Vacuum Pressure Considerations on the Performance and Lifetime of Penning Ion Sources

4 Sep 2020, 17:30
2h
Poster Beam formation and low energy transport P1

Speaker

Dr Scott Lawrie (STFC ISIS Neutron Source)

Description

The ISIS pulsed spallation neutron and muon facility uses a Penning surface-plasma ion source to deliver high current, high repetition rate, long pulse H- beams for accelerator operations. Several variations of the Penning source have been tested, primarily with a view to higher duty-cycle operation in future facilities. It has been noted that the different source configurations vary in their operational stability and wear patterns, despite using the same power supplies, gas feed-rates, magnetic fields, temperature settings etc. It is proposed that the vacuum chamber setup contributes to the observed performance variations. Therefore temporally-resolved vacuum simulations were made of the different setups. The pressure profiles output were used in conjunction with collision cross sections to estimate stripping losses along the beam’s flight path. It was found that up to 20% difference in H- stripping can occur depending on the vacuum environment. Therefore caution must be used when comparing perveance scans of transported beam current from different ion sources and different experimental setups. In addition, the stripped positive ions can back-stream into the ion source, increasing anode wear.

Primary author

Dr Scott Lawrie (STFC ISIS Neutron Source)

Co-author

Dr Olli Tarvainen (STFC Rutherford Appleton Laboratory)

Presentation Materials

Peer reviewing

Paper