Keyword: LLRF
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MOPA30 LCLS-II BCS Average Current Monitor cavity, electron, hardware, MMI 120
  • N.M. Ludlow, T.L. Allison, J.P. Sikora, J.J. Welch
    SLAC, Menlo Park, California, USA
  LCLS-II is a 4th generation light source at the SLAC National Accelerator Laboratory. LCLS-II will accelerate a 30 µA electron beam with a 1 MHz bunch rate with a new superconducting Continuous Waveform (CW) RF accelerator. The Average Current Monitor (ACM) is part of the Beam Containment System (BCS) for the LCLS-II accelerator. The Beam Containment System is a safety system that provides paths to safely shut the accelerator beam off under a variety of conditions. The Average Current Monitor is a beam diagnostic within the BCS that is used to verify that the accelerator is producing the appropriate current level and to limit beam power to allowed values to protect the machine and beam dumps. The average beam current is obtained by measuring the power level induced by the beam in a low Q cavity. By knowing the Q, the beta, and the coupling of the cavity, the instantaneous charge can be calculated, then integrating the instantaneous charge over one millisecond will yield the average current. This paper will discuss progress in the checkout process of the ACM LLRF hardware leading to LCLS-II commissioning.  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA30  
About • Received ※ 16 July 2022 — Revised ※ 05 August 2022 — Accepted ※ 24 August 2022 — Issue date ※ 06 October 2022
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MOPA88 FRIB and UEM LLRF Controller Upgrade controls, cavity, FPGA, operation 256
  • S.R. Kunjir, E. Bernal, D.G. Morris, S. Zhao
    FRIB, East Lansing, Michigan, USA
  • C.-Y. Ruan
    MSU, East Lansing, Michigan, USA
  Funding: Supported by the U.S. DOE Office of Science under Cooperative Agreement DE-SC0000661, the State of Michigan, Michigan State University and U.S. National Science Foundation grant DMR-1625181.
The Facility for Rare Isotope Beams (FRIB) is developing a 644 MHz superconducting (SC) cavity for a future upgrade project. The current low level radio frequency (LLRF) controller at FRIB is not able to operate at 644 MHz. The Ultrafast Electron Microscope (UEM) laboratory within the Department of Physics at Michigan State University designed an LLRF controller based on analog RF components to operate a 1.013 GHz room temperature (RT) cavity. With requirements for improved stability, performance and user controls there was a need to upgrade the analog LLRF controller. The FRIB radio frequency (RF) group designed, developed and fabricated a new digital LLRF controller, with high-speed serial interface between system on chip field programmable gate array and fast data converters and capable of high frequency direct sampling, to meet the requirements of 644 MHz SC cavity and 1.013 GHz UEM RT cavity. This paper gives an overview of the upgraded digital LLRF controller, its features, improvements and preliminary test results.
poster icon Poster MOPA88 [2.818 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA88  
About • Received ※ 01 August 2022 — Revised ※ 03 August 2022 — Accepted ※ 04 August 2022 — Issue date ※ 16 August 2022
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TUPA43 Novel RF Phase Detector for Accelerator Applications detector, controls, cavity, feedback 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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TUPA58 Iterative Tuning of the Beam Feedforward Controller for LANSCE LINAC Digital Low Level RF Control System controls, beam-loading, cavity, neutron 475
  • S. Kwon, A.T. Archuleta, L.J. Castellano, M.S. Prokop, C. Rose, P.A. Torrez, P. Van Rooy
    LANL, Los Alamos, New Mexico, USA
  Funding: USDOE
This paper addresses an iterative particle beam phase and amplitude feedforward controller tuning method based on the gradient search approach. The method does not need an a priori plant model as it only needs data collected in previous experimental runs. The controller is implemented on a field programmable gate array (FPGA) equipped with a real-time operating system and a network connection. Data from each RF pulse is collected and sent via the network to the FPGA for processing. The controller tuning is performed between the RF pulses. Once the tuning is performed, the controller parameters are downloaded to the controller in the FPGA and new controller parameters are applied at the upcoming RF pulse
poster icon Poster TUPA58 [0.998 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA58  
About • Received ※ 01 August 2022 — Revised ※ 09 August 2022 — Accepted ※ 10 August 2022 — Issue date ※ 07 September 2022
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TUPA59 RF System Upgrade for Low Energy DTL Cavity at LANSCE controls, DTL, cavity, MMI 478
  • J.T.M. Lyles, R.E. Bratton, T.W. Hall, M. Sanchez Barrueta
    LANL, Los Alamos, New Mexico, USA
  Funding: Work supported by the United States Department of Energy, National Nuclear Security Agency, under contract 89233218CNA000001.
The Los Alamos Neutron Science Center (LANSCE) 100-MeV Drift Tube Linac (DTL) uses four accelerating cavities. In May of 2021, a new RF amplifier system was commissioned to drive the first 4-MeV cavity. It had been powered for 30 years with a triode vacuum tube RF amplifier driven by a tetrode, along with four more vacuum tubes for anode high-voltage modulation. The new amplifier system uses one tetrode amplifier driven by a 20-kW solid state amplifier (SSA) to generate 400 kWp at 201.25 MHz. The tetrode amplifier is protected for reflected power from the DTL by a coaxial circulator. The new installation includes cRio controls and a fast protection and monitoring system capable of reacting to faults within 10 µs. A new digital low-level RF (LLRF) system has been installed that integrates I/Q signal processing, PI feedback, and feedforward controls for beam loading compensation. Issues with LLRF stability were initially encountered due to interaction from thermal-related RF phase changes. After these issues were solved, the final outcome has been a reliable new RF system to complete the overall upgrade of the LANSCE DTL RF power plant.
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA59  
About • Received ※ 03 August 2022 — Revised ※ 04 August 2022 — Accepted ※ 06 August 2022 — Issue date ※ 12 August 2022
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TUPA69 Improving Cavity Phase Measurements at Los Alamos Neutron Science Center cavity, GUI, controls, neutron 493
  • P. Van Rooy, A.T. Archuleta, L.J. Castellano, S. Kwon, M.S. Prokop, P.A. Torrez
    LANL, Los Alamos, New Mexico, USA
  Control stability of the phase and amplitude in the cavity is a significant contributor to beam performance. The ability to measure phase and amplitude of pulsed RF systems at accuracies of ± 0.1 degrees and ± 0.1 percent required for our systems is difficult, and custom-designed circuitry is required. The digital low-level RF upgrade at the Los Alamos Neutron Science Center is continuing to progress with improved cavity phase measurements. The previous generation of the cavity phase and amplitude measurement system has a phase ambiguity, which requires repeated calibrations to ascertain the correct phase direction. The new phase measurement system removes the ambiguity and the need for field calibration while improving the range and precision of the cavity phase measurements. In addition, the new digital low-level RF systems is designed to upgrade the legacy system without significant mechanical, electrical, or cabling changes. Performance data for the new phase measurement system is presented.  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA69  
About • Received ※ 02 August 2022 — Revised ※ 11 August 2022 — Accepted ※ 21 August 2022 — Issue date ※ 08 September 2022
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