Author: Allen, D.B.
Paper Title Page
WEPFI062 Precise Cavity Tuning System of a Low Output-impedance Second-harmonic Cavity at ISIS 2836
  • Y. Irie, S. Fukumoto, K. Muto, H. Nakanishi
    KEK, Ibaraki, Japan
  • D.B. Allen, D. Bayley, N.E. Farthing, I.S.K. Gardner, R.J. Mathieson, A. Seville, J.W.G. Thomason
    STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
  • J.C. Dooling, D. Horan, R. Kustom, M.E. Middendorf
    ANL, Argonne, USA
  A very low output-impedance (~35ohms) second-harmonic cavity system is being developed for high intensity proton accelerators. The final amplifier is comprised of a grounded cathode scheme with a feedback loop from anode to grid. Due to the Miller effect, the grid voltage waveform is seriously distorted even if only a few percent of sub-harmonic or higher harmonic are mixed in the generator current. Such distortion is much enhanced by the beam loading. In order to eliminate the effect of this distortion upon the phase detector used to achieve precise cavity tuning, a swept bandpass filter was applied to the grid voltage at the phase detector input. Filter design details and the result of high power tests are reported.  
WEPFI063 Progress on the ISIS Synchrotron Low Power RF System Upgrade 2839
  • A. Seville, D.B. Allen, D. Bayley, N.E. Farthing, I.S.K. Gardner, R.J. Mathieson
    STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
  • W.L. Huang
    IHEP, Beijing, People's Republic of China
  The ISIS synchrotron at the Rutherford Appleton Laboratory in the UK now routinely uses a dual harmonic RF system to accelerate beam currents in excess of 230 uA to operate two target stations simultaneously. To give more stable control of the RF voltage at each of the fundamental (1RF) and second harmonic (2RF) cavities, changes have been made to the low power RF (LPRF) control systems. A new FPGA based master oscillator has been implemented using a National Instruments FlexRIO module. The replacement master oscillator has been tested with beam for the first time. This paper reports on the tests of the FlexRIO master oscillator and describes plans for the gradual replacement of the remaining parts of the LPRF system.