On the development of a 15 mA direct current H- multicusp source

A 15 mA de H- multicusp source has been developed for injection into a TR30 cyclotron. This source is also used with a 900 kV tandem accelerator to obtain 10 mA protons at 1.8 MeV. The program is an extension of the 5-7 mA de H- cusp source developed at TRIUMF during 1989-1990. Major efforts include the search for the optimal filament materials, shape, and location; comparison of cusp line confinement and magnetic filtering of electrons at the extraction region; optimization of extraction lense configuration; and upgrading of vacuum and power systems capability. The source is noncesiated and the maximum are power available is only 5 kW. After the H- beams pass through an electron suppression grid and a 20 mm collimator, we obtained 15 mA with 0.66 pi mm mrad 4 rms normalized emittance. At this output the e/H ratio was about 4. The best normalized emittance occurs around 5-7 mA, having a value of 0.37 pi mm mrad. Further development in the near future is planned using cesium and multiple apertures in the hope of increasing de H- currents to 30 mA while holding the normalized emittance below 0.75 pi mm mrad. (C) 1994 American Institute of Physics.