Skip to main content

Lund University Publications

LUND UNIVERSITY LIBRARIES

Beam-based characterization of higher-order-mode driven coupled-bunch instabilities in a fourth-generation storage ring

Tavares, P. F. LU ; Cullinan, F. J. LU ; Andersson, Å LU ; Olsson, D. LU and Svärd, R. LU orcid (2022) In Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 1021.
Abstract

Longitudinal coupled-bunch instabilities are driven by monopole higher-order modes (HOMs) in the active and passive radio-frequency (rf) cavities at the MAX IV 3 GeV electron storage ring. By combining different beam and rf-based techniques, we have performed a systematic survey of the properties of these resonant modes as a function of cavity temperatures and fundamental mode frequency. This information was then used to setup a HOM model that allowed us to infer optimized temperature ranges for the cavities. An important feature of the optimization method is that it takes into account not only the need to minimize the growth rates (given by the resistive component of the sum of HOM impedances) from each individual cavity but also aims... (More)

Longitudinal coupled-bunch instabilities are driven by monopole higher-order modes (HOMs) in the active and passive radio-frequency (rf) cavities at the MAX IV 3 GeV electron storage ring. By combining different beam and rf-based techniques, we have performed a systematic survey of the properties of these resonant modes as a function of cavity temperatures and fundamental mode frequency. This information was then used to setup a HOM model that allowed us to infer optimized temperature ranges for the cavities. An important feature of the optimization method is that it takes into account not only the need to minimize the growth rates (given by the resistive component of the sum of HOM impedances) from each individual cavity but also aims to minimize the total reactive component of the impedance of HOMs that are present in more than one cavity. The resulting small real coherent tune shifts allow the coupled-bunch modes driven by these HOMs to be effectively Landau damped. Further optimization of the cavity temperatures was performed by minimizing the measured electron beam energy spread within the temperature ranges defined by the HOM model. The optimum temperature search was performed at 300 mA stored beam current and in multi-bunch mode using the RCDS (Robust Conjugate Direction Search) algorithm and succeeded in bringing the electron energy spread to within 10% of the zero current value determined solely by quantum excitation and radiation damping.

(Less)
Please use this url to cite or link to this publication:
author
; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Coupled-bunch instability, Higher order mode, Storage ring, Ultra-low emittance
in
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
volume
1021
article number
165945
publisher
Elsevier
external identifiers
  • scopus:85118898527
ISSN
0168-9002
DOI
10.1016/j.nima.2021.165945
language
English
LU publication?
yes
additional info
Publisher Copyright: © 2021 The Authors
id
111b8d41-6e34-4875-8346-ddf6d67920c7
date added to LUP
2021-11-27 12:42:38
date last changed
2023-11-23 13:30:18
@article{111b8d41-6e34-4875-8346-ddf6d67920c7,
  abstract     = {{<p>Longitudinal coupled-bunch instabilities are driven by monopole higher-order modes (HOMs) in the active and passive radio-frequency (rf) cavities at the MAX IV 3 GeV electron storage ring. By combining different beam and rf-based techniques, we have performed a systematic survey of the properties of these resonant modes as a function of cavity temperatures and fundamental mode frequency. This information was then used to setup a HOM model that allowed us to infer optimized temperature ranges for the cavities. An important feature of the optimization method is that it takes into account not only the need to minimize the growth rates (given by the resistive component of the sum of HOM impedances) from each individual cavity but also aims to minimize the total reactive component of the impedance of HOMs that are present in more than one cavity. The resulting small real coherent tune shifts allow the coupled-bunch modes driven by these HOMs to be effectively Landau damped. Further optimization of the cavity temperatures was performed by minimizing the measured electron beam energy spread within the temperature ranges defined by the HOM model. The optimum temperature search was performed at 300 mA stored beam current and in multi-bunch mode using the RCDS (Robust Conjugate Direction Search) algorithm and succeeded in bringing the electron energy spread to within 10% of the zero current value determined solely by quantum excitation and radiation damping.</p>}},
  author       = {{Tavares, P. F. and Cullinan, F. J. and Andersson, Å and Olsson, D. and Svärd, R.}},
  issn         = {{0168-9002}},
  keywords     = {{Coupled-bunch instability; Higher order mode; Storage ring; Ultra-low emittance}},
  language     = {{eng}},
  month        = {{01}},
  publisher    = {{Elsevier}},
  series       = {{Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment}},
  title        = {{Beam-based characterization of higher-order-mode driven coupled-bunch instabilities in a fourth-generation storage ring}},
  url          = {{http://dx.doi.org/10.1016/j.nima.2021.165945}},
  doi          = {{10.1016/j.nima.2021.165945}},
  volume       = {{1021}},
  year         = {{2022}},
}