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

Agenda

  • Run 72 in progress
    • Payload:
      • Housing in Position 1 with Source mover, LEDs, thermometer and a test screw-terminal for NbTi
        • Heatsinking added to motor coil solder joints
      • G101D with Side 2 etched, Position 2. Source pointed at readout side.
        • One QET wired with twisted pair instead of side coax
      • External electrode in Position 3
    • Fridge is cooling normally, Tower = 64 mK, MC = 32 mK. Tower is slowly cooling a few mK per day, saw this in Run70 too. Expect to get to 40 mK next week.
      • 1K Pot running warmer than normal, 2.0 K (normal is 1.7 K). Does not seem to negatively affect cooldown (Still temperature higher than usual but MC/Coldplate normal). Could be that 1K Pot is partially clogged with ice, fingers crossed that it does not get worse.
    • Screw terminal heating test: 15 mA DC current heats the tower only to 100 mK
    • Motor coil heating test: DC current through CoilA heats the tower as much as in the last run. CoilB does not heat nearly as much (not tested this way in last run). It's not obvious that any of the NbTi is being driven normal, but we could take more careful measurements; measured this way, the data is consistent with CoilA at a constant 10 or 20 Ohm.
    • Phonon channels showing good pulses except Side1pE. This one behaves as if the TES is open. Maybe one of the wirebonds broke after the tower checkout (during installation or during cooling). This channel has a complicated wirebonding scheme.
    • Still to do: take some data, try HV, try moving source.
    • Transfer planning: need to cover weekends and travel plans
      • Friday Feb 28 transfer - Matt and all grad students out of town. Jake and Gabe??
  • PuBe storage shielding
  • Budget overage: we have something like $20,000 we could spend on lab stuff before April 1
    • Buy equipment/supplies:
      • Replacement forepump for leak detector
        • This pump is discontinued, but Pfeiffer says they can try repairing ours. Pump has been packaged for shipping
      • Send out spare circulation pump for leakcheck/repair
      • Two lab computers replaced
      • 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
  • Analysis status:
    • Run 71
    • Run 68 (n,gamma with S101)
      • Migdal analysis pending
      • New (n,γ) simulations, modified signal shape
    • NaI studies
      • tried to see Si n-capture gammas with a bag of sand - nothing seen
      • assessing the howitzer for PuBe storage - definitely doesn't shield gamma as well as paraffin drum and lead box
    • 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
  • Future runs?
    • 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?
  • 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.