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Title: High-Efficiency Absorber for Damping the Transverse Wake Fields

Abstract

Transverse wake fields generated by intense beams may propagate long distances in the vacuum chamber and dissipate power in different shielded elements such as bellows, vacuum valves or vacuum pumps. Induced heating in these elements may be high enough to deteriorate vacuum conditions. We have developed a broadband water-cooled bellows-absorber to capture and damp these harmful transverse fields without impacting the longitudinal beam impedance. Experimental results at the PEP-II SLAC B-factory demonstrate high efficiency of this device. This absorber may be useful in other machines like synchrotron light sources or International Linear Collider.

Authors:
; ; ;
Publication Date:
Research Org.:
Stanford Linear Accelerator Center (SLAC)
Sponsoring Org.:
USDOE
OSTI Identifier:
900235
Report Number(s):
SLAC-PUB-12337
TRN: US200711%%316
DOE Contract Number:
AC02-76SF00515
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Special Topics - Accelerators and Beams (PRST-AB)
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; DAMPING; EFFICIENCY; HEATING; IMPEDANCE; LIGHT SOURCES; LINEAR COLLIDERS; STANFORD LINEAR ACCELERATOR CENTER; SYNCHROTRONS; VACUUM PUMPS; VALVES; Accelerators,ACCPHY

Citation Formats

Novokhatski, A., Seeman, J., Weathersby, S., and /SLAC. High-Efficiency Absorber for Damping the Transverse Wake Fields. United States: N. p., 2007. Web. doi:10.1103/PhysRevSTAB.10.042003.
Novokhatski, A., Seeman, J., Weathersby, S., & /SLAC. High-Efficiency Absorber for Damping the Transverse Wake Fields. United States. doi:10.1103/PhysRevSTAB.10.042003.
Novokhatski, A., Seeman, J., Weathersby, S., and /SLAC. Wed . "High-Efficiency Absorber for Damping the Transverse Wake Fields". United States. doi:10.1103/PhysRevSTAB.10.042003. https://www.osti.gov/servlets/purl/900235.
@article{osti_900235,
title = {High-Efficiency Absorber for Damping the Transverse Wake Fields},
author = {Novokhatski, A. and Seeman, J. and Weathersby, S. and /SLAC},
abstractNote = {Transverse wake fields generated by intense beams may propagate long distances in the vacuum chamber and dissipate power in different shielded elements such as bellows, vacuum valves or vacuum pumps. Induced heating in these elements may be high enough to deteriorate vacuum conditions. We have developed a broadband water-cooled bellows-absorber to capture and damp these harmful transverse fields without impacting the longitudinal beam impedance. Experimental results at the PEP-II SLAC B-factory demonstrate high efficiency of this device. This absorber may be useful in other machines like synchrotron light sources or International Linear Collider.},
doi = {10.1103/PhysRevSTAB.10.042003},
journal = {Physical Review Special Topics - Accelerators and Beams (PRST-AB)},
number = ,
volume = ,
place = {United States},
year = {Wed Feb 28 00:00:00 EST 2007},
month = {Wed Feb 28 00:00:00 EST 2007}
}
  • The transverse wake field in a dielectric wake-field accelerator for drive beams with a small nonaxisymmetric component ({ital l}{ne}0) has been calculated in the ultrarelativistic limit. It is found that for the {ital l}th azimuthal mode, where {ital l}{gt}0, the transverse component is comparable to the longitudinal component. This implies that these devices will be subject to a beam-breakup instability as the drive current becomes large.
  • The transverse wake fields in a dielectric wake-field accelerator are calculated for the case of an off-axis drive beam. The calculation is done taking into account the transverse dimensions of the wake-field structure including the ratio of inner to outer radii of the dielectric liner {ital S}. The results indicate that the {ital m}=1 radial transverse wake-field component is much smaller than the {ital m}=0 axial wake field for liners with small hole size ({ital S}{le}0.2). Therefore, beam breakup instabilities can be avoided, even for large drive beam currents, in dielectric wake-field accelerators where {ital S} is small.{lt}UF1col{gt}
  • Theory is presented for excitation of hybrid electric/magnetic ({ital HEM}) wake-field modes by passage of an electron drive bunch in a dielectric-lined cylindrical waveguide. The drive bunch is moving parallel to the waveguide axis, but is displaced by a radial increment r{sub 0}. Knowledge of the amplitudes of all {ital HEM} modes allows calculation of the transverse forces on a bunch or bunches that follow the displaced drive bunch. Approximate formulas for the transverse forces on a trailing bunch are given, valid in the limit of small r{sub 0}. These transverse forces can lead to beam instability, if cumulative transversemore » motion is significant on the time-scale of passage of the bunch through the accelerator module. Constructive interference can be present amongst TM{sub 0m} monopole modes that produce highly-peaked spatiotemporally-localized axial wake-fields, with peak fields at the locations of trailing bunches in a multi-bunch train. In this case, the spectrum of dipole (and higher order) {ital HEM} modes may not enjoy the same degree of constructive interference, and may not have the same axial periodicity as the monopole modes. Further analytical and computational study is needed to determine the limitations that transverse wake fields may impose on a multi-bunch dielectric wake-field accelerator. {copyright} {ital 1999 American Institute of Physics.}« less