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26th SYMPOSIUM PLASMA PHYSICS & RADIATION TECHNOLOGY Dutch Physical Society Section Plasma and Gas Discharge Physics Nederlandse Natuurkundige Vereniging March 11 & 12, 2014 CongresHotel De Werelt - Lunteren This symposium is organized by the board of the Section Plasma- and Gas Discharge Physics of the Dutch Physical Society. Members of the organizing committee Jos Suijker Marcel Simor Tony Donné Gerard van Rooij Klaus Boller Maarten van Kampen Job Beckers Edgar Vredenbregt Srinath Ponduri Clazien Saris Philips TNO Science & Industry FOM DIFFER & Eindhoven University of Technology FOM DIFFER Twente University ASML Eindhoven University of Technology Eindhoven University of Technology Eindhoven University of Technology Eindhoven University of Technology 26th SYMPOSIUM PLASMA PHYSICS & RADIATION TECHNOLOGY Dutch Physical Society Section Plasma and Gas Discharge Physics Programme & Abstracts March 11 & 12, 2014 CongresHotel De Werelt - Lunteren General Information Address The address of the CongresHotel De Werelt is: Westhofflaan 2, 6741 KH Lunteren Telephone: 0318-484641, e-mail: [email protected]. The route to the conference center is signposted in Lunteren. On http://congrescentrum.com/en/de-werelt-lunteren/routedescription-de-werelt you will find a route description to the conference center. If you have any questions about the conference, please contact: Clazien Saris, telephone: 040-2472716, e-mail: [email protected] How to reach Lunteren? Lunteren has its own railway station, which can be reached from the directions Amersfoort (Utrecht) and Ede-Wageningen. You can find the train time tables on: www.ns.nl/reisinfo. The conference center is a 10 to 15 minute walk away from the station. Call 0318-484555 for a taxi. Payment The approximate cost of the attendance of the symposium amounts to A C100,- (one day, NNV-member), A C120,- (one day, non-NNV-member), A C160,- (two days, NNV member), and A C200,- (two days, non-NNV member). The fee is to be paid after the meeting on the basis of an invoice sent to you personally or to your institute/company. Payment by cash at the registration is not possible. Registration deadline is February 28, 2014. If you cancel after this date, you will still be charged the full fee. If you register after this date, accommodation cannot be guaranteed. Summaries The summaries of all the contributions are coded as follows: M: O: A/B: main presentations of 40 minutes by invited speakers. contributions selected for oral presentation (20 minutes). contributions selected for poster presentation. Each oral presentation includes at least five minutes for discussion. There will also be an opportunity to present the orals as posters. Please bear in mind that many people in your audience will be students and colleagues from other disciplines. Poster presentation The size of the poster is 841 x 1189 mm (A-0). The poster session will take place on Tuesday afternoon and Wednesday morning. You are kindly requested to stay with your poster for as long as possible. Poster prize and Oral prize Once again, there will be a prize for the best poster and for the best oral. The jury for the poster and oral prizes consists of members of the organizing committee. Jij en de Nederlandse Natuurkundige Vereniging? De Nederlandse Natuurkundige Vereniging is de beroepsvereniging voor fysici in Nederland en bestaat ruim 90 jaar. De NNV is er voor studenten en voor fysici werkzaam in onderwijs, onderzoek of bedrijfsleven. De NNV wil bijdragen aan excellente wetenschapsbeoefening en aan een sterke kenniseconomie. Meld je ook aan als lid van de NNV via www.nnv.nl. Als NNV-lid ontvang je maandelijks het Nederlands Tijdschrift voor Natuurkunde (NTvN). Zo blijf je op de hoogte van ontwikkelingen in natuurkundig Nederland. NNV-leden kunnen zich (gratis) aanmelden als lid van de sectie Plasma- & Gasontladingsfysica. Het jaarlijkse NNV-symposium FYSICA 2014 vindt plaats op dinsdag 1 april op Universiteit Leiden. Komt allen! Kijk voor meer informatie op: www.nnv.nl www.ntvn.nl www.fysica.nl At the physics frontier Doing research for the next four years? Working on a subject you like in any field of physics? Just out of curiosity or motivated by a technological problem? In an outstanding Dutch research group? Or even in a laboratory abroad for some time? And attending several international congresses? You can do all of this as a PhD student at FOM. At FOM, PhD students are called ’researchers in training’ (onderzoekers in opleiding), oio for short in Dutch. Usually oio positions at FOM are attached to research projects for which university professors have won a grant from FOM. These professors look for candidates to fill their oio positions. Make sure they know that you would like to work on a specific project or in a specific field. Build your own network, find out where you would like to do research and let the people in charge know you are there! More information about FOM’s research programmes, its conditions of employment and current vacancies can be found on our website www.fom.nl. If you would like to talk to somebody about the opportunities then please call our Personnel Department, telephone +31 30 600 12 62. Foundation for Fundamental Research on Matter | P.O. Box 3021 | 3502 GA Utrecht | The Netherlands | www.fom.nl How do you print 20 nm structures using 193 nm light waves? Join ASML as a Physics Engineer to find out. We bring together the most creative minds to develop lithography machines that are key to producing cheaper, faster, more energy-efficient microchips. Our machines image billions of structures in a few seconds. And we intend to be imaging even more billions, because our latest technology will create microchip features of just 20 nm, using light waves of 193 nm. That’s like drawing an extremely fine line using an oversized marker. So we need talented Physicists who can design, model and manipulate at nanometer levels. If you’re up for it, you’ll be part of a multidisciplinary team with plenty of freedom to experiment and learn new skills. www.asml.com/careers /ASML @ASMLcompany PROGRAMME & ABSTRACTS Programme Tuesday March 11 – 2014 09.45 – 10.20 10.20 – 10.30 Registration and coffee Welcome (Africa room) Theory and Modelling (session chair Ute Ebert) 10.30 – 10.35 Intro 10.35 – 11.15 M1 11.15 – 11.35 O1 11.35 – 11.55 O2 11.55 – 12.15 O3 Jonathan Citrin / FOM Differ / CEA Cadarache Simulation and reality: recent advances in tokamak turbulence modelling Enrico Camporeale / CWI Amsterdam Linear mode conversion between cold plasma waves mediated by a density in homogeneity in the ionosphere Fabien Jaulmes / FOM DIFFER Nieuwegein Consequences of the sawtooth reconnection on fast ions in the ASDEX Upgrade tokamak Christoph Köhn / CWI Amsterdam Energy resolved positron and hadron spectrum produced by a negative stepped lightning leader 12.30 – 13.45 Lunch 13.45 – 14.10 14.10 – 15.45 Single slide show (Africa room) Poster session 1: A1 - A24 (America room) Coffee and tea during session Diagnostics (session chair Roger Jaspers) 15.45 – 15.50 Intro 15.50 – 16.30 M2 16.30 – 16.50 O4 16.50 – 17.10 O5 17.10 – 17.30 O6 18.15 – 20.00 Bert Bastiaens / University Twente Spatio-temporal mapping of species in plasmas for pulsed laser deposition Bart Klarenaar / Eindhoven University of Technology Rotational Raman scattering in atmospheric pressure DBD’s in CO₂ Dirk Trienekens / Eindhoven University of Technology Creeping sparks Christopher Vasko / Eindhoven University of Technology Hydrogen peroxide production in micro dielectric barrier discharges for in-situ applications Dinner Evening Lecture (session chair Marco de Baar) 20.00 – 21.00 M3 Bart de Smit / University Leiden Escher and the Droste effect Programme Wednesday March 12 – 2014 08.00 – 09.00 Breakfast Extreme Plasmas (session chair Seth Brussaard) 09.00 – 09.05 Intro 09.05 – 09.45 M4 09.45 – 10.05 O7 10.05 – 10.25 O8 10.25 – 10.45 O9 Jérôme Faure / Lab. For Applied Optics, Palaiseau Acceleration of femtosecond electron bunches using ultrashort and ultraintense laser pulses Siew Jean Goh / University Twente Coherent control of high harmonic generation in a large-volume capillary for seeding of free-electron lasers Daniël Brunner / ASML Veldhoven Physics at the heart of the ASML scanner Gijs ten Haaf / Eindhoven University of Technology Spot size predictions of a focused ion beam based on laser cooling 10.45 – 11.10 11.10 – 12.45 Single slide show (Africa room) Poster session 2: B1 – B24 (America room) Coffee and tea during session 13.00 -14.00 Lunch Applications (session chair Klaus Boller) 14.00 – 14.05 Intro 14.05 – 14.45 M5 14.45 – 15.05 O10 15.05 – 15.25 O11 15.25 – 15.45 O12 15.45 – 16.00 Svetlana Ratynskaia / KTH Stockholm / chair EPS Conference Dust-plasma interaction; experiments and modelling Irem Tanyeli / FOM DIFFER Nieuwegein Nanostructuring of metal surfaces by high fluxes of low energy He ion irradiation Pavlo Kochkin / Eindhoven University of Technology X-ray emission generated by streamer encouter Anna Chvyreva / Eindhoven University of Technology Experimental investigation of surface streamers in SF₆ – N₂ mixtures Presentation NVV prizes for Best Poster 2014 en Best Oral 2014 Summary poster session 1 / March 11 / 2014 A1 The Occurrence and Damage of Arcing on Fuzzy Tungsten, and possible Implications for ITER A2 Implementation of an alkali metal seeder for plasma temperature control A3 Optimal ratio of anode and cathode radius in a Hirsch-Farnsworth fusor A4 Radially resolved bifurcation theory for L-H mode transition dynamics A5 Microwave detection of instabilities in fusion plasmas A6 Investigation of the inception cloud of positive streamers in nitrogen-oxygen mixture A7 Formation dynamics of UV and EUV induced hydrogen plasma A8 Real-time tokamak simulations for plasma state reconstruction with minimal diagnostics A9 Laser Collisional Induced Fluorescence for validation of an argon Collisional Radiative Mode A10 Laser Scattering on a Solar Fuels Microwave Discharge A11 Correction of the Spectral Calibration of the JET Core LIDAR Thomson Scattering Diagnostic Using Ray Tracing A12 Plasma particle lofting A13 Characterization of a dielectric barrier surface discharge for medical applications A14 Plasma driven, water assisted CO2 methanation A15 Plasma accumulation effects in Extreme Ultra-Violet generated plasmas A16 Application of multicomponent diffusion by solving the Stefan Maxwell equations A17 Benchmark of simulation code MSESIM for performance study of future MSE diagnostic on KSTAR A18 Control over Rydberg atoms by Electromagnetically Induced Transparency A19 Fluid models and the reality A20 Plasma oxidation as key mechanism for stoichiometry in Pulsed Laser Deposition grown oxide films A21 Surface modifications and deuterium retention of W and WO3 thin films after high-flux deuterium plasma exposure A22 Chemical Energy Storage based on CO2 Plasmolysis A23 LEONA: High Altitude Plasmas and Thunderstorm High Energy Emissions in Latin America Summary poster session 2 / March 12 / 2014 B1 Nanosecond Pulsed Streamer Corona Plasma with a DC Bias: Energy and Ozone Measurements B2 Oxidation and stoichiometry studies of pulsed laser ablation plasmas B3 Diagnostic studies on CO2 dissociation in atmospheric pressure plasmas B4 Collisional particle in cell simulations of the TU/e fusor plasma B5 Characterisation of a kHz pulsed FE-DBD for chronic wound treatment B6 Formation and dynamics of the atmospheric pressure high current diffuse dielectric barrier discharge between cylindrical electrodes in PECVD reactor B7 Entrainment of impurity ions in high-density edge plasmas B8 Size and density redistribution by a rod obstacle in a cluster jet for quasiphase matching of high harmonic generation B9 Streamer discharge interaction with water droplets B10 Spectroscopic study of the spark for Spark-OES B11 Intense femtosecond laser pulse interaction with nano-clusters for ultrashort neutron pulses B12 Cohesion of neutral and charged particles in subsonic expanding thermal Argon plasmas B13 Plasma and nanoparticles in cylindrical microwave cavities B14 Removal of nox in indoor air by combining pulsed dielectric barrier discharges with TiO2 catalysts B15 Potential profile measurements on the TU/e Fusor through stark effects using LIF diagnostics B16 Laser-cooling simulations of the performance of an ultra-cold ion beam for FIB B17 A numerical model for recovery rate analysis of supercritical fluid B18 Coherence length of an ultracold electron source determined from diffraction patterns B19 Fluid modelling of CO2 dielectric barrier discharge for solar fuels B20 Laser-cooling of a Rb atomic beam: Towards a nanometer spot size FIB B21 Burning Dusty Plasma B22 Creeping sparks B23 FTIR Spectroscopy for description of surface processes in biomedical applications using atmospheric pressure plasma jets B24 Effect of high-flux H plasma exposure on tungsten surface damage during transient heat loads M1 Recent advances in tokamak turbulence modelling J. Citrin1,4 , F. Jenko2 , P. Mantica3 , D. Told2 , C. Bourdelle4 , J. Garcia4 , J.W. Haverkort5,1 , G.M.D. Hogeweij1 , T. Johnson6 , and M.J. Pueschel7 1 FOM Institute DIFFERDutch Institute for Fundamental Energy Research, Association EURATOM-FOM, Trilateral Euregio Cluster, PO Box 1207, 3430 BE Nieuwegein, The Netherlands 2 Max Planck Institute for Plasma Physics, EURATOM Association, 85748 Garching, Germany 3 Istituto di Fisica del Plasma P. Caldirola, Associazione Euratom-ENEA-CNR, Milano, Italy 4 CEA, IRFM, F-13108 Saint Paul Lez Durance, France 5 Centrum Wiskunde and Informatica (CWI), PO Box 94079, 1090 GB Amsterdam, Netherlands 6 Euratom-VR Association, EES, KTH, Stockholm, Sweden 7 University of Wisconsin-Madison, Madison, Wisconsin 53706, USA A grand challenge in magnetic fusion research is quantitative prediction of the energy and particle fluxes which arise from plasma turbulence. This is vital for the interpretation of present-day experiments and extrapolation to future machines. The highest fidelity predictions are achieved by direct numerical simulation of the nonlinear system by massively parallel codes run on high performance supercomputers. Due to advances in supercomputing capabilities, agreement between measured quantities and code predictions have become more routine, although many challenges still remain. In this talk, following a primer on the background physics and tools applied, this progress is illustrated by reviewing recent studies where direct numerical simulation has uncovered a beneficial effect, explaining a hitherto not understood improved energy confinement regime in experiments at the JET tokamak. M2 Unraveling transient composition changes in plasmas for pulsed laser deposition 1 B. Bastiaens1 Laser Physics and Nonlinear Optics group, University of Twente, the Netherlands The generation of coherent light pulses over wide spectral ranges, especially through nonlinear frequency conversion into to the UV, can provide powerful diagnostics for transient plasmas. In particular, these methods are suited to follow the propagation of plasma constituents on the nanosecond time scale and with micrometer