EFFECT OF HE ON THE SWELLING-MICROSTRUCTURE PRODUCED IN MO BY ION-BOMBARDMENT

Pure molybdenum has been bombarded simultaneously with heavy ions and helium in a dual beam accelerator facility to simulate the helium generation and displacement damage expected in a fusion reactor first wall. Compared to the damage produced by the heavy ions (7 MeV Ta+++) alone, simultaneous helium injection results in a high void density that continues to increase with dose. The results suggest continuous void nucleation due to the helium. The swelling during dual beam irradiations is essentially independent of dose at high dose levels. At high doses >40dpa, the helium has little effect on the absolute magnitude of the swelling which is approximately 0.5% with or without helium. Comparisons are made to extrapolated swelling data from fission neutron irradiation studies. © 1979.