A 15 mA dc H Ϫ 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 dc H Ϫ 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 arc power available is only 5 kW. After the H Ϫ beams pass through an electron suppression grid and a 20 mm collimator, we obtained 15 mA with 0.66 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 mm mrad. Further development in the near future is planned using cesium and multiple apertures in the hope of increasing dc H Ϫ currents to 30 mA while holding the normalized emittance below 0.75 mm mrad.

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A microwave-driven ion source being developed at TRIUMF is designed to produce stable, reliable, and gas-efficient negative and positive ion beams for cyclotrons and other accelerators. The source has been tested for H− and achieved 2.1 mA at 0.25 π mm mrad normalized emittance for 500 W of input power at a frequency of 2.45 GHz. The source was operated over one month without interruption for a H− beam stability test and demonstrated 2.5% stability over the period. For positive beam extraction H+, He+, N+, and Ar+ species have been studied. A 2 mA N+ beam was obtained at 0.3 π mm mrad normalized emittance for 1 kW of input power. A beam density as high as 7 mA/cm2 with 45% gas efficiency has been achieved for the Ar+ beam. In this paper the source parameters and characteristics are discussed.

While a 20 mA dc H− source system at 25–30 keV beam energy has been developed at TRIUMF several years ago, another recent demand on the system is to provide a 4 to 5 mA H− at the 4–6 keV energy range. We found that at this low energy range, the existing source/extraction system can only give ∼1 mA with poor emittance due to strong space-charge effect. Fortunately, a very special source/extraction mechanism together with the use of neutralization was discovered and developed to overcome this difficulty. Up to 4 mA with a normalized rms emittance of 0.15 π mm mr has been achieved at 6 keV. This performance finds its usefulness for injection systems where lower beam energy and higher beam intensity are required. A copy of the TRIUMF system was constructed and successfully tested in the summer of 2000 for the “H− Acceleration Project” for the K130 cyclotron at Jyväskylä University, Finland.

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