resolution, while simultaneously unravel chemical processes. After excitation with coherent laser(like) light pulses, the plasma particles decay through collisions and emission of photons. From the fluorescence (Laser Induced Fluorescence), the absolute particle densities and velocity (temperature) can be determined. In contrast to emission spectroscopy which only probes excited states, Laser Induced Fluorescence (LIF) provides direct access to the ground state populations of the plasma constituents. Monitoring plasmas for Pulsed Laser Deposition with LIF can be the key to a much deepened understanding of thin film growth with atomic precision. We have developed a LIF spectroscopic setup that allows us to perform a spatio-temporal mapping of the species in the plasma plume propagating towards the substrate. This makes it possible to relate the plasma composition to the growth of thin films on the substrate. In this presentation, I will discuss the concept of LIF and present recent results of LIF studies on plasmas relevant for the growth of thin films and multilayers of complex oxides. M3 Escher and the Droste effect 1 B. de Smit1,4 University Leiden, The Netherlands One of M.C. Escher’s most intriguing works depicts a man standing in a gallery who looks at a print of a city that contains the building that he is standing in himself. This picture, with the title Print Gallery, contains a mysterious white hole in the middle. In a paper of Hendrik Lenstra and the speaker in the Notices of the American Mathematical Society it is shown that well known mathematical results about elliptic curves imply that what Escher was trying to achieve in this work has a unique mathematical solution. This discovery opened up the way to filling the void in the print. With help from artists and computer scientists a completion of the picture was constructed at the Universiteit Leiden. The white hole turns out to contain the entire image on a smaller scale, which in the Dutch language is known as the Droste effect, after the Dutch chocolate maker Droste. In the talk the mathematics behind Escher’s print and the process of filling the hole will be explained and visualized with computer animations. M4 Acceleration of femtosecond electron bunches using ultrashort and ultraintense laser pulses 1 Jerome FAURE1 Laboratoire dOptique Applique, ENSTA-CNRS-Ecole Polytechnique, Palaiseau, 91761, France The acceleration of electron beams in plasma wakefields has been an extremely active field of research in the past ten years. Tremendous progress have been accomplished, with for example the acceleration of monoenergetic beams at the GeV level in centimeter lengths, or the controlled injection of electrons. In laser-plasma-based accelerators, an intense laser pulse drives a large electric field (the wakefield) which can accelerate electrons to high energies in distances much shorter than in conventional accelerators. These high acceleration gradients, of a few hundreds of gigavolts per meter, hold the promise of compact high-energy particle accelerators. The produced electron bunches have unique properties: their bunch duration can be as short as a few femtoseconds. This makes laser-plasma accelerators particularly attractive for the development of novel applications such as imaging on the femtosecond time scale and atomic spatial scale. In this lecture, we will review the main physical mechanisms that lead to the production and acceleration of relativistic electron beams: non linear laser pulse propagation, relativistic self-focusing, wake field generation, electron injection in plasma waves. The concepts will be illustrated using recent experimental results, providing an overview of the state of the art. Finally, we will introduce our recent project FEMTOELEC, whose goal is to produce femtosecond electron beams at MeV energies in order to probe atomic motion in solids using ultrafast electron diffraction. M5 Dust-plasma interaction; experiments and modelling S. Ratynskaia; Space and Plasma Physics Division, KTH Royal Institute of Technology, Stockholm, SE-100 44, Sweden Dust particles of various nature and origin are found in a great variety of space and laboratory plasmas, where they can acquire large charges and substantially modify basic plasma properties as well as introduce new phenomena. The physics of dust in plasma environments is of relevance for space/astrophysics as well as fusion and plasma processing technology. Dust grains, when embedded in plasmas, get charged by collecting electron and ion fluxes from the ambient. Their equilibrium charge is set up by the balance between plasma currents flowing to the grain and currents emitted by the grain (e.g. photoemission, secondary electron emission, thermionic emission, field-assisted emission). The charged grains effectively interact not only with the external electromagnetic fields by also with the self-consistent plasma fields and hence are also subject to drag forces due to momentum exchange with the plasma species and mainly with ions. For relatively low dust densities, the self-field of a test grain is completely screened by the plasma before it affects its neighboring grains. This implies that collective dust effects and the influence of dust in plasma collective effects are negligible and hence a single particle description of dust can be appropriate. Such conditions are met in some astrophysical/space environments and also in the scrape-off layer (SOL) of fusion devices. On the other hand for environments with dense dust clouds, the dust grains have to to be treated as a distinct plasma species. Here the emphasis is on the difference from multi-component plasmas where dust is treated as a massive species as in contrast to the regimes where the effects of absorption of plasma particles on the dust surfaces and dust charge fluctuations are of importance and cannot be neglected. Classifying by the dust density regimes we will briefly outline the relevant models and exemplify such regimes by the experiments in various plasma environments. O1 Linear mode conversion between cold plasma waves mediated by a density inhomogeneity in the ionosphere 1 Enrico Camporeale1 , Gian Luca Delzanno2 , and Patrick Colestock2 Multiscale Dynamics, Centrum Wiskunde & Informatica, Amsterdam, 1098 XG, Netherlands 2 Los Alamos National Laboratory, Los Alamos, 87545 USA An enhancement of wave activity has been often observed by rockets and satellites in the presence of density depletions (striations) in the upper ionosphere. When a wave packet composed of short wavelength modes travelling in an homogeneous plasma region encounters such an inhomogeneity, it can resonantly excite long wavelength waves via a linear mechanism known as mode conversion. We address here the process of linear mode conversion between lower hybrid and whistler waves, mediated by a density striation, using a scalar-field formalism (in the limit of cold plasma linear theory) which we solve numerically. We show that the mode conversion can effectively transfer a large amount of energy from the short to the long wavelength modes, and we present a general criterion for the width of the striation that, if fulfilled, maximizes the conversion efficiency. This process is interesting in a space weather perspective because whistler waves can affect the lifetime of energetic electrons trapped in the geomagnetic field. O2 Consequences of the sawtooth reconnection on fast ions in the ASDEX Upgrade tokamak F. Jaulmes1 , E. Westerhof1 , B. Geiger2 , and ASDEX Upgrade team2 1 FOM Institute DIFFER, Nieuwegein, The Netherlands 2 Max Planck Institute for Plasma Physics, Garching, Germany This contribution presents an illustration of modelling of energetic ions for the purpose of preparing and analysing an upcoming experimental campaign on the AUG experiment. We have built a time-dependent electromagnetic model of a sawtooth collapse using the approxach of [1]. A complete description of the fast ions behaviour during the complete sawtooth reconnection in a tokamak is obtained by a 3D orbit-following numerical code (as was introduced in [2]). Our code, EBdyna go, is applied to the specific geometry of ASDEX. The trajectories of the ions are described by a complete gyro-orbit integration. Modelling a complete panel of energies and pitch angles, the differentiation expected between fast D and He ions is detailed. The analysis is focussing on the validation possibilities offered by the experiment. In addition, suggestions are given on the optimization of the sawtooth cycle in ASDEX, in order to optimize the flushing of impurities and minimize fast ions losses. References [1] Ya. I. Kolesnichenko, Yu. V. Yakovenko, Nuclear Fusion (1996), volume 36, p.159, Theory of fast ion transport during sawtooth crashes in tokamaks [2] F. Jaulmes, E Westerhof, H. J. de Blank, submitted to Nuclear Fusion (IAEA 13th TM special issue), Redistribution of fast ions during a sawtooth reconnection O3 Energy resolved positron and hadron spectrum produced by a negative stepped lightning leader 1 Christoph Köhn1 , Ute Ebert1,2 Centrum Wiskunde & Informatica (CWI), P.O. Box 94097, 1090 GB Amsterdam, The Netherlands 2 Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven,The Netherlands Gamma-ray flashes with energies up to 40 MeV and beams of electrons and positrons have been detected by satellites above thunderclouds. It is also reported that a significant number of neutrons can be created by photonuclear reactions of the gamma-rays. We simulate the production of positrons and hadrons with a three dimensional Monte Carlo code where we follow individual photons. The initial energy spectrum of these photons is calculated from a negative stepped lightning leader, a hot plasma channel whose interior is electrically neutral. For this purpose we have calculated the motion of electrons upwards ahead of the leader and the production of photons through Bremsstrahlung. For the photons, we include photoionization, Compton scattering, Rayleigh scattering, electron-positron pair production and photonuclear processes. The last two processes are relevant for photon energies above 1 MeV or 8 MeV, resp. We present the angular distribution and the energy spectrum of positrons and their temporal evolution. We will also present the energy spectra of neutrons and protons at production altitude and show how their energy dissipates. O4 Rotational Raman scattering in atmospheric pressure DBDs in CO2 B.L.M. Klarenaar1 , F. Brehmer1,2 , S. Welzel1,3 , H.J. van der Meiden3 , M.C.M. van de Sanden1,3 , and R. Engeln1 1 Plasma & Materials Processing, Eindhoven University of Technology, Eindhoven, 5600 MB, The Netherlands 2 AFS GmbH, Horgau, 86497, Germany 3 Dutch Institute for Fundamental Energy Research (DIFFER), Nieuwegein, 3430 BE, The Netherlands Renewable energy can be stored for utilization at desired times and locations by producing value-added carbohydrates from CO2 . The most energy costly step in this process is the dissociation of CO2 to CO. A promising route to do this, while keeping investment and running costs low, is by using a dielectric barrier discharge (DBD) operated at atmospheric pressure [1] . In situ rotational Raman spectroscopy is used to measure the gas temperature, which is an important parameter for a better understanding of the chemistry in the discharge. The DBD is designed as a quartz flow-tube in parallel plate configuration with a gap of 3 mm, while the tube directly serves as dielectric barrier. The experiments were carried out using pure CO2 flows in the order of 0.2 to 1.6 slm, with the pressure varying from 200 to 1000 mbar. The plasma power input was typically between 20 and 55 W. This resulted in a range of 460 to 565 K for the gas temperature. Rotational Raman spectroscopy was performed with a Nd:YAG laser in its second harmonic (λ = 532 nm) with pulse intensities in the mJ range at a 10 Hz repetition rate. An ultra-narrow-band Bragg grating filter is used to filter away Rayleigh scattering and stray light. A thermal heating theory [2] , assuming a balance between the power input and heat extraction by the reactor, gives a temperature increase which is similar to our measurements. Furthermore, in the conditions under study, a linear relation is found between the rotational gas temperature and the average temperature of the reactor wall (measured by an IR camera). This relation is used to interpret the measured ozone concentration (ex situ, FTIR) at various power settings. [1] Z. Jiang, T. Xiao, V.L. Kuznetsov, and P.P. Edwards, Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences 368, 3343 (2010). [2] B. Eliasson, M. Hirth, and U. Kogelschatz, Journal of Physics D: Applied Physics 20, 1421 (1987). O5 Creeping sparks D.J.M. Trienekens1 , S. Nijdam1 , T. Christen2 , U.M. Ebert3 , and G.M.W. Kroesen1 1 EPG, Eindhoven University of Technology, Eindhoven, 5600 MB, the Netherlands 2 ABB Switzerland Ltd., Baden-Dätwill, 5405, Switzerland 3 Multiscale Dynamics, CWI, Amsterdam, 1090GB, the Netherlands In gas insulated high voltage devices usually solid insulation materials are also present, e.g., for mechanical support of conductors or as enclosure. Even if the gaseous and solid insulation media themselves have sufficient dielectric strength, electric breakdown may still occur because the gas-solid interfaces are usually weaker. For instance, triple points of metal, gaseous, and solid insulation can be critical with respect to inception, and insulator surfaces facilitate propagation of discharges, which may lead to surface flashover. Sparks creeping along insulator surfaces are well-known, but the underlying fundamental physics is poorly understood. The improvement of (nowadays empirical) design rules of insulation devices for the prevention of surface flashover requires thus a deeper understanding of the associated physics. In this research work, the streamer-like initial phase of sparking will be investigated. A setup was built that enables us to study discharges along the surface of an insulating rod. We use stroboscopic imaging at gating frequencies up to 100 MHz to visualize inception and propagation of the discharge. Results indicate that streamers propagate with an increased velocity along the dielectric surface upon contact. Surface discharges, however, do not appear under all circumstances: for some parameters the discharge avoids the surface. The corresponding parameter window for sticking behavior depends on gas composition, pressure, voltage, and repetition frequency. O6 Hydrogen peroxide production in micro dielectric barrier discharges for in-situ applications C.A. Vasko1 , T. Verreycken1 , D. M. Perez Ferrandez2 , E.M.v. Veldhuizen1 and G.M.W Kroesen1 1 Elementary Processes in Gas Dicharge, Einhoven University of Technology, Eindhoven, 5600 MB, The Netherlands 2 Department of Chemical Engineering and Chemistry , Einhoven University of Technology, Eindhoven, 5600 MB, The Netherlands Reactive species produced in atmospheric pressure plasmas may benefit a wide range of applications. Within the framework of this project, the aim is to provide hydrogen peroxide (H2 O2 ), a strong and green oxidant, for the epoxidation