Extraction of H− ions from a DC cusp source

Recent investigations have concentrated on the parameters affecting the quality of the H− beam from a newly developed dc volume multicusp ion source with a single‐stage‐post‐acceleration (SSPA) extraction system for injection into the TRIUMF cyclotron. The experimental results indicate that the beam emittance is nearly independent of the arc current in the range of 10 A to 40 A. Also described are modifications to the extraction system which have significantly reduced the electron contamination in the H− beam.