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Title Requirements and Results for Quadrupole Mode Measurements
  • A. Oeftiger
    CERN, Geneva, Switzerland
Abstract Direct space charge may be quantified, and hence the beam brightness observed, by measuring the quadrupolar beam modes in the CERN Proton Synchrotron (PS). The spectrum of the transverse beam size oscillations (i.e. the quadrupolar beam moment) contains valuable information: the betatron envelope modes and the coherent dispersive mode indicate optics mismatch, while their frequency shifts due to space charge allow a direct measurement thereof. To measure the quadrupolar beam moment we use the Base-Band Q-meter system of the PS which is based on a four electrode stripline pick-up. Past experiments with quadrupolar pick-ups often investigated coasting beams, where the coherent betatron and dispersion modes correspond to single peaks in the tune spectrum. In contrast, long bunched beams feature bands of betatron modes: the mode frequencies shift depending on the transverse space charge strength which varies with the local line charge density. By using the new transverse feedback in the PS as a quadrupolar RF exciter, we measured the quadrupolar beam transfer function. The beam response reveals the distinct band structure of the envelope modes as well as the coherent dispersive mode.
Funding Research supported by the HL-LHC project.
Paper download THA1WE02.PDF [1.650 MB / 6 pages]
Slides download THA1WE02_TALK.PDF [7.315 MB]
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Conference HB2018, Daejeon, Korea
Series ICFA Advanced Beam Dynamics Workshop (61st)
Proceedings Link to full HB2018 Proccedings
Session WG-E
Date 21-Jun-18   08:30–10:30
Main Classification Beam Instruments and Interactions
Keywords space-charge, emittance, synchrotron, quadrupole, pick-up
Publisher JACoW Publishing, Geneva, Switzerland
Editors Volker RW Schaa (GSI, Darmstadt, Germany)
ISBN 978-3-95450-202-8
Published July 2018
Copyright © 2018 by JACoW, Geneva, Switzerland     CC-BY Creative Commons License
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