EPS2005, Session "P-1" Abstracts
Session Author PosterTitle P-1.001 P.Träskelin Molecular dynamics simulation of erosion of tungsten carbide by deuterium bombardment P-1.002 B.N.Bazylev Erosion of dome armour after multiple disruptions and ELMs in ITER P-1.003 I.S.Landman Contamination and radiation losses in post-ELM tokamak plasma P-1.004 T.Lunt Experimental Investigation on the Plasma-Wall Transition P-1.005 TilmannLunt Ion temperature measurements by means of a combined force - Mach - Langmuir probe P-1.006 A.Herrmann Filamentary heat deposition to the first wall in ASDEX Upgrade Fine Structure of Type-I Edge Localized Modes in the Steep Gradient Region in ASDEX P-1.007 B.Kurzan Upgrade P-1.008 D.P.Coster Edge simulations of an ASDEX Upgrade Ohmic shot P-1.009 H.W.Mueller Plasma flow in the scrape-off layer of ASDEX Upgrade P-1.010 R.Dux Tungsten Erosion at Auxiliary Limiters in ASDEX Upgrade P-1.011 V.Rohde Carbon migration at the divertor of ASDEX Upgrade P-1.012 Y.Feng Role of recycling in W7-AS divertor plasmas P-1.013 A.Kirschner Modelling of tritium retention and target lifetime of the ITER divertor Investigation of carbon transport by 13CH4 injection through graphite and tungsten test P-1.014 A.Kreter limiters in TEXTOR Carbon deposition and fuel accumulation in castellated limiters exposed in the SOL of P-1.015 A.Litnovsky TEXTOR P-1.016 C.Busch Impact of the DED on ion transport and poloidal rotation in TEXTOR Modelling of hydrocarbon transport and emission after methane injection into the TEXTOR P-1.017 D.Borodin boundary plasma using the ERO code P-1.018 G.Sergienko High temperature erosion of tungsten exposed to the TEXTOR edge plasma P-1.019 G.Sergienko Tungsten melting under high power load in the TEXTOR edge plasma P-1.020 G.Telesca Screening and radiation efficiency of carbon with Dynamic Ergodic Divertor on TEXTOR On the influence of the magnetic resonances on the heat flux structure of the Dynamic P-1.021 M.W.Jakubowski Ergodic Divertor P-1.022 OliverSchmitz Impact of the Dynamic Ergodic Divertor on the Structure of the Plasma Edge at TEXTOR P-1.023 S.S.Abdullaev Structure of stochastic field lines near the separatrix in poloidal divertor tokamaks P-1.024 V.Philipps Removal of carbon layers by oxygen treatment of TEXTOR P-1.025 A.S.Kukushkin Improved Modelling Of Neutrals And Consequences For The Divertor Performance In Iter P-1.026 O.V.Ogorodnikova Simulation of brittle destruction of different types of graphite using PEGASUS-3D code Parametric investigation of temperature and stress evolution in actively cooled plasma- P-1.027 O.V.Ogorodnikova facing components during high heat fluxes P-1.028 M.K.Salem The Influence of Resonant Helical Field on The Zeff in IR-T1 Tokamak P-1.029 M.Kuldkepp Oxygen impurity profile studies in the EXTRAP T2R reversed field pinch P-1.030 J.JuulRasmussen Turbulent Transport and Mixing of Impurities in the Plasma Edge P-1.031 M.Priego Clustering and pinch of impurities in plasma edge turbulence High Power ICRH scenarios in Tore-Supra a potential route towards improved core P-1.032 F.G.Rimini confinement at high density P-1.033 D.Elbèze Scaling of confinement in the ITPA L-mode database with dimensionless variables Giant Oscillations of Electron Temperature during zero loop voltage discharges on Tore P-1.034 F.Imbeaux Supra P-1.035 Jean-FrançoisArtaud Predictive integrated modelling for ITER scenario The origin of the long time correlations of the density fluctuations in the Scrape off Layer P-1.036 P.Devynck of the Tore Supra Tokamak Electron Temperature Fluctuation Studies in Different Confinement Regimes by Means of P-1.037 V.S.Udintsev Correlation ECE on Tore Supra P-1.038 G.Fuhr Zero Dimensional Model for Transport Barrier Oscillations in Tokamak Edge Plasmas Study of nonlinear phenomena in a tokamak plasma using a novel Hilbert transform P-1.039 R.Jha technique Long range time correlations in the electrostatic fluctuations of a low temperature dc P-1.040 JoyantiChutia magnetised plasma P-1.041 M.Aizawa Transport Properties of Low Aspect Ratio L 1 Helical Systems Transient electron heat transport and reduced density fluctuation after pellet injection