Multipurpose Beam Pulsing System for the 12UD Pelletron Tandem Accelerator at the University of Tsukuba

Abstract

A beam pulsing system has been developed for a 12 MV tandem accelerator. The system consists of a pre-acceleration chopper, a klystron buncher and a post-acceleration chopper. The pre-acceleration chopper comprises a slow chopper and a fast travelling-wave chopper. Pulsed beams with widths in the range from 10 µs to ∼2 s are obtained with the slow chopper, and the repetition periods can be varied from 70 µs to 4 s. The fast chopper produces ion bursts having widths between 0.05 and 0.8 µs with a duty factor of ∼10%. The buncher is operated with the two choppers to obtain beam pulses as narrow as a few nanoseconds. Time-of-flight measurements yielded pulse widths 2–4 ns (FWHM) wide for ions in the mass range 1≦A≦28. The ratio of the dark to peak ion current was usually of the order of 10-4.