8. Feedback and beam stability
Paper Title Page
APS Upgrade Integrated Beam Stability Experiments in the APS Storage Ring  
  • J. Carwardine, N.D. Arnold, R.W. Blake, A.R. Brill, H. Bui, G. Decker, L. Emery, T. Fors, P.S. Kallakuri, R.T. Keane, R.M. Lill, D.R. Paskvan, A.F. Pietryla, N. Sereno, H. Shang, S. Veseli, J. Wang, S. Xu, B.X. Yang
    ANL, Argonne, Illinois, USA
  Funding: The submitted manuscript has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (Argonne) under U.S.Department of Energy Office of Science Contract No. DE-AC02-06CH11357.
An ultra-stable orbit will be essential to take advantage of the beam properties of the multi-bend achromat lattice of the APS Upgrade. Transverse beam dimensions are an order of magnitude smaller than for the present APS (14.7 microns x 2.8 microns in flat-beam mode), and consequently orbit stability tolerances are very challenging. The APS upgrade fast orbit feedback system uses a similar architecture to the present orbit feedback system, but while the present system corrects the orbit at 1.6 kHz using 160 bpms and 38 fast correctors per plane, design specifications for APS Upgrade call for orbit correction at 22kHz using 570 rf bpms and 90 photon bpms along with 160 fast correctors per plane. A major focus of the integrated beam stability R&D has been development and test of a prototype fast orbit feedback system using two sectors of the present APS storage ring for demonstration and validation of design parameters. Hardware/firmware implementation is discussed, and we present results from the R&D program covering both orbit correction and feedback control domains, including a novel algorithm that combines orbit correction for both slow and fast correctors down to DC.
slides icon Slides TUOC02 [9.767 MB]  
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TUPC09 Initial Results from the LHC Multi-Band Instability Monitor 314
  • T.E. Levens, T. Lefèvre, D. Valuch
    CERN, Geneva, Switzerland
  Intra-bunch transverse instabilities are routinely measured in the LHC using a "Head-Tail Monitor" based on sampling a wide-band BPM with a high-speed digitiser. However, these measurements are limited by the dynamic range and short record length possible with typical commercial oscilloscopes. This paper will present the initial results from the LHC Multi-Band Instability Monitor, a new technique developed to provide information on the beam stability with a high dynamic range using frequency domain analysis of the transverse beam spectrum.  
poster icon Poster TUPC09 [17.388 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-TUPC09  
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TUPC10 The Design of Scanning Control System for Proton Therapy Facility at CIAE 319
  • L.C. Cao, T. Ge, F.P. Guan, S.G. Hou, X.T. Lu, Y. Wang, L.P. Wen
    CIAE, Beijing, People's Republic of China
  A new proton therapy facility is being construted at CIAE. As a part of whole control system, the scanning control system is designed to scan the beam for the access of required tumor therapy field. The origin data plan comes from treatment control system. Two set of dipole magnet is driven for changing the beam path. Meanwhile, interfaces between scanning system and other systems is built for beam control and safe considering. In order to acquire high precise feedback control, the beam position and dose monitor ionization chambers will be constructed in the nozzle. Once accident occurs, the scanning system should be able to response instantly to cut off beam and inform safe interlock system simultaneously. The response time of scanning system is at tens of microsecond level, so the scanning controller, feedback controller and the monitor electronics is built in fast mode. Detailed description will be presented in this paper.  
poster icon Poster TUPC10 [0.794 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-TUPC10  
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TUPC11 Design of an Ultrafast Stripline Kicker for Bunch-by-Bunch Feedback 322
  • J. Wang, P. Li, D. Wu, D.X. Xiao, L.G. Yan
    CAEP/IAE, Mianyang, Sichuan, People's Republic of China
  Funding: Work supported by China National Key Scientific Instrument and Equipment Development Project (2011YQ130018), National Natural Science Foundation of China (11475159, 11505173, 11575264 and 11605190)
The CAEP THz Free Electron Laser (CTFEL) will have a fast transverse bunch-by-bunch feedback system on its test beamline, which is used to correct the beam position differences of individual bunches with interval of about 2 ns. In this paper, we are proposing an ultrafast wideband stripline kicker, which is able to provide a kick to the bunch in a 2 ns time window. The structure design and simulation results of this kicker are also discussed.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-TUPC11  
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TUPC12 Beam Transverse Quadrupole Oscillation Measurement in the Injection Stage for the HLS-II Storage Ring 325
  • F.F. Wu, F.L. Gao, L.T. Huang, X.Y. Liu, P. Lu, B.G. Sun, J.G. Wang, J.H. Wei, T.Y. Zhou
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  Funding: Supported by the National Science Foundation of China (Grant No. 11705203, 11575181, 11605202) and the National Key Research and Development Program of China(No. 2016YFA0402000)
Beam transverse quadrupole oscillation can be excited in the injection stage if injected beam parameters(twiss parameters or dispersion) are not matched with the parameters in the injection point of the storage ring. In order to measure the beam transverse quadrupole oscillation in the injection stage for the HLS-II storage ring, some axially symmetric stripline BPMs were designed. Transverse quadrupole component for these BPMs was simulated and off-line calibrated. Beam transverse quadrupole oscillation has been measured when beam was injected into the HLS-II electron storage ring. The spectrum of the transverse quadrupole component showed that beam transverse quadrupole oscillation is very obvious in the injection stage and this oscillation isn't the second harmonic of beam betatron oscillation. The relationship between transverse quadrupole oscillation and beam current was also analyzed and the result shows that the relationship is not linear.
poster icon Poster TUPC12 [0.467 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-TUPC12  
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TUPC13 Early Commissioning of the Luminosity Dither Feedback for SuperKEKB 328
  • M. Masuzawa, Y. Funakoshi, T. Kawamoto, S. Nakamura, T. Oki, M. Tobiyama, S. Uehara
    KEK, Ibaraki, Japan
  • P. Bambade, S. Di Carlo, D. Jehanno, C.G. Pang
    LAL, Orsay, France
  • D.G. Brown, A.S. Fisher, M.K. Sullivan
    SLAC, Menlo Park, California, USA
  • D. El Khechen
    CERN, Geneva, Switzerland
  • U. Wienands
    ANL, Argonne, Illinois, USA
  SuperKEKB is an electron-positron collider, which aims to achieve a peak luminosity of 8×1035 cm-2 s−1 using what is known as the "nano-beam" scheme. This paper reports on the commissioning and performance of a luminosity dither feedback. The system, based on one previously used at SLAC for PEP-II, is employed for collision orbit feedback in the horizontal plane. Twelve air-core Helmholtz coils drive the positron beam sinusoidally at a frequency near 80 Hz, forming a closed bump at the interaction point. A lock-in amplifier detects the amplitude and phase of the corresponding frequency component of the luminosity signal. When the beams are aligned for peak luminosity, the magnitude of the luminosity component at the dithering frequency becomes zero. The magnitude grows as the beams are offset, and the phase shifts by 180 degrees when the direction of the necessary correction reverses. The hardware and algorithm were tested during SuperKEKB Phase II run. The electron beam orbit was successfully adjusted to minimize the amplitude of the dither frequency component of the luminosity signal, and the optimal condition was maintained by continuously adjusting the electron beam orbit.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-TUPC13  
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