General Meeting Summary 7/12/17

DETECTORS AT JLAB (Vardan, Arthur)

• SHMS Aerogel Cherenkov Detector - first ever data of SP-11 with Gore reflector

Configuration: trigger (3/4: S1X, S1Y, S2X, plus one small scintillator paddle - note that X=vertical in spectrometer system), drift chambers, aerogel detector with n=1.011 aerogel

• Rate: ~50k events in ~3 days
• Analysis: cut on coordinates to get tracks in active area of aerogel, multiple track events are about 10% of all events, not yet using drift chamber (DC) information to reduce background
• Results: signal (center) suggests 7-8 photoelectrons in active area (expected were 5 p.e.), left/right of active area see some background
• Suggestions for background investigation: use DC, trigger, aerogel and take good statistics run, in analysis use DC information to reduce background

• Investigate coordinate dependence of photoelectrons as go from inside active area to outside; check number of photoelectrons outside effective area for positive and negative (left/right) PMTs separately - dependence should be similar to that seen for SP-30 and SP-15 aerogel trays
• how are tracks reconstructed presently without magnet? Do we have valid tracks?
• how are coincidences made in software with only one S2Y paddle?
• Another option: look for hits in pre-shower (muon with real track would give a hit)

• Two work spaces have been officially assigned for NPS (clean room in test lab) and HMS aerogel cherenkov detector (EEL) work

PROJECT UPDATES FROM CUA (Salim, Dannie, Casey, Blessed, Richard)

HMS AEROGEL DETECTOR PMT testing (Salim)

• Setup dark box to test 15 HMS PMTs (XP4572) and one reference (XP4500)

• 50 Hz pulser, gate width 15ns

• Result: all PMTs gave a response - nice signals! Seems to suggest that they are not dead. However, showing response is not equivalent to being useful!

• Next test: check for afterpulsing

• Results: all PMTs have afterpulses ~700 ns after the signal
• Some afterpulses are very large - if this spectrum integrated in ADC, this would result in very large charge
• Conclusion: PMTs cannot be used for particle identification and may not even be useful for academic exercises with scintillator

• Discussion of next steps

• Locate specs sheet for XP4572 window glass composition - if not available, perhaps possible to carry out analysis
• remove PMTs from cylinders
• install and test new PMTs
• move on to APD noise tests
• additional ideas on how to test PMT window permeability: use vacuum leak sniffer

CRYSTAL UPDATES (Dannie and Casey)

• Longitudinal transmittance consistent with previous measurements of same subset of crystals

• Light yield shows systematic differences to previous measurements of same crystal

• investigating optical coupling uniformity

• Double peak in pedestal ADC spectrum investigation

• Configuration: NIM crate holds all modules, CAMAC create the ADC LeCroy 2249A, VME the readout (TI, CPU)
• Verified that multiple peaks in pedestal are due to different voltages
• Disconnected signal from ADC and only sent trigger from scintillator (sent through discriminator, logic unit) - still double peak
• Disconnect scintillator trigger and instead send intrinsically discriminated pulser signal of 100 ns width and voltage ~ 1V into ADC - still see double peak
• Conclusion: there is a change in background voltage that ADC integrates resulting in two peaks. Possible sources: 1) ADC, 2) CAMAC crate
• Next steps:

• Try another ADC
• Check CAMAC crate for voltage
• Investigate possibility for NIM crate and ADC

PION AND KAON STRUCTURE FUNCTIONS (Dannie)

• Installed Root software and started investigating codes for kinematic phase space searches and uncertainty projections

Found various issues in code that should be fixed - in progress

CRYSTAL DRAWING PROTOTYPE CALIBRATION (Blessed)

• Completed load cell calibration

• Took additional vibration data in steady state for slip ring setup and data with rotation at sampling rates 10 ms and 1 ms. Data analysis in progress

• Planning to move the setup into vertical configuration to repeat measurements and quantify impact in this nominal operation configuration

• Planning to document results in Wiki