Transients on arc and Convertor Currents in the Multi-Cusp Cesiated Surface Conversion H-Ion Source at Lansce

Abstract

The Multi-cusp Cesiated Surface Conversion H- Ion Source at the Los Alamos Neutron Science Center (LANSCE) has provided beam at ~14 mA, 120 Hz, and 10% D.F. for many years of neutron science research. Recently, random high current transients were discovered in the arc current used to ionize hydrogen in the LANSCE H- ion source, and in the convertor current used to convert protons to H- ions. Most have no effect, but more severe transients can cripple beam output. Hypothesized causes are related to cesiation effects, plasma instabilities, tungsten filament evaporation/sputtering, or from the arc modulator circuitry. A dedicated study was recently done on the LANSCE H- Ion source test stand to determine the cause of these transients. Current understanding indicates that the more severe transients come from a combination of cesiation effects and plasma instabilities. The status of these current transient studies on the LANSCE H- ion source will be discussed.