2020/09/27 (Sunday)
- Lab in-person: Matt
- Virtual partner: 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. Lead/poly shield erected (4 lead walls, 2 poly walls). |
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| Status | Did a partial warming to get helium out of the IVC. Initial LHe transfer 2 days ago… but it seems we started pumping out too early, MC was above 10K yesterday morning, and 1K Pot couldn't cool it. Added exchange gas yesterday to get MC below 10K, but it warmed up again after pumping out the IVC - so still too early. |
| 0940 | Matt Fritts body temperature = 96.9 F |
| 1100 | MB = 40.9% |
| 1205 | MC(Cernox)/Sorb/1K Pot = 11.2/10.7/>7 K. G1(fridge) = 578.0 mbar (3He pump off). These are even higher than early yesterday - maybe just because the bath is low. |
| 1235 | Matt enters lab |
| 1235 | Turbo on IVC = 1.9 nbar. With turbo valved out for 1 minute, IVC = 22 nbar. Lower than yesterday. At least this shows the IVC is thoroughly pumped out. |
| 1240 | MC(Cernox)/Tower = 11.20/11.33 K |
| 1250 | Let some He into IVC. Targeting 4 ubar. When the MC temperature starts falling, close the feed valve. Watch MC fall - also switch to Tower thermometer for a minute, it seems to fall at same rate. Let MC(Cernox) fall to 7.5 K this time - then start pumping out IVC. Right before pumpout, IVC pressure had relaxed to 0.19 ubar. We'll see how low the MC goes; if it starts to rise again before I leave the lab, I'll add more exchange gas. |
| 1255 | MC(Cernox)/Tower = 6.0/6.0 K, falling |
| 1300 | Sorb fell to 6.6 K but is already rising, now 7.8 K. Similarly 1K Pot fell to 5.3 K but is rising, now 6.2 K. Looks like they started rising very close to when the pumpout started. |
| 1315 | MC(Cernox) = 5.4 K, starts rising after that |
| 1321 | Begin LHe transfer @ MB = 37.8% |
| 1330 | Fill LN2 cold trap bath |
| 1330 | MC(Cernox)/Tower = 5.47/5.46 K, slowly rising |
| 1352 | End LHe transfer @ MB = 93.1% |
| 1415 | MC(Cernox)/Tower = 5.85/5.84 K, very slowly rising |
| 1415 | Sorb/1K Pot = 7.8/6.1 K. These were rising until the LHe transfer, then they fell; now they look pretty flat. |
Should I add transfer gas to the IVC again? Comparing the MC temperature pattern with yesterday(blue), it looks more promising today(orange):
Compare current temperatures with the last ordinary initial LHe transfer: a few hours after a normal initial transfer, MC(Cernox)/Sorb/1K Pot = 6.11/6.4/5.13 K. Now MC is similar, Sorb and 1K Pot a little warmer. For a normal initial transfer, the following morning shows MC(Cernox)/Sorb/1K Pot = 5.36/8.4/6.59 K. MC actually goes down overnight, Sorb and Pot go up. MC is not going to go down, so it won't be as low tomorrow as normal, but it might be close.
Studying the curve a little further than shown above, it looks like MC will wind up below 7K. Most extreme case: at the current slope, it will hit 18 K by tomorrow morning - not good. But sorta expecting it to level off….
The near flatness of Sorb/1K Pot is promising (up by 0.1 K in 30 minutes). Yesterday then went up 0.5/0.7 K in 60 minutes. But bath is higher now.
I guess I'll leave it be. If MC is significantly below 10 K tomorrow we'll try the 1K Pot.
Actually it just now occurs to me: DCRCs are on. Could they be contributing to the warming? Let's turn them off.
| 1450 | Turn off the three DAQ programs, then unplug power from DCRC1&4. |
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| Just after this, Sorb and 1K Pot temperatures start falling, leveling out to a new low. Interesting - maybe DCRCs were causing heating - but strange that that should affect these temperatures significantly. MC had a delayed response, started cooling 15 minutes later. | |
| 1455 | MC(Cernox)/Sorb/1K Pot = 6.10/7.8/6.1 K. |
| 1455 | MB = 92.1% |
| 1510 | MC(Cernox) peaks at 6.1 K, then starts cooling slowly. OK, I guess that's good. |
| 1700 | MC(Cernox)/Sorb/1K Pot = 5.67/6.7/5.31 K. |
| 1720 | Matt Fritts body temperature = 97.6 K |