Selection of a Vac-Ion Pump for a Terminal Ion Source

An 800 l/s electrostatic ion pump and a 500 l/s magnetic triode ion pump have been tested to determine which would be most suitable for pumping the hydrogen gas emanating from a duoplasmatron ion source. The ion source and pump will be located in the terminal of a High Voltage Engineering Corporation (HVEC) type MP tandem accelerator. The two pumps were mounted on a pump test stand with a manometer, two needle valves, and two ion gauge controllers. The hydrogen flow to each pump was increased slowly until the pump was near the point of pressure instability. Flow rates and pressure were recorded for approximately 1000 hours. The performance of the magnetic triode ion pump was superior to that of the electrostatic pump. The magnetic triode ion pump has undergone another test pumping the hydrogen gas from a duoplasmatron. Pumping speed measurements, modes of failure, and other details of these continuing tests will be presented.