Electron enhanced hydrogen attack on first wall materials

Abstract

The reactivity of graphite, TiC, and TiB 2 with atomic hydrogen under simultaneous electron bombardment is reported. Methane production yield enhancements in terms of additional methane molecules formed per incident electron are reported from 315 to 510K for oriented pyrolytic graphite and at 315K for TiC. Enhancements for graphite and TiC result in yields from combined atomic hydrogen attack and electron bombardment comparable to hydrogen ion sputtering yields, and these yields are more than an order of magnitude greater than those for atomic hydrogen alone. TiB 2 was not observed to form volatile boron compounds at 315K under electron bombardment, or up to 640K under atomic hydrogen attack alone. Sample temperature, hydrogen flux, electron flux, and electron energy are major interdependent parameters influencing erosion rates.