in JT- P-1.042 H.Takenaga 60U reversed shear plasmas P-1.043 M.Kikuchi Measurement of local electrical conductivity and thermodynamical coefficients in JT-60U P-1.044 Y.Idomura Comparisons of gyrokinetic PIC and CIP codes P-1.045 N.Ohno Intermittent Fluctuation Property of JT-60U Edge Plasmas First results of the Gas Puffing Imaging Diagnostics in a reversed-field pinch plasma First P-1.046 Y.Yagi results of the Gas Puffing Imaging Diagnostics in a reversed-field pinch plasma First results of the Gas Puffing Imaging Diagnostics in a reversed-field pinch plasma Weak temperature dependence of the thermal diffusivity in high-collisionality regimes in P-1.047 J.Miyazawa LHD 3D Simulation of the Magnetic Shear contribution on the Improvement of the Confinement P-1.048 M.ElMouden in Plasma of Tokamak P-1.049 A.Scarabosio Momentum transport and plasma rotation spin up in TCV Simulation of the Absolute TCV Compact Neutral Particle Analyser Charge-Exchange P-1.050 Ch.Schlatter Spectrum Density behavior during eITBs in TCV discharges experimental observations and P-1.051 E.Fable theoretical calculations via transport simulations Electron heat transport dependence on plasma shape and collisionality in EC heated L- P-1.052 Y.Camenen mode TCV plasmas P-1.053 R.O.Dendy Analysis of dissipation in MHD turbulence simulations in two and three dimensions P-1.054 OKwon Numerical Plasma Edge MHD Stability Analysis Revisited Effects of radio frequency waves on dissipative low frequency instabilities in mirror P-1.055 S.S.Kim plasmas P-1.056 R.Jiménez-Gómez Studies of MHD instabilities in TJ-II plasmas P-1.057 T.S.Pedersen First results from the Columbia Non-neutral Torus P-1.058 X.Sarasola Field Line Mapping Results in the CNT Stellarator
P-1.059 J.F.Lyon Recent Developments In Quasi-Poloidal Stellarator Physics P-1.060 B.Stratton Fast soft x-ray camera observation of fast and slow reconnection events on NSTX P-1.061 EDFredrickson Scaling of kinetic instability induced fast ion losses in NSTX P-1.062 M.C.Zarnstorff Equilibrium of High-Beta Plasmas in W7-AS P-1.063 N.N.Gorelenkov Resonant kinetic ballooning modes in burning plasma P-1.064 R.Raman Transient CHI Solenoid-free Plasma Startup in NSTX P-1.065 QingweiYang Investigations of disruption on the HL-2A tokamak A Toroidal Shell Model for Active Stabilization of Resistive Wall Modes and Its P-1.066 HogunJhang Application to KSTAR Plasmas P-1.067 Y.M.Jeon Design of Optimal Plasma Position and Shape Controller for KSTAR P-1.068 E.J.Strait Feedback Stabilization of Resistive Wall Modes in DIII-D P-1.069 J.R.Ferron Control of DIII-D Advanced Tokamak Discharges P-1.070 T.A.Casper Operational Enhancements in DIII-D Quiescent H-Mode Plasmas P-1.071 R.Raman Fueling Requirements for Advanced Tokamak operation P-1.072 B.E.Chapman Initial exploration of the density limit in the MST RFP P-1.073 R.Cavazzana Optical Investigation of Edge Turbulence on RFX-mod P-1.074 E.Gazza Fast optical spectrometer for the charge exchange diagnostic on RFX-mod P-1.075 C.Mazzotta Study of Plasma density profiles evolution using the new scanning interferometer for FTU P-1.076 G.DeTemmerman Mirror Test for ITER Optical Characterisation of Metal Mirrors in Divertor Tokamaks
P-1.077 E.Gauthier Design of a wide-angle infrared thermography diagnostic for JET Neutron energy measurements of Trace Tritium plasmas with NE213 compact spectrometer P-1.078 L.Bertalot at JET Development of new neutron emission spectrometry diagnostics for fusion experiments at P-1.079 A.Hjalmarsson JET Diagnosis of high-energy fuel ions on ITER with neutron emission spectroscopy NES P-1.080 M.Gatu-Johnson Monte Carlo calculations based on NES measurements on JET DT plasmas MPR neutron emission spectroscopy of fast tritons from T D ion cyclotron heating in JET P-1.081 MarcoTardocchi plasmas New method to calculate the Gaunt factor for the refinement of Zeff evaluation in fusion P-1.082 V.Stancalie plasmas First study of 2-D spatial distribution of D-D and D-T neutron emission in JET Elmy H- P-1.083 G.Bonheure mode plasmas with Tritium puff P-1.084 M.E.Notkin Absorption experiments on the CASTOR tokamak P-1.085 A.A.Lizunov Mse-Diagnostic For Multi-Chord Measurents Of Plasma Beta In Gdt P-1.086 P.A.Bagryansky Dispersion Interferometer based on CO2 - laser Investigation of the Upper Hybrid Resonance Cross-Polarization Scattering Effect at the FT- P-1.087 GusakovE.Z. 2 Tokamak P-1.088 A.Popov Spatial Resolution of Poloidal Correlation Reflectometry P-1.089 I.I.Orlovskiy Hilbert Spectrum Analysis of Mirnov Signals P-1.090 K.Yu.Vukolov Mitigation of hydrocarbon film deposition on in-vessel mirrors P-1.091 Yu.V.Gott A Vacuum Photoemission Detector for X-ray Tomography P-1.092 D.P.Kostomarov Calculation of Plasma Boundary Using Video Images
