Glover, M.G.

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.
TUZAPA02	ISIS Upgrades – A Status Report	935
	D.J.S. Findlay, D.J. Adams, T.A. Broome, M.A. Clarke-Gayther, P. Drumm, D.C. Faircloth, I.S.K. Gardner, P. Gear, M.G. Glover, S. Hughes, H.J. Jones, M. Krendler, A.P. Letchford, E.J. McCarron, S.J. Payne, C.R. Prior, A. Seville, C.M. Warsop CCLRC/RAL/ISIS, Chilton, Didcot, Oxon
	Since 2002 several accelerator upgrades have been made to the ISIS spallation neutron source at the Rutherford Appleton Laboratory in the UK, and upgrades are currently continuing in the form of the Second Target Station Project. The paper reviews the upgrade programmes: a new extraction straight, replacement of the Cockcroft-Walton by an RFQ, installation of a second harmonic RF system, replacement and upgrading of installed equipment, design and installation of improved diagnostics in conjunction with beam dynamics simulations, the Second Target Station Project, design and construction of a front end test stand, and the MICE programme. The paper also looks forward to possible future schemes at ISIS beyond the Second Target Station Project.
	Transparencies
THPCH111	Digital Master Oscillator for the ISIS Synchrotron	3062
	C.W. Appelbee, M.G. Glover CCLRC/RAL/ISIS, Chilton, Didcot, Oxon
	Rutherford Appleton Laboratories in Oxfordshire is home to an 800MeV synchrotron particle accelerator called ISIS. Its main function is to direct a beam of protons into a heavy metal target to produce neutrons for scientists to analyse condensed matter. A second harmonic system is being developed to upgrade the beam current from 200uA to 300uA in order to drive a second target station. This is being achieved by the inclusion of four second harmonic cavities to increase the width of the RF bucket. In the past the six fundamental cavities were driven by an analogue master oscillator but the extra cavities will bring more difficultly in the phasing of the system. This could be more easily and precisely controlled by embedding a Direct Digital Synthesis core into an FPGA chip as the heart of a new digital Master Oscillator. This paper describes the initial research and feasibility of such a system for the setting up, phasing and synchronisation of the ten cavities in the ring. It also describes how more of the controls to the oscillator can be encompassed by digital means.