Analysis of the LSC microbunching instability in MaRIE linac reference design
Abstract
In this report we estimate the effect of the microbunching instability in the MaRIE XFEL linac. The reference design for the linac is described in a separate report. The parameters of the L1, L2, and L3 linacs as well as BC1 and BC2 bunch compressors were the same as in the referenced report. The beam dynamics was assumed to be linear along the accelerator (which is a reasonable assumption for estimating the effect of the microbunching instability). The parameters of the bunch also match the parameters described in the referenced report. Additionally, it was assumed that the beam radius is equal to R = 100 m and does not change along linac. This assumption needs to be revisited at later studies. The beam dynamics during acceleration was accounted in the matrix formalism using a Matlab code. The input parameters for the linacs are: RF peak gradient, RF frequency, RF phase, linac length, and initial beam energy. The energy gain and the imposed chirp are calculated based on the RF parameters selfconsistently. The bunch compressors are accounted in the matrix formalism as well. Each chicane is characterized by the beam energy and the R56 matrix element. It was confirmed that themore »
 Authors:
 Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
 Publication Date:
 Research Org.:
 Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
 Sponsoring Org.:
 USDOE
 OSTI Identifier:
 1327984
 Report Number(s):
 LAUR1627252
TRN: US1700331
 DOE Contract Number:
 AC5206NA25396
 Resource Type:
 Technical Report
 Country of Publication:
 United States
 Language:
 English
 Subject:
 43 PARTICLE ACCELERATORS; FREE ELECTRON LASERS; LINEAR ACCELERATORS; BEAM DYNAMICS; BEAM BUNCHING; INSTABILITY; MATRICES; COMPRESSION; COMPRESSORS; GAIN; LENGTH; PEAKS; MATRIX ELEMENTS; ACCELERATION; KILO AMP BEAM CURRENTS; space charge, microbunching instability, electron accelerator
Citation Formats
Yampolsky, Nikolai. Analysis of the LSC microbunching instability in MaRIE linac reference design. United States: N. p., 2016.
Web. doi:10.2172/1327984.
Yampolsky, Nikolai. Analysis of the LSC microbunching instability in MaRIE linac reference design. United States. doi:10.2172/1327984.
Yampolsky, Nikolai. 2016.
"Analysis of the LSC microbunching instability in MaRIE linac reference design". United States.
doi:10.2172/1327984. https://www.osti.gov/servlets/purl/1327984.
@article{osti_1327984,
title = {Analysis of the LSC microbunching instability in MaRIE linac reference design},
author = {Yampolsky, Nikolai},
abstractNote = {In this report we estimate the effect of the microbunching instability in the MaRIE XFEL linac. The reference design for the linac is described in a separate report. The parameters of the L1, L2, and L3 linacs as well as BC1 and BC2 bunch compressors were the same as in the referenced report. The beam dynamics was assumed to be linear along the accelerator (which is a reasonable assumption for estimating the effect of the microbunching instability). The parameters of the bunch also match the parameters described in the referenced report. Additionally, it was assumed that the beam radius is equal to R = 100 m and does not change along linac. This assumption needs to be revisited at later studies. The beam dynamics during acceleration was accounted in the matrix formalism using a Matlab code. The input parameters for the linacs are: RF peak gradient, RF frequency, RF phase, linac length, and initial beam energy. The energy gain and the imposed chirp are calculated based on the RF parameters selfconsistently. The bunch compressors are accounted in the matrix formalism as well. Each chicane is characterized by the beam energy and the R56 matrix element. It was confirmed that the linac and beam parameters described previously provide twostage bunch compression with compression ratios of 10 and 20 resulting in the bunch of 3kA peak current.},
doi = {10.2172/1327984},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2016,
month = 9
}

A microbunching instability driven by longitudinal space charge, coherent synchrotron radiation, and linac wakefields is studied for the linac coherent light source (LCLS) accelerator system. Since the uncorrelated (local) energy spread of electron beams generated from a photocathode rf gun is very small, the microbunching gain may be large enough to significantly amplify rfgun generated modulations or even shotnoise fluctuations of the electron beam. The uncorrelated energy spread can be increased by an order of magnitude to provide strong Landau damping against the instability without degrading the freeelectron laser performance. We study different damping options in the LCLS and discussmore »

Effects of Linac Wakefield on CSR Microbunching in the Linac Coherent Light Source
The design of the Linac Coherent Light Source (LCLS) requires twostage bunch compression for stability against timing and charge jitters. Coherent synchrotron radiation (CSR) induced in these bunch compressors can drive a microbunching instability that may degrade the beam brightness. In this paper, we study effects of the longitudinal wakefield in the accelerator on this instability. We show that significant energy modulation can be accumulated in the linac through the geometrical wakefield and can enhance the CSR microbunching in these compressors. Analytical calculations are compared with numerical simulations to evaluate the gain of microbunching for the entire LCLS accelerator system..