of propene in a chemical catalytic reactor. The gas phase production of H2 O2 with the help of discharges has been reported with varying efficiency from 0.1 g/kWh to 80 g/kWh. Here, atmospheric pressure dielectric barrier discharges operated with humid helium/argon and H2 O2 admixtures are investigated for production H2 O2 . Key parameters are discussed, such as plasma dissipated power, reactor residence time, gas admixture and OH radical density obtained with Laser Induced Flourescence. The challenges of precisely measuring H2 O2 densities may explain the broad range of energy efficiencies reported for similar discharges in literature. O7 Coherent control of high harmonic generation in a large-volume capillary for seeding of free-electron lasers S.J.Goh1 , J.Reinink1 , Y.Tao1 , H.J.M. Bastiaens1 , P.J.M. van der Slot1 ,S.G. Biedron3,4 , M.B. Danailov3 , S.V. Milton3,4 , J. Herek2 , K.J. Boller1 1 Laser Physics and Nonlinear Optics, 2 Optical Sciences, Mesa+ Institute for Nanotechnology, University of Twente, Enschede, The Netherlands 3 FERMI@Elettra, Sincrotrone Trieste S.C.p.A., Basovizza, Trieste, Italy 4 Dept. of Electrical and Computer Engineering, Colorado State University, Fort Collins, Colorado, USA FEL-1 at FERMI@Elettra is a seeded free-electron laser using sub-harmonic seeding to generate soft x-rays down to 10 nm. The current seed laser, a standard solid-state laser followed by frequency quadrupling in nonlinear crystals, has a minimum wavelength of 200 nm. Injecting much shorter seed-laser wavelengths, for which high-harmonic generation (HHG) is of high promise, can shorten the laser output wavelength significantly. However, the minimum seed pulse energy required is not readily available with standard approaches to HHG. To increase the energy available in a particular harmonic for seeding, we use a gas-filled capillary with a large diameter (500 µm), pumped by an 8 mJ, 35 fs Ti:Sapphire laser. A wide capillary allows a large gas volume for HHG, thereby increasing the output energy. We also investigate the coherent control of HHG by shaping the spectral phase of the drive laser using an acousto-optic programmable dispersive filter. Here, we use a learning algorithm with the objective to simultaneously tune and selectively enhance an individual harmonic order. We present first results including pressure dependent harmonic output energy, spectrum and beam stability, as these are important for seeding of FELs. Further, we discuss initial experiments with coherent control that has shown selective enhancement up to a factor of 10. O8 Physics at the heart of the ASML scanner Daniel Brunner and Peter Smorenburg Source Performance and Plasma Technology, ASML, Veldhoven, 5504DR, Netherlands ASML is a world leader in the manufacture of photolithography tools for the semiconductor industry. Next generation lithography tools operating at 13.5 nm wavelength require high power light sources, however, conventional lasers do not exist in this wavelength range. Our EUV source department is developing an EUV light source to fill this gap. The core of our EUV source consists of a laser produced tin plasma. This talk will provide an overview of the physical phenomena occurring in the interaction of a dense plasma with high-power laser pulses. Important processes include ablative hydrodynamic deformation of liquid tin droplets, plasma absorption of electromagnetic radiation, collisional ionization by hot electrons, EUV emission, and plasma expansion. Close simulations ties are kept with the Institute for Spectroscopy RAS (ISAN) which performs both hydrodynamic and plasma simulations to find optimal operation conditions. O9 Spot size predictions of a focused ion beam based on laser cooling G. ten Haaf1 , S.H.W. Wouters1 , S.B. van der Geer2 , P.H.A. Mutsaers1 , O.J. Luiten1 and E.J.D. Vredenbregt1 1 Coherence and Quantum Technology group, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, Netherlands 2 Pulsar Physics, www.pulsar.nl The Atomic Beam Laser Cooled Ion Source (ABLIS) is a new source for focused ion beam instruments, which are used in the semiconductor industry to image and modify structures on the nanometer length scale. The ABLIS employs laser cooling and compression of an atomic beam of rubidium to increase its brightness significantly. By photo-ionization in an accelerator structure, ions are then created and accelerated immediately. The bottleneck for retaining a high brightness is disorder-induced heating: ions, created at random initial positions, heat up due to relaxation of the potential energy associated with these positions. This effect is counteracted by applying an electric field to quickly reduce the ion density. However, since ionization takes place over a finite distance, a larger electric field implies a larger energy spread of the beam and therefore larger chromatic aberrations of the lens system. Here we report on analytical and numerical investigations of the conditions under which the smallest spot sizes can be reached. With particle tracking simulations, a relation was found between the current and the minimum electric field needed to suppress disorder-induced heating. This relation was used to account for chromatic aberration of the lens system. An analytical calculation was performed of the possible spot size of the ABLIS setup, including the finite brightness of the beam and spherical and chromatic aberration of a realistic lens system. The results show that sub-nanometer spot sizes are possible for currents up till 10 pA. The calculation was verified with particle tracking simulations of the whole beam line. O10 Nanostructuring of metal surfaces by high fluxes of low energy He ion irradiation I. Tanyeli1 , L. Marot2 , M.C.M. van de Sanden1 and G. De Temmerman1 1 FOM Institute DIFFER, Dutch Institute For Fundamental Energy Research, Nieuwegein, The Netherlands 2 Dept of Physics, University of Basel, Switzerland High energy (in the range of keV) ion bombardment is known to induce micro-structural changes on metal surfaces. However, recent studies showed that radiation induced surface modifications can be obtained even with low energy (< 50 eV) helium ion irradiation [1,2]. Fibreform nanostructure formation has been observed on tungsten and molybdenum surfaces after exposure to high fluxes of low energy helium ions [2]. The growth process of these nanostructures is identified as a self-growth process of He bubbles. In this study, we investigate the behavior of various metal surfaces such as, iron, titanium, aluminum and copper, under low energy He ion irradiation as a function of surface temperature, plasma exposure time and He ion flux. Different surface morphologies are observed for these metal surfaces. A controlled nanostructure formation on iron surface is obtained consistently with the experiments on tungsten and molybdenum. Nanostructure growth kinetics shows dependency on surface temperature and plasma exposure time. [1] K. Tokunaga, M. J. Baldwin, R. P. Doerner, N. Noda, Y. Kubota, N. Yoshida, T. Sogabe, T. Kato, and B. Schedler, J. Nucl. Mater. 337−339, 887 (2005). [2] G. De Temmerman, et al., JVSTA, 30 (2012) O11 X-ray emission generated by streamer encounter 1 P Kochkin1 , A P J van Deursen1 , and Ute Ebert2 Electrical Engineering, Eindhoven University of Technology, Eindhoven, 5600 MB, The Netherlands 2 Centre for Mathematics and Computer Science (CWI), Amsterdam, 1090 GB, The Netherlands Pulses of x-rays emitted by natural lightning are one of the most intriguing among unsolved problem in physics of lightning. They have been detected from both - natural and rocket-triggered lightning. In natural lightning x-rays were detected during stepped leader process and later were associated with a single step. In triggered lighting x-rays were found to be originated from a tip of a dart leader that also possesses stepping propagation mechanism. Therefore, stepping mechanism is the key to understanding the x-ray pulses generated by lightning. Unfortunately, leader stepping mechanism itself is far from well understood. Negative long laboratory discharges also develop through a formation of a space stem/leader steps and they also generate bursts of x-ray radiation. In this study we investigate the development of a long negative laboratory spark in particular focusing on its x-ray emission. A 2 MV Marx generator delivers high-voltage standard lightning pulse with 1.2/50 µs rise/fall time to a spark gap with conical electrodes. The distance between cone tips was varied between 1 m and 1.75 m. An upper voltage limit is set to about 1 MV level. The voltage is measured by capacitive high-voltage divider. Two Pearson 7427 current probes determine the currents through high-voltage and grounded electrodes. Two LaBr3 scintillator detectors were mounted in EMC-cabinets and recorded the x-rays. Picos4 Stanford Optics camera with intensified CCD is placed in 4 m distance from the spark gap and directed perpendicular to the spark plane. The camera allows us to make ns-fast images of pre-breakdown phenomena in controllable time. We discovered new details of space stem/leader formation and development in long laboratory sparks. The connection moment of positive part of the space stem/leader to negative high-voltage is accompanied by intense x-ray emission. Taking into account our previous study on positive discharge, we conclude that encounter between positive and negative streamers is the most likely mechanism responsible for the x-rays. O12 Experimental Investigation of Surface Streamers in SF6 - N2 Mixtures 1 A. Chvyreva1 , A.J.M. Pemen1 Departement of Electrical Engineering, Eindhoven University of Technology, 5612AZ, The Netherlands Sulfur hexafluoride (SF6 ) is commonly used as a gaseous dielectric in high-voltage equipment due to its excellent insulating properties and chemical stability. However it significantly contributes to the greenhouse effect, and can under certain circumstances (after a discharge event) be poisonous for persons. Therefore, SF6 -nitrogen mixtures are taken into consideration, in order to decrease the negative effects, while still keeping the required dielectric properties. This work presents experiments on streamer discharges in mixtures of SF6 with nitrogen under different experimental conditions. All experiments were performed in a specially designed vessel that allowed setting up and maintaining the parameters of gaseous environment. Discharges under investigation were streamers, propagating along the surface of an epoxy-resin dielectric. They originate on the gas-insulator interface without any contact with electrodes, and are nowadays the major cause of failure of various high voltage technologies. In the present work the voltage of discharge inception was determined for different amounts of SF6 . It was shown, that the inception voltage increases rapidly starting at very small admixtures of SF6 ( 5%), and continues to increase at a lower rate with the further increase of SF6 percentage. The voltage of streamer inception also increases with the increase of gas pressure (in these experiments the concentration of SF6 was kept constant). The velocity of discharge propagation was estimated from the analysis of time-resolved discharge current measurements. The rise-time of the current increased significantly with the addition of SF6 , moreover, for high concentrations of the above the majority of the discharges were originating as leaders, skipping the streamer phase. The fall time of the current behaves in a similar way, thus the total duration of the discharge decreases almost by a factor of 10 (from tens to several nanoseconds for pure nitrogen and 5% SF6 admixture respectively). The main conclusion of the present study is that discharge behavior changes significantly already with a small admixture of SF6 to nitrogen, which gives the possibilities for organizing gas mixtures possessing the positive features of highly electronegative gases, while at the same time significantly decreasing the dangerous influence on the atmosphere. A1 The Occurrence and Damage of Arcing on Fuzzy Tungsten, and Possible Implications for ITER D.U.B. Aussems1 , D. Nishijima2 , C. Brandt2 , G. De Temmerman3 , and N.J. Lopes Cardozo1 1 Science and Tech. of Nucl. Fusion, TU/e, Eindhoven, 5612 AZ, NL 2 CER, UC San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0417, USA 3 DIFFER, Nieuwegein, NL-3430 BE, the Netherlands This research investigated whether unipolar arcing in the divertor of fusion reactors is a potential cause for enhanced wear of the divertor. Unipolar arcing is a discharge between plasma and wall and can be ignited by transient heat loads on the divertor such as Edge-Localized Modes (ELMs). Recent work shows that fuzzy nanostructures develop on the surface of tungsten under the influence of helium and that the incidence of arcing is facilitated by their presence. Unipolar arcs were investigated in the linear-plasma simulator PISCES-A at UCSD under fusion relevant conditions by simulating the transient heat load by a pulsed Nd:YAG laser on a biased fuzzy tungsten target under helium plasma exposure. It was found that 1 µm of fuzz growth is sufficient to initiate arcing, mainly depending on the bias voltage and to a lesser degree, on the surface temperature. Based on these findings, it was argued that if fuzz grows on the ITER divertor, the occurrence of arcing cannot be excluded during ELMs. The average mass loss rate induced by the arc was determined from mass measurements and found to be consistent with the value estimated from the arc current. Based on the mass loss rate the erosion rate of a local arc spot was estimated to be several orders of magnitude higher than the physical sputtering rate. The average arc track depth was estimated by using the measured mass loss and damaged surface area and was found to be one tenth of the fuzzy layer thickness. The conclusion of this scoping study is therefore that arcing in the ITER divertor potentially is an important cause for surface damage and impurity source. Hence it needs to be investigated more comprehensively, and mitigation measures must be developed. A2 Implementation of an alkali metal seeder for plasma temperature control D.C.M. van den Bekerom, N. den Harder, M.C.M. van de Sanden and G.J. van Rooij FOM Institute DIFFER Dutch Institute for Fundamental Energy Research, Association EURATOM-FOM, PO Box 1207, 3430 BE Nieuwegein, The Netherlands, www.differ.nl At present day, our society is largely powered by fossil fuel based power plants that emit large amounts of CO2 , an important greenhouse gas that is the main contributor to global warming. By switching our focus to renewable energies, electricity can be generated in a clean and sustainable fashion, as is done in e.g. solar panels and wind turbines. However, these intermittent sources provide energy whenever there is a supply, and without regard of the instantaneous demand. This mismatch in supply and demand emphasizes the importance of an efficient way to store the surplus energy. In terms of energy density, an effective way to store energy is in the form of chemical bonds. In practice, this means using the surplus energy