Abstract
A magnetic bunch compressor was designed and commissioned to provide higher peak current for the Advanced Photon Source's Low-Energy Undulator Test Line free-electron laser [S. V. Milton et al., Phys. Rev. Lett. 85, 988 (2000)]. Of great concern is limiting emittance growth due to coherent synchrotron radiation. Tolerances must also be carefully evaluated to find stable operating conditions and ensure that the system can meet operational goals. Automated matching and tolerance simulations allowed consideration of numerous configurations, pinpointing those with reduced error sensitivity. Simulations indicate significant emittance growth up to 600 A peak current, for which the normalized emittance will increase from 5 to about $8.5\ensuremath{\mu}\mathrm{m}$. The simulations also provide predictions of emittance variation with chicane parameters and precompressor linac phase, which we hope to verify experimentally.
Highlights
The Advanced Photon Source’s (APS) bunch compressor design is an outgrowth of studies [1] by Emma and Bharadwaj of the Stanford Linear Accelerator Center (SLAC)
They explored a number of designs, including symmetric and asymmetric four-dipole chicanes, with the goal of finding a design that minimized coherent synchrotron radiation (CSR)-induced emittance growth
Most of the emittance growth in such a chicane occurs in the last dipole, because that is where the bunch is shortest. If this dipole can be made weaker, the emittance growth can be reduced. This is the idea behind the asymmetric chicane: the third and fourth dipoles are weaker than the first and second dipoles
Summary
The Advanced Photon Source’s (APS) bunch compressor design is an outgrowth of studies [1] by Emma and Bharadwaj of the Stanford Linear Accelerator Center (SLAC). The method assumes that the wake propagates through the downstream drifts without changing its longitudinal shape, but allows for variation in overall intensity This model is believed to be plausible based on more detailed calculations by Dohlus and Limberg (see [7], in particular, Fig. 3). The second method, used to generate all results presented in this paper, uses Eqs. 53 and 54 from Saldin, Schneidmiller, and Yurkov [5], which give the normalized energy gain seen by a particle inside a uniform bunch These equations are used only to obtain the dependence of the strength of the CSR wake on distance from the end of the dipole. As reported in [4], these two models give comparable results
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Physical Review Special Topics - Accelerators and Beams
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
