SiPM Bias and Board Amplification

Meeting on May 25, 2012 Attendees: Fernando, Elton, Eugene, Beni (JLab), George, Andrei, Zisis (Regina)

1. Bias distribution:
   1. The layer-wise proposal was discussed. It was decided not to proceed with the former due to issues of load on the lines (currently 1-10uA, bias lines could go beyond 8 uA), cost (16 channels/module for $8k) required for extra distribution (probably $60k in total). This would require another wire on the cable, pin on the connector (or larger connector), some space (limitations here). Eugene stated that cost overruns may not be impossible but would have ot come at the expense of another subsystem and only with solid justification.
   2. The mirroring of the U and D boards: we came to a consensus that this should be done: BCAL U: SiPMs 1 & 2 - bias 1, SiPMs 3 & 4 - bias 2, SiPMs 5 & 6 - bias 3, SiPMs 7 & 8 - bias 4. BCAL D: SiPMs 1 & 2 - bias 2, SiPMs 3 & 4 - bias 1, SiPMs 5 & 6 - bias 4, SiPMs 7 & 8 - bias 3.
2. Gain on TDC line and SiPM overbias. It was based on the analysis of the 5 degree Mini BCAL beam test data. It was agreed that these should be x5 and 1.2 V. It was agreed that Chile would provide info on the PDE and noise behaviour as a function of overbias. Also, We should look at 90 degree data in the different layers.

Action Items

1. Simulate Mini BCAL test at 5 degrees.
2. Look at other data sets (90 degrees, etc).
3. Keep in mind that the amplification numbers are based on 2 GeV photons. We should keep in mind higher energies.
4. PDE and S:N versus overbias analysis from Chile.
5. Dynamic range aging effect. Will noise rise because of radiation?

Implementation

1. Discussion of resistor values for new iteration of board see halld-cal listserver