to convert CO2 to CO, that later can be synthesized into any of the conventional fuels. A plasma-chemical reactor is ideal for this purpose, due to its low reactor inertia and proven high conversion efficiency. To optimize the conversion efficiency of the CO2 → CO reaction, it is important to be able to control the plasma temperature. Using a simple particle and power balance, we show that the introduction of alkali atoms enables one to influence the plasma temperature by adjusting the alkali content. We provide an explanation for how the tuning of the temperature improves the existing efficiency–conversion trade-off and show designs of an experiment to verify these ideas. A3 Optimal ratio of anode and cathode radius in a Hirsch-Farnsworth fusor M.Wijnen1 , S.Rouwette2 , J.W.Oosterbeek3 1 Department of Applied Physics 2,3 Department of Science and Technology of Nuclear Fusion Eindhoven University of Techology, Eindhoven, 5612 AZ, The Netherlands While magnetic confinement fusion is reaching the next level with the development of ITER, many other methods to achieve fusion are studied in parallel. One of these methods is electrostatic confinement (IEC) which utilizes electrostatic fields to create fusion. The Eindhoven University of Technology operates the TU/e Fusor, modeled after a Hirsch-Farnsworth fusor. To that end two concentric spherical electrodes are placed in deuterium gas at near-vacuum, the inner electrode at a relative potential of -100 kV which allows for a deuterium plasma to form. As the inner electrode is transparent the ions engage in a radial oscillatory motion through the center. During this oscillatory motion the ions can collide with the background gas allowing for either a fusion or a loss reaction. The parameter to be investigated here is the cathode radius. A higher cathode radius decreases the electrode distance and therefor the distance ions travel before they reach maximum velocity. Since loss mechanisms are predominant at lower energies, the shorter the distance an ion travels at low velocity the less collisions result in a loss. The increase of the cathode radius also means an increase of the cathode volume i.e. the target volume. Ions travel a longer distance at maximum velocity resulting in more fusion collisions. But as the breakdown voltage scales with the pressure times the electrode distance, a decrease of the electrode distance requires a higher pressure and to operate in the same regime. The supposition therefor is that an optimum in the ratio of cathode and anode radius can be established. The neutron production rate will be used as a measure to validate the aforementioned predictions. A4 Radially resolved bifurcation theory for L-H mode transition dynamics W. Weymiens1 , S. Paquay2 , H. J. de Blank1 , and G.M.D. Hogeweij1 1 FOM Institute DIFFER, Dutch Institute for Fundamental Energy Research, Association EURATOM-FOM, PO Box 1207, 3430 BE Nieuwegein, The Netherlands 2 Eindhoven University of Technology, Dept. Applied Physics, Eindhoven, The Netherlands Important for tokamak fusion reactors is the emergence, above a critical heating power, of the H-mode, a state of strongly reduced turbulent heat transport near the last closed magnetic surface. This heat transport bifurcation exhibits hysteresis: the back-transition to the more turbulent L-mode occurs at significantly lower heating power. The many quantitative experimental tests have not yet conclusively discriminated between the multitude of proposed H-mode models. Instead we apply bifurcation analysis to candidate H-mode models to examine the transition characteristics of the L-H transition. The L-H and H-L transitions are fold bifurcations (codimension=1), with heating power as control parameter. Bifurcation analysis shows that the existence and magnitude of the hysteresis between L-H and H-L transitions can be controlled by two types of parameters which depend on e.g. electron density and influx of neutrals. By increasing the first parameter, the hysteresis shrinks and disappears when the two fold bifurcations meet in a cusp bifurcation (codimension=2). Increasing the second parameter causes the hysteresis to be replaced by a limit cycle, corresponding to an oscillating L-H phase. All these phenomena are arranged in parameter space around a codimension=3 bifurcation. Reaction-diffusion systems consisting of coupled radial transport equations for the density, temperature and radial electric field have precisely these bifurcations, and exhibit front propagation analogous to chemical reactions and neural signals. We demonstrate the same bifurcations in more realistic H-mode models where transport coefficients depend on plasma flow shear and in transport models where turbulent fluctuation levels respond dynamically. A5 Microwave detection of instabilities in fusion plasmas Hugo van den Brand1,2 , M.R. de Baar1,2 , M. van Berkel1,2 , W.A. Bongers1 , L. Giannone3 , W. Kasparek4 , J.K. Stober3 , D. Wagner3 , E. Westerhof1 and the ASDEX Upgrade team3 1 High temperature plasma physics, FOM-Institute DIFFER, Nieuwegein, PO Box 1207, 3430 BE, The Netherlands 2 Control Systems Technology Group, Eindhoven University of Technology, P.O. Box 513, 5600 MB, The Netherlands 3 Max-Planck-Institut für Plasmaphysik, EURATOM-IPP, Boltzmansstr.2, D-85748 Garching, Germany 4 Institut für Grenzflächenverfahrenstechnik und Plasmatechnologie, Univ. Stuttgart, D-70569 Stuttgart, Germany Control of performance limiting instabilities will be essential for the successful exploitation of future nuclear fusion reactors. A particular example is provided by the neoclassical tearing modes (NTMs), which manifest themselves in reconnection of magnetic field lines and increase the risk of a sudden and violent termination of the fusion reaction. Direct detection of the position of this instability is investigated with inline Electron Cyclotron Emission (ECE), in which ECE is detected via the transmission line of a heating system. Algorithms and results of NTM detection using inline ECE on ASDEX Upgrade will be shown. Alternatively, NTMs can be prevented by reducing the sawtooth period. A sawtooth crash results in a sudden reformation of the magnetic equilibrium and is capable of creating NTMs. However, if the sawtooth period is small, the resulting NTMs will be small as well. Methods for the detection of the sawtooth period will be shown. A6 Investigation of the inception cloud of positive streamers in nitrogen-oxygen mixture S. Chen1 , S. Nijdam2 , and U.M. Ebert3 Department of Electrical Engineering, Tsinghua University, Beijing, 100084, China 2 EPG, Eindhoven University of Technology, Eindhoven, 5600 MB, the Netherlands 3 Multiscale Dynamics, CWI, Amsterdam, 1090GB, the Netherlands 1 Streamers are known as the beginning stage of the breakdown process. Many researchers have studied the inception voltage under different conditions and derived inception criterion. However, the discharge inception process such as the inception cloud of positive streamers and its break-up are still unknown or little understood. In this paper we will present measurements of streamer inception cloud on nitrogen oxygen mixtures with different ratios. The influence of oxygen content on the inception cloud and streamer break-up characteristics is investigated. In 20% O2 and 2% O2 the size of inception cloud are nearly the same, while in pure nitrogen hardly any inception clouds can be distinguished. Comparing 2% O2 mixture to 20% O2 , the streamer average break-up time increases greatly and so does its jitter, which indicates that the inception cloud is more stable for lower oxygen concentration. A7 Formation dynamics of UV and EUV induced hydrogen plasma A.A. Dolgov1 , C. J. Lee3 , O. Yakushev1 , D.V. Lopaev4 , A. Abrikosov3 , V.M. Krivtsun3 , A. Zotovich4 and F. Bijkerk1,2 1 FOM Institute DIFFER - Dutch Institute for Fundamental Energy Research, the Netherlands, Postcode, the Netherlands 2 MESA+ Institute for Nanotechnology, University of Twente, Enschede, The Netherlands 3 Institute for Spectroscopy, Russian Academy of Science, Troitsk, Moscow, Russia 4 Moscow State University, Moscow, Russia Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Ut purus elit, vestibulum ut, placerat ac, adipiscing vitae, felis. Curabitur dictum gravida mauris. Nam arcu libero, nonummy eget, consectetuer id, vulputate a, magna. Donec vehicula augue eu neque. Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Mauris ut leo. Cras viverra metus rhoncus sem. Nulla et lectus vestibulum urna fringilla ultrices. Phasellus eu tellus sit amet tortor gravida placerat. Integer sapien est, iaculis in, pretium quis, viverra ac, nunc. Praesent eget sem vel leo ultrices bibendum. Aenean faucibus. Morbi dolor nulla, malesuada eu, pulvinar at, mollis ac, nulla. Curabitur auctor semper nulla. Donec varius orci eget risus. Duis nibh mi, congue eu, accumsan eleifend, sagittis quis, diam. Duis eget orci sit amet orci dignissim rutrum. The comparative study of the dynamics of ultraviolet (UV) and extreme ultraviolet (EUV) induced hydrogen plasma was performed. It was shown that for low H2 pressures and bias voltages, the dynamics of the two plasmas are significantly different. In the case of UV radiation, the plasma above the photocathode appears after UV pulse due to electron avalanche, after which discharge structure formation begins. In contrast, for EUV-induced plasma, a spatial discharge structure is formed immediately during radiation pulse through intensive gas ionization. This difference explains why EUV-induced plasmas are much denser at low pressures (less then 10 Pa) and bias voltages (less then 50V). However, at pressures above 30 Pa EUV and UV induced plasmas show similar volt-ampere characteristics. This means that, in certain cases, plasma-chemistry in presence of EUV-induced plasma can be predicted from UV induced plasma experiments A8 Real-time tokamak simulations for plasma state reconstruction with minimal diagnostics Federico Felici1 , B. Maljaars1 , P. Geelen1 , M.R. de Baar1,2 , and M. Steinbuch1 1 Eindhoven University of Technology, Mechanical Engineering, Control Systems Technology Group, 5600MB Eindhoven, The Netherlands 2 FOM-DIFFER, Nieuwegein, The Netherlands A future DEMO will have to rely on a minimal set of diagnostics to provide real-time information about the plasma needed for feedback control. A technique is presented to merge real-time diagnostic data with real-time plasma evolution models in order to obtain a reliable real-time plasma state estimate despite this scarcity of diagnostic data. In this technique, a physics-based predictive model provides an estimate for the plasma state based on the state at the previous time step. Measurements from real-time diagnostics are subsequently used to correct this prediction. This technique is markedly different form traditional practices of equilibrium reconstruction, since the time evolution of the plasma is now explicitly taken into account and inversion of data becomes unnecessary. The method is well known and widely used in many fields of engineering, where it is known as a dynamic state observer or Kalman filter. A dynamic state observer for the tokamak plasma profiles has been developed and ipmwhich makes use of the real-time capable plasma profile evolution code RAPTOR [1]. It has been implemented on the TCV and ASDEX-Upgrade tokamaks and is undergoing validation and testing. Results will also be shown for ITER simulations, demonstrating accurate profile reconstructions with relatively few radial measurement points. [1] F. Felici et al, Nuclear Fusion 51 (2011) 083052 A9 Laser Collisional Induced Fluorescence for validation of an argon Collisional Radiative Model W.A.A.D. Graef1 , E.A.D. Carbone2 , S. Hübner1 , J. van Dijk1 , and G.M.W. Kroesen1 1 Departement of Applied Physics, Eindhoven University of Technology, Eindhoven, P.O. Box 513, 5600MB, The Netherlands 2 Labaratoire de Technologies de la Microélectronique, CEA - LETI, Grenoble, 38054 CEDEX 9, France Collisional Radiative Models (CRM) are widely used for the determination of plasma parameters such as the electron temperature and density. In combination with other techniques, they have also been used to investigate departure of the electron energy distribution from Maxwell [1]. Two of the main building blocks of a CRM are the electron and heavy particle kinetics, and accurate data describing these processes is of vital importance. Usually, comparison and validation of CRMs is performed in steady state. Here, Laser Collisional Induced Fluorescence (LCIF) is employed to study the various particle kinetics. To this end, a time dependent CRM of argon has been developed in the Plasimo plasma modeling platform [2] that can model a LIF experiment. The model allows for the different processes to be studied in detail, including the changes of the escape factors. The results of the model are compared to measurements performed on a low pressure microwave plasma with known characteristics [3-4]. [1] E. A. D. Carbone et al. (2012) J. Phys. D: Appl. Phys. 45 475202 [2] J. van Dijk et al (2009) J. Phys. D: Appl. Phys. 42 194012 [3] J.M. Palomares et al. (2010) Spectrochim. Acta B 65 225 [4] E. A. D. Carbone et al. (2012) J. Phys. D: Appl. Phys. 45 345203 A10 Laser Scattering on a Solar Fuels Microwave Discharge N. den Harder, D.C.M. van den Bekerom and G.J. van Rooij FOM Institute DIFFER - Dutch Institute for Fundamental Energy Research, Association EURATOM-FOM, Trilateral Euregio Cluster, Nieuwegein, The Netherlands In order to transition to a fully sustainable energy infrastructure, efforts have been taken to exploit renewable energy sources. Most of these sources however are intermittent, making energy storage a necessity. Storage in chemical form is one of the promising options, and at DIFFER a possible first step in the generation of Solar Fuels is researched: the dissociation of CO2 molecules in a microwave plasma. The use of a microwave plasma to dissociate CO2 has a background in the literature: Soviet-era research indicates that high energy efficiencies are possible. This energy efficiency is made possible by the non-equilibrium nature of the plasma, which in a CO2 discharge preferentially excites the vibrational degrees of freedom, resulting in dissociation of the molecules. In addition, the plasma approach can be switched on the timescale of seconds, which makes it ideal for load balancing the electricity grid. We have constructed a small-scale pilot reactor in order to investigate optimum conditions. To gain insight in fundamental plasma parameters such as the electron temperature and density, and the neutral gas temperature and density, we are setting up a laser scattering diagnostic. Special care is taken to reduce straylight while maximizing throughput. In this contribution we will report on the design of the scattering setup, modeled Rayleigh-Thomson-Raman spectra and some first results on the plasma parameters. A11 Correction of the Spectral Calibration of the JET Core LIDAR Thomson Scattering Diagnostic Using Ray Tracing J. Hawke1 , R. Scannell2 , M. Maslov2 ,J.B. Migozzi3 , and JET EFDA Contributors* 1 FOM Institute DIFFER Dutch