Author: Fujita, T.
Paper Title Page
TU1C3 Beam-Based Calibration of Sextupole Magnet Displacement with Betatron Tune Shift 192
  • S. Takano, T. Fujita, K. Fukami, H. Maesaka, M. Masaki, K. Soutome, M. Takao, T. Watanabe
    JASRI, Hyogo, Japan
  • K. Fukami, T. Hiraiwa, H. Maesaka, K. Soutome, S. Takano, H. Tanaka, T. Watanabe
    RIKEN SPring-8 Center, Hyogo, Japan
  • K. Ueshima
    QST, Sendai, Miyagi, Japan
  The alignment of sextupole magnets is one of the critical issues for the upcoming 4th generation light sources and future colliders. The alignment error of magnets and the beam offsets in sextupoles should be within a few 10 µm rms to ensure enough dynamic aperture for stable operation and minimize deterioration of beam quality. Considering that the quadrupole field in a sextupole is proportional to the displacement (normal Q for horizontal and skew Q for vertical), we propose a beam-based calibration (BBC) method to measure the sextupole centers by observing the betatron tune shift. The magnetic center is the point where the tune does not change regardless of the sextupole field strength. The key is increasing the XY coupling to obtain a tune shift large enough for the vertical calibration. We studied experimentally the feasibility of the sextupole BBC at SPring-8 and successfully demonstrated the principle for both horizontal and vertical calibration. The tune shift was monitored by bunch-by-bunch feedback electronics with approximately 1e-5 resolution. The measurement resolution of the sextupole center was approximately 10 µm std., which was sufficient for our requirement.  
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DOI • reference for this paper ※ doi:10.18429/JACoW-IBIC2022-TU1C3  
About • Received ※ 31 August 2022 — Revised ※ 10 September 2022 — Accepted ※ 11 September 2022 — Issue date ※ 27 November 2022
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WE2I3 Adaptive Feedforward Control of Closed Orbit Distortion Caused by Fast Helicity-Switching Undulators 374
  • M. Masaki, H. Dewa, T. Fujita, H. Maesaka, K. Soutome, T. Sugimoto, S. Takano, M.T. Takeuchi, T. Watanabe
    JASRI, Hyogo, Japan
  • T. Fukui, H. Maesaka
    RIKEN SPring-8 Center, Innovative Light Sources Division, Hyogo, Japan
  • K. Kubota
    SES, Hyogo-pref., Japan
  • K. Soutome, T. Sugimoto, S. Takano, H. Tanaka, T. Watanabe
    RIKEN SPring-8 Center, Hyogo, Japan
  We developed a new correction algorithm for closed orbit distortion (COD) based on adaptive feedforward control (AFC). The AFC system effectively works for the suppression of the fast COD due to known error sources with repetitive patterns such as helicity-switching undulators. The scheme aims to counteract error sources by feedforward correctors at the position or in the vicinity of error sources so that a potential risk of unwanted local orbit bumps, which is known to exist for the global orbit feedback, can be eliminated in a reliable and accurate manner. This option is especially advantageous when an error source causes an angular distortion of photon beams such as a fast orbit distortion near undulators. Thus, the AFC provides a complementary capability to a so-called fast global orbit feedback (FOFB) for coming next-generation light sources where ultimate light source stability is essentially demanded. In this talk, introduction to the AFC, its theoretical aspect and advantages, the system overview, the experimental results for the effects of AFC will be presented.
M. Masaki, et al., J. Synchrotron Rad. 28, 1758-1768 (2021).
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DOI • reference for this paper ※ doi:10.18429/JACoW-IBIC2022-WE2I3  
About • Received ※ 06 September 2022 — Revised ※ 10 September 2022 — Accepted ※ 11 September 2022 — Issue date ※ 09 October 2022
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MO3C3 Pulse-by-Pulse Photon Beam Position Measurements at the SPring-8 Undulator Beamline 173
  • H. Aoyagi, T. Fujita, K. Kobayashi, H. Osawa, S. Takahashi
    JASRI/SPring-8, Hyogo, Japan
  Funding: This work is partly supported by Japan Society for the Promotion of Science through a Grant-in-Aid for Scientific Research (c), No.18K11943, 21K12530.
This study analyzes a pulse-mode x-ray beam position monitor that enables pulse-by-pulse position measurement in a synchrotron radiation beamline of the synchrotron radiation facility, SPring-8. The monitor is equipped with blade-shaped detection elements utilizing diamond heatsinks to reduce stray capacitance and a microstripline transmission line to improve high-frequency characteristics. The detection elements operate as photocathodes and generate single unipolar pulses with a full width at half-maximum of less than 1 ns, allowing pulse-by-pulse measurement of the synchrotron radiation beam. We confirmed the basic operation of the monitor at the SPring-8 bending magnet beamline*. The detection element’s heat resistance consequently improved. An evaluation test was carried out at the SPring-8 undulator beamline with significantly high synchrotron radiation intensity. We aim to report the evaluation results of the sensitivity and resolution of the monitor measured by exciting a betatron oscillation in the horizontal/vertical direction using beam shakers of the SPring-8 storage ring and the observation results of the pulse-by-pulse photon beam dynamics induced by beam injection.
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DOI • reference for this paper ※ doi:10.18429/JACoW-IBIC2022-MO3C3  
About • Received ※ 07 September 2022 — Revised ※ 09 September 2022 — Accepted ※ 11 September 2022 — Issue date ※ 04 December 2022
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