MO2 —  Monday Session 2   (11-Sep-23   10:50—12:30)
Chair: N. Hubert, SOLEIL, Gif-sur-Yvette, France
Paper Title Page
Non-interceptive Beam Diagnostics in a H⁻ Linac During Operations Using Laser Comb and Virtual Slit  
  • Y. Liu, W. Blokland
    ORNL, Oak Ridge, Tennessee, USA
  Several novel techniques have been recently developed for laser wire based non-interceptive H beam diagnostics. A laser comb ¿ ultrashort laser pulses with macropulse structure ¿ was implemented and used for measuring time-resolved profiles/emittances from a single scan. A virtual slit technique was demonstrated for the precise measurement of short bunches formed in the superconducting linac. Both techniques have been applied to measuring parameters of neutron production H beam at the linac of the Spallation Neutron Source. Key components in the implementation and operation of the laser comb and virtual slit will be described. Applications of the measurement results to the accelerator physics study will also be discussed.  
slides icon Slides MO2I01 [4.378 MB]  
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MO2I02 Fast Orbit Feedback for Diamond-II 1
  • I. Kempf, M.G. Abbott, L. Bobb, G.B. Christian
    DLS, Harwell, United Kingdom
  • S. Duncan
    University of Oxford, Oxford, United Kingdom
  • G. Rehm
    HZB, Berlin, Germany
  Funding: Diamond Light Source and Engineering and Physical Sciences Research Council
The electron beam stability is critical for 4th generation light sources. As opposed to 10% of beam size up to 140 Hz at Diamond, advances in detector speed and resolution at Diamond-II increase the stability requirements to 3% up to 1 kHz. This paper presents a novel control methodology for the fast orbit feedback at Diamond-II, which will stabilise the beam using two arrays of 252 slow and 144 fast correctors and 252 beam position monitors at 100 kHz. In contrast to existing approaches that separate slow and fast feedback loops, our approach is based on a two-matrix factorisation called the generalised singular value decomposition (GSVD), which decouples the system into 144 two-input modes controlled by slow and fast magnets and 108 modes controlled by slow magnets only. The GSVD-based controller is implemented in the existing Diamond storage ring using a centralised communication architecture, such as planned for Diamond-II. We present results from the Diamond storage ring and simulation, which confirm that the proposed approach meets the target specification for Diamond-II.
slides icon Slides MO2I02 [3.686 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-IBIC2023-MO2I02  
About • Received ※ 06 September 2023 — Revised ※ 07 September 2023 — Accepted ※ 11 September 2023 — Issue date ※ 18 September 2023
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MO2C03 Coupled Bunch Mode Zero Correction within the Orbit Feedback Bandwidth 7
  • P.S. Kallakuri, A.R. Brill, J. Carwardine, L. Emery, N. Sereno
    ANL, Lemont, Illinois, USA
  Funding: Work supported by U. S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
The fast orbit feedback (FOFB) bandwidth for Advanced photon source upgrade (APS-U) will be DC-1 kHz and the synchrotron frequency will be between 100-560 Hz. This frequency overlap places coupled bunch mode 0 (CBM0) induced horizontal orbit motion inside the orbit feedback bandwidth, potentially affecting our ability to achieve beam stability goals. Longitudinal feedback kicker is not strong enough to damp CBM0 oscillations. We developed new beam-based feedback method to suppress CBM0 oscillations with low level RF phase as actuator. It uses existent FOFB framework with no changes to the feedback algorithm. Effectiveness of this method is verified using present APS operations lattice where synchrotron frequency is outside orbit feedback bandwidth*. In the present work, low alpha lattice is created to emulate APS-U setting where synchrotron frequency is inside the orbit feedback bandwidth. Experiments with this lattice successfully demonstrated CBM0 correction within FOFB bandwidth. Combined operation of orbit feedback and CBM0 correction is stable, and CBM0 oscillations are damped. We achieved better orbit motion suppression and corrector drive efforts are reduced as well.
* P. Kallakuri et al., ’Coupled bunch mode zero correction using orbit measurements and RF system phase feedback’, doi:10.1103/PhysRevAccelBeams.25.082801
slides icon Slides MO2C03 [1.326 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-IBIC2023-MO2C03  
About • Received ※ 14 July 2023 — Revised ※ 07 September 2023 — Accepted ※ 13 September 2023 — Issue date ※ 25 September 2023
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MO2C04 SOLEIL New Platform for Fast Orbit Feedback 11
  • R. Bronès, A. Bence, J. Bisou, N. Hubert, D. Pédeau, G. Pichon
    SOLEIL, Gif-sur-Yvette, France
  SOLEIL is upgrading its Fast Orbit Feedback platform to withstand coming obsolescence of electronic BPM and future evolutions of the machine. This new platform has to be compatible with current boundary devices such as BPM electronics or corrector power supplies, but it also shall evolve to interface future versions of these systems. A MTCA based platform was designed and installed. It is integrated in the control system by mean of a OPCUA server, and care has been taken to seamlessly toggle the closing of the feedback loop on the former or new FOFB platform. This paper will present the first tests and results conducted to commission this new system.  
slides icon Slides MO2C04 [30.176 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-IBIC2023-MO2C04  
About • Received ※ 06 September 2023 — Revised ※ 09 September 2023 — Accepted ※ 26 September 2023 — Issue date ※ 01 October 2023
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