Teleconference link:	https://umn.zoom.us/j/8797896096 or https://umn.zoom.us/my/fritts
Access code:	879-789-6096

Agenda

Budget overage: we have something like $20,000 we could spend on lab stuff before April 1
- Start a run with either GeHV or SiHV:
  - note: Matt will be in Sudbury next week
  - GeHV:
    - our GeHV prototype (G101c) is at TAMU to have Side 2 metal etched away
    - work should take ~1 week
    - warning from Mark Platt: some bond pads have many wirebond stubs (left from my repairs). In his experience photoresist doesn't completely cover stubs so a little circle of Al will be removed by the etching. He fears that some pads may wind up unusable. Gives it a 50% success probability. We may be able to come up with weird bonding schemes to connect lost channels - or we may have to sacrifice some channels…
  - SiHV:
    - SLAC will package and bond S104. (well actually Rich P balked about Matt C doing all the bonding work, but Matt C might do it anyway.)
    - may be done in ~1 week
    - Tc's measured at SLAC are right in the same range of S101 measured here (60s-70s mK)
  - Stepper motor - do we want to modify the heatsinking?
- Buy equipment/supplies:
  - Replacement forepump for leak detector
  - Send out spare circulation pump for leakcheck/repair
  - Replace old lab computers
    - Prisca says there's money in the next budget specifically for computers, so don't upgrade everything now. Maybe do a few.
    - Two machines in the lab are particularly old. Got recommendations from Chad ~$200
  - NbTi cables for tower-free detector&cold electronics mounting
    - could get 2@25-wire for 4K-CP, 2@25-wire for CP-MC. And maybe 2@25-wire, longer, to try 4K-MC (colder SQUETs)
  - SQUIDs for new cold electronics
  - Copper-clad NbTi bell wire for a new source mover motor - quote at $930 for one motor
- Budget spend-down Spreadsheet
Run 71 complete. To do:
- Some measurements of source holder for simulation purposes
- Measure interchannel capacitances for absolute charge calibration
  - actually this is not really doable at room temperature with germanium because the crystal is conductive
Analysis status:
- Run 71
  - Paper draft - seeking comments
  - Analysis organization page
- Run 68 (n,gamma with S101)
  - Migdal analysis pending
  - New (n,γ) simulations, modified signal shape
- Run 70
  - analysis team includes Pramod, Matt, 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
  - Will study the activation peak background
- Run 67 (USD detector with novel time-dependent gain)
  - Dongming has characterized lots of microscopic processes, wants us to write a paper
  - Matt working on rough model of detector behavior
- SiHV event reconstruction
  - Derek working on this
  - Hongguang developing connection to DMC
Next run?
- plan to wait till January
- Re-run USD1?
  - use Co source
  - experiment with varying the amount of shield, distance of Ba source, see how background rate affects time variations in gain
  - maybe use source mover
- Position reconstruction with source mover
  - improve motor heatsinking?
  - run with GeHV prototype - would probably want to rebond it for standard direct contact biasing
  - some day get a SiHV prototype again, run with that
- Improved neutron calibration runs
  - under discussion with Anthony - working on grant proposal for new measurements with more NaI and whatever other improvements
  - more NaI coincidence detectors
  - can we improve Ge?
    - try again with standard bias, maybe no-tower setup?? Would this improve it?
    - try polishing bias side for “true” vacuum interface?
    - or - use a HVeV detector? can we get a high enough signal rate?
  - or should we re-do SiHV? with one of the new “pathfinder” detectors, whichever they give to us
- Future 150mm runs
  - 150mm w/phonons - we considered designing new 600mK rod to accommodate 150mm cans. Could rethink this in terms of no-tower setup maybe…
  - We have 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.
  - Last discussion of this was a year ago, we were aiming for May 2019 to fab a detector
- 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?
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
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 |