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Bayley, D.

Paper Title Page
MOPCH114 Progress on Dual Harmonic Acceleration on the ISIS Synchrotron 309
 
  • A. Seville, D.J. Adams, D. Bayley, N.E. Farthing, I.S.K. Gardner, M.G. Glover, A. Morris, B.G. Pine, J.W.G. Thomason, C.M. Warsop
    CCLRC/RAL/ISIS, Chilton, Didcot, Oxon
 
  The ISIS facility at the Rutherford Appleton Laboratory in the UK is currently the most intense pulsed, spallation, neutron source. The accelerator consists of a 70 MeV H- Linac and an 800 MeV, 50 Hz, rapid cycling, proton Synchrotron. The synchrotron beam intensity is 2.5·1013 protons per pulse, corresponding to a mean current of 200 μA. The synchrotron beam is accelerated using six, ferrite loaded, RF cavities with harmonic number 2. Four additional, harmonic number 4, cavities have been installed to increase the beam bunching factor with the potential of raising the operating current to 300 μA. As ISIS has a busy user schedule the time available for dual harmonic work has been limited. However, much progress has been made in the last year and encouraging results have been obtained. This paper reports on the hardware commissioning and beam tests with dual harmonic acceleration.  
MOPCH118 Wideband Low-output-impedance RF System for the Second Harmonic Cavity in the ISIS Synchrotron 321
 
  • Y. Irie
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
  • D. Bayley, G.M. Cross, I.S.K. Gardner, M.G. Glover, D. Jenkins, A. Morris, A. Seville, S.P. Stoneham, J.W.G. Thomason, T. Western
    CCLRC/RAL/ISIS, Chilton, Didcot, Oxon
  • J.C. Dooling, D. Horan, R. Kustom, M.E. Middendorf, G. Pile
    ANL, Argonne, Illinois
  • S. Fukumoto, M. Muto, T. Oki, A. Takagi, S. Takano
    KEK, Ibaraki
 
  Wideband low-output-impedance RF system for the second harmonic cavity in the ISIS synchrotron has been developed by the collaboration between Argonne National Laboratory, US, KEK, Japan and Rutherford Appleton Laboratory, UK. Low output impedance is realized by the feedback from plate output to grid input of the final triode amplifier, resulting in less than 30 ohms over the frequency range of 2.7 - 6.2 MHz which is required for the second harmonic cavity. The vacuum tubes in the driver and final stages are both operated in class A, and a grid bias switching system is used on each tube to avoid unnecessary plate dissipations during a non-acceleration cycle. High power test was performed with a ferrite-loaded second harmonic cavity, where the bias current was swept at 50 Hz repetition rate. The maximum voltage of 12kV peak per accelerating gap was obtained stably at earlier period of an acceleration cycle. A beam test with this system is planned at the ISIS synchrotron in order to investigate how the low impedance system works under heavy beam loading conditions, and is capable of mitigating the space charge detuning at the RF trapping stage.