Abstract: Neutron sputtering from metal foils

Experiments to determine the material removed (sputtering) from the surfaces of metal foils during irradiation with 14.8 MeV (d, t) neutrons will be described. Neutron activation analysis was used to measure the sputtered material. This is an integral technique which determines quantitatively the number of atoms on the collector. Six experiments were done using the Lawrence Livermore Laboratories rotating target (d, t) neutron source and one experiment was done at the (d, Be) source at the University of California, Davis. In each experiment a large number of collector--target assemblies were located at various distances from the neutron source. The collector--target assemblies were housed in a stainless steel ultrahigh vacuum system and all irradiations were performed in a high-vacuum environment approx.1x10-7 torr to 5x10-9 torr (approx.1.3x10-5 Pa to 6.5x10-7 Pa). For these experiments the mean (d, t) neutron energy was 14.8 MeV in the forward direction, and for the different beam-on times and various source to sample distances the target fluences ranged from 1x1014 to 2.6x1016 (d, t) n/cm2. A (d, Be) source is highly anisotropic and is peaked in the forward direction. For the 20μA, 40 MeV deuteron beam used at the University of California, Davis, the average (d, Be) neutron energy was about 15 MeV, and at the point of closest approach to the Be target fluxes of approx.2x1013 n/cm2 s are produced