UMN CDMS Wiki archive
start › cdms › k100 › run_diary › 20170630

2017/06/30 (Friday)

Previous Day

Status Transferred LN2 yesterday. Left exchange gas in IVC.
0855 Lab = 22.1 C, 44% humidity
0855 MC(Cernox)/Sorb = 79.8/135.6 K, IVC = 1.9 mbar, DIB3 pA/pB/pD-chassis = 74.3 Ω / 1.10 MΩ / 2.4 nS, qIbias-pD = 0.38 nS
Overnight: MC(Cernox) bottomed out, Sorb has been increasing from 128 K minimum. There's something weird with G2 since yesterday - it is continuously spiking. This is the pump outlet (pump is isolated), so hopefully it's not something with the pump - maybe the gauge has a problem. G1 (fridge+Trap 2) has been increasing, from 540 to 560 mbar, presumably because upper part of fridge is warming as seen in sorb thermometer.
DIB3 resistances during cooldown
image updated with <77K data
  • DIB3pA (Side2 pA, outer ring) shows low resistance leak to chassis - the resistance actually goes down as temperature falls, like a direct metal contact.
  • DIB3pB (Side2 pC) rises to a level consistent with same-side interchannel resistances
  • DIB3 pD (Side1 pC) rises higher to a resistance characteristic of opposite-side interchannel resistances
  • The qInner Side 1 continuity through the bias resistor increases to values similar to the opposite-side resistances, though it ends up even higher
0910 Begin blowing out LN2 from main bath
0930 Looks like blowout it finished. Stop pressurizing bath.
actually it looks like the helium gas cylinder is empty. Replacing it.
1000 Now LN2 blowout looks finished.
1000 Pump IVC down to 46 ubar helium exchange gas using scroll pump.
1005 Begin pumping out main bath. P1 falls to 1 mbar in 7 minutes, looks good. Also pump out 1K Pot.
1020 Fill main bath and 1K Pot with helium gas.
1030 Start a forward throughput test like yesterday. Mix is open to fridge and to Trap 2. Start pumping on still side with 3He pump, opening V6 just enough to get flow, 12.7%. Watch to see if the condenser side (G2) starts to fall.
Condenser pressure is not falling very quickly. This is bad. It's decreasing maybe 3 mbar/min, but it was falling at a similar rate before we started pumping.
1045 Have opened V6 further, now 13.3%, enough that still pressure is low enough for P1 to start to read. Still is down to 5.5 mbar. Condenser pressure continues to drop at the same rate, 3.4 mbar/min. But pressure is lower than yesterday - maybe this is OK.
1050 Close V6, no longer pumping on still. Then open V14 to fill still with mixture from dump. Condenser pressure starts to rise - good!
1055 Pump mixture to dump, prepare for the standard throughput test.
Throughput test procedure, Cold Trap 2:
  1. All mixture in dump, LN2 traps cold, condenser & still valves open (3He pump on - optional)
  2. Open V9, V13b, V12b+speedivalve, V3. Wait for G1 to be close to G2.
  3. Close V12b+speedivalve and V3, open V1
  4. monitor G1
1055 81 K Throughput Test Result: let G1 rise to 620 mbar before Step 3, then it falls to 70 mbar and begins to rise. Throughput: 39.7 mbar/min. Compare with Run 62, a little lower. But good!
