Nanostructure formation on tungsten exposed to low-pressure rf helium plasmas: A study of ion energy threshold and early stage growth
2010; Elsevier BV; Volume: 415; Issue: 1 Linguagem: Inglês
10.1016/j.jnucmat.2010.10.050
ISSN1873-4820
AutoresM.J. Baldwin, T. Lynch, R.P. Doerner, J.H. Yu,
Tópico(s)Fusion materials and technologies
ResumoNanostructure formation on W targets is explored as a function of He+ impact energy, εi, in the range 20 ⩽ εi ⩽ 57 eV. Six targets are exposed at 1120 K for 6 h to pure He plasmas, generated by a low-pressure rf Helicon source. One target is additionally exposed to Ar plasma pre-treatment. It is found that He ions of impact energy 32–37 eV are necessary for nanostructure formation to be observed in this type of plasma, as determined by SEM. At 57 eV a nanostructured surface forms readily (similar to that observed by Baldwin and Doerner, Nuclear Fusion 48 (2008) 035001 in the PISCES–B device), but growth is retarded in the Ar pre-treatment case. Thermal desorption shows that nanostructuring is accompanied by increased trapping of He in degenerate vacancies and clusters, but is reduced by a factor of 8 as a result of Ar pre-treatment.
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