Institute for Fundamental Energy Research, Association EURATOM-FOM, 3430 BE Nieuwegein, Netherlands 2 CCFE, Culham Science Centre, Abingdon, Oxon, OX14 3DB, UK 3 JBM Optique, 4 Rue du Calvaire Btiment 11, 92210 Saint Cloud, France * See the Appendix of F. Romanelli et al., Proceedings of the 24th IAEA Fusion Energy Conference 2012, San Diego, US This work isolated the cause of the observed discrepancy between the electron temperature (Te ) measurements before and after the JET Core LIDAR Thomson Scattering (TS) diagnostic was upgraded. In the upgrade process, stray light filters positioned just before the detectors were removed from the system. Modelling showed that the shift imposed on the stray light filters transmission functions due to the variations in the incidence angles of the collected photons impacted plasma measurements. To correct for this identified source of error, correction factors were developed using ray tracing models for the calibration and operational states of the diagnostic. The application of these correction factors resulted in an increase in the observed Te , resulting in the partial if not complete removal of the observed discrepancy in the measured Te between the JET core LIDAR TS diagnostic, High Resolution Thomson Scattering (HRTS), and the Electron Cyclotron Emission (ECE) diagnostics. A12 Plasma particle lofting L.C.J. Heijmans, S. Nijdam, J. Beckers and G.M.W. Kroesen Department of Applied Physics, Eindhoven University of Technology P.O. Box 513, 5600 MB Eindhoven, The Netherlands Particles can be lofted from a surface when a plasma is applied above it. Like a surface, any particle on it will be charged by the plasma. Therefore it feels an upward force in the plasma sheet electric field. If this force is higher than the adhesive force, the particle is removed from the surface. The particle charge can fluctuate highly due to the discrete nature of the electron and ion flux. This may cause a significant increase in removal force. This study aims at quantitatively determining the removal force. Knowledge of the adhesive force is essential for a complete force balance. We plan to use a piezo actuator to vibrate the surface. Herewith the adhesive force can be determined by finding the needed acceleration for particle release. Furthermore this setup can be used to change the effective adhesive force. This helps to quantitatively determine the force due to the plasma. In addition to measuring sticking particles, floating particles can be measured. It will be attempted to gain insight in the charge fluctuations by looking at their floating height. This will differ with changing charge and thus electric force. A13 Characterization of a dielectric barrier surface discharge for medical applications K. Hijnen, P. Smits, A. Sobota, E.M. van Veldhuizen, G.M.W. Kroesen Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600MB Eindhoven, The Netherlands A growing field in plasma physics is that of medical applications. The presented research focuses on the prototype development of a device that will prevent infection by using a compact dielectric barrier discharge in close proximity to the targeted skin. The discharge will be in atmospheric air, making it easy to implement as a non-invasive method for disinfection. The disinfecting effect relies on the bactericidal properties of discharge reaction products such as ozone, nitrous oxides and hydroxyl radicals. Ozone and nitrous oxides are health hazards when inhaled so, to assess safety, the production of these gases is characterized using absorption spectroscopy and mass spectrometry, respectively. The close proximity of the discharge to the skin also raises concerns about temperature. Temperature parameters for the device and for gas and plasma species will be determined using a combination of surface measurements and optical emission spectroscopy. Together with power measurements, an extensive characterization of the prototype will be obtained. The poster will show some initial results and outlines of future work. A14 Plasma driven, water assisted CO2 methanation. W.F.L.M. Hoeben, E.J.M. van Heesch, W. Boekhoven, F.J.C.M. Beckers, T. Huiskamp and A.J.M. Pemen Departement of Electrical Engineering, Eindhoven University of Technology, Eindhoven, P.O. Box 513, 5600 MB, The Netherlands Back conversion of carbon dioxide to synthetic hydrocarbons prevents the depletion of precious fossil fuels, indispensable for sustaining life via e.g. the production of pharmaceutics, crop protecting chemicals and food conservation agents. With regard to the growing interest in Power-To-Gas (P2G) Technology, this back conversion process is the key to convenient & efficient storage and transportation of energy in the near future. The CO2 methanation process CO2 + 4H2 → CH4 + 2H2 O is both of exothermic nature and kinetically hindered, therefore the use of a catalytic material at non-ambient process conditions is inevitable. Plasma chemical methanation may be an interesting alternative to conventional methanation, due to its ability to provide other chemical reaction pathways of lower activation energy than classical thermal chemistry (1). Nowadays, the combination of plasmas with catalysis is widely studied for further enhancing reaction rates and selectivity (2,3). In this contribution we report first results on direct formation of methane from carbon dioxide and water vapour in a non-thermal plasma, without additional catalyst (4). The mechanism is explained via plasma-induced dissociation of carbon dioxide and water to a.o. carbon monoxide and hydrogen. At the stainless steel high voltage electrodes of the plasma reactor, d-metal catalytic activity seems to exist, where dissociative adsorption of CO, CO2 and H2 induces carbon hydrogenation to methane. (1) (2) (3) (4) A. Fridman, Plasma Chemistry, Cambridge University Press, 2008 E. Jwa et al., Fuel Proc. Technol. 108, 2013, p89 S. Mahammadunnisaa et al., Int. J. Greenh. Gas Con. 16, 2013, p361 W. Hoeben et al., submitted to J. CO2 Util. (Elsevier) A15 Plasma accumulation effects in Extreme Ultra-Violet generated plasmas R.M. van der Horst, S. Nijdam, J. Beckers and G.M.W. Kroesen Department of Applied Physics, Technische Universiteit Eindhoven, PO Box 513, 5600MB Eindhoven, The Netherlands In order to meet the demand of increasing computer speed and memory capacity, industries are striving to reduce the size of computer chips. This miniaturization can be achieved by reducing the wavelength in lithography machines to Extreme Ultra-Violet (EUV, 92 eV). The low-pressure (around 1 Pa) transparent background gas (e.g. H2 and He) in the lithography machine is partially ionized by the absorption of EUV photons. The study of these low-density (1015 m−3 ) pulsed plasmas is interesting and experimentally challenging. The electron density is measured with microwave cavity resonance spectroscopy (MCRS). In MCRS measurements the resonance frequency in a cavity is determined, this frequency depends on the electron density in the cavity. In this research the plasma accumulation is studied in an EUV-generated plasma in argon. The EUV source generates EUV pulses with a repetition frequency between 500 Hz and 10 kHz. The accumulation of plasma is clearly observed at frequencies above 1 kHz. A16 Application of multicomponent diffusion by solving the Stefan Maxwell equations J.F.J. Janssen1 ,K.S.C. Peerenboom 1 , J.L.G. Suijker 2 , and J. van Dijk1 1 Applied Physics, Eindhoven university of Technology, 5600 MB, The Netherlands 2 Philips Lighting, Lightlabs, Eindhoven, 5600 JM, The Netherlands High intensity discharge lamps (HID lamps) are widely used for commercial lighting because of their high efficacies from a compact source. Current HID lamps contain mercury which is a toxic species. In order to reduce the environmental impact the feasibility of a mercury free lamp is investigated. The investigation focusses on using salts like InI or SnI as a buffer species. By using these species a dominant background gas like mercury is no longer present. As a consequence the diffusion algorithms based on Fick’s law are no longer applicable and the Stefan-Maxwell equations must be solved. This system of equations is modified with conservation rules to set a coldspot pressure for saturated species and enforce the mass dosage for unsaturated species. The radiative energy transport is taken into account by raytracing. Quantum mechanical simulations have been used to calculate the potential curves and the transition dipole moments for indium with iodine and tin with iodine. The results of these calculations have been used to predict the quasistatic broadening by iodine. A17 Benchmark of simulation code MSESIM for performance study of future MSE diagnostic on KSTAR 1 A.G.G. Lange1 , J. Ko2 , and M.F.M. de Bock1 Science and Technology of Nuclear Fusion, Eindhoven University of Technology, Eindhoven, The Netherlands 2 National Fusion Research Institute, Daejeon, Korea For control of fusion plasmas in energy relevant tokamaks, information on the current distribution in the plasma core is required. A Motional Stark Effect (MSE) diagnostic, aimed at measuring the current distribution,will be installed on the KSTAR tokamak in 2015. For design purposes, it is relevant to investigate the performance of this diagnostic. This is done in two steps: (1) the benchmarking of a simulation code, MSESIM, and (2) the usage of this code and tested components to analyse the throughput of the system. The benchmark is executed by comparison of simulations with spectrum measurements of the 2012 and 2013 campaign. This article describes the first step and outlines the second. A18 Control over Rydberg atoms by Electromagnetically Induced Transparency A.F.M. Monden, C. Ravensbergen, R.W.M. van Bijnen, S.J.J.M.F. Kokkelmans, O.J. Luiten and E.J.D. Vredenbregt Department of Applied Physics, Eindhoven University of Technology, The Netherlands Rydberg atoms are a candidate for performing quantum simulations due to their strong interactions. Crucial property is the blockade effect: in the vicinity of a Rydberg atom, the level of a second one shifts. We measured the radius of this blockade effect to be as large as 16.3 ± 0.1µm for the 103S state. To create Rydberg atoms in a cloud of ultracold Rubidium, a two step excitation process is used. First a 780 nm laser (the probe laser) is used to excite Rb atoms from the ground state to the first excited state, then a 480 nm laser (the coupling laser) excites to a Rydberg state. To get control over this transition the coupling laser has to be frequency locked on the desired transition. Due to the narrow line width of this transition direct locking of the laser to an atomic line is not possible. The coupling laser will be locked to an ultra stable cavity. Electromagnetically Induced Transparency (EIT) will be used to find the second atomic resonance to set the cavity resonance frequency. Rubidium vapor becomes transparent for the probe laser if both lasers are resonant with there atomic transition. The absorption of the probe laser in a rubidium vapor cell will be measured as function of the frequency of the cavity locked coupling laser to find minimum absorption. We calculated the electric susceptibility of as function of the detunings of both lasers. The transparency is related to the imaginary part of the electric susceptibility. A19 Fluid models and the reality 1 A.H. Markosyan1 , J. Teunissen1 , S. Dujko1,2 and U. Ebert1,3 Centrum Wiskunde & Informatica (CWI), Amsterdam, The Netherlands 2 Institute of Physics, University of Belgrade, Belgrade, Serbia 3 Department of Applied Physics, Eindhoven University of Technology, Eindhoven, The Netherlands The present work compares several fluid models for streamer discharges including only recently developed the high order fluid model by Dujko et al [J. Phys. D, 46:5202, 2013]. We have considered the classical first order model using the local field approximation and second order fluid model using the local energy approximation with drift-diffusion approximation. The simulation results with all three fluid models are presented and compared. As a reference, we use particle-in-cell/Monte Carlo (PIC/MC) model. All tested are performed in 1D case for Ne and N2 at STP. We consider wide range of reduced electric fields. Our simulation results show large deviations between models the models for various properties of negative planar fronts. We discuss the practical and theoretical aspects of applicability of each the fluid models considered in this work. A20 Plasma oxidation as key mechanism for stoichiometry in Pulsed Laser Deposition grown oxide films R. Groenen, K. Orsel, H.M.J. Bastiaens, K.J. Boller, G. Koster, A.J.H.M. Rijnders Inorganic Materials Science, MESA+ Institute for Nanotechnology, University of Twente, Enschede, 7500AE, The Netherlands Pulsed Laser Deposition (PLD) has been established in recent years as a versatile thin film deposition technique. PLD utilises the transient particle flow of a laser-induced plasma to achieve a fully controlled (also crystalline) growth of thin films of complex materials, including complex oxides. These materials exhibit a large variety of interesting physical properties, which are highly sensitive to slight deviation from ideal stoichiometry. Key mechanisms involved in optimized PLD thin film growth conditions haven0 t been fully understood, and better insight in the relation between growth parameters, plasma plume characteristics and film characteristics is necessary in obtaining full control over stoichiometry, doping, defect density of PLD grown thin films and herewith improved thin film properties. We present a unique overview on the influence of growth parameters on the characteristics of the PLD plasma plume using Optical Self-Emission (OSE) imaging and spectroscopy, supported with Laser Induced Fluorescence (LIF) measurements. It is shown that in a relatively small background gas pressure regime, from 10−2 mbar to 10−1 mbar oxygen pressure, a transition from nonstoichiometric to stoichiometric growth of SrTiO3 films occurs as measured with X-ray Diffraction (XRD). In this pressure regime, OSE spectroscopy and LIF measurements also show a transition from incomplete to full oxidation of species in the plasma plume. This suggests that the oxidation of species in the plasma is a crucial mechanism for the stoichiometric reconstruction of the synthesised oxide thin films. A21 Surface modifications and deuterium retention of W and WO3 thin films after high-flux deuterium plasma exposure A. Gallo1 , M. Passoni2 , D. Dellasega2 , A. Pezzoli2 and P.A.Zeijlmans van Emmichoven1 1 FOM Institute DIFFER, Dutch Institute For Fundamental Energy Research, Nieuwegein, The Netherlands 2 Dipartimento di Energia and NEMAS-Centre for NanoEngineered Materials and Surfaces, Politecnico di Milano, Italy Future magnetic confinement fusion devices like ITER will be fueled by hydrogen isotopes. Plasma facing components will suffer from deuterium and tritium retention. This issue is expected to be particularly serious for the tungsten divertor. The aim of the present work is to study the effect of deuterium plasmas on tungsten oxide films that may possibly serve as diffusion barriers for deuterium. Tungsten and tungsten oxide nanostructured thin films created via pulsed laser deposition have been exposed to deuterium plasma in Magnum-PSI, a linear plasma generator capable of simulating ITER-relevant conditions: high ion flux (1024 m-2 s-1 ), high electron density (1020 m-3 ) and low electron temperature (1 - 2 eV). Post-exposure characterization including optical microscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDXS), Raman spectroscopy and thermal desorption spectroscopy (TDS) has been performed in order to investigate film morphology, crystalline structure, composition and deuterium retention. The metallic tungsten samples show blister formation, amorphization of the film and a deuterium inventory consistent with previous experiments. Tungsten oxide films exhibit lower deuterium retention (up to two orders of magnitude), no blister formation or other damages, but stronger amorphization and significant oxygen loss. A22 Chemical Energy Storage based on CO2 Plasmolysis Adelbert P.H.Goede1 , Waldo A.Bongers1 , Martijn F.Graswincke1 , Richard M.C.M van de Sanden1 , and Martina Leins2 , Jochen Kopecki2 , Andreas Schulz2 , Mathias Walker2 1 Dutch Institute for Fundamental Energy Research, PO Box 1207, 3430 BE Nieuwegein, NL 2 Institute of Interfacial Process Engineering and Plasma Technology, 70569 Stuttgart, Germany Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Ut purus elit, vestibulum ut, placerat ac, adipiscing vitae, felis. Curabitur dictum gravida mauris. Nam arcu libero, nonummy eget, consectetuer id, vulputate a, magna. Donec vehicula augue eu neque. Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Mauris ut leo. Cras viverra metus rhoncus sem. Nulla et lectus vestibulum urna fringilla ultrices. Phasellus eu tellus sit amet tortor gravida placerat. Integer sapien est, iaculis in, pretium quis, viverra ac, nunc. Praesent eget sem vel leo ultrices bibendum. Aenean faucibus. Morbi dolor nulla, malesuada eu, pulvinar at, mollis ac, nulla. Curabitur auctor semper nulla. Donec varius orci eget risus. Duis nibh mi, congue eu, accumsan eleifend, sagittis quis, diam. Duis eget orci sit amet orci dignissim rutrum. An energy storage scheme for Renewable Energy (RE) based on the plasmolysis of CO2 into CO and O2 has been experimentally investigated, demonstrating high energy efficiency (> 50%) combined with high energy density, instant up-down ramping and use of abundant materials. The key parameter controlling energy efficiency has been identified as the reduced electric field. Basic plasma parameters including density and temperature are derived from a simple particle and energy balance model, allowing parameter specification of an upscale 100 kW prototype development unit. With RE powered plasmolysis as the critical element, a CO2 neutral energy system becomes feasible when complemented by effective capture of CO2 at the input (CCU) and by separation of CO at the output gas stream followed by downstream chemical processing into hydrocarbon fuel (P2G). Such chemical energy storage system can be implemented either centralised (off-shore wind farm) or distributed (local energy network). Elements of such model energy storage system will be presented. A23 LEONA: High Altitude Plasmas and Thunderstorm High Energy Emissions in Latin America Fernanda T. São Sabba Instituto Nacional de Pesquisas Espaciais, INPE, São Jose dos Campos, SP, Brazil South America’s combination of intense thunderstorm activity and geomagnetic characteristics creates a unique natural laboratory for investigating a variety of atmospheric phenomena and their possible coupling. Its large latitudinal extent, from 12◦ N to 55◦ S, encompass equatorial, tropical and subtropical regions with meteorological conditions that makes South America the second most active thunderstorm and lightning, and consequently one of the most active Transient Luminous Events (TLEs) region of the globe. TLEs are optical emissions from transient plasma discharges excited in the upper atmosphere by the electromagnetic field of underlying lightning flashes from thunderstorms. More recently, measurements of High Energy Emissions from Thunderstorms - HEET from space, such as thunderstorms gamma ray emissions, named Terrestrial Gamma Ray Flashes - TGFs, revealed that they also produce high energy emissions. Since 2002, five different campaigns have been performed in Brazil to make TLE observations, more than 700 events, mainly sprites, have been recorded over South American thunderstorms during Brazilian campaigns so far. This paper will review the main results of these observations and of the studies performed within the Atmospheric and Space Electrodynamical Coupling - ACATMOS group at INPE. It will introduce the LEONA: Transient Luminous Event and Thunderstorm High Energy Emission Collaborative Network in Latin America. The team unites scientists of research institutions from several countries to investigate TLEs, HEET and related phenomena. LEONA will also provide ground support to several upcoming satellite and stratospheric balloon missions to perform TLE and HEET measurements, such as the TARANIS French Micro-satellite and the ASIM mission onboard the International Space Station (ISS), scheduled to be launched in 2017, and the COBRAT mission, to fly long and short duration balloons performing these measurements in South America, starting in 2017. B1 Nanosecond Pulsed Streamer Corona Plasma with a DC Bias: Energy and Ozone Measurements 1 T. Huiskamp1 , A.J.M. Pemen1 , N. Takamura2 , and T. Namihira3 Electrical Energy Systems Group, Eindhoven University of Technology, Eindhoven, 5600 MB, The Netherlands 2 Graduate School of Science and Technology, Kumamoto University, Kumamoto, 860-8555, Japan 3 Bioelectrics Research Center, Kumamoto University, Kumamoto, 860-8555, Japan Matching a pulse source to a plasma load is one of the fundamental challenges to overcome in order to maximize the full potential of pulsed discharges for air purification applications [1]. In this contribution we show results of an experiment which investigates the matching of a nanosecond pulse source to a corona plasma reactor which is aided by a bias voltage. The corona plasma reactor is a wire cylinder reactor as is commonly used in pulsed power plasmas. The main variable in this experiment is the DC-voltage on a secondary electrode which is situated on a dielectric layer against cylinder of the reactor. The pulse source is the nanosecond pulse source of the Kumamoto University, Japan [2]. We varied the amplitudes of the pulsed voltage, as well as the DC voltage and investigate its effect on the corona plasma with energy measurements and ozone measurements. The results show that for low applied DC voltages, the matching of the pulse source to the reactor increases, but that applying too high DC voltages, this effect decreases. [1] G. Winands et al., Plasma Science, IEEE Transactions on, vol. 36, no. 1, pp. 243–252, 2008. [2] D. Wang et al., Plasma Science, IEEE Transactions on, vol. 38, no. 10, pp. 2746–2751, 2010. B2 Oxidation and stoichiometry studies of pulsed laser ablation plasmas K. Orsel1 , H.M.J. Bastiaens1 , R. Groenen1 , G. Koster1 , K. Beks-Peerenboom2 , J. van Dijk2 , A.J.H.M. Rijnders1 , K.-J. Boller1 1 Mesa+, University of Twente, Enschede, The Netherlands 2 Elementary Processes in Gas Discharges, Eindhoven University, Eindhoven, The Netherlands Pulsed Laser Deposition (PLD) is a versatile technique to deposit complex materials. However, knowledge on the PLD process is based largely on experimental research examining what parameters appear to provide the best result for a specific setup and material. The goal of our research is to progress towards an improved understanding and control of PLD for scaling up to large-area deposition while maintaining full control on film growth, i.e., to the level of atomic precision. To map the spatial and temporal evolution of the ablation plasma, we built a PLD test system that allows for in-situ laser induced fluorescence imaging and absorption spectroscopy measurements. From this, it is possible to generate a 3D map of the absolute material flux towards the substrate, which is essential for obtaining a fundamental understanding of the plasma chemistry and evolution. The stoichiometry of the plasma plume, the oxidation of specific species and the propagation speed of the material can all be controlled by varying the ablation laser fluency, the background pressure and the background gas mixture (typically Ar and O2 ). This in turn allows us to fine-tune the properties of the layers that are grown with these plasmas. Here, we present our recent results on the oxidation and stoichiometry of species in plasmas created by laser ablation of SrTiO3 and LaAlO3 [1]. [1] K. Orsel, H.M.J. Bastiaens, R. Groenen, G. Koster, A.J.H.M. Rijnders, K.-J. Boller, Temporal and spatial mapping of oxidized species in pulsed laser deposition plasmas, Journal of Instrumentation 8, pp. C10021 (2013) B3 Diagnostic studies on CO2 dissociation in atmospheric pressure plasmas S. Welzel1,2 , F. Brehmer1,3 , M.C.M. van de Sanden1,2 , and R. Engeln2 1 Dutch Institute for Fundamental Energy Research (DIFFER), PO Box 1207, 3430 BE Nieuwegein, The Netherlands 2 Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands 3 AFS GmbH, Von-Holzapfel-Str. 10, 86497 Horgau, Germany The conversion of CO2 into CO and subsequent hydrogenation into gaseous or liquid hydrocarbon(ate)s form the basis for the integration of renewable energy into a future CO2 neutral energy system as well as into chemical industry. The application of non-equilibrium plasmas offers a promising route to overcome the initial energy demanding CO2 dissociation step. Dielectric barrier discharges (DBDs) are known as useful tools in plasma-assisted gas conversion. However, in the particular case of DBDs operated in undiluted CO2 the conversion yields remain typically below 10 % under flowing gas conditions. The main objective is therefore to unravel main reaction mechanisms which may explain the relatively low efficiency. Ex-situ and in-situ infrared absorption spectroscopy along with optical emission spectroscopy were employed to study the CO2 conversion in mid-frequency (kHz) driven DBDs at atmospheric pressure. Absolute densities of CO, O2 and O3 were established downstream the plasma reactor. The emission of electronically excited species (CO2 + , CO) along with ro-vibrational absorption lines of CO and CO2 in their (electronic) ground state were monitored in-time. The results suggest electron-impact CO2 excitation and ionisation followed by potentially surface enhanced recombination. The stochiometric CO:O2 ratio is described by a uniform trend as function of the number of charges transferred during the residence time of CO2 in the active plasma zone. The verification of this specific scaling parameter in filamentary DBDs is particularly surprising and highlights further a mainly electron-driven CO production. B4 Collisional particle in cell simulations of the TU/e fusor plasma S.M.M. Rouwette1 , J.W. Oosterbeek2 , A.J. Wolf3 , H.M.M. de Jong4 , S. Nijdam5 , M. Wijnen6 , R.J.E. Jaspers7 1,3,5,6 Department of Applied Physics 2,4,7 Department of Science and Technology of Nuclear Fusion Eindhoven University of Technology, Eindhoven, 5612 AZ The Netherlands The Eindhoven University of Technology houses a Hirsch-Farnsworth type Fusor. This is an Inertial Electrostatic Confinement (IEC) device, consisting of a spherical vacuum chamber (10-2 -101 Pa), that serves as the anode and a nearly transparent spherical cathode at up to -100 kV. The vacuum vessel is filled with Deuterium gas, and breakdown is initiated to create a fusion plasma. D-D fusion creates neutrons, neutron rates of 106 neutrons per second are regularly obtained . The large potential difference will accelerate D+ and D2+ ions towards the center. The D-D fusion reaction has an maximum cross section at 1 MeV collisional energy. So the higher the potential difference, the larger the fusion probability. The fusor could be a viable and cost effective neutron source. Even though it is simple in design, the physics involved is not trivial at all. Different operating modes create different plasmas. In one of these modes, called star mode, micro channels are formed. Drastically enhancing the neutron production with respect to a uniform discharge. The differences in plasma conditions between these modes are studied using a Collisional Particle In Cell (PIC) modeling method, in addition to diagnostic measurements. Current diagnostics focus on neutron output, potential profiles and spectral emission of the plasma. An existing C++ PIC code based on an Argon plasma has been altered to model the behavior of the Fusor. This includes implementing the Fusor specific geometry, hydrogen reactions and neutron production. Ongoing work will involve adding a spectrum output and optimization of the code for maximum performance. B5 Characterisation of a kHz pulsed FE-DBD for chronic wound treatment M. van der Schans1 , P. Smits1 , A. Sobota1 , E.M. van Veldhuizen1 , A.J.M. Pemen2 and G.M.W. Kroesen1 1 Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600MB Eindhoven, The Netherlands 2 Department of Electrical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600MB Eindhoven, The Netherlands Currently, many novel medical applications that benefit immensely from the synergistic effects of the constituents and products of non-thermal plasma are being developed. One such application is the treatment of chronic, infected wounds. Using a kHz pulsed floating electrode dielectric barrier discharge (FE-DBD) operated in air, pathogen killing agents such as UV radiation, electric fields and reactive molecules and radicals can be delivered directly to the wound. Optimising the operation conditions requires a detailed analysis of not only the plasma itself, but also of the involved chemistry and biology. Still, the first step towards producing an effective device for medical treatment is the electrical and physical characterisation of the plasma, which is the subject of this study. Power dissipation measurements and a method to measure the electric field using coherent anti-Stokes Raman scattering (CARS) will be presented. B6 Formation and dynamics of the atmospheric pressure high current diffuse dielectric barrier discharge between cylindrical electrodes in PECVD reactor S.A.Starostin1 , S.Welzel1,2 , J.B.Bouwstra3 , M.C.M. van de Sanden1,2 and H.W. de Vries1 1 Dutch Institute For Fundamental Energy Research (DIFFER), P.O. Box 1207, 3430 BE Nieuwegein, The Netherlands 2 Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands 3 FUJIFILM Manufacturing Europe b.v., P.O. Box 90156, Tilburg, The Netherlands Novel non-thermal plasma sources have been receiving increased attention in relation to development of the atmospheric pressure plasma enhanced chemical vapor deposition (APPECVD) technology. The atmospheric pressure glow-like (APGD) and Townsend like (APTD) modes of the dielectric barrier discharge (DBD) are the promising toools for advanced deposition and processing