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Title: Transverse mode-coupling instability and space charge

Abstract

Transverse mode-coupling instability (TMCI) is known to limit bunch intensity. Since space charge (SC) changes coherent spectra, it affects the TMCI threshold. Generally, there are only two types of TMCI with respect to SC: the vanishing type and the strong space charge (SSC) type. For the former, the threshold value of the wake tune shift is asymptotically proportional to the SC tune shift, as it was first observed twenty years ago by M. Blaskiewicz for exponential wakes. For the latter, the threshold value of the wake tune shift is asymptotically inversely proportional to the SC, as it was shown by one of the authors. In the presented studies of various wakes, potential wells, and bunch distributions, the second type of instability was always observed for cosine wakes; it was also seen for the sine wakes in the case of a bunch within a square potential well. The vanishing TMCI was observed for all other wakes and distributions we discuss in this paper: always for the negative wakes, and always, except the cosine wake, for parabolic potential wells. At the end of this paper, we consider high-frequency broadband wake, suggested as a model impedance for CERN SPS ring. As expected, TMCImore » is of the vanishing type in this case. Furthermore, SPS Q26 instability, observed at strong SC almost with the same bunch parameters as it would be observed without SC, cannot be TMCI.« less

Authors:
 [1];  [1];  [2]
  1. Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
  2. The Univ. of Chicago, Chicago, IL (United States)
Publication Date:
Research Org.:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
OSTI Identifier:
1477559
Alternate Identifier(s):
OSTI ID: 1497100
Report Number(s):
arXiv:1711.11110; FERMILAB-PUB-17-693-APC-CD
Journal ID: ISSN 2469-9888; PRABCJ; 1639914
Grant/Contract Number:  
AC02-07CH11359
Resource Type:
Journal Article: Published Article
Journal Name:
Physical Review Accelerators and Beams
Additional Journal Information:
Journal Volume: 21; Journal Issue: 10; Journal ID: ISSN 2469-9888
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS

Citation Formats

Zolkin, Timofey, Burov, Alexey, and Pandey, Bipul. Transverse mode-coupling instability and space charge. United States: N. p., 2018. Web. doi:10.1103/PhysRevAccelBeams.21.104201.
Zolkin, Timofey, Burov, Alexey, & Pandey, Bipul. Transverse mode-coupling instability and space charge. United States. doi:10.1103/PhysRevAccelBeams.21.104201.
Zolkin, Timofey, Burov, Alexey, and Pandey, Bipul. Thu . "Transverse mode-coupling instability and space charge". United States. doi:10.1103/PhysRevAccelBeams.21.104201.
@article{osti_1477559,
title = {Transverse mode-coupling instability and space charge},
author = {Zolkin, Timofey and Burov, Alexey and Pandey, Bipul},
abstractNote = {Transverse mode-coupling instability (TMCI) is known to limit bunch intensity. Since space charge (SC) changes coherent spectra, it affects the TMCI threshold. Generally, there are only two types of TMCI with respect to SC: the vanishing type and the strong space charge (SSC) type. For the former, the threshold value of the wake tune shift is asymptotically proportional to the SC tune shift, as it was first observed twenty years ago by M. Blaskiewicz for exponential wakes. For the latter, the threshold value of the wake tune shift is asymptotically inversely proportional to the SC, as it was shown by one of the authors. In the presented studies of various wakes, potential wells, and bunch distributions, the second type of instability was always observed for cosine wakes; it was also seen for the sine wakes in the case of a bunch within a square potential well. The vanishing TMCI was observed for all other wakes and distributions we discuss in this paper: always for the negative wakes, and always, except the cosine wake, for parabolic potential wells. At the end of this paper, we consider high-frequency broadband wake, suggested as a model impedance for CERN SPS ring. As expected, TMCI is of the vanishing type in this case. Furthermore, SPS Q26 instability, observed at strong SC almost with the same bunch parameters as it would be observed without SC, cannot be TMCI.},
doi = {10.1103/PhysRevAccelBeams.21.104201},
journal = {Physical Review Accelerators and Beams},
issn = {2469-9888},
number = 10,
volume = 21,
place = {United States},
year = {2018},
month = {10}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1103/PhysRevAccelBeams.21.104201

Citation Metrics:
Cited by: 2 works
Citation information provided by
Web of Science

Figures / Tables:

Figure-1 Figure-1: First five SSC harmonics Yk($\tau$) for a bunch in a square potential well, bunch in a parabolic potential well (generalized Hofmann-Pedersen distributions with n ¼ 0; 1=2; 1) and the Gaussian bunch. The harmonics are presented in dimensionless units: τ is measured in units of τb or in unitsmore » of σb for the SSCG case.« less

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