Optimized Filling of the ALS Storage Ring

The Storage Ring at the Advanced Light Source is capable of being filled in selectable buckets. Typically, 276 consecutive buckets out of 328 possible are selected. 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 filling in an orderly manner, yielding bunch heights uniform to within 17%. At fill time, multiple bunches are injected into the Storage ring first, then, using feedback, selected single bunches are used to top off the fill.