General Meeting Summary 7/31/14
- Discussion about most recent results of PbWO4 crystal radiation tests - one of the goals of these tests is to test the efficiency of curing
- 3x3x16 cm^3 crystals were irradiated by an additional 122 krad dose. The total accumulated dose is thus 187 krad. Transmittance measurements were made in the transverse direction (with current crystals samples cannot do measurements in longitudinal direction) at distances ranging from 2 mm to 150 mm from the radiated edge. Significant point-to-point variation was observed in that range. The expected depth of radiation dose of 3-5 cm seems consistent with this observation. Comparison with measurements at total accumulated dose of 65 krad seems to suggest that there is an effect on the transmittance. The transmittance seems to be reduced at the larger accumulated dose of 187 krad.
- Uncertainties on the transmittance measurement are estimated by measuring at the same points several times and evaluating the mean and RMS values of the distributions. Possible optimizations in the procedure and reduction in uncertainty could include the positioning and background measurements for each scan.
- Discussion about the path forward with crystal radiation studies
- Confirm and optimize transmittance measurement method
- Understand the apparent drop in transmittance with radiation dose, in particular, are the bumps and valleys observed real
- Possibly add more radiation to study the drop in transmittance with radiation dose and also try to cure it
- Prototype construction is ongoing
- Includes copper box, GMS splitter, curing LEDs, 9 wrapped SICCAS crystals, PMTs and dividers
- For the initial test only 4 curing LEDs are mounted, PMTs and crystals are in dry contact, and PMTs are not mu-metal shielded
- Update on performance of full-size PWO crystals in PANDA geometry provided by SICCAS
- Report by Rainer discusses the analysis of five crystal samples delivered by SICCAS in June 2014. According to contract, all crystals were grown using the Czochralsky method and one was produced using raw materials prepared for production at BTCP. The report shows a significant rejection ratio, but also shows that some of the crystals pass the requirements on optical parameters, light-output, and radiation hardness.
- Results were not available during meeting, but publication later on shows that all three experiments that were submitted were approved
- RCS and pi0 photoproduction are the second NPS run group approved after DVCS/pi0 SIDIS from PAC40
- NSF MRI reviews were very good to excellent, but proposal was not funded.
- Discussion about path forward.
- EU hardware part of proposal was not funded this time, but with approval of RCS there may be new opportunities
- EIC R&D proposal does not yet have detailed news on funding or funding level
ITEMS FOR NEXT MEETING:
- NPS prototype and PWO studies
NEXT MEETING: THUR, 21 AUGUST at 9:00 AM (EST)