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Agenda

Run 69 (GeHV n,gamma NR calibration) status
- Fridge is working fine. But Tower cooldown is very slow
  - Tower reached 71 mK first day and is falling about 4-5 mK per day. But MC lower, reached 32 mK first day.
  - We've seen slow cooldowns before. Had not seen it with this detector though.
  - Is new electrode cooling slowly? (only 6 clamps rather than 12.) Is it related to the somewhat early pumpout when cooling to 4K?
- DCRC refurb?
  - DCRC55(1) is at FNAL for Sten to test. Unknown how long it will take him. Nick emailed him asking to send it back.
- PuBe source availability:
  - there is one block of a couple weeks around April when we can borrow it
  - Kevin is amenable to weekend use - it would need to be returned on Sunday for 24-hour activation before Monday classes
  - Kevin said we can use it the week before and the week of Spring Break, needed back the Monday after break. (March 9-25.)
- Heat-sinking modification (previous analysis). We left the 4K shield completely off, but did not anchor the 4K and Still Tower stages together.
  - Coldplate and Still running a little warmer than previous runs. This suggests that leaving off the heat-sinking is counterproductive - the 4K heat sinking was probably taking heat away from the tower rather than toward the tower. (Suggests that the heatsinking of the striplines to 4K is not very efficient.)
- Calibration source:
  - Smoke-detector Am source mounted at center of detector Side 2 (bias side), as in the last run.
  - The detector was kept in the source safe with the Cf-252 source for 2 weeks to preactivate it. (Currently source in its small poly container is with detector in purge cabinet.)
Run 68 (n,gamma with S101) analysis:
- Working on analysis task list
- Data not yet looked at:
  - Trigger study data: now processed
  - Hold-time runs at different biases done, haven't looked at them yet
  - Have reprocessed -80V Na data. Used -125V balancing factors, still need to check if those are optimal (if not we should redo it)
Future 150mm runs
- 150mm w/phonons - need to design 600mK rod to accommodate 150mm cans
- Received 4/3-inch DIBs from TAMU - now we can house either detector for phonon readout (would need to machine faces on 4/3-inch housing for DIBs)
- S1501 and S1502 sent back to TAMU
- We have decided we can run 8 phonon channels
  - Preferred DIB-pad layout: two DIBs separated by 120 degrees
  - Himangshu's mask design: PDF download
  - Will use existing vacuum-interface electrode, mounted on side opposite the phonon side
  - Will connect directly to two DCRCs, with one diverter board to route one tower wire to HV connection
  - We'll want LEDs - are there some mounted on the DIBs? We can mount external LEDs too - existing electrode has mounts.
- First 150mm phonon detector will be monolithic, but “donut+hole” arrangement (active veto) proposed as well.
- Aiming for May to finish fabrication and start run.
Other future runs
- Future HVeV runs?
  - Berkeley can help us with a Soudan-style housing mount (3“ or 4”?)
  - then use original tower, can try different heatsinking for colder SQUID card
  - would need to install optical fiber
    - through top or through stripline tube? need vacuum feedthrough
    - Look at Prisca's deuterium lamp/monochromator/filters, glass UV fiber
  - Is PuBe NR calibration feasible?
    - 1×1×0.4 cm^3 is 630× smaller than SNOLAB detector. Anthony estimates 25 events/day (over full spectrum) for Si, 250 events/day for Ge. any chance we could get multiple chips?
    - Nick's idea: sandwich between two 4“ Ge detectors for gamma coincidence (large solid angle coverage)
- Other ideas:
  - run SiHV with Nick's movable Am source (or with multiple Am sources)
  - run SiHV with no 4K heatsinking
  - re-run USD1? do we have any additional ideas to test it?
  - anything else?