Vienna University of Technology (TU Wien) slides provided by F. Aumayr EURATOM – ÖAW: Contribution of the Austrian Fusion Association 2006 Innsbruck University W. Schustereder Material Research Division Max-Planck-Institut für Plasmaphysik, EURATOM Association Garching, Germany

Vienna University of Technology (TU Wien) Slow ion-surface interactions with relevance to fusion edge plasma Innsbruck University [Sputtering and electron emission due to ion impact on plasma relevant surfaces (graphite, tungsten,...) [Speciality: (slow) multiply charged ions (e.g. C q+ up to q=6) [Experimental techniques: Sensitive quartz crystal micro-balance, AFM/STM Electron emission: yield, statistics and energy distribution [Modelling of the plasma sheath potential in the presence of electron emission [Fragmentation and molecular reactions during atomic and molecular ion impact on surfaces + Sticking

Need of fundamental understanding of PWI processes Well defined laboratory experiments Specific modelling and extrapolation to ITER n

Electron emission due to ion-impact on carbon and tungsten tiles Electron emission and plasma sheath potential Tore Supra carbon tile E/m (keV/amu)

Electron emission due to impact of singly/multiply charged carbon ions on carbon tiles Electron emission and plasma sheath potential eV in collaboration with S. Kuhn et al., Univ. Innsbruck Sheath potential in front of an electron emitting wall

Modelling of the plasma sheath potential in the presence of electron emission sheath model: in collaboration with preliminary results: N. Schupfer et al. Plasma Phys. Contr. Fusion, (2006)

Total sputtering yields due to impact of singly and multiply charged ions sensitivity: 0.5% monolayer per minute stability: 3mHz/min RMS noise at 6 MHz ( f/f ) a-C:H W Be WO x BeO x...

Research topic: Ion/surface collisions Energy range of interest: ~ eV Low collision energy: enough energy to break molecular bonds, fragmentation pattern is characteristic for both the projectile and the surface Projectiles: Hydrogen molecules: H 2 +, H 3 +, D 2 +, D 3 +, HD +, HD 2 + Hydrocarbons, i.e.: CD 3 +, C 2 H 6 +, C 2 H 4 +, C 2 D 6 +, C 2 D 4 + small hydrocarbon molecules, present in most vacuum devices, therefore important for modelling Plasma-wall interactions, break down graph for C 2 H 6 + well known. Surfaces: Stainless steel: data available, used for comparison Diamond surfaces: nanocristalline diamond on W-C bond with 6% Co; terminal step in air or H-atmosphere Beryllium: first experiments Tungsten Plasma sprayed Tungsten (Collaboration with IPP Garching): ongoing experiments Stainless steel with different surface coatings: Beryllium, Tungsten in cooperation with D. Skalny (Bratislava)

Fragmentation and molecular reactions during (molecular) ion impact on surfaces IBK

Fragmentation and molecular reactions during (molecular) ion impact on surfaces IBK

Fragmentation and molecular reactions during (molecular) ion impact on surfaces

First fragmentation experiments on beryllium surfaces Preliminary results: Higher impact energy required than for SS

Sticking coefficient of CD 3 + on plasma- sprayed tungsten (PSW) surfaces W. Schustereder et al., NIMB, to be published Hydrocarbon sticking properties on realistic surfaces TW6-TPP-CNDSTICK

Outlook: PWI related tasks Chemical Erosion of C by D/H and other ions Erosion yield for higher hydro-carbons C x H y Erosion of redeposited layers (a-C:H layer) Erosion Modelling Effect of mixed layers: W, Be and C Sputtering of W and Be Potential Sputtering of WO x and BeO x Electron emission studies Modelling of sheath voltage Fragmentation of molecular ions Sticking coefficients for hydro-carbons C x H y

Tragic message Prof. HP Winter