The field evaporation of deuterated titanium as a neutron generator ion source

摘要

The field evaporation of deuterated titanium films is being investigated as a deuterium ion source for deuterium-tritium neutron generators. It has been found that titanium and deuterated titanium films having thicknesses of up to at least 70 layers assume a body-centered-cubic crystal structure when grown on <110> oriented tungsten substrates. Deuterated titanium films having thicknesses exceeding 50 atomic layers have been controllably field evaporated from the surface of tungsten tips in less than 20 ns. At ion current densities exceeding ～ 10~6 A/cm~2 and film thicknesses greater than ～20 layers, space charge effects decrease the ratio of D to TiD_x ions to less than 1. Decreasing the evaporation rate such that ion current densities are of the order of 10~5 A/cm~2 increases the D to TiD_x ratio for the evaporation of a film thickness of greater than ～20 layers by the reduction in space charge effects that can inhibit the dissociation of titanium-deuterium complexes. Atomic deuterium ion yields of ～10~(-7) μC of D~+/tip have been observed and yields of >10~(-6) μC of D~+/ tip should be possible using larger tip radii. The field evaporation of titanium from an array of microfabricated tips has been demonstrated for the first time.