IPAC2011 - List of Authors (Gardner, I.S.K.)

Paper	Title	Page
MOPC164	Upgrade of the ISIS Synchrotron Low Power RF System	466
	A. Seville, N.E. Farthing, I.S.K. Gardner, R.J. Mathieson, J.W.G. Thomason STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom D.B. Allen STFC/RAL, Chilton, Didcot, Oxon, United Kingdom
	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 run two target stations simultaneously. In order to give more stable control of the phase 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. In addition to this a new FPGA based master oscillator has been commissioned for the first time, and further changes using digital technologies to replace other components of the LPRF system are to be investigated. This paper reports on the LPRF hardware commissioning and reliability.

WEPS025	First Beam Experiments at ISIS with a Low Output-impedance Second Harmonic Cavity	2538
	Y. Irie, S. Fukumoto, K. Muto, H. Nakanishi, T. Oki, A. Takagi KEK, Ibaraki, Japan D. Bayley, 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 ANL, Argonne, USA M.E. Middendorf ORNL RAD, Oak Ridge, Tennessee, USA
	A Low Output-Impedance (LOI) rf drive, which may be suitable for future high intensity accelerator applications, has been developed jointly by ANL, ISIS and KEK for an ISIS synchrotron second harmonic cavity. The cavity is ferrite-loaded, and is driven by a high-power triode (240 kW plate dissipation) with a plate-to-grid feedback circuit. The impedance is designed to be 20~30 ohms over a 2-6 MHz frequency range. Beam induced voltage has been measured with the ISIS beam, and compared with that calculated from the designed output impedance.

WEPS106	Status of Injection Upgrade Studies for the ISIS Synchrotron	2760
	C.M. Warsop, D.J. Adams, D.J.S. Findlay, I.S.K. Gardner, S.J.S. Jago, B. Jones, R.J. Mathieson, S.J. Payne, B.G. Pine, A. Seville, H. V. Smith, J.W.G. Thomason, R.E. Williamson STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom J. Pasternak Imperial College of Science and Technology, Department of Physics, London, United Kingdom C.R. Prior, G.H. Rees STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
	ISIS is the spallation neutron source at the Rutherford Appleton Laboratory in the UK. Operation centres on a high intensity proton accelerator, consisting of a 70 MeV linac and an 800 MeV rapid cycling synchrotron, which provides a beam power of 0.2 MW. Obsolescence issues are motivating plans to replace the ageing 70 MeV linac, and this paper summarises the status of studies looking at how a new, higher energy linac (~180 MeV) could be used to increase beam power in the existing synchrotron. Reduced space charge and optimized injection might allow beam powers in the 0.5 MW regime, thus providing a very cost effective upgrade. The key areas of study are: design of a practical injection straight and magnets; injection painting and dynamics; foil specifications; acceleration dynamics; transverse space charge; instabilities; RF beam loading; beam loss and activation; diagnostics and possible damping systems. Results from work on most of these topics suggest that beam powers of ~0.5 MW may well be possible, but a number of topics, particularly transverse stability, still look challenging. Conclusions so far are presented, as is progress on R&D on the main intensity limiting issues.

Paper

Title

Page

Upgrade of the ISIS Synchrotron Low Power RF System

466

A. Seville, N.E. Farthing, I.S.K. Gardner, R.J. Mathieson, J.W.G. Thomason
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
D.B. Allen
STFC/RAL, Chilton, Didcot, Oxon, United Kingdom

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 run two target stations simultaneously. In order to give more stable control of the phase 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. In addition to this a new FPGA based master oscillator has been commissioned for the first time, and further changes using digital technologies to replace other components of the LPRF system are to be investigated. This paper reports on the LPRF hardware commissioning and reliability.

WEPS025

First Beam Experiments at ISIS with a Low Output-impedance Second Harmonic Cavity

2538

Y. Irie, S. Fukumoto, K. Muto, H. Nakanishi, T. Oki, A. Takagi
KEK, Ibaraki, Japan
D. Bayley, 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
ANL, Argonne, USA
M.E. Middendorf
ORNL RAD, Oak Ridge, Tennessee, USA

A Low Output-Impedance (LOI) rf drive, which may be suitable for future high intensity accelerator applications, has been developed jointly by ANL, ISIS and KEK for an ISIS synchrotron second harmonic cavity. The cavity is ferrite-loaded, and is driven by a high-power triode (240 kW plate dissipation) with a plate-to-grid feedback circuit. The impedance is designed to be 20~30 ohms over a 2-6 MHz frequency range. Beam induced voltage has been measured with the ISIS beam, and compared with that calculated from the designed output impedance.

WEPS106

Status of Injection Upgrade Studies for the ISIS Synchrotron

2760

C.M. Warsop, D.J. Adams, D.J.S. Findlay, I.S.K. Gardner, S.J.S. Jago, B. Jones, R.J. Mathieson, S.J. Payne, B.G. Pine, A. Seville, H. V. Smith, J.W.G. Thomason, R.E. Williamson
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
J. Pasternak
Imperial College of Science and Technology, Department of Physics, London, United Kingdom
C.R. Prior, G.H. Rees
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom

ISIS is the spallation neutron source at the Rutherford Appleton Laboratory in the UK. Operation centres on a high intensity proton accelerator, consisting of a 70 MeV linac and an 800 MeV rapid cycling synchrotron, which provides a beam power of 0.2 MW. Obsolescence issues are motivating plans to replace the ageing 70 MeV linac, and this paper summarises the status of studies looking at how a new, higher energy linac (~180 MeV) could be used to increase beam power in the existing synchrotron. Reduced space charge and optimized injection might allow beam powers in the 0.5 MW regime, thus providing a very cost effective upgrade. The key areas of study are: design of a practical injection straight and magnets; injection painting and dynamics; foil specifications; acceleration dynamics; transverse space charge; instabilities; RF beam loading; beam loss and activation; diagnostics and possible damping systems. Results from work on most of these topics suggest that beam powers of ~0.5 MW may well be possible, but a number of topics, particularly transverse stability, still look challenging. Conclusions so far are presented, as is progress on R&D on the main intensity limiting issues.