http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Test system for creation and trapping of low energy H- ions
H+ ions as probe particles are required by a proposed antiproton gravitational acceleration experiment at Los Alamos National Laboratory. These particles are utilized to calibrate the influence of the patch effect (electric stray on a material surface) and the inhomogeneity of the magnetic field. The required number of H- ions is 10,000 to 20,000 per cycle at a cycle rate of < 0.5 Hz. The use of an external H- source faces some difficulties so the in situ H-production in an ion launching trap is investigated. We have demonstrated in situ production of H-. Electron impact ionization ofH2 produces trapped H+ and H2+ and H2+,and H2 reacting with H2 produces H3+. H-is produced by surface charge exchange of the trapped positive hydrogen ions at a cesiated HAVAR(TM) trap electrode. Proper timing of switched trapping potentials projects the positive ions to the cesiated surface and subsequent further switching traps the H- ions. The overall efficiencies (conversion and trapping) were, respectively, up to 8%, 20% and 7% for (H+/H-), (H2+/H-) and H3+/H-) conversions. Their relative contributions to the H- production depend on the switching times. The absolute number of trapped H- ions from H+ is estimated to be around 56,0001︢2,000 ions for an average kinetic energy of the H- 3.30︢.5 eV. This research demonstrates the viability of this method to support an antiproton gravitational acceleration experiment.
Issued also on microfiche from University Microfilms Inc.