Laboratory for Sustainable Energy, Technical University of Denmark. Collective Thomson scattering (CTS) is a many-sided diagnostic for determining several parameters of magnetically confined fusion plasmas. Among these are the fast ion density resolved in time, space, and velocity, the ratio of fuel ions, or the (toroidal or poloidal) bulk ion drift velocities. However, CTS measurements also depend on parameters which are not parameters of direct interest: the nuisance parameters such as the electron temperature, impurities in the plasma, the local magnetic field etc. These may or may not be diagnosed by other measurements, but always have finite uncertainty. This uncertainty in nuisance parameters limits the accuracy with which parameters of interest can be determined. In CTS experiments, one measures the spectral power density of scattered radiation resolved in a set of channels. From these measurements and from prior estimates of the nuisance parameters, the parameters of interest are inferred. We fit the measured data through a complex and computationally expensive forward model of CTS by a least square method as maximum likelihood estimator but do account for uncertainties in nuisance parameters. The prior estimates of the nuisance parameters and the CTS measurements are combined to give the posterior estimate of the parameters of interest through Baye’s rule.

193 PP5P Long-Range Correlations in Turbulent Fusion Plasmas

By Mathias Hoﬀmann and

Jens Madsen Volker Naulin Anders H. Nielsen Jens J. Rasmussen

Association EURATOM - Risø DTU, Risø National Laboratory for Sustainable Energy, Technical University of Denmark, P.O. Box 49, DK-4000 Roskilde, Denmark In the plasma of a thermonuclear fusion reactor a variety of physical processes occur. The turbulence in the edge of the plasma is of specifc relevance, because it is responsible for mass and energy losses. High levels of losses do not only reduce the efficiency of the device, but can in extreme cases also damage the plasma facing components. For engineering purposes the probability of the occurence of extreme transport events has to be known. Thus a deeper understanding of the statistical properties of the turbulence is essential. Experiments have shown that plasma edge turbulence is strongly intermittend and the corresponding fluctuations are self-similar. Thus fusion plasma shows memory-effects and long-range correlations (persistence) in space and time, which lead to anomalous diffusion across the magnetic field. In this work, a characteristic property of the plasma turbulence, the Hurst parameter, a suitable measure of persistence in time series, is studied by a number of scale- invariant statistical methods (structure functions, scaled window variance method, spectral behavior). A comparison between these different algorithms is made. Data taken from a Langmuir-probe measurement in the edge of the world’s largest nuclear fusion research facility, the Joint European Torus (JET), and from simulations of an interchange model (ESEL-code) are analyzed and compared. Langmuir-probes are heat-resistant conductors and measure, in the present case, the ion saturation current in the plasma edge. This current is related to the density and the square root of the temperature of the plasma. The results reveal that the Hurst parameter depends systematically on the probe position with reference to the plasma surface by with typical values in the range 0.5 to 0.8.

194 PP6P mm-Wave Technology for the collective Thomson scattering diagnostic

By Vedran Furtula and

P.K. Michelsen, H. Bindslev, S.B. Korsholm, F. Leipold, M. Salewski, F. Meo, D. Moseev, S.K. Nielsen, M. Stejner

1 Risø DTU, Technical University of Denmark In a fusion plasma, highly energetic particles - like fusion born alphas - carry a large fraction of the free energy, despite having a relatively low density. These fast ions will therefore be important for the overall plasma dynamics and instabilities studies. Therefore, it is essential to develop diagnostics to reveal the dynamics of the fast ions. Through numerous experiments researchers have demonstrated that mm-wave based collective Thomson scattering (CTS) is a reliable way of extracting the desired data from the plasma. The fundamental idea behind the CTS diagnostic is that powerful mm-waves (105 GHz)generated by gyrotrons (100 kW) are scattered by microscopic fluctuations in the plasma caused by the dynamics of the fast ions. The scattered radiation is detected by a set of quasi-optical mirrors at the tokamak walls and the wave information is guided through many meters of overmoded waveguides towards a CTS radiometer. In the radiometer the wave information is first converted down to an intermediate frequency (IF, 4-15 GHz) signal and then to a digital signal where all the necessary signal processing is done using a computer. In our CTS system, the wave information is down-converted using a heterodyne system where the radio frequency (RF) signal (100-110 GHz) is converted to IF by mixing with an local oscillator (LO, 95 GHz) that is close enough in frequency to the detected signal. Since the input signal is very small, low noise amplifiers are required components in the IF line together with the narrowband bandpass filters that determine the spectral resolution of the system. The conversion to a discrete signal is done by a coaxial detector diode that converts power to a voltage signal aquired by the ADC. This poster will overview the principle of the CTS receivers designed and produced at Risø DTU.

195 KF1P Morphology and solar cell performance of thin-ﬁlms of polyﬂuorene:fullerene blends

By Ana Soﬁa Anselmo1 and

Krister Svensson1, Jan van Stam1, Ellen Moons1, Lars Lindgren2, Mats Andersson2, Jakub Rysz3, Andrzej Budkowski3, Andrzej Bernasik4, Ulrich H¨ormann5, Julia Wagner5, Andreas Opitz5, Wolfgang Br¨utting5.

196 KF2P How to calibrate optical tweezers in viscoelastic media

By Kirstine Berg-Sørensen1 and

Mario Fischer1 Andrew C Richardson2 S. Nader S. Reihani3 Lene Oddershede2

1 Department of Physics, Technical University of Denmark, Kgs Lyngby, Denmark2 Niels Bohr Institute, University of Copen- hagen, Denmark3 Institute for Advanced Studies in Basic Science, Zanjan, Iran

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