Beam bunch feedback
When the electromagnetic fields that are excited by the passage of a bundle of charged particles persist to act upon bunches that follow, then the motions of the bunches are coupled. This action between bunches circulating on a closed orbit can generate growing patterns of bunch excursions. Such growth can often be suppressed by feedback systems that detect the excursion and apply corrective forces to the bunches. To be addressed herein is feedback that acts on motions of the bunch body centers. In addition to being useful for suppressing the spontaneous growth of coupled-bunch motions, such feedback can be used to damp transients in bunches injected into an accelerator or storage ring; for hadrons which lack strong radiation damping, feedback is needed to avoid emittance growth through decoherence. Motions excited by noise in magnetic fields or accelerating rf can also be reduced by using this feedback. Whether the action is on motions that are transverse to the closed orbit or longitudinal, the arrangement is the same. Bunch position is detected by a pickup and that signal is processed and directed to a kicker that may act upon the same bunch or some other portion of the collective beam pattern. Transverse motion is an oscillation with angular frequency {nu}{perpendicular}{omega}{sub o} where {omega}{sub o} is the orbital frequency 2{pi}{line_integral}o. Longitudinal synchrotron oscillation occurs at frequency {omega} {sub s} = {nu}{sub s}{omega}{sub o}. The former is much more rapid, {nu}{perpendicular} being on the order of 10 while {nu}{sub s} is typically about 10{sup minus 1} to 10 {sup minus 2}.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 367235
- Report Number(s):
- LBL-37764; CBP-Note-154; CONF-941186-4; ON: DE96013460; TRN: 96:023264
- Resource Relation:
- Conference: Joint US-CERN-Japan topical course on accelerator physics and technology: frontiers of accelerator technology, Maui, HI (United States), 3-9 Nov 1994; Other Information: PBD: Sep 1995
- Country of Publication:
- United States
- Language:
- English
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