The Storage Ring at the Advanced Light Source is capable of filling into selected buckets. The nominal fill pattern is 276 consecutive buckets out of 328 possible, filled to a total of 400 mA. It has been found that the amount of charge injected is not uniform bucket-to-bucket, sometimes varying by 100% or more. This variability causes problems with beam stability, and it may shorten the beam lifetime. We have devised a feedback system that allows for beam stacking in an orderly manner, yielding uniform bunch heights with 17% variation or less. At fill time, multiple bunches are injected into the Storage ring first , then, using feedback, selected single bunches top off the fill.
Last updated: September 13, 2002
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