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Title: Study of Collective Effects for the PEP Low-Emittance Optics

Experimental studies have been performed on the PEP storage ring run at 7.1 GeV in the low-emittance mode. The motivation for this work is to explore the capability of PEP as a dedicated synchrotron radiation source. The long straight sections and low emittance available at PEP make its use for this purpose very attractive, and would produce a source of very high brightness x-ray beams for the scientific community. During the studies, single-bunch current limitations were measured as a function of RF voltage. Thresholds were in the range of 1-2 mA per bunch, which is lower than expected based upon transverse impedance estimates from the PEP collider optics. An increase in threshold current by about 50% was realized by modifying the optics to reduce the magnitude of the horizontal beta functions in the straight sections and at the RF locations. The reason for the lower than expected thresholds has not been resolved. To permit its effective use as a synchrotron radiation source, a beam current of 50-100 mA is desired, which will require that PEP be run in the multibunch mode. Our goal in this study was to investigate the multibunch operating mode to ascertain that reasonable beam intensities weremore » possible. By utilizing many low intensity (0.1-0.25 mA) bunches, stable and reproducible currents of 15-20 mA were achieved. In an attempt to improve this value, one of the idle RF stations was operated in a tune-splitting mode, with only partial success. By adjusting the tuner positions of the unused RF stations, up to 33 mA was ultimately stored, albeit with some evidence for instability. Possible approaches to improving the multibunch stability are discussed.« less
Authors:
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Publication Date:
OSTI Identifier:
1000485
Report Number(s):
LBL-25582
TRN: US201101%%632
DOE Contract Number:
DE-AC02-05CH11231
Resource Type:
Technical Report
Research Org:
Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA (US)
Sponsoring Org:
Accelerator& Fusion Research Division
Country of Publication:
United States
Language:
English
Subject:
99; BEAM CURRENTS; BRIGHTNESS; IMPEDANCE; INSTABILITY; OPTICS; PEP STORAGE RINGS; STABILITY; SYNCHROTRON RADIATION SOURCES; THRESHOLD CURRENT