Author: Mathieson, R.J.
Paper Title Page
THPPC025 Improvements to ISIS RF Cavity Tuning 3332
  • R.J. Mathieson, D. Bayley, N.E. Farthing, I.S.K. Gardner, A. Seville
    STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
  The ISIS facility at the Rutherford Appleton Laboratory in the UK routinely accelerates proton beam currents in excess of 230 uA to run two neutron spallation target stations. The accelerator consists of a 70 MeV H linac and an 800 MeV, 50 Hz, proton synchrotron. The synchrotron beam is accelerated using six fundamental (h=2), and four second harmonic (h=4) ferrite loaded RF cavities each having its own drive amplifier and bias system. Each RF cavity is driven as a high Q tuned RF circuit; the resonant frequency being controlled by biasing the ferrite using a current from the bias regulator system. The cavity is kept at the correct resonant frequency by an analogue feedback loop comparing the phase of the cavity voltage to the phase of the demand voltage at the amplifier, and a 50Hz digital correction function calculated from the estimated frequency response of the system. This paper describes work improving the performance of the tuning system by introducing better system identification of the tuning loop and a time varying transfer function.