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Meeting time: 12:00pm Eastern Zoom connection information Join ZoomGov Meeting https://jlab-org.zoomgov.com/j/1603800887?pwd=aXVmSnN6aWZWN3RBdXB4RUhGckZJdz09 Meeting ID: 160 380 0887 Passcode: 903612 US Tool free phone: (833) 568 8864 Find your local number: https://jlab-org.zoomgov.com/u/ab8341cjcG
- Activity updates
- General discussion
- Timing resolution requirements: https://dilbert.physics.wm.edu/Tracking/36 (David)
Recording on Zoom: , Passcode: hi#Y%tB9
Participants: B. Moffit, R. Michaels, D. Armstrong, M. Gericke, H. Liu, P. King
- Bob is setting up the 3820 scaler test stand in TEDF
- I have been delayed in getting the OU test stand set up due to issues with my server
- Timing resolution discussion
- David hasn't discussed his conclusions with the optics group yet, so his conclusions may be modified if they point out something he missed
- The requirement for timing are to be able to recognize good coincidences and reject accidentals as much as possible; for this, David thinks the 4ns binning on the FADCs would be fine
- Considerations for specific running conditions
- LH2 target w/o the sieve: we probably won't run with beam currents above 100pA, due to pileup and the ~5kHz limitation on the DAQ rate from the APV/MPD readout. At 100pA, there are about 50kHz/sector of Mollers and randoms are negligible. At 100nA, there would be 50MHz/sector and the GEM occupancy in a 75ns window would be 3.75.
- 12C target with and without sieve: simulations give 4MHz/uA of Mollers with no sieve, so running at 0.5uA would give ~2MHz (or less when using the sieve). GEM occupancy in 75ns would be 15%. But assuming that we need a separation of 3 4-ns bins in the trigger scintillator to recognize we had two hits, there's only 0.2% of pileup events that would be indistinguishable.
- Pion ID by using time-of-flight from trigger scintillator to pion detector: this can't really be done, even if we had <0.5ns time resolution.
- Bryan says that the FADC firmware gives a pulse integral and the interpolated time between the two samples crossing the threshold. He suspects that the interpolated time may be at the few 100ps level.
- Discussing triggering
- The FADC lookback is 8us.
- What is the buffer time for the APV? David will ask Zeke about this
- The signals will have to go from the detector array to the electronics, then back to the GEMs to trigger the APVs. What would this time be?
- What will the PMT pulses look like? Michael says that the pulses out of the ring 5 prototype are ~50ns FWHM. So 4-ns binning should give a pretty good representation of the waveform.