P-1.093 V.Yu.Sergeev Fast Electron Studies In T-10 Plasmas By Means Of Carbon Pellet Injection P-1.094 G.VanWassenhove Study of the ICRH antenna coupling at TEXTOR P-1.095 S.Nowak Electron Cyclotron Current Drive experiments in the FTU tokamak P-1.096 E.Barbato Interpretation od LHCD efficiency scaling with the electron temperature P-1.097 E.Giovannozzi Plasmoid drift during vertical pellet injection in FTU discharges P-1.098 G.Granucci Quantification of suprathermal current drive on FTU P-1.099 A.V.Voronin Injection of intense plasma jet in the spherical tokamak Globus-M P-1.100 IJenkins Off-Axis NBI fast ion dynamics in Trace Tritium Experiment P-1.101 N.V.Sakharov Behavior of Ions in Auxiliary Heating Experiments in Globus-M Spherical Tokamak P-1.102 V.A.Kornev First experiments on NBI in the TUMAN-3M tokamak P-1.103 V.B.Minaev Study of the Beam - Plasma Interaction in the Globus-M Spherical Tokamak P-1.104 L.N.Khimchenko Radiative power piculiarities during impurity pellet injection into T-10 plasmas P-1.105 V.G.Kapralov Recent results of hydrogen pellet injection P-1.106 N.B.Rodionov ICRF Heating together with neutral beams in Volume Neutron Sources JUST-T P-1.107 T.Bolzonella Overview of global MHD behaviour in the modified RFX Reversed Field Pinch P-1.108 G.Cenacchi The scientific program of the Ignitor experiment P-1.109 W.Kernbichler Simple criteria for optimization of trapped particle confinement in stellarators P-1.110 W.Kernbichler Neoclassical transport for LHD in the 1/ nu regime analyzed by the NEO code Calculation of neoclassical transport in stellarators with finite collisionality using P-1.111 W.Kernbichler integration along magnetic field lines P-1.112 K.Schoepf Fast Ion Confinement in Tokamak Current Hole Regimes P-1.113 A.Nicolai Modelling of Plasma Rotation under the Influence of Helical Perturbations in TEXTOR Modelling of the penetration process of externally applied magnetic perturbation of the P-1.114 Y.Kikuchi DED on TEXTOR P-1.115 R.Preuss Stellarator scaling considering uncertainties in machine parameters P-1.116 D.Sharma Role of stochasticity in W7-X edge transport P-1.117 R.Coelho Effect of Alfvén resonances on the penetration of error fields on a rotating viscous plasma P-1.118 J.-E.Dahlin Advanced Reversed Field-Pinch Confinement Scaling Laws P-1.119 Y.Q.Liu A Uniform Framework to Study Resistive Wall Modes P-1.120 A.K.Wang An improved fluid description on toroidal ITG modes P-1.121 J.Urban Methodology of electron Bernstein wave emission simulations A Novel ST Configurative Events with Controllable and Reproducible Alternative Self- P-1.122 S.Sinman organization Process P-1.123 B.Labit Drift waves in the TORPEX toroidal plasma device Experimental studies of plasma production and transport mechanisms in the toroidal device P-1.124 M.Podesta TORPEX P-1.125 T.Hiraishi Formation of Very Deep Potential Well with Electrode Biasing in a Toroidal Device P-1.126 A.Stark Ion dynamics in a collisionless magnetic reconnection experiment P-1.127 F.M.Aghamir Eigen Modes of a Dielectric Loaded Coaxial Plasma Waveguide Study of Gas Admixture Influences On The Pinch Dynamics In A 90 kJ Filippov Type P-1.128 A.R.Babazadeh Plasma Focus P-1.129 V.A.Rantsev-Kartinov Local Destruction of Magnetic Surfaces and Impurity Distributions in Òokamak
