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CREX Main << PREX II Main

Optics and Q2

  1. Energy Measurement (Doug) (non-invasive)
    • Priority High
    • Can be performed Day shift Monday or Tuesday?
    • look for 1e-3 accuracy. Non invasive.
  2. Optics Data (Cip) (1-1.5 shifts)
    • requires access to prepare, about 8-10 hrs data, access to backout
    • Sieve in, VDC data. thin Carbon
    • about 500k per run
    • use target lock, about 1 uA
    • no raster
    • Does not (strictly) require counting mode quartz detectors
    1. Beam position dependence Completed. (Got +/- 3mm)
      • shift beam +/- 4mm in horizontal , retake dp = 0 optics
    2. Vertical beam position dependence Completed
      • shift beam +/- 2mm in horizontal , and +/-3mm in vertical.
      • Used both thick and thin C targets due to small thin target size
    3. Target Z comparison Completed
      • use 90 degree Carbon target, Compare y-targ reconstruction to 45 degree carbon target
    4. Retake Optics Data (Cip) (Completed)
      • including dp = 0, +-1% (scale all magnets)
  3. Dynamic Thermal-Induced Density Rearrangement (Bob, Chandon, Siyu, Cip) (4 hours)
    • High Priority (unless we can measure significant density variation at low current)
    • requires access to prepare, 3 hrs data + analysis, access to backout
    • Sieve in. S0 on, GEMs on, VDC Off. Production raster.
    • Does not require counting mode in quartz detectors _except_ for actually measuring Q2
    • 1uA
    • Pb10
    • Measure scattering density over target x vs y
    • 70uA
    • Repeat measurement of scattering density over target x vs y
    • If different, do the same on a pristine target
    • Evaluate Q2 (for specific sieve holes?) in each case
  4. Cavity vs Striplines (Cip) (~1.5 hrs) summary
    • High Priority
    • measure carbon hole location with 50nA cavity lock and spot++
    • measure carbon hole with 0.5uA tgt lock and spot++
    • show these are the same, within a 1mm or so
  5. Final Q2 measurement Completed? (Bob, Chandon, Siyu, Dustin) (4 hours?)
    • Repeat of Q2 measurement, with improved pedestal noise control. Requires long (1hr +) access to reduce noisy pedestals
    • Detector counting mode.
    • S0 trigger
    • Lead target
    • production raster and beam position
    • Use cavity lock, low current
  6. VDC/GEM Rate study (Bob, Chandon, Siyu)
    • Completed (awaiting results)
    • Requires access, 3 hrs data, access to back out
    • Detector counting mode.
    • S0 trigger
    • Lead target
    • production raster and beam position
    • Use cavity lock, low current
    • start at low S0 rate (50kHz?) and go up in rate to 500 kHz, in several steps (50, 100, 200, 500 kHz)
    • turn off VDC, continue up to 2MHz rates in GEMs (1MHz, 2MHz)
    • Compare Q2 measurements at each rate from GEMS and VDC to look for rate dependence
  7. Q2 from damaged target (Bob)
    • Completed (awaiting results)
    • measure Q2 from most damaged target (Pb10?)
    • compare to Q2 from pristine target
    • If these are different - we need a plan to correct for damage or measure all used targets
    • can be combined with previous study, add 1 hr for target move and measurement


  1. Stubby Quartz / Blinded Quartz (Dustin) (4 hours?)
    • Very High priority. Wednesday Swing? Thursday Day?
    • Longish access to setup and back out, but short data taking period (production conditions).
    • Replace detector quartz with superelastic stub or blinding cap (alternate US/DS and L/R)
    • Integrating measurement. Could normalize increased gain just by lowering beam current in production condition.
    • If surprising results found, continue test or plan second test
  2. Rescattering measurement (Bob, Cip?) (~1 shift)
    • Detailed Rescattering Runplan
    • High Priority
    • repeat of previous measurements, but new optics and a crucial cross-check
    • Detune spectrometer up in momentum, to dump elastic peak into spectrometer wall.
    • Measure (integrating mode) signal in main detectors. Requires HV boot-strap to get higher gain (is 10x possible?)
    • should scale all spectrometer magnets.
    • At each dipole setting, also take data with nominal septum
    • Once the elastic peak is out of the focal plane, it should be possible turn on the S3 and S0 scintillator. This should be done when possible, and the T1/T2/T3 trigger rate recorded for each run.
    • If possible, the GEMS should be turned on at this time also (once the elastic peak is out of the focal plane and trig scintillators are on), and spectrometer runs should be taken for the "septum nominal" runs.
  3. Thin Lead Target to check for inelastics at high-resolution (Bob) (~1.5 hour, including setup/backout)
    • Low Priority - Probably skip it
    • valuable illustration and cross-check for presentation/publication
    • Does NOT require detector counting mode - could be done anytime with low current running
  4. Pole tip re-scattering (Bob, Cip?)
    • Requires investigation or planning - do we have an idea here?
    • Q2 or septum mis-tune, to increase interception on pole tip and improve poletip rescattering estimate
  5. A_T detectors (Dustin)
    • Significant asymmetries found in A_T detectors, requires investigation and planning. A_t detectors now blinded.
  6. Thin C12 to measure diamond background spectrum? (Bob)
    • All our optics data was taken with this, so presumably we have enough for this measurement already
  7. Thick C12 to measure diamond background fraction? (nope - priority none)
    • I'm unclear on the value of this, since we are not set up terribly well for yields at very different rates, the radiation is so different, and I don't know how accurately the targets are known.


  1. Linearity Studies (PITA + current scans) (Caryn)
    • These are ongoing - should continue regularly. ~ 1 hour every 3 days.
  2. Linearity LED tests
    • This will be studied off line


  1. Sign check
    • run Moller, Compton, and parity DAQ for quick PITA scan
    • Have we already done this? Parasitic with any PITA scan

Moller polarimetry

  1. Repeat measurements
    • about 2x/week. Goal: 1-1.5 shifts per measurement.
    • need enough granularity to track changing polarization.
  3. Copper false/asymmetry
  4. Target uniformity

Compton polarimetry

  1. No-target runs
  2. Laser polarization optimization
  3. Laser polarization flip
  4. linearity studies