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start › cdms › k100 › meetings › 20200131
Teleconference link: https://umn.zoom.us/j/8797896096 or https://umn.zoom.us/my/fritts
Access code: 879-789-6096

Agenda

  • Planning Run 72
    • Ge HV detector (G101“d”) almost ready, Side 2 channels etched off at TAMU, may get shipped on Monday
      • was able to etch without any damage to Side 1 (half-dipped)
      • Wirebonding miscommunication - Mark wirebonded three of the six Side1 channels to the wrong DIB pads
        • He offered to fix this but said it could fail because some pads are mostly covered with stubs
        • If he leaves it as is we can't use the HV board, but we could run with 3 DCRCs (instead of only 2 with board)
        • Nick says in 3DCRC mode we can still pretty easily connect HV
        • Currently planning to leave bonding as is and go this route for this run
    • Plan movable source in Position 1, detector Position 2, electrode Position 3. Use CDMS2 p4-length side coaxes, these seem OK
    • Movable source prep - add epoxied wiring heatsinks
    • No news on S104 mounting/bonding at SLAC
  • 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
      • 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
  • Analysis status:
    • Run 71
    • 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
  • 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.