Field desorption ion source development for neutron generators

A new approach to deuterium ion sources for deuterium-tritium neutron generators is being developed. The source is based upon the field desorption of deuterium from the surfaces of metal tips. Field desorption studies of microfabricated field emitter tip arrays have been conducted for the first time. Maximum fields of 3 V/Å have been applied to the array tip surfaces to date, although achieving fields of 2 V/Å to 2.5 V/Å is more typical. Both the desorption of atomic deuterium ions and the gas-phase field ionization of molecular deuterium have been observed at fields of roughly 2 and 2-3 V/Å, respectively, at room temperature. The desorption of common surface adsorbates such as hydrogen, carbon, water, and carbon monoxide is observed at fields exceeding ∼1 V/Å. In vacuo heating of the arrays to temperatures of the order of 800 °C can be effective in removing many of the surface contaminants observed.