Erosion and Redeposition Behavior of Selected NET-Candidate Materials under High-Flux Hydrogen, Deuterium Plasma Bombardment in PISCES.

摘要

Plasma erosion and redeposition behavior of selected candidate materials for plasma-facing components in the NET-machine have been investigated using the PISCES-A facility. Materials studied include SiC-impregnated graphite, 2D graphite weaves with and without CVD- SiC coatings, and isotropic graphite. These specimens were exposed to continuous hydrogen or deuterium plasmas under the following conditions: electron temperature range from 5 to 35eV; plasma density range from 5 x 10 sup 11 to 1 x 10 sup 12 cm sup -3 ; flux range from 5 x 10 sup 17 to 2 x 10 sup 18 ions cm sup -2 s sup -1 ; fluence of the order from 10 sup 21 to 10 sup 22 ions/cm sup 2 ; bombarding energies of 50 and 100eV; target temperature range from 300 to 1000/degree/C. The erosion yield of SiC-impregnated graphite due to deuterium plasma bombardment is found to be a factor of 2 to 3 less than that of isotropic graphite materials. A further factor of 2-3 reduction in the erosion yield is observed in when redeposition associated with reionization of sputtered particle becomes significant. From postbombardment surface analysis with AES, the surface composition in terms of the Si/C of SiC-impregnated graphite ratio is found to increase from 0.15 to 0.7 after hydrogen plasma bombardment to a fluence around 4 x 10 sup 21 ions/cm sup 2 at 350/degree/C. However, the final surface composition appears to remain unchanged up to 4 x 10 sup 22 ions/cm sup 2 , the highest fluence in the present study. Significant surface morphological modifications of SiC-impregnated graphite are observed after the high-fluence plasma exposure. Several structural problems such as coating-substrate adhesion have been pointed out for SiC-coated 2D graphite weave. 11 refs., 6 figs., 1 tab. (ERA citation 13:046171)