1110 Open mixture from dump to trap 2 to fridge, both sides.
1120 Begin LHe transfer
1120 MC(Cernox) = 81.3 K, Sorb = 143.4 K, IVC = 46 μbar, Fridge(G1) = 643 mbar
1150 MC(Cernox) = 81.1 K, Sorb = 136.6 K, IVC = 0.74 μbar, Fridge(G1) = 634 mbar
1200 The IVC pressure dropped more than it should have, so probably the gas that was in there was mostly air. Let some He back in, 40 μbar
1210 MC(Cernox) = 70.2 K, Sorb = 86.1 K, IVC = 40 μbar, Fridge(G1) = 620 mbar
1225 MC(Cernox) = 56.8 K, Sorb = 34.5 K, IVC = 30 μbar, Fridge(G1) = 580 mbar. DIB3 pA/pB/pD-chassis = 86.6 Ω / 1.2 MΩ / 1.6 nS, qIbias-pD = 0.26 nS
1240 MC(Cernox) = 46.1 K, Sorb = 9.2 K, IVC = 22 μbar, Fridge(G1) = 539 mbar. DIB3 pA/pB/pD-chassis = 94.2 Ω / 0.18 nS / 1.3 nS, qIbias-pD = 0.17 nS
I think I was plugged into the wrong lead on pB.
1250 MC(Cernox)/Sorb/1K Pot = 40.3/8.1/6.4 K, IVC = 22 μbar, Fridge(G1) = 527 mbar.
1300 MC(Cernox)/Sorb/1K Pot = 31.7/7.0/5.56 K, IVC = 16 μbar, Fridge(G1) = 510 mbar. DIB3 pA/pB/pD-chassis = 60.4 Ω / 1.79 MΩ / 1.2 nS, qIbias-pD = 0.18 nS
MB still at minimum, though it giggled up from -1.0 to -0.9 once.
1310 MC(Cernox)/Sorb/1K Pot = 25.5/6.5/5.20 K, IVC = 16 μbar, Fridge(G1) = 503 mbar, MB = 1.4%
1420 MC(Tower)/Sorb/1K Pot = 4.22/5.2/4.11 K, IVC = 1.4 μbar, Fridge(G1) = 478 mbar, MB = 25%. DIB3 pA/pB/pD-chassis = 17.7 Ω / 16 nS / 0.86 nS, qIbias-pD = 0.16 nS
Start pumping out IVC with turbo pump, rather late. Distracted by a meeting.
1500 Finish 4K electrical checkout:
  • Phonons to chassis: as before DIB1pD/DIB3pA (Side 2 pB/pA) are very leaky at 41/20 Ω, other Side 2 channels around 40 nS or less, Side 1 all OK.
  • LEDs: can't read voltages on any of them. Do we normally check at 4K? FET Tsense voltage readable but unstable.
  • DIB3 pD (Side1 pC) SQUID bias-to-return is high at 1.6 MΩ, should be around 100 Ω. Was ok before.
1505 MC(Tower)/Sorb/1K Pot = 4.30/6.2/4.92 K, Fridge(G1) = 533 mbar, MB = 34.8%.
Temperatures and fridge pressure creeping up, not sure why
1515 Helium cylinder has gone empty. Why?? It had a lot in it, 940 PSI. This is a problem because we don't have a spare.
1530 Borrow a cylinder from Goldman lab with 2320 PSI to start. Start pressurizing Dewar again.
1535 MC(Tower)/Sorb/1K Pot = 4.31/6.8/5.32 K, Fridge(G1) = 532 mbar, MB = 33.1%. Cylinder 2310 PSI.
1555 MC(Tower)/Sorb/1K Pot = 4.30/6.4/5.00 K, Fridge(G1) = 481 mbar, MB = 35.0%. Cylinder 2300 PSI.
Temperatures & fridge pressure went down again, I guess they went up when the transfer stopped.
1610 MC(Tower)/Sorb/1K Pot = 4.32/6.3/4.94 K, Fridge(G1) = 472 mbar, MB = 37.0%. Cylinder 2290 PSI.
slow transfer. try increasing regulator pressure from 2.0 to 2.75 PSI.
1620 MC(Tower)/Sorb/1K Pot = 4.32/6.3/4.96 K, Fridge(G1) = 460 mbar, MB = 46.0%. Cylinder 2270 PSI.
1630 MC(Tower)/Sorb/1K Pot = 4.33/6.3/4.97 K, Fridge(G1) = 457 mbar, MB = 62.8%. Cylinder 2240 PSI.
1640 MC(Tower)/Sorb/1K Pot = 4.35/6.4/4.99 K, Fridge(G1) = 456 mbar, MB = 82.7%. Cylinder 2220 PSI.
1650 End LHe transfer at MB = 90.6%
1700 Turbo = 3 nbar, IVC = 22 nbar

Next Day