P-1.130 E.A.Evangelidis Angular momentum coupling in tokamaks P-1.131 F.Porcelli Long term evolution of 3D collisionless magnetic reconnection Qualitative similarities between edge localised modes ELMs in fusion plasmas and P-1.132 C.Ionita complex space charge configurations CSCCs in low-temperature plasmas P-1.133 Z.P.Xu Diagnosis of Wire-Array Z-Pinch Implosion Using X-ray Framing Cameras P-1.134 S.Dan'ko Elaboration of High-Current Drivers Aimed at the Inertial Fusion Energy Inertial Fusion Reactor Physics effect of Activation and Radiation Damage of Materials, P-1.135 J.M.Perlado and Tritium emissions. P-1.136 Ph.Nicolaï A practical nonlocal model for electron transport in magnetized laser-plasmas P-1.137 WenluZhang Evolution of Rayleigh-Taylor Instability with Arbitrary Density Profiles P-1.138 M.Kaluza Self-Generated Magnetic Field Distributions in Multiple-Beam Produced Plasmas P-1.139 N.Ozaki Laser-driven flyer impact experiments on LULI 2000 laser facility Optical investigation of flyer disk acceleration and collision with massive target on the P-1.141 T.Pisarczyk PALS laser facility Numerical modelling of strong shock waves and craters for the experiments using single P-1.142 S.Borodziuk and double solid targets irradiated by high power iodine laser PALS Experimental characterization of a strongly coupled solid density plasma generated in a P-1.143 G.Gregori short-pulse laser target interaction Ion energy measurements in laser-generated plasmas at INFN-LNS and PALS research P-1.144 L.Torrisi centre P-1.145 K.B.Fournier Absolute x-ray yields from laser-irradiated Ge-doped aerogel targets P-1.146 B.Sharkov Stopping Power Measurements for 100-keV/u Cu2 Ions
P-1.147 J.Wolowski Interaction of high-energy laser pulses with plasmas of different density gradients Thomson scattering of electron plasma waves stimulated by Raman backscattering in P-1.148 S.Depierreux gasbag plasmas P-1.149 S.F.Martins High intensity B field generation in underdense plasmas and the Inverse Faraday Effect P-1.150 J.E.Santos Stimulated Raman Scattering with broadband effects P-1.151 M.D.Barriga-Carrasco H2 distributions after traversing plasma targets Heating of Tantalum Plasma for Studies on the Activation of the 6.238 keV Nuclear Level P-1.152 R.Fedosejevs of Ta-181 P-1.153 L.O.Silva Stimulated Brillouin scattering by broadband radiation sources Analysis of the propagation of a laser beam through a preformed plasma using imaging P-1.154 KevinLewis diagnostics P-1.155 F.Girard Experimental multi-keV x-ray conversion efficiencies from laser exploded germanium foil. P-1.156 JonHowe Periodic features modifying the Heb line profile from an aluminium plasma P-1.157 N.V.Vvedenskii Generation of Terahertz Radiation during Optical Breakdown of a Gas P-1.001, Monday June 27, 2005
Molecular dynamics simulations of erosion of tungsten carbide by deuterium bombardment
Petra Träskelin, Kai Nordlund, Juhani Keinonen
Association Euratom-TEKES, Accelerator Laboratory, P.O.B. 43, FI-00014 University of Helsinki, Finland
The selection of plasma facing materials for present and next-generation fusion devices is still an open question. Refractory metal carbides are interesting candidates due to their low sputtering yields. Metal carbides are not only naturally present at the interfaces between the carbon first wall and the metallic parts underneath in fusion reactors, but also formed when hydrocarbon molecules which have been eroded under particle bombardment react with metal parts in other sections of the plasma chamber. Mixed WC layers could therefore be formed due to redeposition of eroded hydrocarbon molecules. The most relevant metal carbide to be considered in this context is tungsten carbide. By us- ing a reactive WCH-potential we have performed molecular dynamics simulations to elucidate processes occurring under device operation at the reactor first walls. Tungsten carbide is an extremely hard material and might provide a compromise between the materials which are cur- rently dominating in the plasma chamber, tungsten and carbon, since the erosion yield is small. The erosion due to low-energy H on these surfaces was investigated in more detail by per- forming cumulative simulations of deuterium impinging onto WC structures. As a result, we see that amorphous WC surface layers are formed regardless of the initial WC structure. Loosely bound hydrocarbons on these surfaces can erode by