Keyword: feedback
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MOYD3 EIC Transverse Emittance Growth Due to Crab Cavity RF Noise: Estimates and Mitigation cavity, emittance, simulation, target 6
  • T. Mastoridis, P. Fuller, P. Mahvi, Y. Matsumura
    CalPoly, San Luis Obispo, California, USA
  Funding: This work is partially supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics, under Award Number DE-SC-0019287.
The Electron-Ion Collider (EIC) requires crab cavities to compensate for a 25 mrad crossing angle and achieve maximum luminosity. The crab cavity Radio Frequency (RF) system will inject low levels of noise to the crabbing field, generating transverse emittance growth and potentially limiting luminosity lifetime. In this work, we estimate the transverse emittance growth rate as a function of the Crab Cavity RF noise and quantify RF noise specifications for reasonable performance. Finally, we evaluate the possible mitigation of the RF noise induced emittance growth via a dedicated feedback system.
slides icon Slides MOYD3 [0.223 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOYD3  
About • Received ※ 28 July 2022 — Revised ※ 01 August 2022 — Accepted ※ 07 August 2022 — Issue date ※ 04 October 2022
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MOPA33 Waker Experiments at Fermilab Recycler Ring experiment, space-charge, kicker, impedance 124
  • O. Mohsen, R. Ainsworth, N. Eddy
    Fermilab, Batavia, Illinois, USA
  Attaining high-intensity hadron beams is often limited due to the transverse collective instabilities, whose understanding is thus required to see and possibly extend the intensity limitations. To explore such instabilities, a novel artificial wake system, the waker, has been built and tested at the Fermilab Recycler Ring (RR). In this report, we show recent upgrades of the waker. Also, we present experimental studies of instabilities at various space charge and wake parameters.  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA33  
About • Received ※ 03 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 28 August 2022
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MOPA43 Dee Voltage Regulator for the 88-Inch Cyclotron cyclotron, detector, controls, power-supply 147
  • M. Kireeff, P. Bloemhard, T. Hassan, L. Phair
    LBNL, Berkeley, California, USA
  Funding: This work was supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under Contract No. DE-AC02-05CH11231
A new broadband Dee voltage regulator was designed and built for the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory. The previous regulator was obsolete, consequently, it was difficult to troubleshoot and repair. Additionally, during operation, it displayed problems of distortion and stability at certain frequencies. The new regulator uses off-the-shelf components that can detect and disable the RF during sparking events, protecting the RF driver system. Furthermore, it improves the tuning of the cyclotron and allows consistency in operation.
poster icon Poster MOPA43 [1.032 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA43  
About • Received ※ 02 August 2022 — Revised ※ 04 August 2022 — Accepted ※ 16 August 2022 — Issue date ※ 09 September 2022
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TUZE6 Studies of Ion Instability Using a Gas Injection System simulation, emittance, injection, experiment 347
  • J.R. Calvey, M. Borland, L. Emery, P.S. Kallakuri
    ANL, Lemont, Illinois, USA
  Funding: Work supported by U. S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
Ion trapping occurs when a negatively charged beam ionizes residual gas inside an accelerator vacuum chamber, and the resulting ions become trapped in the beam potential. Trapped ions can cause a variety of undesirable effects, including coherent instability and incoherent emittance growth. Because of the challenging emittance and stability requirements of next generation light sources, ion trapping is a serious concern. To study this effect at the present APS, a gas injection system was designed and installed at two different locations in the ring. The system creates a controlled and localized pressure bump of nitrogen gas, so the resulting ion instability can be studied. Measurements were taken under a wide variety of beam conditions, using a spectrum analyzer, pinhole camera, and bunch-by-bunch feedback system. The feedback system was also used to perform grow-damp measurements, allowing us to measure the growth rate of individual unstable modes. This paper will present some of the results of these experiments. Simulations using the IONEFFECTS element in the particle tracking code elegant will also be presented.
slides icon Slides TUZE6 [2.425 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUZE6  
About • Received ※ 03 August 2022 — Revised ※ 07 August 2022 — Accepted ※ 10 August 2022 — Issue date ※ 24 August 2022
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TUPA27 Longitudinal Feedback Dynamics in Storage Rings with Small Synchrotron Tunes HOM, simulation, synchrotron, cavity 405
  • R.R. Lindberg
    ANL, Lemont, Illinois, USA
  Funding: This work was supported by U.S. Dept. of Energy Office of Sciences under Contract No. DE-AC02-06CH11357.
