Study of helium effects in SiC/SiC composites under fusion reactor environment

Helium release behavior from He-ion implanted SiC/SiC, monolithic beta -SiC , and SiC fiber (Hi-Nicalon) was studied using the thermal desorption metho d with annealing temperatures between 500 degreesC and 1600 degreesC in 100 degreesC increments. Helium release from SiC/SiC composites began below 50 0 degreesC, while from monolithic beta -SiC, helium release was observed ab ove 1000 degreesC. The magnitude of the helium released from beta -SiC was 1/10 to 1/50 of the helium released from the composites. Helium release fro m the fiber became apparent above 1300 degreesC. Helium release from compos ites at low temperature might be attributed to helium release from the carb on interphase. Behavior of transmuted helium in the SiC/SiC composites unde r fusion reactor conditions is discussed. (C) 2000 Elsevier Science B.V. Al l rights reserved.