the swift chemical sputtering mechanisms. The threshold for C erosion from WC due to D by this mechanism is less than 10 eV, much less than the threshold of about 60 eV predicted by physical sputtering models. This means that also mixed WC-like materials can be expected to be subject to chemical erosion of C down to very low energies of impinging D or T particles, just like C-based divertor materials. The W erosion yields are not subject to chemical erosion, meaning that there is preferential chemical sputtering of C. The C content in thin WC layers formed by C redeposition might thus be reduced under D bombardment. P-1.002, Monday June 27, 2005
Erosion of dome armour after multiple disruptions and ELMs in ITER B.N. Bazylev1, G.Janeschitz2, I.S. Landman1, S.E. Pestchanyi1 1Forschungszentrum Karlsruhe, IHM, P.O. Box 3640, 76021 Karlsruhe, Germany 2Forschungszentrum Karlsruhe, Fusion, P.O. Box 3640, 76021 Karlsruhe, Germany
In the future tokamak ITER a part of confined plasma is dumped onto the divertor armour, during intense transient events such as disruptions and bursts of the Edge Localized Mode (ELM). This may result in a surface melting and further evaporation. During one ITER discharge about 103 ELMs are expected, and during ITER operation several hundred disruptions, interspaced by ELMs may occur. The heat load of a single giant ELM or a disruption causes a plasma shield being formed from evaporated material in front of the target. This shielding layer is a source of intense radiation at GW/m2 level with durations of 0.5 ms for ELMs and up to 10 ms for the disruptions. Intense radiation from the vapour shield may leads to enhanced erosion of nearby dome armour. Pure sintered W or tungsten lamellae are foreseen as armour for the dome. In case of W armour the main mechanisms for damage are surface melting and melt motion. Melt motion in the thin layer may produce surface roughnesses and droplet splashing thus causing erosion and determining the lifetime of the armour. For tungsten dome armour the results of fluid dynamics simulation of the melt motion erosion after repetitive radiation heat loads caused by multiple disruptions with the energy deposition Q of 10-30 MJ/m2 and the duration t of 1-10 ms and of multiple ELMs with Q= 1-3 MJ/m2 and t = 0.1-0.5 ms are presented. For different single disruptions and ELMs, the heat loads at the divertor surface and the radiation at the lateral walls are calculated using the two-dimensional MHD code FOREV-2D. Reduction of the radiation heat load due to absorption in the material vaporized from the dome surface is taken into account. The target melt motion erosion is calculated by the fluid dynamics code MEMOS-1.5D in the ‘shallow water’ approximation, with the surface tension and viscosity of molten metal taken into account. The evaporation and melt motion erosion for different types of tungsten armour is analyzed. P-1.003, Monday June 27, 2005
Contamination and radiation losses in post-ELM tokamak plasma I. S. Landman, G. Janeschitz, S.E. Pestchanyi Forschungszentrum Karlsruhe, IHM, Post box 3640 D-76021, Karlsruhe, Germany
Future tokamaks such as ITER are going to operate in the H-mode regime with repetitive edge localized instabilities. At each burst of ELM the lost DT plasma comes from the scrape-off layer at the divertor armour surface. After such a pulse of the size 0.3-0.5 ms and 1-3 MW/m2 the surface emits eroded and then ionized armour materials (carbon or tungsten) backwards. The resulting contamination of the SOL may cause enhanced penetration of the impurities into the pedestal and core regions, which reduces the reactor performance, for instance because of increased radiation losses.
In the last few years the influx of eroded material and accumulation of the impurity rich plasma in the SOL have been investigated with the MHD code FOREV-2D, in which radiation transport in a multi-fluid plasma is one of most developed features. In this work further progress is reported on the behaviour of impurities in the post-ELM plasma. The penetration of impurities inside the pedestal region of ITER and in the core is modelled and radiation losses are estimated.