We analyze the dynamics of multibunch longitudinal instabilities including bunch-by-bunch feedback under the assumption that the synchrotron tune is small. We find that increasing the feedback response does not always guarantee stability, even in the ideal case with no noise. As an example, we show that if the growth rate of a cavity-driven mode is of the order of the synchrotron frequency, then there are parameter regions for which the instability cannot be controlled by feedback irrespective of its gain. We verify these calculations with tracking simulations relevant to the APS-U, and find that the dynamics do not depend upon whether the longitudinal feedback relies on phase-sensing or energy-sensing technology. Hence, this choice should be dictated by measurement accuracy and noise considerations.
poster icon Poster TUPA27 [1.180 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA27  
About • Received ※ 26 July 2022 — Revised ※ 05 August 2022 — Accepted ※ 07 August 2022 — Issue date ※ 26 August 2022
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TUPA43 Novel RF Phase Detector for Accelerator Applications detector, controls, LLRF, cavity 446
  • J.M. Potter
    JP Accelerator Works, Los Alamos, New Mexico, USA
  A novel phase detector has been developed that is suitable for use in an rf phase locked loop for locking an rf source to an rf accelerator structure or phase locking the accelerator structure to a fixed or adjustable frequency rf source. It is also useful for fast phase feedback to control the phase of an accelerator rf field. The principle is applicable to a wide range of frequencies and amplitudes. The phase is uniquely and unambiguously determined over 360°, eliminating the need for external phase shifters or phase references. The operation of this phase detector is described in detail. An application is described that uses a DDS-based LLRF source as the rf input to a high-power rf system.  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA43  
About • Received ※ 02 August 2022 — Revised ※ 04 August 2022 — Accepted ※ 05 August 2022 — Issue date ※ 06 October 2022
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TUPA65 Machine Learning for the LANL Electromagnetic Isotope Separator controls, dipole, ion-source, electron 490
  • A. Scheinker, K.W. Dudeck, C.P. Leibman
    LANL, Los Alamos, New Mexico, USA
  Funding: Los Alamos National Laboratory Electromagnetic Isotope Separator Project.
The Los Alamos National Laboratory electromagnetic isotope separator (EMIS) utilizes a Freeman ion source to generate beams of various elements which are accelerated to 40 keV and passed through a 75-degree bend using a large dipole magnet with a radius of 1.2 m. The isotope mass differences translate directly to a spread in momentum, dp, relative to the design momentum p0. Momentum spread is converted to spread in the horizontal arrival location dx at a target chamber by the dispersion of the dipole magnet: dx = D(s)dp/p0. By placing a thin slit leading to a collection chamber at a location xc specific isotope mass is isolated by adjusting the dipole magnet strength or the beam energy. The arriving beam current at xc is associated with average isotope atomic mass, giving an isotope mass spectrum I(m) measured in mA. Although the EMIS is a compact system (5 m) setting up and automatically running at an optimal isotope separation profile I(m) profile is challenging due to time-variation of the complex source as well as un-modeled disturbances. We present preliminary results of developing adaptive machine learning-based tools for the EMIS beam and for the accelerator components.
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA65  
About • Received ※ 18 July 2022 — Revised ※ 07 August 2022 — Accepted ※ 08 August 2022 — Issue date ※ 10 August 2022
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WEZD3 Magnetron R&D Progress for High Efficiency CW RF Sources of Industrial Accelerators injection, controls, power-supply, experiment 597
  • H. Wang, K. Jordan, R.M. Nelson, S.A. Overstreet, R.A. Rimmer
    JLab, Newport News, Virginia, USA
  • J.N. Blum
    VCU, Richmond, Virginia, USA
  • B.R.L. Coriton, C.P. Moeller, K.A. Thackston
    GA, San Diego, California, USA
  • J.L. Vega
    The College of William and Mary, Williamsburg, Virginia, USA
  • G. Ziemyte
    UKY, Kentucky, USA
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177, and DOE OS/HEP Accelerator Stewardship award 2019-2022.
After the demonstration of using high efficiency magnetron power to combine and aim to drive a radio frequency accelerator at 2450MHz in CW mode [1], we have used trim coils adding to a water-cooled magnetron and three amplitude modulation methods in an open-loop control to further suppress the 120Hz side-band noise to -46.7dBc level. We have also successfully demonstrated the phase-locking to an industrial grade cooking magnetron transmitter at 915MHz with a 75kW CW power delivered to a water load by using a -26.6dBc injection signal. The sideband noise at 360Hz from the 3-Phase SCRs DC power supply can be reduced to -16.2dBc level. Their power combing scheme and higher power application to industrial accelerators are foreseeing.
[1] H. Wang, et al, Magnetron R&D for High Efficiency CW RF Sources for Industrial Accelerators, TUPAB348, 12th Int. Particle Acc. Conf. IPAC2021, Campinas, SP, Brazil.
slides icon Slides WEZD3 [3.074 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEZD3  
About • Received ※ 18 July 2022 — Revised ※ 25 July 2022 — Accepted ※ 08 August 2022 — Issue date ※ 11 August 2022
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WEPA69 The Impact on the Vertical Beam Dynamics Due to the Noise in a Horizontal Crab Crossing Scheme emittance, cavity, electron, hadron 788
  • Y. Hao
    BNL, Upton, New York, USA
  • Y. Luo
    Brookhaven National Laboratory (BNL), Electron-Ion Collider, Upton, New York, USA
  Funding: Work Supported BY Brookhaven Science Associates, LLC under contract NO. DE-SC0012704 with the U.S. Department of Energy.
