Author: Borrell, R.G.
Paper Title Page
MOPPR061 Computing Bunch Charge, Position, and BPM Resolution in Turn-by-Turn EMMA BPMs 924
  • A. Kalinin, J.K. Jones
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • R.G. Borrell
    WareWorks Ltd, Manchester, United Kingdom
  • G. Cox
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  • D.J. Kelliher, S. Machida
    STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
  • I.W. Kirkman
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  The NS-FFAG electron model ‘EMMA’ and its Injection and Extraction Lines are equipped with a total of 53 EPICS VME BPMs*. In the BPMs, each opposite button signal pair is time-domain-multiplexed into one channel as a pulse doublet. The recording of turn-by-turn data into the BPM memory is triggered by the bunch itself on each of its passages. For each accelerating cycle, the BPMs deliver a snapshot of a turn-by-turn trajectory measured in each of 42 cells. Additional BPMs (two pairs) are used to obtain a Poincare map. We describe the EPICS architecture, and a set of Python data processing algorithms that are used to automatically set a BPM intensity range, to eliminate an error due to tails of the doublet pulses, to calculate the bunch charge and position, and, for a set of injections, to find the BPM resolution. We use three types of button pickup mappings** that allow: to eliminate bunch charge signal dependence on offset, to get a linear offset response, and to eliminate ‘quadrupole’ signal dependence on offset as well (which is used in resolution calculation). We present beam measurement results collected in 2011 runs.
* A. Kalinin et al., Proc. of IPAC’10, MOPE068, p. 1134, (2010.
** I. Kirkman, these proceedings.