Apr 28, 2011 SiPM Electrical and Cooling

Action Items from previous meetings

1. Check impact of material at low end of readout, both in the tubes for cooling fluid but also in the Cu cooling plate. Need to check effect on particle trajectories.
2. Retest one of the original arrays to verify new setup reproduces previous results (Carl)
3. Simplest scheme might not work with Fernando's bias distribution and needs to be checked.(Jack)

Tentative Agenda

1. Announcements
2. Action Items
3. Schedule, reporting, and manpower (Elton)
4. SiPM testing (Carl and Yi)
   • Acceptance of First Article
5. Mechanical cooling (Jim)
6. Mechanical drawings (Chuck)
7. Temperature compensation (Jack)
8. Preamp-summing (Fernando)
   • Will present a discussion of cabling and grounding next week.
9. Discussion of production testing

Minutes

Attending: Jim, Elton, Carl, Jack, Fernando, Chris

1. Announcements
2. Action Items
3. Schedule, reporting, and manpower (Elton)
   • Much progress, but no updates to the EVMS schedule
4. Mechanical cooling (Jim)
   • New modular design discussed having a phi-symmetric light guide as well as two-piece copper plate.
   • Suggested mods: make SiPM holder one piece (instead of 4), increase thickness of holder to 3/8", increase size of thermal plate to cover all amplifiers.
   • Investigating the fabrication of light guide "column of 10" by talking to various companies. Chuck has spoken to Core Six Precision Glass in Williamsburg producing n=1.5 fused silica products with good transmission above 300 nm.
   • Removal tool developed to extract arrays from sockets. Modifies commercial tool for our use. Will see how it works.
5. Mechanical drawings (Chuck)
   • No update
6. Temperature compensation (Jack)
   • Discussion regarding connection of thermister leads to electronic boards. Much discussion with Jack and Fernando agreeing that they might have a solution. This idea will be detailed and reported back to group.
7. Electronic Boards (Chris)
   • A few of the U boards have been completed and Chris passed them around to show
   • A summing unit prototype board was ordered and expected next week,
   • Components for the prototype are coming in. Expect stuffed board in about two weeks.
8. Preamp-summing (Fernando)
   • A new optimized preamp for array has been completed and should be tested by Sasha and Vitaly next week.
   • Will present a discussion of cabling and grounding next week.
9. SiPM testing (Carl and Yi)
   • Summary plots of first article tests were presented by Carl.
   • The samples look very uniform and meet specifications
   • Samples measured at temperatures between 22-24 deg C.
   • Gain is about 0.57x10^6 at Vop -Vbr = 0.9 V. The gain at 0.75x10^6 is achieved at about Vop-Vbr =1.3 V (consistent with expectations). However, Hamamatsu claims the over bias of 0.9 should give the later gain. This discrepancy is still to be resolved, but still meets specifications. In the following we give values at the measured gain and the value extrapolated to the higher gain in parenthesis:
   • PDE = 21+/-1%. (26-27%)
   • Dark Rate (DR) = 15+/-1.6 MHz (24 MHz)
   • Ratio of JLab DR (22-24 deg) /Hamamatsu DR (25 deg) ~ 0.9 consistent expectations
   • Parameters (Dr, gain, PDE and cross talk) measured different biases. DR and gain very linear in bias. The PDE and cross talk are not linear, which is not quite understood.
   • Report writing is next. Goal is to have a draft by next week.