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Title: Experimental Characterization of the Transverse Phase Space of a 60-MeV Electron Beam Through a Compressor Chicane

Abstract

Space charge and coherent synchrotron radiation may deteriorate electron beam quality when the beam passes through a magnetic bunch compressor. This paper presents the transverse phase-space tomographic measurements for a compressed beam at 60 MeV, around which energy the first stage of magnetic bunch compression takes place in most advanced linacs. Transverse phase-space bifurcation of a compressed beam is observed at that energy, but the degree of the space charge-induced bifurcation is appreciably lower than the one observed at 12 MeV.

Authors:
; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Stanford Linear Accelerator Center (SLAC)
Sponsoring Org.:
USDOE
OSTI Identifier:
899565
Report Number(s):
SLAC-PUB-12346
TRN: US0701978
DOE Contract Number:
AC02-76SF00515
Resource Type:
Journal Article
Resource Relation:
Journal Name: Phys.Rev.ST Accel.Beams 9:114201,2006
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; BIFURCATION; COMPRESSION; COMPRESSORS; ELECTRON BEAMS; LINEAR ACCELERATORS; PHASE SPACE; SPACE CHARGE; SYNCHROTRON RADIATION; Accelerators,ACCPHY

Citation Formats

Zhou, F., Kabel, A., Rosenzweig, J., Agustsson, R., Andonian, G., Cline, D., Murokh, A., Yakimenko, V., and /UCLA /SLAC /Brookhaven. Experimental Characterization of the Transverse Phase Space of a 60-MeV Electron Beam Through a Compressor Chicane. United States: N. p., 2007. Web. doi:10.1109/PAC.2007.4440740.
Zhou, F., Kabel, A., Rosenzweig, J., Agustsson, R., Andonian, G., Cline, D., Murokh, A., Yakimenko, V., & /UCLA /SLAC /Brookhaven. Experimental Characterization of the Transverse Phase Space of a 60-MeV Electron Beam Through a Compressor Chicane. United States. doi:10.1109/PAC.2007.4440740.
Zhou, F., Kabel, A., Rosenzweig, J., Agustsson, R., Andonian, G., Cline, D., Murokh, A., Yakimenko, V., and /UCLA /SLAC /Brookhaven. Mon . "Experimental Characterization of the Transverse Phase Space of a 60-MeV Electron Beam Through a Compressor Chicane". United States. doi:10.1109/PAC.2007.4440740. https://www.osti.gov/servlets/purl/899565.
@article{osti_899565,
title = {Experimental Characterization of the Transverse Phase Space of a 60-MeV Electron Beam Through a Compressor Chicane},
author = {Zhou, F. and Kabel, A. and Rosenzweig, J. and Agustsson, R. and Andonian, G. and Cline, D. and Murokh, A. and Yakimenko, V. and /UCLA /SLAC /Brookhaven},
abstractNote = {Space charge and coherent synchrotron radiation may deteriorate electron beam quality when the beam passes through a magnetic bunch compressor. This paper presents the transverse phase-space tomographic measurements for a compressed beam at 60 MeV, around which energy the first stage of magnetic bunch compression takes place in most advanced linacs. Transverse phase-space bifurcation of a compressed beam is observed at that energy, but the degree of the space charge-induced bifurcation is appreciably lower than the one observed at 12 MeV.},
doi = {10.1109/PAC.2007.4440740},
journal = {Phys.Rev.ST Accel.Beams 9:114201,2006},
number = ,
volume = ,
place = {United States},
year = {Mon Feb 12 00:00:00 EST 2007},
month = {Mon Feb 12 00:00:00 EST 2007}
}
  • Purpose: For TrueBeam Monte Carlo simulations, Varian does not distribute linac head geometry and material compositions, instead providing a phase space file (PSF) for the users. The PSF has a finite number of particle histories and can have very large file size, yet still contains inherent statistical noises. The purpose of this study is to characterize the electron beam PSF with parameters. Methods: The PSF is a snapshot of all particles' information at a given plane above jaws including type, energy, position, and directions. This study utilized a preliminary TrueBeam PSF, of which validation against measurement is presented in anothermore » study. To characterize the PSF, distributions of energy, position, and direction of all particles are analyzed as piece-wise parameterized functions of radius and polar angle. Subsequently, a pseudo PSF was generated based on this characterization. Validation was assessed by directly comparing the true and pseudo PSFs, and by using both PSFs in the down-stream MC simulations (BEAMnrc/DOSXYZnrc) and comparing dose distributions for 3 applicators at 15 MeV. Statistical uncertainty of 4% was limited by the number of histories in the original PSF. Percent depth dose (PDD) and orthogonal (PRF) profiles at various depths were evaluated. Results: Preliminary results showed that this PSF parameterization was accurate, with no visible differences between original and pseudo PSFs except at the edge (6 cm off axis), which did not impact dose distributions in phantom. PDD differences were within 1 mm for R{sub 7} {sub 0}, R{sub 5} {sub 0}, R{sub 3} {sub 0}, and R{sub 1} {sub 0}, and PRF field size and penumbras were within 2 mm. Conclusion: A PSF can be successfully characterized by distributions for energy, position, and direction as parameterized functions of radius and polar angles; this facilitates generating sufficient particles at any statistical precision. Analyses for all other electron energies are under way and results will be included in the presentation.« less
  • After compressing electron bunches with a half-meter long, four-dipole chicane at 8 MeV, we have measured full width at half maximum (FWHM) bunch lengths of less than 1 ps for charges from 0.1 to 1.1 nC. The uncompressed FWHM bunch lengths varied from 10 to 20 ps, and we achieved compression ratios in excess of 40 and peak currents greater than 1 kA. Bunch lengths for low charges were measured using a transversely deflecting rf cavity; bunch lengths for high charges were inferred from the energy spread induced in the beam by its longitudinal space-charge force as it drifted frommore » the end of the compressor to the spectrometer. {copyright} {ital 1996 The American Physical Society.}« less