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Title: Damping trapped modes in an in-vacuum undulator at a synchrotron radiation light source

Abstract

In-vacuum undulators have been widely operated in many synchrotron radiation facilities across the world. They usually are required to be operated at a smaller magnet gap than those of other undulators. Thus, operating challenges including impedance effects on the stored electron beam are introduced by these devices. In this paper, we report the efforts in solving the problem of coupled-bunch instabilities caused by an in-vacuum undulator in the SPEAR3 storage ring. Using beam based measurements, cold rf measurements, and numerical simulations, the source of the beam instabilities is characterized as trapped modes in the vacuum chamber. Using numerical models, we explored several approaches to reduce the strength of the trapped modes and found that ferrite dampers were the most effective and simplest way for mode damping in our SPEAR3 in-vacuum undulator. The results of the first rf cold measurement on an in-vacuum undulator equipped with these ferrite dampers agree well with numerical simulations.

Authors:
; ; ;
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1512540
Alternate Identifier(s):
OSTI ID: 1527148
Grant/Contract Number:  
AC02-76SF00515; AC02-05CH11231
Resource Type:
Published Article
Journal Name:
Physical Review Accelerators and Beams
Additional Journal Information:
Journal Name: Physical Review Accelerators and Beams Journal Volume: 22 Journal Issue: 5; Journal ID: ISSN 2469-9888
Publisher:
American Physical Society
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS

Citation Formats

Tian, Kai, Sebek, James J., Ringwall, Andrew D., and Li, Zenghai. Damping trapped modes in an in-vacuum undulator at a synchrotron radiation light source. United States: N. p., 2019. Web. doi:10.1103/PhysRevAccelBeams.22.050702.
Tian, Kai, Sebek, James J., Ringwall, Andrew D., & Li, Zenghai. Damping trapped modes in an in-vacuum undulator at a synchrotron radiation light source. United States. doi:10.1103/PhysRevAccelBeams.22.050702.
Tian, Kai, Sebek, James J., Ringwall, Andrew D., and Li, Zenghai. Tue . "Damping trapped modes in an in-vacuum undulator at a synchrotron radiation light source". United States. doi:10.1103/PhysRevAccelBeams.22.050702.
@article{osti_1512540,
title = {Damping trapped modes in an in-vacuum undulator at a synchrotron radiation light source},
author = {Tian, Kai and Sebek, James J. and Ringwall, Andrew D. and Li, Zenghai},
abstractNote = {In-vacuum undulators have been widely operated in many synchrotron radiation facilities across the world. They usually are required to be operated at a smaller magnet gap than those of other undulators. Thus, operating challenges including impedance effects on the stored electron beam are introduced by these devices. In this paper, we report the efforts in solving the problem of coupled-bunch instabilities caused by an in-vacuum undulator in the SPEAR3 storage ring. Using beam based measurements, cold rf measurements, and numerical simulations, the source of the beam instabilities is characterized as trapped modes in the vacuum chamber. Using numerical models, we explored several approaches to reduce the strength of the trapped modes and found that ferrite dampers were the most effective and simplest way for mode damping in our SPEAR3 in-vacuum undulator. The results of the first rf cold measurement on an in-vacuum undulator equipped with these ferrite dampers agree well with numerical simulations.},
doi = {10.1103/PhysRevAccelBeams.22.050702},
journal = {Physical Review Accelerators and Beams},
number = 5,
volume = 22,
place = {United States},
year = {2019},
month = {5}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
DOI: 10.1103/PhysRevAccelBeams.22.050702

Figures / Tables:

FIG. 1 FIG. 1: Vertical coupled bunch instability growth rates in the IVU chamber.

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