Particle Release from Niobium Irradiated with 14-MeV Neutrons

The particle release from cold-rolled niobium surfaces under 14-MeV-neutron impact to a total dose of 4.6 \ifmmode\times\else\texttimes\fi{} ${10}^{15}$ neutrons/${\mathrm{cm}}^{2}$ was investigated under ultrahigh-vacuum conditions and at ambient temperature. The type and amount of material released and deposited on a substrate surface was determined independently by four analytical techniques. Surprisingly, there were two types of deposits---one in the form of large chunks, the other a more even layer covering the surface. The chunk emission cannot be explained by existing neutron-sputtering theories.