Notes from Meeting Jan 23, 2009

• HAPPEX Detector

• Space at JLab has been found for assembling the original HAPPEX detector for H-III.
• The detectors have been located in a log and should soon be recovered.
• W&M student Anatoly Ponomarev will work on this, and might join H-III

• HAPPEX Target

• Dave will send memo soon requesting Kees fund construction of 25cm and 20cm cell.

• Compton Photodetector

• Discussed Diana's analysis of HIGS data (halog 1503, 1505).
• Questions exist about excessive peak width, vs. simulation, for higher energy gammas.
• She'll summarize results with rise/fall widths, peak position, and arithmetic mean (cutting low-E background) vs photon energy in a later plot.
• Giudo points out that EGS4 might be better simulation, or at least more complete, than standard-issue GEANT 4.

• PMT / ADC studies

• Luis tested ADC gains with battery.
• Noise is somewhat higher than pedestal.
• Will perform tests with terminated cable line to check conditions for 30 ppm noise (like with the battery) vs. 8 ppm noise (like with an unterminated input).

• Source/Accelerator

• Dustin reports concern about the pace of progress on the double-wein, especially given the likely shortening of the summer down period.

• Helicity Flip Rate

• We MUST converge on a helicity-flip rate for PREX.
• 60 Hz cancellation must be taken into account in the flip scheme.
• KK points out that PREX statistical width requires 240Hz or higher.
• Bob thinks the parity DAQ will be robust at 240Hz.
  • Luis is nominated to test a crate at high-flip rate with a large number of new ADCs.
• The Compton DAQ presently has long dead period for readout, and at 240Hz with will be unsustainable.
  • One option (a) is a full replacement of DAQ by the time PREX runs.
  • Another (b) is modification of the existing DAQ.
  • Likely we need to plan for (a) but hope that (b) works. We don't have time to explore before we need to choose a rep rate.
• The same question needs to be asked of the Moller DAQ.