CPS Summary 1/23/18

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  • Polarized Wide Angle Compton Scattering - much interesting science, but limitation in current for target (90nA electron beam)
  • CPS concept: dump electrons and use photons (bremsstrahlung)
  • CPS challenge is to control radiation, but our studies have shown that is works! - photon flux is ~30 times higher (equivalent photon rate 1x10^12 gamma/s) and opens a new range of polarized physics opportunities at JLab
  • CPS details:
  • magnet with tapered pole gap, radiation hard, space between poles filled with copper (Cu core), main shielding is tungsten powder
  • shielding logic: design so that have radiation dose comparable to that with that of number of photons on target
  • Discussion of CPS simulation results
  • comparative study of 90nA electron beam and a pure photon beam producded from 2.7nA electron beam on a 10% radiator (CPS)
  • Studies included: heat load on target, accumulated damage from neutron/photon, activation dose rate around the target, impact of CPS (radiation and damage due to CPS)
  • Result of simulation studies show that CPS concept design works. Some additional shielding in backward region is needed to keep the dose rate <5mrem/hr - currently have 100 mrem/hr in the backward region. Additional shielding may affect placement of diagnostics girder and instrumentation


  • Discussion about rotation scheme and mechanical movement and material


  • Discussion about new physics with a K-long beam
  • In general, challenges include: numerical, analysis, and formalism - the experiment would provide data to address these


  • Experiment will access KLp --> Ksp and KLp --> pi+Lambda at a KL rate of 10^4 KL/s - this is 2500 times SLAC
  • Main background is from neutrons, key goal for radcon is a dose rate of 1mrem/hr at the ceiling above the Gluex detector
  • Discussion about the number of days required (currently 100 days in proposal)

* Next steps:

  • get PAC approval
  • for proposal may include for CPS: tagger area, first engineering changes for Hall D, simulations with CPS only
  • evaluate different configurations for different number of days to address questions about required beam time


  • Remove condition from polarized WACS experiment
  • requires a lab internal review
  • aim is to have the required documentation from PAC by November 2018, so CPS collaboration has to have the document ready in ~5 months from January 2018
  • Get PAC approval for KLong experiment
  • need documentation of basic CPS features by June
  • To be done for CPS HC in next 6-9 weeks:
  • Add polarized target and check shielding optimization, e.g. how much W and how much Pb etc.
  • Determine what engineering items to include in internal review document, e.g., temperature, pressure drop, power
  • Meet every 3 weeks