Teleconference link:	https://fnal.zoom.us/j/9082275310
Domestic:	1-646-558-8656 (US toll)
Domestic:	1-408-638-0968 (US toll)
Access code:	908-227-5310

Agenda

Run 71 status
- New movable source design with no potentiometer, end-contact sensors instead at -13.10 mm and +41.67 mm
- This cooldown: no IVC leak, fridge working fine. Base is 32 mK. All channels working.
- Performing hot LED flashes to restore phonon collection efficiency after running the motor - seems to work.
- Studying stepper motor behavior indicates that it only can move a few steps at a time, then needs to cool
  - Heating during stepping - tried smoothing capacitors and changing dwell
  - DC testing shows resistance increase of ~10 Ohm @detector which can explain heating.
  - Solder joint to NbTi may cause local (runaway) heating to drive ~7 cm of NbTi normal
  - Conclusion: only moving around 4 steps every move
- Adopted a move method of 6 or 4 steps at a time, with a 6 or 4 minute pause to cool
  - this amounts to 1 mm per hour
- Clear evidence that we are moving: Nov 22
- We moved in the +y direction until hitting the end stop. Then tried to move backward but apparently we moved to far (by about 0.7 mm) and jammed it. Increasing the current to provide higher torque, we were able to unjam it
- Established that when moving in the -y direction, we have 100% step efficiency - i.e. the number of steps we sent to the motor controller is an accurate measure of how far we moved.
- Found the nearest blocker: Nov 23
- Ending the run by taking data at various positions, taking data: Nov 25
Should we design and build new cold hardware?
- Soudan towers didn’t perform thermally as well as they should have (graphite tubes too conductive)
- Soudan towers had requirements we can relax
  - FET heat not a consideration for phonon-only devices
  - Materials don’t need to be as radiopure
- Soudan tower concept
  - Design description from Walter Ogburn’s thesis
- NEXUS setup
  - More detailed CAD
  - NbTi cable thermal conductance: G=3.11e-8*T^1.19 W/mK (for 1m, 40 wires, base = 100 mK)
  - Tekdata NbTi, MDM-25 quote: ~$715 each
  - Cheap ($10/inch^2) SC flex PCB inside MC can Photo
SQUET recall
- Martin wants 5 of our 9 SQUETs sent back to Colorado. He wants good SQUIDs.
- A lot of issues to deal with:
  - there are bad SQUID chips
  - we need to change shunt resistances for iZIPv6 versus HV, but don't want to wirebond too many times
  - some SQUETs have problems at the pins
    - can we get spare SQUETs with the SQUID chips removed? Could theoretically glue good SQUID chips onto good SQUET.
- Anthony says we may be able to get alternative SQUID chips
- We have 1.5-ish months to deal with this
Analysis status:
- Run 68 (n,gamma with S101)
  - Migdal analysis pending
  - New (n,γ) simulations, modified signal shape
- Run 70
  - analysis team includes Pramod, Matt, maybe Zach - should coordinate, have meetings
  - Need to look at the recent PuBe data, work on a low-threshold energy quantity, see if we can see a hint of (n,γ) signal. Also develop cuts and look for low-energy junk
- Run 67 (USD detector with novel time-dependent gain)
  - Dongming has characterized lots of microscopic processes, wants us to write a paper
  - Matt will work on rough model of detector behavior
- SiHV event reconstruction
  - Derek working on this
  - Hongguang developing connection to DMC
Lab and infrastructure
- Leak detector: After pump rebuild, pump no longer turned. Jake and Derek fixed this problem. However, it still doesn't seem to be able to pull a good vacuum. Using scroll pump assist in order to use leak detector. | Teleconference link: | https://fnal.zoom.us/j/9082275310 |