UMN CDMS Wiki archive
start › cdms › k100 › run_diary › 20200915

2020/09/15 (Tuesday)

Previous Day

  • Lab in-person: Matt
  • Virtual partner: Nick, group meeting, Zach&Michael
Setup Run 73. DIB 1/3/4 → Stripline 43/48/41 → pi-filters 1/2/3 → Cable 3/1/2 → nothing/nothing/accessory_interposer → HV_Conn 1/3/2 → HV 1/2 → DCRCX(4)/DCRC55(1)-master; DCRC33(2) → HV control. DCRCs on overnight. Lead/poly shield erected (4 lead walls, 2 poly walls).
Status: Warming up to deal with cryo problems: 1K Pot partial blockage, helium in IVC. Softened vacuum in cryostat jacket and recovered mixture yesterday. MC/Still Heaters on @ 20/30 mW.
0300 Recovery = 380082.29 / 0.21 cuft/hr
0600 Recovery = 380082.86 / 0.15 cuft/hr
0600 MC(Cernox)/Sorb = 114/250 K. Sorb thermometer reaches maximum.
0900 Recovery = 380083.26 / 0 cuft/hr. Reco is stopping occasionally, probably because external pressure is closing the check valve. MB pressure rises from 160mbar to 180mbar during periods where reco stops, then falls again.

todo:

  • pump out LN2 cold traps
  • pump out LHe cold trap and fridge lines
  • maybe cryoclean mixture. Is this necessary? Running the fridge also cryocleans it. If the trap was saturated, maybe additional cleaning would help. Can judge this by how much contamination is in LN2 Cold Trap 1
  • redo plastic taped over stripline elbow
  • isolate 1K Pot (maybe. Depends on whether there's concern that it will overpressurize. )
  • power down DCRCs
  • close MB recovery line, turn off webcam automater

How soon before we can cool again? We want 1K Pot warm enough to pump out. After it is warm enough we want to pump out Cryostat Vacuum Jacket thoroughly, preferably overnight. Options:

  1. Start cooling tomorrow (Wednesday). We'd have to assume that the 1K Pot will be warm enough to pump out by the end of today. We definitely don't know that for sure. We would want to go into the lab late today/tonight to start pumping out cryostat vacuum jacket. Then tomorrow, pump out pot and IVC, proceed to LN2 transfer
  2. Start cooling Thursday. Should start pumping out vacuum jacket late Wednesday in that case. More likely that the 1K Pot will be warm enough.
  3. Start cooling Friday - not good, then the LN2 blowout and initial LHe transfer would be on Saturday
  4. Start cooling Monday - that's certainly long enough for the Pot, but it's a long delay for the run.
1015 Matt Fritts body temperature = 98.5 °F
1030 Recovery = 380083.38 / 0.09 cuft/hr
1055 Matt enters lab
1100 MC(Cernox) = 139 K.
1105 Take LN2 Trap 1 out of bath to warm up
1140 Check warm LN2 Trap 1 contents: 29.3 mbar. Pump out with Scroll Pump
1200 Check warm LN2 Trap 2 contents: 31.2 mbar. Pump out with Scroll Pump
1200 Recovery = 380083.5 / 0.09 cuft/hr
1210 Open V1 to check Condenser and LHe Trap contents: 6.0 mbar. Pump out with Scroll Pump.
Note: P1(Still) has been at 0.24 mbar, rising slowly over last 12 hours from about 1.1 mbar. You'd have thought this would be equal to the condenser side.
1215 Close off Condenser side and pump out Still side with Scroll Pump.
1240 Turn of MIDAS DAQ programs (trigger, tower, dcrc), then power down DCRCs. Short HV leads together to ground electrode.
1245 Recovery = 380083.55. Close MB recovery valve. MB+1KPot = 150 mbar. Close 1K Pot Needle valve and Speedivalve, leaving some helium in the 1K Pot.
1320 MC(Cernox) = 150 K.
1320 Matt leaves lab

Next Day