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Warsop, C. M.

Paper Title Page
MOPC121 Progress on Dual Harmonic Acceleration on the ISIS Synchrotron 349
 
  • A. Seville, D. Bayley, I. S.K. Gardner, J. W.G. Thomason, C. M. Warsop
    STFC/RAL/ISIS, Chilton, Didcot, Oxon
  • D. J. Adams
    STFC/RAL/ASTeC, Chilton, Didcot, Oxon
  
  The ISIS synchrotron at the Rutherford Appleton Laboratory in the UK is currently undergoing an RF upgrade. Four, h=4 cavities have been installed in addition to the existing 6, h=2, cavities and should be capable of increasing the operating current from 200 to 300 μA. Two of the four cavities have been in operation for the last 2 user cycles improving trapping lossess and increasing operating currents beyond 200 μA. The remaining two cavities were commissioned in the spring of 2008. This paper reports on hardware commissioning, beam tests and beam simulation results.  
MOPC130 Space Charge Loss Mechanisms Associated with Half Integer Resonance on the ISIS Synchrotron 373
 
  • C. M. Warsop, D. J. Adams, B. G. Pine
    STFC/RAL/ISIS, Chilton, Didcot, Oxon
  
  ISIS is the spallation neutron source at the Rutherford Appleton Laboratory in the UK. Operation centres on a 50 Hz proton synchrotron, which accelerates ~3·1013 ppp from 70 to 800 MeV, corresponding to mean beam powers of 0.2 MW. Beam loss limits operational intensity, and a main contributing mechanism is the action of half integer resonance under high space charge. Progress on studies using particle in cell simulations to explore the evolution of envelope motion, associated 2:1 parametric halo, growth of particles from the outer core, and effects of dispersion and longitudinal motion is presented. Comparisons are made with relevant theoretical models and progress on experimental studies summarised, presently emphasising the simplified 2D coasting beam case.  
TUPC109 Analysis of Measurement Errors in Residual Gas Ionisation Profile Monitors in a High Intensity Proton Beam 1317
 
  • R. E. Williamson, S. J. Payne, B. G. Pine, C. M. Warsop
    STFC/RAL/ISIS, Chilton, Didcot, Oxon
  
  ISIS is the pulsed neutron and muon source based at the Rutherford Appleton Laboratory in the UK. Operation is centred on a loss-limited 50 Hz proton synchrotron which accelerates ~3·1013 protons per pulse from 70 MeV to 800 MeV, corresponding to a mean beam power of 0.2 MW. Beam profile measurements are a key component of both ISIS operational running and R&D beam studies. Understanding and quantifying limitations in these monitors is essential, and has become more important as work to optimise and study the beam in more detail has progressed. This paper presents 3D field and ion trajectory modelling of the ISIS residual gas ionization profile monitors, including the effects of non-uniformity in longitudinal and transverse drift fields, and beam space charge. The simulation model allows comparison between the input beam profile, and that deduced from ion currents. The resulting behaviour, corrections and errors are then compared with experimental data from the ISIS synchrotron.  
THPC102 Image Simulations on the ISIS Synchrotron 3215
 
  • B. G. Pine, C. M. Warsop
    STFC/RAL/ISIS, Chilton, Didcot, Oxon
  
  ISIS is the spallation neutron source at the Rutherford Appleton Laboratory in the UK. Operation centres on a loss-limited 50 Hz proton synchrotron, which accelerates ~3·1013 ppp from 70 to 800 MeV, corresponding to mean beam powers of 0.2 MW. A significant proportion of beam loss is attributable to space charge effects. One such effect is the image field which forms in the beam pipe. Off-centre beams resulting from closed orbit errors generate fields, which can perturb the beam and cause loss. Of particular interest on ISIS is the rectangular, varying aperture, vacuum vessel, as compared with the more usual constant aperture circular or elliptical geometries. A new 2D space charge code, Set, was developed to study these effects. The code simulates the effects of space charge using a 2D particle-in-cell model of the beam distribution, including an appropriate treatment of the rectangular beam pipe, and details of the ISIS lattice. The effects of images on closed orbits, driving terms, and the evolution of beam distributions at ISIS operational intensities were explored.  
THPP096 Injection Optimisation on the ISIS Synchrotron 3587
 
  • B. Jones, D. J. Adams, C. M. Warsop
    STFC/RAL/ISIS, Chilton, Didcot, Oxon
  
  The ISIS Facility at the Rutherford Appleton Laboratory in the UK produces intense neutron and muon beams for condensed matter research. At its core is a 50 Hz proton synchrotron which, as the commissioning of a new dual harmonic RF system concludes, can accelerate 3.75·1013 protons per pulse from 70 to 800 MeV, delivering a mean beam power of 0.24 MW. The multi-turn charge-exchange injection process strongly affects transverse beam distributions, space charge forces and beam loss, which ultimately limits operational intensity. The evolution of longitudinal distributions and subsequent trapping efficiency is also intimately linked with injection. Optimising injection is therefore a key consideration for present and future upgrades. This paper summarises injection studies including 2D space-charge simulations of the ISIS injection process using the ORBIT code. Comparisons of simulation results with measurements for a range of beam intensities are presented and an assessment is made of a correlated painting scheme in contrast to the usual anti-correlated configuration.  
THPP083 Megawatt Upgrades for the ISIS Facility 3554
 
  • J. W.G. Thomason, D. J. Adams, D. J.S. Findlay, I. S.K. Gardner, B. Jones, A. P. Letchford, S. J. Payne, B. G. Pine, A. Seville, C. M. Warsop, R. E. Williamson
    STFC/RAL/ISIS, Chilton, Didcot, Oxon
  • D. C. Plostinar, C. R. Prior, G. H. Rees
    STFC/RAL/ASTeC, Chilton, Didcot, Oxon
  
  ISIS is the spallation neutron source at the Rutherford Appleton Laboratory in the UK. Presently, it runs at beam powers of 0.2 MW, with upgrades in place to supply increased powers for the new Second Target Station due to start operation in autumn 2008. This paper outlines schemes for major upgrades to the facility in the megawatt regime, with options for 1, 2 and 5 MW. The ideas centre around new 3.2 GeV RCS designs that can be employed to increase the energy of the existing ISIS beam to provide powers of ~1 MW or, possibly as a second upgrade stage, accumulate and accelerate beam from a new 0.8 GeV linac for 2-5 MW beams. Summaries of ring designs are presented, along with studies and simulations to assess the key loss mechanisms that will impose intensity limitations. Important factors include injection, RF systems, instabilities, longitudinal and transverse space charge.