Understanding the release of helium atoms from nanochannel tungsten: a molecular dynamics simulation

The design of highly radiation-tolerant plasma-facing materials (PFMs) is of great importance for fusion reactors. Our recent experiments have shown that nanochannel tungsten (W) films have clearly superior radiation tolerance properties. In the present work, helium clustering and release from nanochannel tungsten were studied by molecular dynamics simulations. The effects of temperature and vacancy concentration on the helium release from a tungsten cylinder were investigated. Our results show that nanochannel W that consists of thin W cylinders releases He atoms more quickly than bulk W with flat surfaces, thus greatly reducing the He concentration and suppressing the formation and growth of He bubbles, which leads to increased radiation tolerance. Moreover, the microstructural changes due to increasing He fluence are smaller in nanochannel W than those in bulk W. Although vacancies in nanochannel W will trap He atoms, the nanochannel W also has a stronger tendency to stabilize helium retention than bulk W. The mechanism of helium release from nanochannel W was also examined. The results reported here are beneficial for guiding future work in the design of radiation resistant PFMs.