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Title: Transverse mode-coupling instability and space charge

Journal Article · · Physical Review Accelerators and Beams
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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.

Research Organization:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Organization:
USDOE Office of Science (SC), High Energy Physics (HEP)
Grant/Contract Number:
AC02-07CH11359
OSTI ID:
1477559
Alternate ID(s):
OSTI ID: 1497100
Report Number(s):
arXiv:1711.11110; FERMILAB-PUB-17-693-APC-CD; PRABCJ; 104201
Journal Information:
Physical Review Accelerators and Beams, Journal Name: Physical Review Accelerators and Beams Vol. 21 Journal Issue: 10; ISSN 2469-9888
Publisher:
American Physical SocietyCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 5 works
Citation information provided by
Web of Science

References (11)

Fast head-tail instability with space charge journal August 1998
Stability issues of low-energy intense beams conference January 1999
Bunches with Local Elliptic Energy Distributions journal January 1979
Transverse Schottky noise spectrum for bunches with space charge journal November 2009
Threshold of transverse mode coupling instability with arbitrary space charge journal November 2017
Simulation of transverse modes with their intrinsic Landau damping for bunched beams in the presence of space charge journal July 2015
Head-tail modes for strong space charge journal April 2009
Nested head-tail Vlasov solver journal February 2014
Two particle model for studying the effects of space-charge force on strong head-tail instabilities journal January 2016
Transverse mode coupling instability threshold with space charge and different wakefields journal March 2017
Transverse modes of a bunched beam with space charge dominated impedance journal December 2009

Figures / Tables (25)

Figure-1(p. 5)figure Figure-1
Table II(p. 6)table Table II
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Figure 19(p. 19)figure Figure 19
Table III(p. 20)table Table III
Table IV(p. 21)table Table IV
Figure 20(p. 22)figure Figure 20
Figure 21(p. 23)figure Figure 21
Figure 22(p. 24)figure Figure 22

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