He−, H2−, and Other Negative Ion Beams Available from a Duoplasmatron Ion Source with Gas Charge Exchange

Abstract

Negative helium‐ion beams have been produced in a commercial negative‐ion source in which positively charged beams from a duoplasmatron ion source are converted in a gas charge exchange canal. Beams of negative helium ions with currents up to 30 mμA have been injected into a tandem Van de Graaff accelerator, and α‐particle beams have been obtained from the accelerator with energies up to 19 MeV and currents up to 20 mμA. The results of several experiments which were performed to determine the source operating characteristics for negative helium ions are presented. In addition to the peak corresponding to the He⁻ beam, many other peaks are observed in the momentum distribution of the beam from the negative ion source. Confirming evidence has been found for the existence of the H₂⁻ ion.