Feedback and beam stability
Paper Title Page
MOPP026 A Longitudinal Kicker Cavity for the BESSY II Booster 149
 
  • T. Atkinson, M. Dirsat, A.N. Matveenko, A. Schälicke, B. Schriefer, Y. Tamashevich
    HZB, Berlin, Germany
  • T. Flisgen
    FBH, Berlin, Germany
 
  As part of the global refurbishment of the injector systems at BESSY II, a new longitudinal kicker cavity and suitable feedback will be installed in the booster. Both a flexible bunch charge and spacing is essential for efficient injection. Such a cavity is needed to mitigate the unwanted couple bunch instabilities associated with these elaborate filling patterns and the HOMs of additional accelerating structures. This paper covers the conceptual design, simulation strategy, manufacture and bench tests of the longitudinal kicker cavity before it is installed in the ring.  
poster icon Poster MOPP026 [4.756 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2019-MOPP026  
About • paper received ※ 02 September 2019       paper accepted ※ 07 September 2019       issue date ※ 10 November 2019  
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MOPP027 First Beam-based Test of Fast Closed Orbit Feedback System at GSI SIS18 153
 
  • R. Singh, A. Doring, P. Forck, K. Lang, S.H. Mirza, D. Rodomonti, D. Schupp, M. Schwickert, H. Welker
    GSI, Darmstadt, Germany
  • A. Bardorfer
    I-Tech, Solkan, Slovenia
 
  Funding: European Unions Horizon 2020 Research and Innovation programme under Grant Agreement No. 730871 (ARIES). German Academic Exchange Service under Personal Reference No. 91605207.
The SIS18 synchrotron of GSI will be used as a booster ring for the SIS100 synchrotron built in the scope of the FAIR project. In order to preserve the beam quality during the whole acceleration ramp, a new closed orbit feedback (COFB) system is implemented at the SIS18 which operates with the existing BPMs and steerer magnets. The system aims for a bandwidth of several 100 Hz and robustness against the variation of the response matrix and the beam rigidity during the ramp. The architecture of the system and the results of the first beam-based test of the COFB hardware are presented. As a first step, the orbit correction is performed over the entire ramp using the response matrix corresponding to injection energy only taking the beam rigidity into account. Experimental observations of the bandwidth limitations arising from the temporal delay of the steerer power supplies and the spatial model variation during the ramp are compared with simulations. It is found that the temporal and the spatial model mismatch have similar effect on the achievable bandwidth of the COFB.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2019-MOPP027  
About • paper received ※ 07 September 2019       paper accepted ※ 08 September 2019       issue date ※ 10 November 2019  
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MOPP028 Longitudinal Bunch-by-Bunch Feedback Systems for SuperKEKB LER 158
 
  • M. Tobiyama, J.W. Flanagan, T. Kobayashi, S. Terui
    KEK, Ibaraki, Japan
  • J.D. Fox
    Stanford University, Stanford, California, USA
 
  Longitudinal bunch-by-bunch feedback systems to suppress coupled bunch instabilities with minimum bunch spacing of 2 ns have been constructed in SuperKEKB LER. Through the grow-damp and excite-damp experiments with several filling patterns and the transient-domain analysis of unstable modes, the behaviors of possible impedance sources have been evaluated. The measured performance of the system, together with the performance of the related systems such as slow phase feedback to the reference RF clock are reported.  
poster icon Poster MOPP028 [0.519 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2019-MOPP028  
About • paper received ※ 03 September 2019       paper accepted ※ 08 September 2019       issue date ※ 10 November 2019  
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MOPP030 Preliminary Test of XBPM Local Feedback in TPS 162
 
  • P.C. Chiu, J.-Y. Chuang, K.T. Hsu, K.H. Hu, C.H. Huang
    NSRRC, Hsinchu, Taiwan
 
  TPS is 3-GeV synchrotron light source which have opened for public users since September 2016 and now offers 400 mA top-up mode operation. The requirements of the long term orbit stability have been gradually more and more stringent. The report investigates the long-term orbit stability improved by applying local XBPM feedback.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2019-MOPP030  
About • paper received ※ 02 September 2019       paper accepted ※ 09 September 2019       issue date ※ 10 November 2019  
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MOPP031 Optimisation of the ISIS Proton Synchrotron Experimental Damping System 166
 
  • A. Pertica, D.W. Posthuma de Boer, R.E. Williamson
    STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
  • J. Komppula
    CERN, Meyrin, Switzerland
 
