MC6: Beam Instrumentation, Controls, Feedback and Operational Aspects
T05: Beam Feedback Systems
Paper Title Page
TUPOST001 Parasitic Optimization of the Transfer Beamline Efficiency at ELSA 835
 
  • S. Witt, K. Desch, D. Elsner, D. Proft
    ELSA, Bonn, Germany
 
  The 3.2 GeV electron accelerator ELSA in Bonn consists of three acceleration stages each interconnected by tunable transfer beamlines. The steering of the electron beam through the transfer line from linear accelerator to the Booster Synchrotron is currently adjusted by hand, which limits a systematic improvement of the transfer efficiency. An automated optimization using the ‘‘simulated annealing’’ technique has been developed and integrated into the control system to improve the situation. It allows for a continuous optimization without interfering with usual beamtime for experiments by utilizing the 6s off-time in between injections into the stretcher ring. In a simulation using the actual accelerator’s settings as starting parameters, transmission rates have been increased significantly. The methods and results with the accelerator hardware are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOST001  
About • Received ※ 06 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 16 June 2022
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TUPOST005 RF Voltage Calibration Using Phase Space Tomography in the CERN SPS 841
 
  • D. Quartullo, S.C.P. Albright, H. Damerau, A. Lasheen, G. Papotti, C. Zisou
    CERN, Meyrin, Switzerland
 
  Voltage calibration using longitudinal phase-space tomography is a purely beam-based technique to determine the effective RF voltage experienced by a bunch. It was applied in the SPS, separately to each of its six accelerating travelling wave structures. A low spread in voltage errors was obtained by carefully optimizing the number of acquired bunch profiles. The technique moreover provided the relative phases of the cavities, which allowed their alignment to be checked. Pairs of cavities were measured as well to validate the consistency of the single-cavity voltages. The beam measurements were repeated after several months to confirm the reproducibility of the results. Longitudinal beam dynamics simulations, including the full SPS impedance model, were performed as a benchmark. The aim was to verify that the effect of the cable transfer-function on the bunch profiles can be neglected, as well as collective effects and small errors in the accelerator parameters.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOST005  
About • Received ※ 30 May 2022 — Revised ※ 13 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 25 June 2022
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TUPOST006 Frequency-Dependent RF Voltage Calibration Using Longitudinal Tomography in the CERN PSB 845
 
  • D. Quartullo, S.C.P. Albright, H. Damerau
    CERN, Meyrin, Switzerland
 
  Longitudinal phase-space tomography reconstructs the phase-space distribution from a set of bunch profiles and the accelerator parameters, which includes the RF voltage. The quality of the reconstruction depends on the accuracy to which these parameters are known. Therefore, it can be used for beam-based RF voltage calibration by analysing oscillations of a mismatched bunch. The actual RF voltage may be different from the programmed one due to uncertainties of the electrical gap voltage measurements and intensity effects. Tomography-based RF voltage calibration was systematically performed with low-intensity bunches in all four rings of the PS Booster (PSB) at injection and extraction energy. For each of the three RF cavities present in a given ring, the calibration was performed separately to extract the voltage errors while avoiding any influence of phase misalignments. The number of synchrotron oscillation periods available for the voltage calibration was constrained by the short duration of the PSB flat-bottom and top. Longitudinal beam dynamics simulations using the full PSB impedance model were performed to benchmark the results provided by the calibrations.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOST006  
About • Received ※ 30 May 2022 — Revised ※ 13 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 14 June 2022
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TUPOST007 New Generation of Very Low Noise Beam Position Measurement System for the LHC Transverse Feedback 849
 
  • D. Valuch
    CERN, Meyrin, Switzerland
  • V. Stopjakova
    Slovak University of Technology (STU), Faculty of Electrical Engineering and Information Technology, Bratislava, Slovak Republic
 
  Recent studies showed that the transverse feedback system noise floor in the Large Hadron Collider (LHC) must be reduced by at least factor of two in order to operate the machine with large beam-beam tune shift as foreseen in the High Luminosity (HL) LHC. Also, the future feedback system foreseen to suppress the LHC Crab Cavity noise relies on improved noise performance of the beam position measurement system. An upgrade program was launched to lower the LHC transverse feedback system noise floor during the LHC Long Shutdown II. A new generation, very low noise beam position measurement module was developed and tested with beam. Innovative methods in the RF receiver, digital signal processing, thorough optimization of every element in the signal chain from pickup to the kickers allowed to achieve a significant reduction of the system noise floor. This unprecedented noise performance opens also new possibilities for auxiliary instruments, using the position data from the transverse feedback. The paper presents the new system, notable implementation details and measured performance.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOST007  
About • Received ※ 18 May 2022 — Revised ※ 13 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 30 June 2022
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TUPOST009 Online Correction of Laser Focal Position Using FPGA-Based ML Models 857
 
  • J.A. Einstein-Curtis, S.J. Coleman, N.M. Cook, J.P. Edelen
    RadiaSoft LLC, Boulder, Colorado, USA
  • S.K. Barber, C.E. Berger, J. van Tilborg
    LBNL, Berkeley, California, USA
 
  Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award Numbers DE-SC 00259037 and DE-AC02-05CH11231.
High repetition-rate, ultrafast laser systems play a critical role in a host of modern scientific and industrial applications. We present a prototype diagnostic and correction scheme for controlling and determining laser focal position at 10 s of Hz rate by utilizing fast wavefront sensor measurements from multiple positions to train a focal position predictor. This predictor is used to determine corrections for actuators along the beamline to provide the desired correction to the focal position on millisecond timescales. Our initial proof-of-principle demonstrations leverage pre-compiled data and pre-trained networks operating ex-situ from the laser system. We then discuss the application of a high-level synthesis framework for generating a low-level hardware description of ML-based correction algorithms on FPGA hardware coupled directly to the beamline. Lastly, we consider the use of remote computing resources, such as the Sirepo scientific framework* , to actively update these correction schemes and deploy models to a production environment.
* M.S. Rakitin et al., "Sirepo: an open-source cloud-based software interface for X-ray source and optics simulations", Journal of Synchrotron Radiation 25, 1877-1892 (Nov 2018).
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOST009  
About • Received ※ 20 May 2022 — Revised ※ 14 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 23 June 2022
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TUPOST011 Simulation Studies of Intra-Train, Bunch-by-Bunch Feedback Systems at the International Linear Collider 861
 
  • R.L. Ramjiawan, D.R. Bett, P. Burrows, C. Perry
    JAI, Oxford, United Kingdom
  • D.R. Bett
    CERN, Meyrin, Switzerland
  • R.M. Bodenstein
    JLab, Newport News, Virginia, USA
  • G.B. Christian
    DLS, Oxfordshire, United Kingdom
 
  The International Linear Collider (ILC) is a proposed electron-positron collider targeting collision energies from 250 GeV to 1 TeV. With design luminosities of order 1034 cm2s-1, a beam-based, intra-train feedback system would be required near the Interaction Point (IP) to provide nanometre-level stabilisation of the beam overlap in the collisions. Here we present results from beam-tracking simulations of the 500 GeV ILC, including the impact of beam-trajectory imperfections on the luminosity, and the capability of the IP feedback system to compensate for them. Effects investigated include the position jitter introduced by the damping ring extraction kicker, short-range and long-range wakefields, and ground motion. The feedback system was shown to be able to correct for beam-beam offsets of up to 200 nm and stabilise the collision overlap to the nanometre level, within a few bunch crossings.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOST011  
About • Received ※ 03 June 2022 — Revised ※ 11 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 22 June 2022
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TUPOST037 Reconstruction of Transverse Phase Space From Transverse Feedback Data for Real Time Extraction of Vital LHC Machine Parameters 937
 
  • G. Kotzian, M.E. Soderen, P.S. Solvang, D. Valuch
    CERN, Meyrin, Switzerland
  • V. Stopjakova
    Slovak University of Technology (STU), Faculty of Electrical Engineering and Information Technology, Bratislava, Slovak Republic
 
  The LHC transverse feedback system (ADT) provides bunch by bunch, turn by turn, normalized and digitized beam position signals from four pick-ups per plane and for each beam. Together with already existing powerful computer-based observation systems, this data can be used to reconstruct in real-time the transverse phase space coordinates of the centre-of-charges, for each individual bunch. Such information is extremely valuable for machine operation, or transverse instability diagnostics. This paper aims on discussing and evaluating methods of combining four position signals for such analysis in the presence of noise and with active transverse feedback. Comparisons are made based on the extraction of vital parameters like the fractional tune or transverse activity. Analytical and numerical results are further benchmarked against real beam data.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOST037  
About • Received ※ 20 May 2022 — Revised ※ 13 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 04 July 2022
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TUPOPT026 Design and Status of Fast Orbit Feedback System at SOLARIS 1059
 
  • G.W. Kowalski, K. Gula, R. Panaś, A.I. Wawrzyniak, J.J. Wiechecki
    NSRC SOLARIS, Kraków, Poland
 
  SOLARIS storage ring has been built with basic set of diagnostic and feedback systems. FOFB system, as much more advanced and not as critical for startup was envisioned as later addition to the design. Now, we are in the process of implementing this addition. The system’s workhorse is Instrumentation Technologies Libera Brilliance+ with its Fast Acquisition data path and customizable FPGA modules. Feedback algorithm running in hardware provides fast calculations and direct communication with fast power supplies. The hardware installation is almost finished with configuration and software works running in parallel. First measurements of response matrix and proof-of-concept tests were performed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOPT026  
About • Received ※ 08 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 30 June 2022
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FRIXGD1 Status and Prospects in Fast Beam-Based Feedbacks 3112
 
  • W. Höfle
    CERN, Meyrin, Switzerland
 
  Fast beam-based Feedback systems play an important role in circular accelerators to mitigate instabilities and reduce the impact of injection oscillations and perturbations on beam quality, both in the longitudinal and transverse planes. The status and prospects of such beam-based feedback systems for circular accelerators are reviewed. This includes progress towards the fundamental limits in noise and feedback gain and the possibilities of modern digital systems to extract large amounts of data that can be used to characterise beam properties. The talk concentrates on machines with hadrons and gives an outlook on possible developments for future accelerator projects under study.  
slides icon Slides FRIXGD1 [3.562 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-FRIXGD1  
About • Received ※ 08 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 20 June 2022  
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