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research article

Geometric beam coupling impedance of LHC secondary collimators

Frasciello, Oscar
•
Tomassini, Sandro
•
Zobov, Mikhail
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2016
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

The High Luminosity LHC project is aimed at increasing the LHC luminosity by an order of magnitude. One of the key ingredients to achieve the luminosity goal is the beam intensity increase. In order to keep beam instabilities under control and to avoid excessive power losses a careful design of new vacuum chamber components and an improvement of the present LHC impedance model are required. Collimators are among the major impedance contributors. Measurements with beam have revealed that the betatron coherent tune shifts were higher by about a factor of 2 with respect to the theoretical predictions based on the LHC impedance model up to 2012. In that model the resistive wall impedance has been considered as the dominating impedance contribution for collimators. By carefully simulating also their geometric impedance we have contributed to the update of the LHC impedance model, reaching also a better agreement between the measured and simulated betatron tune shifts. During the just ended LHC Long Shutdown I (LSI), TCS/TCT collimators were replaced by new devices embedding BPMs and TT2-111R ferrite blocks. We present here preliminary estimations of their broad -band impedance, showing that an increase of about 20% is expected in the kick factors with respect to previous collimators without BPMs. (C) 2015 Elsevier B.V. All rights reserved.

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Type
research article
DOI
10.1016/j.nima.2015.11.139
Web of Science ID

WOS:000368632900012

Author(s)
Frasciello, Oscar
Tomassini, Sandro
Zobov, Mikhail
Salvant, Benoit
Grudiev, Alexej
Mounet, Nicolas  
Date Issued

2016

Publisher

Elsevier Science Bv

Published in
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Volume

810

Start page

68

End page

73

Subjects

Wakefields

•

Impedance

•

LHC collimators

•

GdfidL

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
THEOS  
Available on Infoscience
February 16, 2016
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/123715
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