10/03/97 Update
10/03/97 Update
October 3, 1997
The PEP-II HER ring and it's injection system have been operating at 8.5 GeV with 1 to 10 Hz injection rate over the past two weeks. The work has concentrated on feedback commissioning and optical lattice studies.
The betatron functions have been measured around the ring and very carefully in the interaction region. Now that we have gone to the full strength IR quadrupoles (Q4/5) the measured betas differ from the design by a few tens of percent. We are investigating the source(s) of these offsets.
The transverse and longitudinal feedback systems have been tuned with single bunches and tested at high beam currents with multibunches. Many grow-damp experiments with the beam have been done to compare to theory and to calibrate the required feedback power and gain.
The RF feedbacks (direct loop, comb filter, and DC ripple loop) (Paul Corredoura, Rich Tighe, Stephanie Allison, and many other) have been successfully tested in the field with beam.
Yesterday, most the feedback loops were used simultaneously and a beam current of 303 mA was achieved in 291 bunches with a lifetime of 116 minutes. Up to about 200 mA the beam is stable and acceptable for (future) collisions. At 300 mA the beam is somewhat unstable with horizontal oscillations which are under investigation. The loops still need more tuning and the measured beam spectra are being analyzed. Most of the feedback loops add a little noise to the beam and these noise sources are being looked into.
The vacuum beam lifetime is still improving. At 50 mA the lifetime is 10 hours.
Two rounds of background studies (Tom Mattison, et al) have been done looking at synchrotron radiation and lost particle effects at the interaction point.
This beam run ends October 13. We intend to start again with HER and part-turn LER studies in January.
Thanks again to everyone for their strong contributions and especially to Uli Wienands for his direction of the HER studies and Tom Himel for program coordination at the Main Control Center (MCC).
Cheers, John
Suggestions to: John Seeman
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