Field desorption ion source development for neutron generators

TL;DR

This paper introduces a novel deuterium ion source for neutron generators based on field desorption from microfabricated tips, demonstrating effective ionization and surface cleaning techniques.

Contribution

It presents the first study of field desorption from microfabricated emitter arrays and explores optimal field strengths for ionization and surface contaminant removal.

Findings

Maximum fields of 30 V/nm applied to emitter tips.

Atomic deuterium ions desorbed at ~20 V/nm.

Surface contaminants removed by heating to 800°C.

Abstract

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 30 V/nm have been applied to the array tip surfaces to date, although achieving fields of 20 V/nm to possibly 25 V/nm is more typical. Both the desorption of atomic deuterium ions and the gas phase field ionization of molecular deuterium has been observed at fields of roughly 20 V/nm and 20-30 V/nm, respectively, at room temperature. The desorption of common surface adsorbates, such as hydrogen, carbon, water, and carbon monoxide is observed at fields exceeding ~10 V/nm. 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.