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Upgrades to PEP-II Tune Measurements [electronic resource].

Published
Washington, D.C. : United States. Dept. of Energy. Office of Energy Research, 2002.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
Physical Description
vp : digital, PDF file
Additional Creators
Stanford Linear Accelerator Center, United States. Department of Energy. Office of Energy Research, and United States. Department of Energy. Office of Scientific and Technical Information
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Summary
The tune monitors for the two-ring PEP-II collider convert signals from one set of four BPM-type pickup buttons per ring into horizontal and vertical differences, which are then downconverted from 952 MHz (twice the RF) to baseband. Two-channel l0-MHz FFT spectrum analyzers show spectra in X-window displays in the Control Room, to assist PEP operators. When operating with the original system near the beam-beam limit, collisions broadened and flattened the tune peaks, often bringing them near the noise floor. We recently installed new downconverters that increase the signal-to-noise ratio by about 5 dB. In addition, we went from one to two sets of pickups per ring, near focusing and defocusing quadrupoles, so that signals for both planes originate at locations with large amplitudes. We also have just installed a tune tracker, based on a digital lock-in amplifier (one per tune plane) that is controlled by an EPICS software feedback loop. The tracker monitors the phase of the beam's response to a sinusoidal excitation, and adjusts the drive frequency to track the middle of the 180-degree phase transition across the tune resonance. We plan next to test an outer loop controlling the tune quadrupoles based on this tune measurement.
Report Numbers
E 1.99:slac-pub-9215
slac-pub-9215
Subject(s)
Other Subject(s)
Note
Published through SciTech Connect.
07/30/2002.
"slac-pub-9215"
Fisher, Alan S.
Type of Report and Period Covered Note
Topical;
Funding Information
AC03-76SF00515
View MARC record | catkey: 14687355