Laboratory study of the transport and condensation of hydrocarbon radicals and its consequences for mitigating the tritium inventory in the ITER-FEAT divertor

• Published in: Journal of nuclear materials 2001-03, Vol.290, p.394-397
• Main Authors: Arkhipov, I.I., Federici, G., Gorodetsky, A.E., Ibbott, C., Komarov, D.A., Makhankov, A.N., Markin, A.V., Mazul, I.V., Tivey, R., Zakharov, A.P., Zalavutdinov, R.Kh
• Format: Article
• Language: English
• Subjects: Carbon; Fusion reactor; Growth; Redeposition
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/S0022-3115(00)00484-0

The surface loss probability β of CH 3 radicals at a-C:H surfaces has been determined by analysis of the carbon deposition profiles along a tube flow reactor directly coupled with a methane RF discharge. β is equal to (1.0±0.2)×10 −3 for a methyl to atomic hydrogen flux ratio of 10:1. β remains the same in the temperature range 300–800 K and decreases slightly between 800 and 1200 K. The deposition rate drops drastically in the range 400–800 K. Above 800 K the carbon deposition is regained. From separate experiments on magnetron sputtering of graphite by D ions, it is inferred that at 300 and 900 kinetic CH x species react at the C:D surface with the same probability. In contrast, the deposition of thermal C x H y radicals decreases by a factor of 25 with a temperature rise from 320 to 400 K, remaining at this low level up to 1000 K. The implications of these results for co-deposition in the ITER-FEAT divertor are discussed.