The confined DT plasma is modelled as a fluid in which an impurity of W- or C-ions is assumed. The impurity concentration at the boundary (the separatrix) is calculated with FOREV-2D as a function of time. A self-consistent two-dimensional model for pedestal and core plasma diffusion and equilibrium in ITER magnetic field configuration is developed. The plasma transport is based on the conductivities corresponding to the neo-classical theory (ions) and a semi-empirical model for temperature gradient turbulences. P-1.004, Monday June 27, 2005
Experimental Investigation on the Plasma-Wall Transition
G.Fußmann1, T.Lunt1, N.Ezumi2
1Institut für Physik, Humboldt-Universität zu Berlin, AG Plasmaphysik 2Nagano National College of Technology, Tokuma, Nagano
The streaming of an argon plasma through a ‘magnetic’ nozzle magnetic field configuration of the linear plasmagenerator PSI-2 towards an absorbing target plate was studied experimentally by means of Laser Induced Fluorescence. This non-perturbative diagnostic allows the measurement of the ion velocity distribution, and thus the streaming velocity and the ion temperature in particular. Due to the nozzle effect induced by an inhomogeneous B-field, the transition to supersonic flow velocities can take place far away from the edge of the electrostatic sheath that builds up at the absorbing target plate. Two different situations were observed: under standard neutral gas pumping conditions half-sided Maxwellian ion-distributions as predicted by theory with Mach numbers around M~0.5 were found. Decreasing the neutral density by maximum pumping affords, supersonic fluxes with distributions clearly deviating form the Maxwellian case are finally observed. Emphasis will be put on the interpretation of the half-sided distribution functions.
P-1.005, Monday June 27, 2005
Ion temperature measurements by means of a combined force - Mach - Langmuir probe
T.Lunt1, C.Hidalgo2, E.Calderón2
1Institut für Physik, Humboldt-Universität zu Berlin, AG Plasmaphysik 2Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, CIEMAT
Chavers et al. [1] have proposed recently the use of a force sensor to measure momentum fluxes in a plasma experiment. It has been shown experimentally that forces as small as several mN are measurable in a non-fusion plasma discharge. Here we report on a combined force – Mach – Langmuir probe. Comparing the force on the probe head, 2 which is proportional to cs , with the difference of ion saturation currents at the two
opposite collectors (Mach probe), ∆Is ∝ cs, the speed of sound cs can be obtained. If additionally the electron temperature is known from Langmuir probe measurements, the ion temperature can be deduced. This could be a valuable diagnostic for the edge layer of fusion devices which is until now only hardly covered by other methods. We will report on measurements that are currently performed in the plasmagenerator PSI-2 in Berlin.
[1] D.G.Chavers, et al. Momentum flux measuring instrument for neutral and charged particle flows, Review of Scientific Instruments, Vol. 73, No. 10, Oct. 2002 P-1.006, Monday June 27, 2005
Filamentary heat deposition to the first wall in ASDEX Upgrade
A. Herrmann1, J. Neuhauser1, V. Rohde1, W. Bobkov1, T. Eich1, A. Kirk2, B. Kurzan1, H.-W. Müller1, ASDEX Upgrade team 1 Max-Planck-Institut für Plasmaphysik, EURATOM-IPP Association, Garching, Germany 2 EURATOM/UKAEA Fusion Association, Culham Science Centre, Abingdon, UK
The investigation of heat deposition to non-divertor components in present experiments and its extrapolation to a next step device as ITER is essential because it would effect the design and the necessary heat receiving capacity of the first wall. Measurements in different tokamaks reveal that a fraction of up to 50 % of the energy ejected during ELMs from the plasma is deposited outside the divertor. Heat fluxes of a few tens of MW/m2 with deposition times in the order of a few hundred microseconds are observed by thermography in ASDEX Upgrade. Independent investigations of the heat and particle transport in the outer midplane of ASDEX Upgrade by reciprocating Langmuir probes, fast Thomson scattering system and thermography reveal a burst like or filamentary structure. The Thomson scattering system running in burst mode detects well separated density and temperature blobs in the plasma edge and the SOL moving radially outward. A fast reciprocating Langmuir probe in the outer midplane measures temporally structured ion saturation currents during ELMs. These measured bursts may be interpreted as filaments ejected from the plasma edge rotating toroidally and moving radially outward. Snapshot like thermographic measurements of the heat load pattern at outside limiters show a poloidally structured heat deposition which can be interpreted as filamentary heat deposition with toroidal mode numbers of 10-25 lasting a few hundred microseconds. A subset of filaments shows a fine structure in the heat deposition pattern on a few millimetre scale. This filamentary heat deposition contributes with less than 1 % to the overall heat load on non- divertor components. Nevertheless, they cause the maximum heat flux and as a consequence the maximum surface temperature which is the main concern for the first wall design in a next step device. Most