applications. The investigation of the APGD dynamics between plane parallel electrodes was already presented in literature. However from the practical point of view the cylindrical electrode geometry is more beneficial for in-line roll-to-roll process. At the same time the electric field and gas flow pattern between cylindrical electrodes will be strongly non-uniform which would affect discharge properties. In present contribution we studied the formation and time evolution of the high current dielectric barrier discharge in the operating roll-to roll AP PECVD reactor with parallel bi-axial cylindrical electrode geometry. The discharge was sustained in the mixture of nitrogen, oxygen with the addition of tetraethyl orthosilicate as a precursor for silica-like film deposition. The behavior of the transient plasma in curvilinear geometry was visualized by means of fast imaging from two orthogonal directions. The formation and propagation of lateral ionization waves with the transverse light emission structure similar to the low pressure glow discharge was observed at time scale below 1 microsecond. The instantaneous current density determined from the fast imaging data and voltage-current waveforms was 1 A/cm2 . Despite plasma non-uniformity at nanosecond time scale the deposition process on the web-rolled polymer results in smooth and dense silica-like layers. B7 Entrainment of impurity ions in high-density edge plasmas G.A. van Swaaij1 , A. Kirschner2 , L. Krah1 , W. J. Goedheer1 FOM Institute DIFFER, Association EURATOM-FOM, P.O. Box 1207, 3430 BE Nieuwegein, The Netherlands 1 Institute for Energy and Climate Research - Plasma Physics, Forschungszentrum Jülich GmbH, Association EURATOM-FZJ, Jülich, Germany 1 In the next generation of tokamaks including ITER, the ion density will reach very high values (ni > 1020 m−3 ) near the strike point of the divertor. The ion temperature at this location is fairly low (Ti < 10 eV). In present devices, the basic impurity transport near the divertor can be summarized as follows: sputtered and chemically eroded wall atoms are released as neutrals and travel along more or less straight paths until they are ionized. Once they are ionized, Coulomb collisions with the plasma ions push the impurities away from their respective magnetic field lines. The effective ion collision rate is proportional to ni · Ti−1.5 . In ITER-divertor relevant plasmas, the collision timescale will be of the same order as, or smaller than, the Larmor period. The impurities thus collide with the plasma ions so efficiently that they are not strongly magnetized at all. In the present work, a Boltzmann equation solver is used to calculate the time-dependent impurity velocity distribution. These results were combined with simulations using the 3D Monte Carlo code ERO. In a flowing plasma, the transverse diffusion of heavy impurity ions was found to be surprisingly small. This is because the impurities are very quickly accelerated to the plasma velocity, which exceeds the impurities thermal velocity. However, this leads to a new problem: the kinetic energy of the impurity ions gets very high. For W+ ions, the energies may become large enough to produce significant sputtering at the plasma-facing wall. B8 Size and density redistribution by a rod obstacle in a cluster jet for quasi-phase matching of high harmonic generation Y. Tao1 ,S.J. Goh1 ,P.J.M. van der Slot1 ,H.J.M. Bastiaens1 , F.A. van Goor1 ,E.T.A. van der Weide2 ,R. Hagmeijer2 ,S.G. Biedron4 , S.V. Milton4 ,M.B. Danailov5 ,J.L. Herek3 and K.-J. Boller1 1 Laser Physics and Nonlinear Optics,3 Optical Sciences, MESA+ Institute for Nanotechnology, 2 Department of Mechanical Engineering, University of Twente, Enschede, 7500AE, The Netherlands 4 Colorado State University, Colorado, USA 5 FERMI@Elettra, Sincrotrone Trieste S.C.p.A., Basovizza, Trieste, Italy We investigate the the possibility to realize a fully coherent XUV light source generating wavelengths down to 4 nm by using high-order harmonic generation (HHG) in an ionized medium. Due to the strong ionization, current p We investigate the possibility to realize a fully coherent XUV light source generating wavelengths down to 4 nm by using high-order harmonic generation (HHG) in an ionized medium. Due to the strong ionization, current phase-matching techniques for HHG are not suitable. Instead, we will investigate quasi-phase matching (QPM) over an extended interaction length to increase the output pulse energy. For this, we will prepare a cluster jet from a 5 mm long supersonic nozzle operated at high backing pressure (up to 75 bar). The modulation for QPM is obtained by placing either an array of wires or slits on top of the exit of the nozzle. Here, we report on the characterization of the modulated argon cluster jet. We apply Rayleigh scattering imaging and interferometry to infer the cluster size and total atomic number density distribution in the jet. Initial experiments concern the modulation of the jet by placing a 2 mm rod above the nozzle. The first results on the cluster size and density distribution will be compared with the simulation results from our 2D fluid dynamics model. B9 Streamer discharge interaction with water droplets 1 A. Dubinova1 , C. Rutjes1 , J. Teunissen1 and U. Ebert1 Multiscale Dynamics, CWI, Amsterdam, 1098XG, The Netherlands We study the interaction between streamer discharges and water droplets with numerical simulations. We assume that a water droplet is a spherical dielectric with a radius of 10 µm to 1 mm, with a relative permittivity of 80. Droplets change the local electric field due to polarization effects, and surface emission can affect the ionization level. These factors may facilitate discharge initiation and propagation near the droplet. B10 Spectroscopic study of the spark for Spark-OES T.H.M. van de Ven, S. Nijdam and G.M.W. Kroesen Departement of Applied Physics, Eindhoven University of Technology, Eindhoven, P.O. Box 513, 5600 MB, The Netherlands Spark-optical emission spectroscopy (OES) has been used for decades in the metal industries for the determination of concentrations of additives in metals. The technique involves the ablation and excitation of material from a solid metallic sample by a spark plasma. By measuring the emission it is possible to determine the concentrations in the sample. Although extensively used, little research has been done on the physics of the spark. It is expected that the temperature of the spark has an extensive influence on the concentration measurements. The temperature profile of the spark will be determined using the Boltzmann plot technique; both in the visible wavelength region as in the VUV. Using Abel transformation a lateral profile can be made which gives insight in the structure of the spark. Both spark-to-spark and measurement-to-measurement deviations are of interest. The goal is to understand the influence of the temperature distribution on the emission spectra in order to gain an overall improvement in measurement reproducibility. B11 Intense femtosecond laser pulse interaction with nano-clusters for ultrashort neutron pulses , Seth Brussaard1 , Maarten de Bock 2 , Jom Luiten 1 and Niek Lopes Cardozo 2 Coherence Quantum Technology, Applied Physics, Eindhoven University of Technology, Eindhoven, 5600 MB, The Netherlands Science and Technology of Nuclear Fusion, Applied Physics, Eindhoven University of Technology, Eindhoven, 5600 MB, The Netherlands Kevin Verhaegh 1 2 1 2 The interaction of an ultrashort, intense laser pulse with a jet of nano-clusters produces extremely high ion charges and high ion energies in a very short time. This can be used for various applications, such as highly intense x-ray sources, neutron sources and nucleosynthesis. To tailor the ion energy distribution understanding the physics underlying the laser-cluster interaction is of paramount importance. A first goal is to create a simplified analytical model that describes and predicts the laser-cluster interaction. This is compared to experimental results from literature and fully relativistic particle tracer simulations. A second goal is to use this model to investigate whether the ion dynamics can be tailored such that nuclear fusion reactions are induced inside a nano-cluster, possibly leading to ultrashort neutron pulses. B12 Cohesion of neutral and charged particles in subsonic expanding thermal Argon plasmas 1 R.H.J.Westermann1 , R. Engeln 2 ,M.C.M.v.d.Sanden 1 Department of Applied Physics, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, the Netherlands 2 Dutch institute for fundamental energy research, P.O.Box 1207, 3430 BE Nieuwegein Abstract Expanding thermal plasmas are interesting in a fundamental as well as a technical point of view. The fundamental point of view deals with the processes between neutral and charged particles mutually. In a technical regard, expanding thermal plasmas are often used in the manufacturing of solar cells and semi-conductors. Here, in this investigation, the aim is to acquire fundamental insight in the processes between the charged and neutral particles. Therefore the electron continuity equation including ambipolar diffusion and three-body recombination, the Poisson equation and the electron heat equation including Ohmic heating and three-body recombination energy, have been analytically solved. The calculated processes, Ohmic heating and three-body recombination will be compared with Thomson-Rayleigh scattering diagnostic measurements. Since Ohmic heating is the main process in hot plasmas and the three-body recombination process dominates in cold plasmas with respect to the subsonic expanding area, the results deviate from the three-body recombination process and the Ohmic heating mechanism as well. So the results of the performed calculations indicate the presence of both Ohmic heating and three-body recombination. B13 Plasma and nanoparticles in cylindrical microwave cavities F.M.J.H. van de Wetering, S. Nijdam, J. Beckers & G.M.W. Kroesen Eindhoven University of Technology, Department of Applied Physics, P.O. Box 513, 5600 MB Eindhoven, the Netherlands Low-pressure acetylene plasmas are able to spontaneously form (under certain conditions) dust particles, resulting in a cloud of charged particles up to micrometer sizes levitated in the plasma. A capacitively coupled plasma is ignited in a cylindrical discharge chamber that simultaneously serves as microwave resonator. Microwave cavity resonance spectroscopy (mcrs) is used to determine the electron density of the plasma. However, the accuracy of this method is directly influenced by the presence and abundance of the dust particles. This is studied in more detail by using multiple cavities. The spatial distribution of the dust is visualized with laser light scattering and video imaging thereof. The charge of the particles is also an important parameter in industrial plasma environments, where electromagnetic fields can be used to deflect or attract the particles. To gain more insight into the charging and discharging mechanisms, mcrs is complemented with other electrical measurements when the plasma is switched on and off, providing the important timescales related to these processes. B14 Removal of nox in indoor air by combining pulsed dielectric barrier discharges with TiO2 catalysts V.R.Chirumamilla1 , W.F.L.M. Hoeben 1 , F.J.C.M. Beckers1 , E.J.M. van Heesch1 , F.J.C.M. Beckers1 , and A.J.M. Pemen 1 1 Department of Electrical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands Nowadays, Indoor air quality (IAQ) is gaining importance as people spend substantial amount of their time indoors and IAQ became a determining factor for healthy life. This motivates us to develop a smart plasma based air purifier. One of the main inorganic pollutants that we encounter indoor is NOX . Various techniques have been proposed for NOX removal and low temperature plasmas looks to be an attractive option because of their ability to produce high density of energetic and chemically active species that can aid in NOX reduction (F.J.C.M. Beckers, W.F.L.M. Hoeben, A.J.M. Pemen and E.J.M. van Heesch, J. Phys. D: Appl. Phys., 46, 2013.). To increase the selectivity and reduce the by-products formation, the synergy between the plasma and catalyst has been exploited in the recent years (J. Christopher Whitehead, Pure Appl. Chem., Volume 82: 1329-1336, 2010). In this paper, an experimental study on NOX removal using synergy between plasma and catalyst in a packed bed pulsed DBD reactor will be carried out. The reactor chamber consists of a quartz tube of approximately 10 mm diameter with a stainless steel electrode in the centre of 0.4 mm diameter that is connected to the pulsed power high voltage source. The steel mesh over the reactor acts as ground electrode. The reactor is filled with different catalysts such as extruded pellets of TiO2 , TiO2 spheres coated with Cu-Mn-Oxide with different weight percentages and different particle sizes to study the NOX removal efficiency. FTIR will be used as diagnostic tool to study NO, NO2 and other by-products. Operating characteristics such as pulse repetition rate, initial NOX concentration, residence time, and specific energy input will be studied. Pulse frequency will be varied to vary the energy densities. Energy yields and the products spectrum will be presented. A comparison between the In-plasma catalytic system and the post plasma catalytic system will be made regarding the removal efficiencies, by-products formed and energy densities. As the reactor and the catalyst temperature can be controlled, an attempt will be made to study the effect of temperature on the catalyst activation. B15 Potential profile measurements on the TU/e Fusor through stark effects using LIF diagnostics. A.J. Wolf1 , R.J.E. Jaspers1 , G.M.W. Kroesen2 and J.W. Oosterbeek1 1 Department of Science and Technology of Nuclear Fusion 2 Department of Applied Physics, Eindhoven University of Technology, PO Box 513, 5600MB, The Netherlands We present a proposal for an experimental study of the central potential profile structure of a Farnsworth-Hirsh type spherical Inertial Electrostatic Confinement (sIEC) fusion reactor, by employing laser induced fluorescence (LIF) plasma diagnostics for direct highly localized E-field measurements[1] . The work is conducted on the experimental Fusor reactor developed at the TU/e, which supports a maximal operating voltage of 100kV at 100mA. Spherically confined ions directed towards the central negatively biased cathode grid, create an intense plasma region in the focus area of the reactor, creating favourable conditions for fusion reactions to occur. Prior work indicates a direct link between the shape of the space-charge induced central potential profile and the fusion rate performance[2] . Research suggests that formation of a double potential well, effectively behaving as a virtual cathode in the focus of the reactor, is essential to maximize fusion rate performance. Previous work has delivered experimental evidence for double potential well formation, however extended effort is required to gain insight in the dynamics of the potential well formation and