Several recent and future colliders have adopted the crab crossing scheme to boost performance. The lower RF control noise of the crab cavities has been identified as one of the significant sources that impact the transverse beam quality in the crabbing plane. However, through beam-beam interaction and other coupling sources, the effect may also affect the non-crabbing plane. In this paper, we report the simulation observations of the beam dynamics in the non-crabbing plane in the presence of phase noise in the crab cavity.
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA69  
About • Received ※ 03 August 2022 — Revised ※ 07 August 2022 — Accepted ※ 09 August 2022 — Issue date ※ 06 September 2022
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WEPA71 Unified Orbit Feedback at NSLS-II operation, quadrupole, target, photon 795
  • Y. Hidaka, Y. Li, R.M. Smith, Y. Tian, G.M. Wang, X. Yang
    BNL, Upton, New York, USA
  Funding: This work is supported by U.S. DOE under Contract No. DE-SC0012704.
We have developed an orbit correction / feedback program to unify the existing orbit-related feedback systems for stable beam operation at NSLS-II. Until recently only a handful of beamlines have been benefiting from long-term orbit stability provided by a local bump agent program. To expand this to all the beamlines as well as correct more frequently, a new slow orbit feedback program called unified orbit feedback (UOFB) was written from scratch that works with the fast orbit feedback transparently, while accumulated fast corrector strength is continuously shifted to the slow correctors and RF frequency is adjusted for circumference change. UOFB can lock 3 different types of local bumps to the target offsets/angles for days: those for insertion device (ID) sources with only ID RF beam position monitors (BPM) or mixtures of ID RF BPMs and X-ray BPMs, and those for bending magnet sources with arc BPMs between which orbit correctors, dipoles and quadrupoles exist. Furthermore, this feed-back can accommodate beamline user requests to enable / disable the feedback loop for their beamline and to change bump target setpoints without turning off the loop.
poster icon Poster WEPA71 [2.541 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA71  
About • Received ※ 02 August 2022 — Revised ※ 09 August 2022 — Accepted ※ 12 August 2022 — Issue date ※ 31 August 2022
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THXD2 6D Phase Space Diagnostics Based on Adaptive Tuning of the Latent Space of Encoder-Decoder Convolutional Neural Networks controls, solenoid, network, electron 837
  • A. Scheinker
    LANL, Los Alamos, New Mexico, USA
  We present a general approach to 6D phase space diagnostics for charged particle beams based on adaptively tuning the low-dimensional latent space of generative encoder-decoder convolutional neural networks (CNN). Our approach first trains the CNN based on supervised learning to learn the correlations and physics constrains within a given accelerator system. The input of the CNN is a high dimensional collection of 2D phase space projections of the beam at the accelerator entrance together with a vector of accelerator parameters such as magnet and RF settings. The inputs are squeezed down to a low-dimensional latent space from which we generate the output in the form of projections of the beam’s 6D phase space at various accelerator locations. After training the CNN is applied in an unsupervised adaptive manner by comparing a subset of the output predictions to available measurements with the error guiding feedback directly in the low-dimensional latent space. We show that our approach is robust to unseen time-variation of the input beam and accelerator parameters and a study of the robustness of the method to go beyond the span of the training data.  
slides icon Slides THXD2 [19.086 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-THXD2  
About • Received ※ 18 July 2022 — Revised ※ 05 August 2022 — Accepted ※ 08 August 2022 — Issue date ※ 09 August 2022
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FRXE1 Bayesian Algorithms for Practical Accelerator Control and Adaptive Machine Learning for Time-Varying Systems network, controls, experiment, electron 921
  • A. Scheinker
    LANL, Los Alamos, New Mexico, USA
  • R.J. Roussel
    SLAC, Menlo Park, California, USA
  Particle accelerators are complicated machines with thousands of coupled time varying components. The electromagnetic fields of accelerator devices such as magnets and RF cavities drift and are uncertain due to external disturbances, vibrations, temperature changes, and hysteresis. Accelerated charged particle beams are complex objects with 6D phase space dynamics governed by collective effects such as space charge forces, coherent synchrotron radiation, and whose initial phase space distributions change in unexpected and difficult to measure ways. This two-part tutorial presents recent developments in Bayesian methods and adaptive machine learning (ML) techniques for accelerators. Part 1: We introduce Bayesian control algorithms, and we describe how these algorithms can be customized to solve practical accelerator specific problems, including online characterization and optimization. Part 2: We give an overview of adaptive ML (AML) combining adaptive model-independent feedback within physics-informed ML architectures to make ML tools robust to time-variation (distribution shift) and to enable their use further beyond the span of the training data without relying on re-training.  
slides icon Slides FRXE1 [34.283 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-FRXE1  
About • Received ※ 08 August 2022 — Revised ※ 10 August 2022 — Accepted ※ 12 August 2022 — Issue date ※ 27 September 2022
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