Helium retention in krypton ion pre-irradiated nanochannel W film

摘要

Nanochannel tungsten (W) film is a promising candidate as an alternative to bulk W for use in fusion applications. In previous work it has been shown to have good radiation resistance under helium (He) irradiation. To further understand the influence of the irradiation-induced displacement cascade damage on helium retention behaviour in a fusion environment, in this work, nanochannel W film and bulk W were pre-irradiated by 800 keV Kr~(2+) ions to the fluence of 2.6 × 10~(15) ions cm~(-2) and subsequently irradiated by 40 keV He~+ ions to the fluence of 5 × 10~(17) ions cm~(-2). The Kr~(2+) ion pre-irradiation greatly increases helium retention in the form of small clusters and retards the formation of large clusters. It can effectively inhibit surface helium blistering under high temperature annealing. Compared with bulk W, no cracks were found in the nanochannel W film post-irradiated by He~+ ions at high fluence. The release of helium from the nanochannel W film is more than one order of magnitude higher than that of bulk W whether they are irradiated by single He~+ ions or sequentially irradiated by Kr~(2+) and He~+ ions. Moreover, swelling of the bulk W is more serious than that of the nanochannel film. Therefore, nanochannel W film has a higher radiation tolerance performance in the synergistic irradiation.