[Zurück]

F. Aumayr, G. Kowarik, M. Brunmayr:
"Electron emission from tungsten induced by slow, fusion-relevant ions";
Poster: 23rd Intern. Conf. on Atomic Collisions in Solids (ICACS 23), Phalaborwa/South Africa; 19.08.2008; in: "Book of Abstracts 2008 23rd Intern. Conf. on Atomic Collisions in Solids (ICACS 23)", (2008), S. 177.

Numerical codes are nowadays available to model the behavior of the boundary
of fusion plasmas and the plasma wall interaction. These codes rely on our knowledge
on various plasma-wall-interaction processes (physical and chemical sputtering, electron
emission and reflection, transport processes, etc.). However, there are uncertainties in
the present day predictions due to the lack of detailed knowledge about the involved
processes.
We have therefore studied electron emission due to the interaction of slow singly
and multiply charged ions with sputter-cleaned polycrystalline tungsten surfaces.
Tungsten has recently been introduced as a wall material for fusion, because it exhibits
favorably low sputtering yields and a very low tritium (= fusion fuel) retention as
compared to carbon fiber composite wall material. Projectiles in our experiments range
from low Z to heavy ions. Investigations are carried out in the eV to keV impact energy
region as typical for fusion edge plasma conditions. Total electron emission yields were
determined by a current method using a retarding grid [1]. The ions were produced by in
ECR ion source and subsequently decelerated down to velocities of less than 106 m/s.
From our results the underlying mechanisms for kinetic and potential electron emission
[2] can be identified. Implications of the experimental results for plasma-edge modeling
[3] are also discussed.
This work was supported by the European Communities under the Contract of
Association between EURATOM and the Austrian Academy of Sciences as well as by
Austrian FWF.
[1] D. Hasselkamp, Springer Tracts in Modern Physics, 123 (1992) 1 - 95
[2] F. Aumayr and HP. Winter, Springer Tracts in Modern Physics 225 (2007) 79 - 112
[3] N. Schupfer, D.D. Tskhakaya sr., R. Khanal, S. Kuhn, F. Aumayr, S. Figueira da
Silva, and HP. Winter Plasma Physics and Controlled Fusion 48 (2006) 1093 - 1103