  The ISIS Neutron and Muon Source, located in the UK, consists of a H linear accelerator, a rapid cycling proton synchrotron and two extraction lines delivering protons onto heavy metal targets. One of the limiting factors for achieving higher intensities in the accelerator is the head-tail instability present in the synchrotron, around 2ms after injection. In order to mitigate this instability, an experimental damping system is being developed for the ISIS synchrotron. Initial tests using a split electrode BPM as a pickup and a ferrite loaded kicker as a damper showed positive results. This paper describes the different developments made to the damping system and planned improvements to optimize its performance for use in normal operations.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2019-MOPP031  
About • paper received ※ 04 September 2019       paper accepted ※ 09 September 2019       issue date ※ 10 November 2019  
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MOPP032 Fast Feedback Using Electron Beam Steering to Maintain the X-Ray Beam Position at a Monochromatic X-Ray Diagnostic at Diamond Light Source 171
 
  • C. Bloomer, G. Rehm, A. Tipper
    DLS, Oxfordshire, United Kingdom
 
  A new feedback system is being developed at Diamond Light Source, applying a modulation to the position of the electron beam to keep the synchrotron X-ray beam fixed at the sample-point. Beamline detectors operating in the 100-1000Hz regime are becoming common, and the X-ray beam stability demanded by beamlines is thus of comparable bandwidths. In this paper we present a feedback system operating at these bandwidths, using a diagnostic instrument permanently installed in the X-ray beam path to measure the error in beam position at the sample point, and fast air-cored magnets to apply a small modulation to the electron beam to compensate. Four magnets are used to generate electron beam bumps through an ID straight. This modulation of the beam away from the nominal orbit is small, less than 10 microns, but should be sufficient to compensate for the bulk of the X-ray motion observed at the sample. It is small enough that the impact on the machine will be negligible. This system aims to maintain X-ray beam stability to within 3% of a beam size, at bandwidths of up to 500Hz.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2019-MOPP032  
About • paper received ※ 09 September 2019       paper accepted ※ 10 September 2019       issue date ※ 10 November 2019  
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MOPP033 Preliminary Design of Mu2E Spill Regulation System (SRS) 176
 
  • M.A. Ibrahim, E. Cullerton, J.S. Diamond, K.S. Martin, P.S. Prieto, V.E. Scarpine, P. Varghese
    Fermilab, Batavia, Illinois, USA
 
  Funding: This work was supported by the U.S. Department of Energy under contract No. DE-AC02-07CH11359.
Direct µ->e conversion requires resonant extraction of a stream of pulsed beam, comprised of short micro-bunches (pulses) from the Delivery ring (DR) to the Mu2e target. Experimental needs and radiation protection apply strict requirements on the beam quality control and regulation of the spill. The objective of the Spill Regulation System (SRS) is to maintain the intensity uniformity of a stream of ~25K pulses as 1012 protons are extracted at 590.08kHz over a 43msec spill period. To meet the specified performance, two regulation elements will be driven simultaneously: a family of three zero-harmonic quadrupoles (tune ramp quads) and a RF Knock-Out (RFKO) system. The SRS will use two separate control loops to control each regulation element simultaneously. It will be critical to coordinate the SRS’ processes within the machine cycle and within each spill interval. The SRS has been designed to have a total Gain-Bandwidth product of 10KHz, which can be used to mitigate several sources of ripple in the spill profile.
 
poster icon Poster MOPP033 [0.522 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2019-MOPP033  
About • paper received ※ 30 August 2019       paper accepted ※ 08 September 2019       issue date ※ 10 November 2019  
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WECO01
Characterisation of Closed Orbit Feedback Systems  
 
  • G. Rehm
    DLS, Oxfordshire, United Kingdom
 
  Closed orbit feedback is applied at nearly all synchrotrons. Detailed investigations continue to be performed on the mathematical modelling of the spatial part (i.e. related to Orbit Response Matrix) and the dynamic part (i.e. the controller). This talk will serve as a summary of the ARIES workshop on closed orbit feedback organized by ALBA in November 2018. Benefits of recent advances compared to the traditional implementations will be highlighted.  
slides icon Slides WECO01 [4.912 MB]  
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WECO02 Towards an Adaptive Orbit-Response-Matrix Model for Twiss-Parameter Diagnostics and Orbit Correction at Delta 477
 
  • S. Koetter, T. Weis
    DELTA, Dortmund, Germany
 
  At DELTA, a 1.5-GeV electron storage ring operated by the TU Dortmund University, preliminary tests of an adaptive orbit-response-matrix model were conducted. Closed orbit perturbations corrected by the slow orbit feedback can be buffered and used to update a fit of the bilinear-exponential model with dispersion (BE+d model). This model is a representation of the orbit-response matrix depending on the beta functions, the betatron phases and the tunes in both planes. This work introduces a new fitting recipe to obtain good estimates of the aforementioned quantities and evaluates a BE+d-model represented orbit-response matrix for orbit correction. Numerical studies are shown along with measurement results.  
slides icon Slides WECO02 [0.657 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2019-WECO02  
About • paper received ※ 04 September 2019       paper accepted ※ 08 September 2019       issue date ※ 10 November 2019  
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