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Title: Effect of crab cavity high order modes on the coupled-bunch stability of High-Luminosity Large Hadron Collider

Journal Article · · Physical Review Accelerators and Beams
ORCiD logo [1];  [1];  [1];  [1];  [1];  [2]
  1. European Organization for Nuclear Research (CERN), Geneva (Switzerland)
  2. Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
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High frequency High Order Modes can significantly affect the coupled-bunch stability in a circular accelerator. With a large enough shunt impedance they may drive a coupled-bunch transverse instability. We have developed an analytical model and implemented it in the NHT Vlasov solver. The results show that the instability is characterized by the excitation of many azimuthal intra-bunch modes, which have similar growth rates, that make the traditional remedies such as a flat resistive feedback and chromaticity inefficient in suppressing it. For the High Luminosity Large Hadron Collider this could result in a significant increase of the stabilizing Landau octupole current, up to $$\sim 100$$ A ($$\sim 20\%$$ of the maximum available current). In order to limit the increase below 10 A ($$\sim 2\%$$), the transverse shunt impedance has to be kept below 1 M$$\Omega$$/m.

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:
1523429
Report Number(s):
arXiv:1812.00659; FERMILAB-PUB-18-706-APC; PRABCJ; 1706259
Journal Information:
Physical Review Accelerators and Beams, Vol. 22, Issue 5; ISSN 2469-9888
Publisher:
American Physical Society (APS)Copyright Statement
Country of Publication:
United States
Language:
English

References (11)

Beam-beam collision scheme for storage-ring colliders journal July 1989
Beam dynamics aspects of crab cavities in the CERN Large Hadron Collider journal October 2009
Crab cavities for colliders: past, present and future journal April 2016
High-Energy LHC design journal September 2018
Nested head-tail Vlasov solver journal February 2014
Beam Instabilities in Hadron Synchrotrons journal April 2016
Design, prototyping, and testing of a compact superconducting double quarter wave crab cavity journal April 2015
New compact TEM-type deflecting and crabbing rf structure journal June 2009
Design evolution and properties of superconducting parallel-bar rf-dipole deflecting and crabbing cavities journal January 2013
Cryogenic test of a proof-of-principle superconducting rf-dipole deflecting and crabbing cavity journal August 2013
Compensation of the long-range beam-beam interactions as a path towards new configurations for the high luminosity LHC journal December 2015

Figures / Tables (16)

FIG. 1(p. 2)figure FIG. 1
FIG. 2(p. 2)figure FIG. 2
FIG. 3(p. 3)figure FIG. 3
FIG. 4(p. 5)figure FIG. 4
FIG. 5(p. 5)figure FIG. 5
TABLE I(p. 5)table TABLE I
FIG. 6(p. 6)figure FIG. 6
TABLE II(p. 6)table TABLE II
FIG. 7(p. 7)figure FIG. 7
FIG. 8(p. 7)figure FIG. 8
FIG. 9(p. 7)figure FIG. 9
TABLE III(p. 7)table TABLE III
FIG. 10(p. 8)figure FIG. 10
FIG. 11(p. 9)figure FIG. 11
TABLE IV(p. 10)table TABLE IV
TABLE V(p. 10)table TABLE V

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