optimization. The goal of this study is to obtain direct measurements of the potential profile to investigate the fusion rate performance in terms of the profile behaviour and the various operational parameters of the Fusor. [1] Yoshikawa k. et al (2001) Nucl Fusion 41(6):717-720 [2] Gu Y. et al (2000) IEEE Trans. on Plasma Sc. 28(1):331-346 B16 Laser-cooling simulations of the performance of an ultra-cold ion beam for FIB S.H.W. Wouters1 , G. ten Haaf1 , J.F.M. van Rens1 , S.B. van der Geer2 , P.H.A. Mutsaers1 , O.J. Luiten1 and E.J.D. Vredenbregt1 1 Coherence and Quantum Technology group, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, Netherlands 2 Pulsar Physics www.pulsar.nl In order to improve the resolution of nano-fabrication using Focused Ion Beams (FIBs) we are developing an ultra-cold ion source based on photo-ionization of an ultra-cold atomic beam. Initial calculations have shown that an ion beam brightness of 107 A/m2 sr eV at a longitudinal energy spread of less than 1 eV at a current up to 10 pA can be achieved. Combined with high performance focusing optics, this would lead to a nanometer-sized spot at which sample manipulation can be performed. Here we present the results on both the experimental realization of the efficient high-flux atom source and numerical calculations on the 2D laser cooler. The starting point of our FIB is a high-flux atom source which consist of a Knudsen cell connected to a collimating tube. This tube introduces a high flux into the opening angle of the laser cooler while minimising the flux that can not be captured. Hence, the lifetime of the source is extended and the demand on the vacuum is decreased. The performance of this source is characterised using Laser Induced Fluorescence. It is shown that the transverse velocity is distributed according to theoretical predictions. The atomic flux was found an order of magnitude lower than expected. The brightness of the atomic beam is increased by laser cooling and compression in the transverse direction by means of two sets of counter-propagating red-detuned lasers and a magnetic quadrupole field. Numerical calculations have been performed on this 2D laser cooler in order to find an optimal set of parameters. These reveal a length of only 6 cm is sufficient for cooling and compressing the atomic beam to a brightness higher than 107 A/m2 sr eV at currents up to 1 nA. Progress on both the evaluation of the high-flux atom source and the numerical calculations on laser cooling and compression will be presented. B17 A numerical model for recovery rate analysis of supercritical fluid J. Zhang1 , A.H. Markosyan2 , M. Seeger3 , E.M. van Veldhuizen3 , E.J.M. van Heesch3 , and U. Ebert2,4 1 Department of Electrical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands 2 Centrum voor Wiskunde en Informatica (CWI), P.O. Box 94079, 1090 GB Amsterdam, The Netherlands 3 ABB Switzerland Ltd, Corporate Research, Segelhofstrasse 1, CH-5405 Baden- Dattwil, Switzerland 4 Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, the Netherlands Super critical fluids (SCFs), widely researched in chemistry field, have recently drawn scientists’ attention to its potential in the area of electrical switching. The reason is that SCF combines the advantages of liquids and gases: high density and high heat conductivity (corresponding to high dielectric strength); large mass transfer ability such as the low viscosity and the high diffusion (corresponding to fast dielectric recovery capability). Existing data about breakdown voltage inside SCF have proved the satisfying dielectric strength of, but the dielectric recovery process after the breakdown inside SCF is still unexplored. The goal of this work is to study the discharge inside a SCF in detail by a numerical model. SC nitrogen is chosen to be the studied medium in this work, because of its relatively low critical pressure of 3.94 MPa and critical temperature of 126 K. Experiments with SC nitrogen can be preceded at room temperature. Nitrogen is the major component of the Earth’s atmosphere, so the environmental impact is minimized by application of SC nitrogen. We present a mathematical model to study the recovery characteristic of a SCF. We have simulated the streamer-to-spark transition and the discharge & post-discharge phase inside the SC nitrogen breakdown. B18 Coherence length of an ultracold electron source determined from diffraction patterns E.J.D. Vredenbregt, M.W. van Mourik, W.J. Engelen and O.J. Luiten Department of Applied Physics, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, Netherlands We have developed a new class of electron source by using near-threshold, ultrafast photoionization of laser-cooled, trapped rubidium atoms. Several properties of electron pulses extracted from such an ultracold source have already been investigated, showing in particular that temperatures in the few Kelvin range can be achieved with hundreds of electrons in a picosecond pulse. The ultralow source temperature - three orders of magnitude lower than conventional photoemission sources - allows us to produce intense electron pulses with large intrinsic transverse coherence length. Recently we have applied the source to produce the first diffraction patterns using ultrathin polycrystalline and single-crystal graphite samples. Here we show that the transverse coherence length of the source can be directly determined from the observed ring and spot patterns. We find that the measured values corrrespond quite well with expectations based on measured source size and source temperature. For a sample size of 200 µm, the results imply a coherence length on the order of ten nm, which is sufficient to study the structure of crystals of protein-sized molecules. The ultimate goal is to demonstrate few-shot electron diffraction of macromolecules and thus enable dynamical studies of biomolecules in an ambient environment. B19 Fluid modelling of CO2 dielectric barrier discharge for solar fuels S. Ponduri1 , M.M. Becker2 , D. Loffhagen2 , S. Welzel 1,3 , M.C.M. van de Sanden 1,3 , R. Engeln 1 1 Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands 2 Leibniz Institute for Plasma Science and Technology, Felix-Hausdorff-Str. 2,17489 Greifswald, Germany 3 Dutch Institute for Fundamental Energy Research (DIFFER), P.O. Box 1207, 3430 BE Nieuwegein, The Netherlands Electricity generated from solar energy is expected to reach grid parity soon and the natural next step is to store the excess energy in the form of high energy density hydrocarbons that are compatible with the existing transport infrastructure. In this context CO2 can be used as the carbon source for hydrocarbons so that another equally important challenge of greenhouse gas emissions can be addressed simultaneously. Dielectric barrier discharge (DBD) is being investigated as a test candidate to explore the efficacy of non thermal plasma processing in dissociation of CO2 into CO, the most energy intensive step in fuel production process. A one-dimensional fluid model of a pure CO2 discharge comprising particle balance equations for electrons, 39 chemical species, electron energy balance equation and Poisson’s equation for determination of electric field has been used to determine the most important channels of CO production in addition to ascertain the validity of Fridman’s model of vibrational up-pumping in CO2 dissociation. The role of O radicals that are also produced in CO2 dissociation has been followed in space and time along with many relevant plasma parameters and chemical species. A link between the experimental results which involve many more filaments that are spatially distributed as opposed to single filament considered in the model is established. B20 Laser cooling of a Rb atomic beam: Towards a nanometer spot size FIB J.F.M. van Rens1 , S.H.W. Wouters1 , G. ten Haaf1 , P.H.A. Mutsaers1 , O.J. Luiten1 and E.J.D. Vredenbregt1 1 Coherence and Quantum Technology group, Department of Applied Physics, Eindhoven University of Technology, Netherlands Focused Ion Beams (FIBs) are an essential tool in the semiconductor industry for defect analysis, circuit modification, etc. To keep up with constantly decreasing dimensions of components on integrated circuits, brighter ion sources are required to achieve smaller spot sizes. A new source concept is the Atomic Beam Laser-cooled Ion Source (ABLIS), which uses laser light pressure to cool down and compress a rubidium atomic beam. Photo-ionization of this intensified Rb beam followed by focusing should then result in a heavy ion FIB capable of milling with a nanometer spot size. Laser cooling of rubidium requires multiple laser frequencies as a result of hyperfine splitting. To understand the role of the so-called repump laser field in laser cooling, a rate equation model has been made to study the population dynamics of the six relevant energy levels of rubidium through the laser cooling stage. The predictions are tested with Monte Carlo simulations, in which Rb atoms travel through a one-dimensional magneto-optical trap. Both model and simulations show that a repump field with 10% of the intensity of the cooling laser field is sufficient for successful cooling. An electro-optical modulator is used to implement the repump field in the set-up. First laser cooling experiments show an increased laser-induced fluorescence signal at a position far from the source, signalling increased flux density. The goal is now to investigate whether it is possible to cool the atomic beam down to 100 µK. Subsequently, a magnetic quadrupole will be installed in the set-up to magneto-optically compress the beam as well. B21 Burning Dusty Plasma Rémy JUTTIN1 , Leroy SCHEPERS2 , and Job BECKERS2 1 Polytech Orléans, Orléans, 45072 cedex 2, France 2 Applied Physics, TU/e, Eindhoven, P.O. Box 513, 5600MB, The Netherlands Nowadays, most processes in the plasma sheath the space charge region at the border of a discharge - are not completely understood. Some models have been suggested in order to predict the behavior of plasma and several parameters in the sheath. Experimentally, it is difficult to measure them because methods to do so tend to disturb the plasma. Here, we introduce one microparticle into the plasma which is used as a probe. The initial position of the particle is where electrostatics forces equilibrate gravity. In order to probe the sheath also at different position, the particle size is changed gradually by reaction with oxygen. B22 Creeping sparks B. Rouch1 , D.J.M. Trienekens2 , and S. Nijdam2 1 Polytech Orléans, 45000 Orléans, France 2 EPG, Eindhoven University of Technology, Eindhoven, 5600 MB, the Netherlands Gas insulated high voltage devices usually contain solid insulation for mechanical support or as an enclosure. Although the dielectric strength of the gaseous and solid insulation may be sufficient individually, detrimental breakdown can still can occur because the gas-solid interface may be weaker. An insulator surface can for instance modify the local electric field, or emit electrons, and facilitate discharges along its surface flashover. The underlying fundamental physics of these creeping sparks however is poorly understood. To be able to use design rules based on knowledge rather than experience we need to gain a deeper understanding of the associated physics. In this research work, the streamer-like phase that precedes sparking will be investigated. We are currently setting up an experiment to measure charges present on a dielectric surface while a discharge is propagating on this surface. For this experiment, we use a BSO crystal, which exhibits the Pockels effect, with a thin coating of sample material. The polarization of light passing through the BSO crystal is changed under the application of an external electric field. This enables us to visualize the charge of a streamer on the sample surface. The measured electric field however is a summation of the electric field resulting from charges present in the electrode and charges present in the streamer and on the surface. To eliminate the electric field due to electrode charges, we need to calculate this field, for which we use COMSOL. We measure the voltage pulse used to generate the discharge and use this as input for the simulation. We then calculate the time-dependent electric field in 3D. B23 FTIR Spectroscopy for description of surface processes in biomedical applications using atmospheric pressure plasma jets A.Desaunay1 , A.Sobota2 , and O.Guaitella2,3 Polytech Orléans, Orléans, 45072 cedex 2, France 2 EPG, Eindhoven University of Technology, Eindhoven, 5600 MB, The Netherlands 3 LPP, Ecole Polytechnique, Palaiseau, 91128 cedex, France 1 Nowadays, there are more and more applications with plasma in the biomedical area. Sterilization decontamination, dental and dermatology are examples of applications using plasma to treat the patient. However, the interaction between plasma and organic surfaces is not known yet. Indeed, this is important to learn about these interactions to continue to use plasma in biomedical applications. This project concerns cold atmospheric pressure plasma jets that can be used in biomedical applications and for surface modifications. The goal of this project is to use FTIR Spectroscopy in order to determine processes in a plasma jet interaction on different types of surfaces. B24 Effect of high-flux H plasma exposure on tungsten surface damage during transient heat loads 1 G.G. van Eden1 , T. W. Morgan1 , and G. De Temmerman1 FOM Institute DIFFER, Nieuwegein, 3430 BE, Netherlands Making accurate predictions of the lifetime of Plasma Facing Components (PFCs) in the ITER divertor is of paramount importance for the successful operation of this machine. A key concern for this are transient heat loads caused by Edge-Localized Modes (ELMs), disruptions and Vertical Displacement Events (VDEs). In order to investigate the thermal response of tungsten (W) to such conditions, ELMs were replicated by a millisecond laser with and without the presence of a high-flux H plasma in the linear plasma generator Magnum-PSI. From fast IR-thermography, the temperature evolution of consecutive transients is recorded in order to assess changes in power handling capabilities over time of the tungsten surface. Surface damage, quantified by the arithmetic roughness parameter, has been measured and found to be linearly dependent on the surface peak temperature and pulse number of the transient for temperatures >1100 ◦ C. Similarly, linear growth of grains was observed for temperatures >1500 ◦ C and found to occur even after applying a single ms pulse. The presence of plasma exposure seemed to to have little effect on damage evolution when considering the transient peak temperature although the onset temperature of melting is found lowered compared with loading to plasma and laser sequentially. Next to this, a reduction in power handling capabilities was observed by measuring the relative change in ∆T after 1000 laser pulses which was found to be an increase of 50 % for heat fluxes >36 MJ m−2 s−1/2 (laser only) and 30 % at 15.1 MJ m−2 s−1/2 (during simultaneous plasma and laser exposures).
