Aug 25, 2011 SiPM Electrical and Cooling

Action Items from previous meetings

1. Add hardware voltage limits to bias circuit (Jack) Investigation in progress
2. Investigate whether there is sufficient room to add an additional layer to the electronics at the inside of the Bcal (Fernando).

Tentative Agenda

1. Announcements
2. Action Items
3. Schedule, reporting, and manpower (Elton)
4. SiPM testing (everyone)
   • Light source / optics
   • Electronic boards
   • Cabling
   • Cooling plate
   • Other?
5. Mechanical (Jim)
6. Mechanical drawings (Chuck)
7. Geometry (Elton)
8. Temperature compensation (Jack)
9. Preamp-summing (Fernando)
10. Granularity (Elton)

Minutes

Attending: Carl, Chris, Jim, Chuck, Yi, Elton, Jack, Eugene, Fernando

1. Announcements
2. Action Items
3. Schedule, reporting, and manpower (Elton)
   • Updated the EVMS
4. SiPM testing (everyone)
   1. Light source / optics (Carl)
      • Hall A has finished with the dark box
      • Start to construct the reflective surface
      • Move light source from original testing site to EEL and other required components
      • Elton: Would like to keep the existing setup in tact for sample testing of individual SiPMs before production test setup is operational
      • Need to purchase key elements
      • Yi: Software for one QDC must be expanded to multiple boards
   2. Electronic boards
      • Should add test points to measure the voltage bias on each SiPM (for the test setup but also on the Bcal module)
      • Power supplies: Received chassis and PS for +/-5V. Expecting PS for bias soon. Hovanes will also use the supplies to begin programing slow controls
      • The readout boards were sketched by Fernando on the white board. He plans to begin layout next week. Gain will be 66, as it was for 16-channel preamps for testing first articles.
      • Expect readout boards the second week in October.
      • Pulse generator is needed. Fernando will order.
   3. Cabling (Chris)
      • Cabling and connectors for the connection of readout boards to QDCs have been ordered.
      • Chris has begun the layout of the small interface connector boards to the QDCs
   4. Cooling plate (Jim)
      • Have a model that is ready to receive specific dimensions from Fernando once the board outline is completed
      • Will consist of Al plate with tubing glued in with thermal epoxy. Plan to use water at about 65 deg. Fernando should have the board outline in about a week
   5. Other?
5. Mechanical (Jim)
   • Will move forward on mechanical pieces that do not depend on the addition of the inner layer. These include: cooling plate (with mod for U board), SiPM holder, cage assembly.
   • Jim will produce a sketch of the monitoring interface to the box to send to Athens for feedback.
6. Mechanical drawings (Chuck)
   • Chuck has the list from Jim, and will start making the drawings for those components
7. Geometry (Elton)
8. Temperature compensation (Jack)
   1. Jack showed data on his measurements of SiPM response as a function of temperature. Measurements ranged form 3 to 20 deg. Within that range the systematic changes with the bias compensation was quite small. However, the variation was +/-3% at a fixed temperature.
      • Discussion about possible sources of the variation. Should probably monitor the light source to check stability.
   2. Zener diode to protect the SiPM. Discussion about where to add this diode and whether the noise introduced would be a problem. The power supply itself could be set to limit the bias to the supply chain.
      • There needs to be further discussion and understanding of possible noise before adding to the circuit diagram.
9. Preamp-summing (Fernando)
   • Is planning to check the layout options for adding an additional layer to the Bcal
10. Granularity (Elton)