Tune mode

Notes from Jay Benesch 10/31/13

Tune beam: at 60 Hz rep rate

1. Pulse structure
   • 250 us of beam, bunches at 499 MHz, so 124,750 bunches
   • 100 us of nothing
   • 4 us of beam, bunches at 499 MHz, so 1996 bunches
   • 1.524% duty cycle.

The transit time per pass is a bit under 5 us so the blip at the end allows the BPMs to measure the five (six) passes in the linacs independently with adequate accuracy.

1. Current:
   • Tune beam is typically 4-8 uA.
   • Crew chief permission is needed for higher current. One can run 200 uA tune beam.
   • 4 uA is the minimum needed for good readings on the old 4-channel BPM electronics. On SEE electronics, like that installed in most of the west arc this down and all the line to hall D, 1 uA tune beam reads fine.