JACoW logo

Joint Accelerator Conferences Website

The Joint Accelerator Conferences Website (JACoW) is an international collaboration that publishes the proceedings of accelerator conferences held around the world.

Title Luminosity Reduction Caused by the Full-Detuning LLRF Scheme on the HL-LHC Crab Cavities
  • E. Yamakawa, R. Apsimon, A.C. Dexter
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • P. Baudrenghien, R. Calaga, F.J. Galindo Guarchpresenter
    CERN, Geneva, Switzerland
Abstract The High-Luminosity LHC (HL-LHC) crab cavities (CCs) will be installed on both sides of IP1 (ATLAS) and IP5 (CMS) to compensate for the geometric luminosity reduction due to the crossing angle. To cope with the increased beam current (0.55 A DC for LHC, 1.1 A for HL-LHC), the operation of the LLRF system has been changed: rather than fully compensating the transient beam loading, we allow the phase to vary along the turn (100 ps peak-peak with 1.1 A DC). This has been implemented at LHC since July 2017. The CCs have high loaded Q (5e5) and the available RF power is insufficient to follow the bunch phase modulation. The crabbing voltage is not modulated, causing a phase error w.r.t. the individual bunch centroids, leading to transverse kicks of the centroids and an asymmetric crabbing of the bunch cores. We present an analytical model for the resulting luminosity reduction and validate with particle tracking simulations. Due to the symmetry of the bunch filling patterns for the counter-rotating beams, the peak luminosity is reduced by only 2% for nominal HL-LHC parameters at IPs 1 and 5, which is within tolerable limits.
Paper download MOPMF022.PDF [0.518 MB / 4 pages]
Export download ※ BibTeX LaTeXText/WordRISEndNote
Conference IPAC2018, Vancouver, BC, Canada
Series International Particle Accelerator Conference (9th)
Proceedings Link to full IPAC2018 Proccedings
Session MC1 Poster Session
Date 30-Apr-18   16:00–17:30
Main Classification 01 Circular and Linear Colliders
Sub Classification A01 Hadron Colliders
Keywords luminosity, cavity, simulation, proton, LLRF
Publisher JACoW Publishing, Geneva, Switzerland
Editors Shane Koscielniak (TRIUMF, Vancouver, BC, Canada); Todd Satogata (JLab, Newport News, VA, USA); Volker RW Schaa (GSI, Darmstadt, Germany); Jana Thomson (TRIUMF, Vancouver, BC, Canada)
ISBN 978-3-95450-184-7
Published June 2018
Copyright © 2018 by JACoW, Geneva, Switzerland     CC-BY Creative Commons License
cc Creative Commons Attribution 3.0