New ion source filament for prolonged ion source operation
D. Prevost, K. Jayamanna, L. Graham, S. Varah, C. Hoehr
TRIUMF
Oral Presentation
None
The TR13 cyclotron at TRIUMF, the prototype of the ACSI TR19, operates with an external multi-cusp negative ion source. The filament in the ion source, through which a high current flow creates an arc to create a plasma to ionize the hydrogen, is shaped like a half circle. The filament is mounted in duplicate on the removable end plate of the ion source for easy access. Over time, the Ta wire of the filament losses material and wears thin. This is reflected in a dropping current flowing through the filament. To avoid breakage and therefore loss of proton beam, the filament is being replaced when the current drops to about 100 A at the TR13. At normal operation the filament in the ion source needs to be replaced on average every three months to ensure beam delivery, which causes the cyclotron to be off for a day each time.
To prolong this time interval, a new spiral filament was designed and tested. We estimate that with this filament a change is not necessary for well over a year. The design and operational experiences will be discussed.
This is a practical subject, although it is peculiar that it takes a day to swap out a filament on an external ion source.