Improved HOM-mitigation for future SPS 33-Cell 200 MHz traveling-wave accelerating structures
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Published:2019-12-02
Issue:36
Volume:34
Page:1942018
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ISSN:0217-751X
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Container-title:International Journal of Modern Physics A
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language:en
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Short-container-title:Int. J. Mod. Phys. A
Author:
Kramer P.12ORCID,
Vollinger C.1
Affiliation:
1. CERN, 1211 Geneva 23, Switzerland
2. Institute of High Frequency Technology (IHF), RWTH Aachen University, Melatener Str. 25, 52074 Aachen, Germany
Abstract
The CERN SPS 200 MHz traveling-wave (TW) accelerating structures pose an intensity limitation for the planned High Luminosity (HL-) LHC upgrade. Higher-order modes (HOMs) around 630 MHz have been identified as one of the main sources of longitudinal multi-bunch instabilities. Improved mitigation of these HOMs with respect to today’s HOM-damping scheme is therefore an essential part of the LHC injectors upgrade (LIU) project. The basic principles of HOM-couplers in cavities and today’s damping scheme are reviewed. Before illustrating the numerous requirements, an improved damping scheme for the future 33-cell structures must be fulfilled. These are, among others, the mitigation of HOMs situated in the lower part of the structure where there are no access ports for extraction, a sufficient overall damping performance and an acceptable influence on the fundamental accelerating passband (FPB). Different approaches tackling these challenges are investigated and their performance, advantages and pitfalls are evaluated by ACE3P and CST electromagnetic (EM) field solver suites.
Funder
the National Energy Research Scientific Computing Center
Publisher
World Scientific Pub Co Pte Lt
Subject
Astronomy and Astrophysics,Nuclear and High Energy Physics,Atomic and Molecular Physics, and Optics
Reference8 articles.
1. P. Kramer and C. Vollinger, Proc. 13th Int. Computational Accelerator Physics Conf. (Key West, USA, 2018), pp. 35–41.