Yellow Report Detector Polarimetry-Ancillary
Working Group Status: June 15, 2020
Brief summary of the Polarimetry-Ancillary Working Group as of June 15, 2020
- All systems are at a stage that drafting of the Yellow Report section can begin. An Overleaf document will be set up soon.
- Luminosity monitor
- Location and preliminary layout of luminosity monitor exists - layout will be refined based on synchrotron radiation studies and beam pipe desing
- Mature GEANT4 simulation exists
- Event generation scheme validated by comparison to HERA data
- Detector technology under study - PbWO4 too slow (and probably not radiation hard enough) to measure bunch-by-bunch. Tungsten powder/sci-fi detector (similar to sPHENIX concept) under study
- Compton polarimeter
- Location of Compton at IP12 defined
- Space is very tight and the trajectory of the laser, back-scattered photons, and scattered electrons places requirements on the beamline magnet apertures and sizes. This has been studied by two independent simulations - a summary of requirements is being collected and a discussion with the machine design group will be scheduled.
- Rate studies indicate that a single pass (pulsed) laser will be sufficient (no cavity necessary). 1064 nm is perhaps adequate, but 532 nm provides reduced measurement times, requires less aggressive detector segmentation.
- Event-generator level studies indicate a photon (electron) detector with vertical position resolution on the order of 100 um (50 um) is desirable to measure the transverse beam polarization.
- Horizontal segmentation in the electron detector and a calorimeter for the photons will allow longitudinal (hopefully null) polarization measurements.
- Bunch-by-bunch polarization measurements will require <10 ns time resolution. Diamond strips may be a possibility.
- GEANT4 simulation under development - will inform detector technology choice.
- Also need information on impact of wake field on the electron detector and synchrotron backgrounds.
- Investigating longitudinal Compton close to detector IR
- Hadron polarimeters
- Will use existing H-Jet and carbon polarimeters
- Backgrounds will be challenging at high beam frequency - origins of these backgrounds under study via Monte Carlo
- Possible issues with carbon target heating due to wake field - simulations underway
- Verification of analyzing powers (and detector acceptance) for deuteron, helium-3 beams possible during remaining RHIC running. Breakup contributions can also be studied.