of the ELM energy is deposited as ‘background’ with moderate heat fluxes. Diagnostic improvements at ASDEX Upgrade allow now a combined investigation of the filamentary transport in the SOL by Langmuir probes and thermography for the same ELM. The evolution of the ELM structure can be resolved with a time resolution down to 100 µs by thermography. A further improvement of the temporal resolution can be achieved by ELM sorting according to the start of the ELM. In addition, the combined measurements allow proofing the assumption of toroidal rotation and radial movement necessary to interpret the probe measurements. The results of these combined measurements and its interpretation in the framework of existing filamentary transport models is presented in the paper. P-1.007, Monday June 27, 2005
Fine Structure of Type-I Edge Localized Modes in the Steep Gradient Region in ASDEX Upgrade
B. Kurzan, H. D. Murmann, J. Neuhauser and the ASDEX Upgrade Team
Max-Planck-Institut für Plasmaphysik, EURATOM Association, Boltzmannstr. 2, D-85748 Garching
The steep edge pressure gradient characteristic of the H-mode in tokamaks is relaxed by quasi-periodically occuring edge-localized modes (ELMs). In the following type-I ELMs are investigated. It is expected that during an ELM field-aligned structures at the plasma edge are observed experimentally. 1D radial plasma profiles have been obtained so far by Thomson scat- tering and reflectometry. These profiles are obtained either along a radial line with a resolution of several millimeters, or are averaged in the poloidal direction, or in time. These profiles only show a flattening during the ELM. Radially and poloidally localized maxima have been found in the scrape-off layer by many diagnostics on several tokamaks. The Thomson scattering diagnostic in ASDEX Upgrade was recently upgraded by a new data acquisition system. It is now possible to measure the fine structure of an ELM in the electron density and temperature in the steep gradient and pedestal region, where the ELM originates, as predicted theoretically. For this the 5 lasers of the Thomson diagnostic, which are
staggered radially by 1:5 mm and which for this investigation are located on the low field side of the tokamak, are fired within 2 µs. 2D images in the poloidal plane of the steep gradient and pedestal region are thus obtained. Before the ELM a locked precursor structure with a toroidal mode number of 10 is frequently observed in the 2D images for the co-injected plasmas investigated so far. During the ELM lo- calized maxima (‘blobs’) around the separatrix and corresponding minima (‘holes’) towards the pedestal are observed frequently during an ELM. The deduced toroidal mode numbers of the blob structures are in the range between 8 and 20. This is in agreement with theoretical predictions for the most unstable peeling-ballooning modes. This new experimental result con- firms the physical model that type-I ELMs originate indeed in the steep gradient region, and not e. g. in the scrape-off layer where such structures were observed so far. The number of independent filaments existing in the scrape-off layer was scaled from the Thomson scattering results to be around 80 during the ELM. The particles lost to the divertor by these filaments is in the range of the globally lost particles during an ELM of some percent. This is in agreement with results obtained with Langmuir probes on other tokamaks. P-1.008, Monday June 27, 2005
Edge simulations of an ASDEX Upgrade Ohmic shot D.P. Coster, A. Chankin, G. Conway, L. Kaveeva∗, C. Konz, M. Reich, T. Ribeiro, V. Rozhansky∗, J. Schirmer, B.D. Scott, S. Voskoboynikov∗ and the ASDEX Upgrade Team Max-Planck-Institut f¨urPlasmaphysik, EURATOM Association, D-85748 Garching bei M¨unchen,Germany ∗St. Petersburg State Polytechnical University, St. Petersburg, Russia
Excellent measurements of the upstream edge electron and ion temperatures, electron density and electric field have been made for the AUG “standard” Ohmic shot. SOLPS simulations have been performed to produce the best possible match of the upstream temperature and density measurements under various assumptions, producing estimates of the radial energy and particle transport coefficients. Under the assumption of equal power flows via the electrons and ions at the core boundary, the ion thermal diffusivity was found to be 0.52 m2s−1 and the electron thermal diffusivity 0.44 m2s−1. The ion neo-classical thermal diffusivity was found to be about 0.1 m2s−1. For slightly lower density conditions, gyro-fluid turbulence simulations based on the experimentally mea- sured gradient lengths found the ion thermal diffusivity to be 0.15 m2s−1 and the electron thermal diffusivity 0.49 m2s−1, but with about 1/6 of the power in the ion channel. In addition, when run with the drift terms enabled in SOLPS, the calculated radial electric field compares well with that measured. P-1.009, Monday June 27, 2005
Plasma flow in the scrape-off layer of ASDEX Upgrade
H.W. Müller1, V. Bobkov1, V. Rohde1, M. Maraschek1, J. Neuhauser1, A. Schmid1, M. Tsalas2 and ASDEX Upgrade Team1 1 Max-Planck-Institut für Plasmaphysik, EURATOM-Association, D-85748 Garching, Germany 2 NCRS Demokritos, Inst. of Nuclear Technology - Rad. Prot., Attica, Greece
