General Meeting Summary 5/8/14

NPS PROTOTYPE STATUS:

• HV dividers: currently have 11 dividers working and three additional ones are available. One of the latter needs to be fixed. In general, there are enough working dividers for the prototype tests though.

• Prototype machining and its assembly have been completed. All components fit well mechanically.

• PMT sensitivity to IR light

• Earlier tests suggested that PMT is sensitive to IR light. To quantify by how much one shortens the PMT lifetime with IR curing the relation of PMT anode current vs. LED driving current was studied. The anode current at a typical PMT operating high voltage of 1600 V was about 760 nA. The R4125 maximum anode current is given as ~0.1mA by the manufacturer. With anode current of about 0.07mA the LED should thus not be dangerous for the PMT. However, there will be an effect on the lifetime and additional studies ongoing to see if one can improve the lifetime with LEDs of higher peak wavelength, e.g., >1000 nm and better filters.

• Efficiency of curing with the IR LEDs will be checked with crystals irradiated with 20 krad.

• Crystals

• The 10 new SIC crystals have arrived. Preliminary inspection by eye suggests that all crystals are in good condition. Measurements of dimensions of randomly selected crystals show good uniformity. Transmittance measurement is in good agreement with the earlier measurement of the PbWO4 crystal from HC photon detector (see 17 April report).

• What is the density of the new crystals? - could obtain from dimensions and weight

• IR curing system has been constructed and its efficiency will be tested with irradiated crystals. Irradiation of crystals will be complete next week.

DISCUSSION ABOUT PAC42 PROPOSALS - DUE DATE: 2 JUNE

• pi0 photoproduction: Background simulations for pi0 exclusive photoproduction proposal show that one can control multi-pion and eta backgrounds well. Should be able to do a good job on the cross section measurement. M. Amaryan contacted recently about extending the s-range of the measurement and perhaps including recent CLAS results. Discussions ongoing.

• RCS: proposal preparations are going well. Should have draft in 1-2 weeks. Discussion about including what one gets for free from charged pion production in HA.

• Discussion about submitting two proposal documents, but specify them as a rungroup with largely same beamtime similar to the DVCS/SIDIS proposals in PAC40.

• Discussion about including an appendix to one of the two proposals on completed and ongoing activities with the NPS prototype.

ITEMS FOR NEXT MEETING:

• NPS design and prototype

• Electronics tests

• RCS/pi0 proposal status

NEXT MEETING: THUR, 22 MAY at 9AM (EST)