Mar 22, 2011 SiPM Electrical and Cooling

Action Items from previous meetings

1. Determine if swapped bias pins was accidental or in design (Chris)
2. Develop front and back views of jumper sheets. Also get latest version of drawings (Jack)

Tentative Agenda

1. Announcements
2. Action Items
3. Schedule, reporting, and manpower (Elton)
4. SiPM production testing (everyone)
5. Mechanical assembly (Scot)
6. Mechanical (Jim)
7. Mechanical drawings (Chuck)
8. Temperature compensation (Jack)
9. Preamp-summing (Chris)

Minutes

Attending: Fernando, Jack, Carl, Chuck, Tina, Yi, Jim, Tom, Elton, Chris

1. Announcements
2. Action Items
3. Schedule, reporting, and manpower (Elton)
4. SiPM production testing (everyone)
   1. Yi found that there is a temperature gradient between the cooling plate and the SiPM sensor. Initially the gap (filled with silicon pad) was 3 mm. The estimated temperature difference was about 3 deg C.
      • The gap was reduced to less than 1 mm. The change reduced the temperature difference to less than 1 deg C and the gain variation from 20% down to 5-6%.
      • To prepare for measurements at room temperature, the system was left untouched without cooling and the temperature increased to 35 deg C. This is an indication of gradients that would exist in the setup even at room temperature.
      • The power consumption of the electronics is about 2W/SiPM
   2. The filter wheel in the setup died. Carl will check the warranty (it was bought new last year) and evaluate our options. The system could be used as is for the test at low light intensities if the appropriate filter is placed into the housing.
   3. A plate will be made to press the SiPMs onto the cooling plate to ensure better contact during production.
5. Mechanical assembly (Scot)
6. Mechanical (Jim)
   1. Modifications to wand for gluing light guides have come in
      • Still need to oder nuts and bolts
   2. Design of no-go gauges for light guides is in design. There will be gauges for individual light guides as well as a gauge to test an entire column.
      • Chile has requested we made an extra so they can use it to check dimensions also.
   3. Assembled 2 readout assemblies, suggested updates to design were shown
      • increase the standoff to minimize excess cables
      • remove ribs, rotate connector board
      • put in the power feed on the bottom of the board
      • new design features will improve assembly considerably
7. Mechanical drawings (Chuck)
8. Temperature compensation (Jack)
   • Checked on the availability of 0.01% resistors to be used for the 85KOhm. Companies advertise but do not seem to have stock. Will investigate in order to match the requirement with available options before production boards are ordered.
   • We need to request the Hamamatsu data sheets to be used as a basis for selection of jumper settings.
9. Preamp-summing (Fernando)
   • There was some discussion regarding the location of the distribution boxes that will feed 5V and bias to the SiPMs. They need to be located relatively close to the SiPMs to limit the voltage drop in the cable.
   • Two modules were assembled
   • Developed considerable infrastructure for testing assemblies
   • Overall the assembly went well. Elton tested all outputs for each Bias voltage setting. Some problems were found.
   • After initial fixes, each assembly has #37 analog signal (U-board counting) missing (the corresponding T signal is not brought out).
   • Fernando requested that Jack check the jumper settings for this sensor.