Sputtering of niobium by energetic neutrons and protons: A round-robin experiment

This paper presents the results of a round-robin neutron-sputtering experiment in which six independent research groups have participated. Targets of cold-rolled niobium prepared by two standard techniques were used by all participants. Three participating groups used (d,t) neutrons of about 14.8 MeV, one group used (d,Be) neutrons produced by 40-MeV deutrons on a thick Be target, and two groups used 16-MeV protons in transmission. The emission of micrometer-sized particles was observed by two groups and not observed by the other four. This particle emission was observed by two of the groups who used (d,t) neutrons in their irradiations. Chunk emission was observed for only one of the two standardized target types used in the round robin. The round-robin results support the concept that the neutron-sputtering yield of Nb, including atomic and chunk emission, has an estimated probable value no larger than 10−4 atoms per neutron. However, sputtering yields in the range 1.4×10−5 to ≲2.6×10−3 are reported here. The probable value for the sputtering yield was found to be independent of the two target preparations and the method of analysis, whether or not chunks were observed during analysis.