Author: Chase, B.E.
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MOPMW026 Resonant Control for Fermilab's PXIE RFQ 447
  • D.L. Bowring, B.E. Chase, J. Czajkowski, J.P. Edelen, D.J. Nicklaus, J. Steimel, T.J. Zuchnik
    Fermilab, Batavia, Illinois, USA
  • S. Biedron, A.L. Edelen, S.V. Milton
    CSU, Fort Collins, Colorado, USA
  Funding: Work supported by Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359.
The RFQ for Fermilab's PXIE test program is designed to accelerate a < 10 mA H CW beam to 2.1 MeV. The RFQ has a four-vane design, with four modules brazed together for a total of 4.45 m in length. The RF power required is < 130 kW at 162.5 MHz. A 3 kHz limit on the maximum allowable frequency error is imposed by the RF amplifiers. This frequency constraint must be managed entirely through differential cooling of the RFQ's vanes and outer body and associated material expansion. Simulations indicate that the body and vane coolant temperature should be controlled to within 0.1 degrees C. We present the design of the cooling network and the resonant control algorithm for this structure, as well as results from initial operation.
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW026  
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WEPOR042 LLRF Control of High Loaded-Q Cavities for the LCLS-II 2765
  • C. Serrano, L.R. Doolittle, G. Huang, A. Ratti
    LBNL, Berkeley, California, USA
  • S. Babel, M. Boyes, B. Hong
    SLAC, Menlo Park, California, USA
  • R. Bachimanchi, C. Hovater
    JLab, Newport News, Virginia, USA
  • B.E. Chase, E. Cullerton, J. Einstein
    Fermilab, Batavia, Illinois, USA
  Funding: This work was supported by the LCLS-II Project and the U.S. Department of Energy, Contract DE-AC02-76SF00515
The SLAC National Accelerator Laboratory is planning an upgrade (LCLS-II) to the Linear Coherent Light Source with a 4 GeV CW Superconducting Radio Frequency (SCRF) linac. The nature of the machine places stringent requirements in the Low-Level RF (LLRF) system, expected to control the cavity fields within 0.01 degrees in phase and 0.01% in amplitude, which is equivalent to a longitudinal motion of the cavity structure in the nanometer range. This stability has been achieved in the past but never for hundreds of superconducting cavities in Continuous-Wave (CW) operation. The difficulty resides in providing the ability to reject disturbances from the cryomodule, which is incompletely known as it depends on the cryomodule structure itself (currently under development at JLab and Fermilab) and the harsh accelerator environment. Previous experience in the field and an extrapolation to the cavity design parameters (relatively high QLc≈ 4×107 , implying a half-bandwidth of around 16 Hz) suggest the use of strong RF feedback to reject the projected noise disturbances, which in turn demands careful engineering of the entire system.
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOR042  
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THPOY020 Neural Network Modeling of the PXIE RFQ Cooling System and Resonant Frequency Response 4131
  • A.L. Edelen, S. Biedron, S.V. Milton
    CSU, Fort Collins, Colorado, USA
  • D.L. Bowring, B.E. Chase, J.P. Edelen, J. Steimel
    Fermilab, Batavia, Illinois, USA
  As part of the PIP-II Injector Experiment (PXIE) accel-erator, a four-vane radio frequency quadrupole (RFQ) accelerates a 30-keV, 1-mA to 10-mA H' ion beam to 2.1 MeV. It is designed to operate at a frequency of 162.5 MHz with arbitrary duty factor, including continuous wave (CW) mode. The resonant frequency is controlled solely by a water-cooling system. We present an initial neural network model of the RFQ frequency response to changes in the cooling system and RF power conditions during pulsed operation. A neural network model will be used in a model predictive control scheme to regulate the resonant frequency of the RFQ.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOY020  
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