Notes from Phone Meeting November 16, 2007

• Meetings

• We will hold PREX "semiweekly" meetings at 11am on November 30 and December 21.
• Dustin is organizing local meetings with students on off-weeks
• The PREX collaboration meeting will be held at JLab on December 7 (three weeks from our last meeting).
• We will plan on semiweekly meetings to be held Mondays, at 2pm starting in January. Please check your spring schedules and tell Kent if this doesn't work for you.

• Compton Polarimeter

• Gregg has posted a report on measurements of pedestal widths and related Flash ADC readout at CMU.
  • 30ms continuous data taking isn't yet possible. Hopefully it will be set up soon. For now, 30 ms of data is taken by recording 2.5uS time units over a total period of about 300 seconds. Paul believes that this avoids the frequency range of greatest concern, and so isn't directly relevent.
  • With the measured pedestal width and presumed signal statistics, we see that pedestal width might be expected to be 10% of the counting statistics width.
  • Next steps: 1) use 30 ms continuous windows to test pedestals; 2) use source to demonstrate that observed width is compatible with counting rate, in range 10-100 kHz.
• Dustin has had no luck in isolating free PbW0₄ crystal from PRIMEX collaborators. Gregg reminds us that he was offered one crystal that is already instrumented, and he doesn't know if we will be allowed to detach the PMT to use our own. (Update: Dustin has been told that we may use this detector, and that we can detach the existing PMT and attach our own, as desired.)
• Abduhrahim on cavity status:
  • "Medium" gain cavity could only lock for brief time (less than 1sec). Modifications made to components of locking electronics didn't improve things, and no the original performance has't een recovered.
  • Optics realigned from laser to cavity. This reduced power loss before the cavity, and made the system more robust under small changes.
  • Work with several beam simulation codes to improve optics configuration
  • Next week they'll return to trying to lock with electronics, as is.
  • G.C. asks to look over the electronics schematic.
• Tharanga reports on new green laser development.
  • New single TEC oven is very stable, better than +/- 0.1 C
  • New optics configuration to avoid lossy elements. Now ~700 mW injected to PPLN crystal.
  • Present green output about 30-40 mW from 700 mW green.
  • M² of green output estimated to be around 1.5-1.7
• Dustin: Infrared cavity not yet turned on, but he thinks Sirish has verified that slow controls function.
• There is some question about the health of the photodetector. It had been seeing very high rates as a background monitor for the current experiment (CSR).

• Lumi Monitor

• Material for new lightguides received. Substrate is reported to be pure Al, with probably accounts for the brittle nature of the existing light guides.
• No new progress on boxes after Kent's visit to W&M the previous week. Brian will pursue the design and materials questions with the shop.
• ND filters are on order to test cutting methods.

• PMT linearity studies

• Significant non-linearity apparent in approximately the bottom half of the ADC range. This appears to be the cause of most of our trouble with the linearity studies.
• If further tests verify that this is a general problem with the ADCs, we will return to establishing linearity characteristics while restricting measurements to the linear region of the ADC range.

• 18-bit ADCs

• We presently have two 18-bit adcs, both installed in the Right HRS crate. We will pull the current-mode version of the 18-bit adc from that crate, for study in Luis' test setup.
• Brian Hahn reports that he is still working on "greenmonster" control of the new adc gain settings.

• Cavity Receivers

• They have arrived. There was an unfortunate cabling accident that cost the running experiment some time. This has been fixed, and they are now connected to ADC channels in the Right HRS crate.
• There has been no comunication with the electronics group on commissioning these boards. Bob will contact the electronics group to set a schedule for commissioning/calibrating the boards to make them useful in high-current mode, and also a schedule for a test of low-current mode.