Although scrape-off layer (SOL) physics in divertor tokamaks is relatively well understood, the situation is worse for in/out asymmetries in the SOL, divertor plasma parameters and the plasma flows. For example low field side profile and transport analysis reveales fast radial transport to the outer wall, while an investigation of low-to-high field side hydrogen and carbon fluxes indi- cate dominant high field side recycling. Global SOL plasma flows, driven e.g. by drift effects, poloidal pressure asymmetries or plasma rotation, migth reconcile these findings. In this paper we focus on measurements in ASDEX Upgrade which were performed by Langmuir probes on a reciprocating manipulator close to the outer midplane in connection with probes in the divertor. Two different probe arrangements were used with the manipulator probes; simple pin probes and in-plane probes. The in-plane mounted probes allow for higher heat fluxes onto the probe and reduce the uncertainty in the probe area for the flow measure- ments. In addition to well established lower divertor diagnostics and Langmuir probes at the inner heat shield the Langmuir probe arrays in the upper divertor have been refurbished and re- arranged, allowing now for detailed measurements there during vertical shift experiments and in upper single null configurations (including shot to shot reversal of the toroidal magnetic field). We carried out experiments in ohmic-/L-mode and in H-mode. At low densities in ohmic plasmas with lower single null (LSN) configuration the upward midplane flow at the magnetic low field side (LFS) reached velocities of M ≈ 0.7, showing a maximum about 1−2cm outside the separatrix. Increasing the plasma density caused a reduction of the Mach number, but the flow in the outer midplane is still directed towards the inner divertor. First measurements in H- mode discharges indicate that the Mach numbers in H- and L-mode are similar. In general the flow stagnation point at the LFS is located below the midplane in LSN discharges. Therefore the flow with parallel sound velocities near 105 ms−1 offers a high potential for mass transport in the SOL from the outer midplane to the inner divertor in lower single null configurations. Our measurements will be discussed in relation to the results of other tokamaks. Further measurements are still in progress at ASDEX Upgrade (e.g. upper single null discharges are planned) and more details will be reported and discussed at the conference. P-1.010, Monday June 27, 2005
Tungsten Erosion at Auxiliary Limiters in ASDEX Upgrade
R. Dux1, V. Bobkov1, A. Herrmann1, K. Krieger1, R. Neu1, T. Pütterich1, V. Petrzilka2, V. Rohde1, ASDEX Upgrade Team1 1 Max-Planck-Institut für Plasmaphysik, EURATOM Association, Garching, Germany 2 Association EURATOM/IPP.CR, Prague, Czech Republic
In order to test the reactor compatibility of high-Z plasma facing components (PFC), a step- by-step increase of tungsten coated PFCs towards a full tungsten machine is pursued at ASDEX Upgrade. At present, almost 70% of the total PFC area consists of W-coated graphite tiles. The enhancements for the 2005 campaign focused on the auxiliary limiters, which receive the highest load of the main chamber components. ASDEX Upgrade has 12 poloidal limiters on the low field side: a pair of side limitersfor each of the 4 ICRH antennas and a pair of guard limiters at each side of the 2 neutral beam ducts, which are between the two ICRH antenna doublets. The toroidal width of the guard limiters was increased from 10 to 20 cm and the radial distance to the plasma was changed from 12mm to 6mm behind the position of the ICRH limiters to allow for a better power load sharing between the limiters. One of the ICRH limiters and one guard limiter is equipped with W-coated tiles. The tungsten influx from the limiters was measured on 9 lines-of-sight using a WI spectral line at 400,8 nm.
During the 2004 campaign, measurements of W influx from a guard limiter pointed towards a dominant fast D particle contribution to the average deposited energy per deuterium ion and the sputtering of tungsten. For ICR heating on the close-by antenna doublet, which has a
minimum toroidal distance of ¡ 0.8m to the guard limiter, the W influx per heating power was
observed to increase by a factor of ¡ 1.5 compared to pure NBI injection. Post mortem analyses of the coated tiles by x-ray fluorescence and Rutherford backscattering confirm a net erosion of several hundreds of nm. During the present campaign the tungsten influx from the tungsten ICRH side limiter was measured in dedicated H-mode plasmas identical to the ones performed during 2004. An in- crease by a factor of 100 was found compared to the W influx density at the old guard limiter, reflecting the fact that the ICRH limiters are the components closest to the low field side plasma. Also the ICR induced local W influx from the antenna side limiter has strongly increased, where the above mentioned enhancement factor compared to NBI heating can be on the order of 20.
Details of the influence of ICRH as well as of the relation of W sputtering by thermal impu- rity ions and by fast D from NBI will be investigated during the ongoing campaign and will presented at the conference.
P-1.011, Monday June 27, 2005
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