Development of the Penning ionization gauge source for higher current

For the first phase of the GSI high current project, an improvement of Penning ionization gauge (PIG) ion sources is necessary. Therefore, we carry out several PIG source development activities. A test bench for PIG ion sources was set up. It was equipped with the same source magnet, the same beam line, and the same computer control as at the accelerator injector. It has been partly operational since the beginning of 1997. Contrary to the UNILAC accelerator with a typical pulse width of up to 5 ms at a repetition rate of 50 Hz, the synchrotron injection requires a pulse length of about 200 μs at 0.3 Hz. Therefore, the use of lower repetition rates is possible. Thus, more power can be applied to the discharge and increased ion currents can be extracted. This mode requires higher cathode heating, which decreases the lifetime of the filament. The use of monocrystalline LaB 6 cathodes drastically reduces the necessary heating power at the same electron current, which should increase the lifetime of the filament and the cathode. The yield of ions from solids was improved by the use of optimized combinations of target and sputtering gas. The use of xenon instead of argon as the sputtering gas for the uranium target yielded a current enhancement of 40%. To achieve a shift of the charge-state distribution to higher charge states, an optimized gas feeding is one option. In collaboration with JINR Dubna, we developed a pulsed gas feeding system. Two piezovalves directly mounted to the source allowed us to control the pressure in the source.