Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, November Activities relevant to PWI in fusion devices of Slovenian Fusion Association (SFA) (Association EURATOM - MHST) Compiled by Iztok Čadež Jožef Stefan Institute, Ljubljana, Slovenia Association EURATOM-MHEST (SFA)

Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, November Physics projects in the field of PWI 2. Overview of results on individual projects 3. Status of collaborations

Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, November P2. Interaction of vibrationally excited hydrogen with fusion relevant materials (VEVOF) P3. Heterogeneous catalytic recombination of neutral hydrogen atoms on fusion relevant materials P5. Application of ion beam analytical methods to the studies of plasma wall interaction in tokamaks (IBAF) P6. Deuterium retention and release from materials – complementary method to tritium methods 1. Physics projects in the field of PWI

Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, November Overview of results of individual projects

Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, November P2: Interaction of vibrationally excited hydrogen (H 2, D 2 ) with fusion relevant materials (VEVOF) Iztok Čadež 1, Primož Pelicon 1, Sabina Markelj 1, Zdravko Rupnik 1, Milan Čerček 2, Tomaž Gyergyek 2, and Vida Ž igman 3 1 Microanalytical Centre, Department for Low and Medium Energy Physics (F2), JSI 2 Plasma Physics Laboratory, Department for Reactor Physics (F8), JSI, Ljubljana 3 University of Nova Gorica, Nova Gorica Processes of interest: Vibrational distributionthermal desorption recombinative desorption 1.- Vibrational distribution of hydrogen molecules from thermal desorption and recombinative desorption. Ratio of atomic to molecular species - Ratio of atomic to molecular species 2. Interaction of vibrationally excited molecules with plasma-facing materials: - Change of vibrational distribution caused by interaction with surfaces, - Transfer of vibrational energy to the wall and its effects on erosion yields, and - Wall sticking probability for excited molecules. Our main goal is to acquire as much as possible experimental information on reactions and properties of vibrationally excited hydrogen H 2, D 2, HD … that is relevant to edge plasma and PWI!

Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, November B New set-up for vibrational spectroscopy of vibrationally excited hydrogen molecules using guiding magnetic field for incident electron beam and ion extraction was constructed and tested during previous two years and it started to be used last year. Diagnostic technique is based on the detection of H- ions produced by dissociative electron attachment (DEA) at and below about 4 eV incident electron energyy: H 2 (X 1 g +,v) + e H 2 - (X 2 u + ) H - + H We are the only using this experimental technique that was originally developed at UPMC, Paris.

Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, November Present status of our final goal of experimental set-up developed and available ( … ) - Vibrational spectroscopy – developed and available ( … ) to be developed and tested - Atom/molecule ratio (+ion branch) – to be developed and tested available but still to work - Test atmosphere – partially dissociated neutral hydrogen gas or low temperature hydrogen plasma – partially available but still to work developed and available ( … ) - In situ and in real time H and D depth profiling by Li ERDA – developed and available ( … ) to be developed and tested - Sampling – to be developed and tested

Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, November Source of VEHM Recombination of hydrogen atoms on surfaces of different fusion relevant materials (W, C,Ta) Recombination of hydrogen atoms on surfaces of different fusion relevant materials (W, C,Ta) Hydrogen molecules dissociate on tungsten filament Hydrogen molecules dissociate on tungsten filament Vibrational spectroscopy of molecules produced by recombination Vibrational spectroscopy of molecules produced by recombination H 2 /W

Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, November Almost negligable D - production Cu H2H2 D2D2 H2H2 D2D2 Ta Measurements are performed also on W, Teflon, and C (in progress) We plan to use similar source of vibrationally excited molecule for spectroscopy experiment by injection into plasma.

Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, November Search for mechanisms for production of vibrationally excited hydrogen molecules: Recombination of hydrogen atoms on surfaces after permeation through membranes (Pd, Ta) Recombination of hydrogen atoms on surfaces after permeation through membranes (Pd, Ta) Study with Pd: An attempt with Ta: Fragmentation of hydrocarbons? Fragmentation of hydrocarbons?

Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, November Search for mechanisms for production of vibrationally excited hydrogen molecules: Vibrationally excited molecules from hydrogen atoms source: Vibrationally excited molecules from hydrogen atoms source: Experiment performed in collaboration with IPP, Garching (Th. Schwarz-Selinger)

Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, November Test atmospheres for exposure of samples to vibrationally excited hydrogen molecules hot-filament dissociation of hydrogen produces partially dissociated neutral test atmosphere; vibrationally excited molecules are produced by atom recombination on the wall; diagnostics: DTVE coupled to the test chamber; Partially dissociated neutral gas Low-temperature plasma

Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, November In-situ hydrogen depth profiling in samples exposed to controlled atmosphere

Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, November S=2.1x10 -7 ± 0.6x10 -7, k = 3.6x cm 2 /s ± 2.4x cm 2 /s.

Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, November P2 - Work plan for immediate future - H 2 (v) and D 2 (v) production by recombination in the cell - Vibrational relaxation by wall collisions (sampling) - Development of the H2v source for spectroscopy experiment in collaboration with FZJ (S. Brezinsek) - Modeling of the gas cell - Upgrading of experiment – addition of the + ion side for atom to molecule ratio determination

Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, November P3: Heterogeneous catalytic recombination of neutral hydrogen atoms on fusion relevant materials Miran Mozetič, Alenka Vesel and Aleksander Drenik Department of Surface Engineering and Optoelectronics (F4), Jožef Stefan Institute, Ljubljana, Slovenia Motivation Predicting the density of neutral atoms in confined spaces (such as plasma reactors, fusion edge plasma, tokamak pump ducts) Measuring the neutral atom density by means of catalytic probes

Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, November Detailed overview of the existing experimental data on hydrogen recombination on different materials So far there is no satisfactory understanding of recombination Experimentally obtained values are often contradicting Not all fusion relevant materials have been measured yet material W0.05 – 0.7 quartz6x10 -5 – 6x10 -2 pyrex10 -5 – Work performed since last TF PWI meeting

Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, November Measurements of recombination coefficient by Smiths side arm diffusion method Opening to main part of plasma reactor Catalytic walls Catalytic endplate 0 L max min Recombination coefficient strongly depends on material form (different polymorphous or amorphous forms of carbon) Example: Carbon – values of strongly differ for graphite, sputtered carbon deposits and hydrogenated amorphous carbon Drenik A., Vesel A., Mozetic M., Measuring probability coefficient for heterogeneous recombination of hydrogen atoms on surface of fusion relevant materials. V: 33rd EPS Conference on Plasma Physics, Roma, Italy, June 19-23, 2006.

Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, November Measurement of neutral hydrogen atom density in Textor First catalytic probe for TEXTOR was constructed and preliminary tested in TEXTOR Non-magnetic materials: Catalyst: gold (previously nickel) Thermocouple: W – Re (previously optical fiber) Detailed measurements are planed Probe temperature (voltage from TC) during a plasma pulse in Textor

Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, November P3 – Future plans Systematic measurements in TEXTOR and needed adaptations of existing probe Construction of a fibre – optic catalytic probe compatible with the scheduled redesign of the limiter lock system in TEXTOR Construction of a new plasma system with chambers more suitable for Smiths side arm diffusion method.

Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, November New proposal of this group: P8: cleaning of carbon deposits Idea: use neutral oxygen atoms at room temperature O atoms do not etch carbon fibres at RT O atoms do etch hydrogenated carbon at RT O atoms cause fromation of an extremely thin oxide film on Be and W If the thin oxide film cannot be tolerated, use N atoms instead of O atoms: HC + N HCN (pumped away) Subtasks: Development remote source of O or N The O (N) density over 1022 m-3 The O (N) density 10m away from the source over 0.5x1022m-3 Systematic study on reaction probability between the deposit and O (N) atoms Discussions with potential partner groups are in progress

Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, November P5: Application of ion beam analytical methods to the studies of plasma wall interaction in tokamaks (IBAF) P. Pelicon, D. Hanžel, M. Kavčič, I. Čadež, Z. Rupnik, J. Simčič, S. Markelj, M. Budnar, Z. Grabnar Microanalytical Centre, Department for Low and Medium Energy Physics (F2), Jožef Stefan Institute, Ljubljana

Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, November Detectors for -PIXE -RBS -STIM -Secondary Electrons motorized 5-axis vacuum goniometer (VG Omniax) 2 optical microscopes Chopper for dose normalization Ion microbeam OM triplet lens Installed in June 2000 proton beam size: High current mode (PIXE, RBS, SE, PBW) 100 pA: 0.9 x 1 µm Low current mode (STIM), 10 4 ions/sec: 0.5 x 0.8 µm

Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, November Model castellated structure has been exposed in the erosion-dominated conditions of tokamak fusion reaktor TEXTOR at Forschungszentrum Jülich 1 Measured C section 1 A. Litnovsky et al, J. Nucl. Mater , 917 (2005).

Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, November

Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, November Areal distribution of molybdenum (islands) measured by Li-beam excited X-ray emission (LIXE) and simultaneously measured hydrogen lateral distribution by Li-beam ERDA over an area of 1240 x 450 µm2. Surface lateral distribution of hydrogen at the plasma-exposed surface is anti-correlated with the distribution of molybdenum deposit. Hydrogen retention is higher in the surface of uncoated graphite. Lateral mapping of hydrogen at plasma-exposed surface of castellated limiter 1240 µm Hydrogen 450 µm Mo Lα

Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, November RBS/ERDA measurement setup: Beam: 4230 keV 7 Li 2+, Sample tilted 75° RBS detector at 160°, ERDA detector at 30° ERDA detector equipped with 11 µm Al foil Dose controlled by mesh charge integrator (Tungsten mesh, wire diameter 38 micrometers density of 3.2 lines/mm, open area of 77.4 %) ERDA of hydrogen with 7 Li ions, P. Pelicon et al., NIM B 227, 591 (2005) 1) ERDA study of H and D permeation through Pd (and Ta) membrane 2) Determination of elastic cross section for 7 Li-D scattering: - Measurement with standard a-C:D target - Relative measurement of elastic signal vs. protons from reaction 7 Li(d,p) 8 Li. ERDA beam line is under reconstruction in order to incorporate UHV experimental chamber

Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, November P6. Deuterium retention and release from metal surfaces – a complementary method to nuclear tritium methods V. Nemanič, B. Zajec, M. Žumer Department of Surface Engineering and Optoelectronics (F4), Jožef Stefan Institute, Ljubljana, Slovenia

Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, November during an exposure of D 2 at 1 mbar, room temperature, the absorption kinetics is slow, but detectable. The UHV system was well outgassed, no water was detected prior D 2 admission. during the desorption, only HD, D 2 and H 2 were released, no HDO. V. Nemanič, B. Zajec, The influence of deuterium exposures on subsequent outgassing rate of an UHV system, Vacuum 81, 556 (2006) Systematic measurements of the ultimate detection limit of the UHV system regarding deuterium retention versus hydrogen background were examined

Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, November several deep bulk sites exist where hydrogen is much more tightly bound than at regular interstitial sites, they have a little impact on regular permeation their number could often be estimated only by modeling by arbitrarily set energy levels and their distributions difficult to make direct observation by present experimental techniques unfortunately, a complex mathematical treatment can not be compared easily to the experimental data Long term repetitive thermal extraction in high vacuum to determine the concentration of deeply trapped H atoms.

Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, November Experiment kinetics of hydrogen redistribution confirmed by observing outgassing rate in several minute extractions in vacuum at 780 °C over three months with no exposure to the air - outgassing rate of untreated sample AISI stored in residual gas (0.001 mbar H 2 in 24 h at R.T.) - stored for 3-10 days at 1 mbar D 2 at R.T. - charged at 489 °C, 10 minutes at 1 bar D 2 - outgassing rate repeated after some days

Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, November Experimental details AISI304 sample, plate mm p = mbar C = H/cm 3 p = mbar N = H 2 /cm 2 RF coil to all metal UHV system sample in a quartz tube TC

Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, November P6: Conclusions Kinetics of hydrogen evolution from stainless steel is governed by diffusion from the ordinary sites (fast process) and recombination at the surface (relatively fast process), described by diffusivity D, that is usually measured at high p and T by release of H from deep states (slow process), observed in long term experiments at high T. deep states could be populated by impact of energetic ions in fusion reactor (H +, D +, T + ) impact on decomissioning?

Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, November Activate collaborations in previous year: P2: FZ, Jülich ( hydrogen recombination on W and graphite, spectroscopy of H 2 (v) and D 2 (v)), IPP, Garching ( diagnostics and use of atomic hydrogen source); FOM, Rijnhuizen (some preliminary discussions on spectroscopy experiment). P3: FZ, Jülich (H recombination on provided samples, plasma cleaning of TEXTOR wall), CIEMAT (in preparation). P5: FZ, Jülich (lateral μ-mapping of H and D on PFC, study of Mo deposition on limiter, micro analysis of co-deposited flakes, calibration of deuterium ERDA measurements). P6: Application for EFDA technology project; ENEA, Frascati (hydrogen and deuterium retention); IFP-CNR, Milano. 3. Status of collaborations