Author: Kelliher, D.J.
Paper Title Page
TUPRO075 Initial Analysis of the 4D Transfer Map in the Emma Non-Scaling Fixed Field Alternating Gradient Accelerator 1214
 
  • C.S. Edmonds, A. Wolski
    The University of Liverpool, Liverpool, United Kingdom
  • D.J. Kelliher, S. Machida
    STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
  • B.D. Muratori, A. Wolski
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • B.D. Muratori
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
 
  Funding: STFC
The EMMA non-scaling Fixed Field Alternating Gradient accelerator (ns FFAG) is a ring consisting of 42 quadrupole pairs. The dipole fields which guide particles around the ring are arrived at through offsetting the quadrupoles from a reference axis. In the ideal case, first order 4D transfer maps will describe the turn by turn progression of a particle bunch in transverse phase space. This contribution sees the use of experimental data to calculate the 4D transfer map for EMMA at several different momenta, and a comparison made with maps produced through simulation.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRO075  
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TUPRI009 Study of Resonance Crossing in Non-scaling FFAGs using the S-POD Linear Paul Trap 1571
 
  • D.J. Kelliher, S. Machida, C.R. Prior, S.L. Sheehy
    STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
  • K. Fukushima, K. Ito, K. Moriya, H. Okamoto, T. Okano
    HU/AdSM, Higashi-Hiroshima, Japan
 
  Experiments on EMMA have shown that with rapid acceleration (~10 turns) a linear non-scaling FFAG can accelerate through several integer tunes without detrimental effects on the beam [1]. Proton and ion applications such as hadron therapy will necessarily have a slower acceleration rate, so their feasibility depends on how harmful resonance crossing is in this regime. A simple and useful tool to answer such fundamental questions is the S-POD linear Paul trap at Hiroshima University, which can be set up to simulate the dynamics of a beam in an FFAG. We report here results of experiments to explore different resonance crossing speeds, quantify beam loss and study nonlinear effects. We also discuss the implications of these experimental results in terms of limits on acceptable acceleration rates and alignment errors.
[1] S.Machida et al, Nature Physics, N8, 243-257 (2012)
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI009  
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THPRO084 Beam Dynamics Observations of Slow Integer Tune Crossing in EMMA 3082
 
  • J.M. Garland, H.L. Owen
    UMAN, Manchester, United Kingdom
  • D.J. Kelliher, S. Machida
    STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
  • B.D. Muratori
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
 
  When the betatron tune is an integer in a cyclical accelerator, dipole-field errors can drive the coherent addition of betatron amplitude to the bunch eventually causing particle loss. Transverse integer tune crossing in a linear non-scaling FFAG is inevitable due to finite chromaticity. In EMMA (Electron Machine with Many Applications), as many as 6 integers may be crossed is as little as 6 turns at maximum acceleration over the 10 – 20 MeV energy range. This fast integer tune crossing, of the order 1 integer per turn, was shown to have little effect on the coherent amplitude growth and charge loss rate. Slower acceleration inside an RF bucket in EMMA allowed the experimental exploration of slower integer tune crossing speeds, of the order of a factor ten slower. The effect on the coherent oscillation amplitude was observed and the charge loss at integer tune crossings indicated resonant effects on the bunch. Simulations in Zgoubi allowed a more detailed analysis and the mechanism of slower resonance crossing in a non-scaling FFAG is discussed, including the importance of coupled longitudinal-transverse decoherence on the effective emittance.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO084  
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