Duopigatron ion source studies: II

Recent experimental studies with a duopigatron gas discharge ion source are described. Experiments include measurements of the ion current, mass and energy distributions and current density profiles as a function of the aperture sizes of the source electrodes. Larger aperture diameters were required to minimize damage to the original ion source [configuration described in Rev. Sci. Instrum. 49, 435(1978)] observed during its operation on the Sandia Target Test Facility. The best new configuration produces a 200 mA ion beam at an arc current of 13 A and contains 52% D+. In addition to the performance measurements, extensive mass analyses of the ionic impurities produced in the ion source were carried out. The large aperture sources produce beams that contain ca. 0.5% contaminants. Typical mass spectra are described and the sources of the impurities discussed. Difficulties with the duopigatron including loss of source efficiency (ion current as a function of arc current) and filament contamination are presented and discussed