| Status | Run 74 in progress. LHe transfer yesterday, IVC started leaking at around 4K for a third time. |
| 0930 | IVC = 25 μbar. It has gone down a lot since yesterday, still not sure why this happens. Maybe some helium is condensing as the IVC sits at 4K. If so then pumping on the IVC may cause a cooling effect. Or maybe some parts near the top have slowly gotten cooler. |
| 1040 | IVC = 34 μbar. |
| 1045 | MC(Cernox)/Sorb/1K Pot = 4.26/5.6/4.64 K |
| 1140 | IVC = 40 μbar. |
| 1400 | Matt enters lab |
| 1400 | MB = 33.2% |
| 1400 | MC(Cernox)/Sorb/1K Pot = 4.26/5.6/4.66 K, G1(fridge) = 550 mbar |
| 1405 | IVC = 34 μbar. Start pumping IVC with Turbo Pump |
| 1420 | MC(Cernox)/Sorb/1K Pot = 4.26/5.8/4.67 K, G1(fridge) = 550 mbar |
| | no indication that pumping the IVC has a cooling effect |
| 1420 | Turbo on IVC = 1.4 μbar after 15 minutes pumping. With Turbo valved out for 1 minute, IVC = 25 μbar. |
| | We'll stop pumping the IVC for the time being |
| | As a test, we'll pump the mixture to the dump, to eliminate the possibility that the leak is from the dilution unit into the IVC. (The pattern of when the leak appears and disappears disfavors this, but we'll check.) |
| 1425 | Start pumping mixture to dump. This has a cooling effect - MC dips to 3.95 K, then rises again. 1K Pot dips to 4.37 and rises. Sorb dips to 5.4 K and rises. |
| 1430 | IVC = 30 μbar. I wasn't watching when I started pumping out the mixture, maybe it dipped too |
| 1430 | Fill LN2 cold trap bath |
| 1435 | P1(Condenser) is pumped down to 0.075 mbar. |
| 1435 | IVC = 30 μbar. Start pumping IVC with Turbo Pump |
| 1450 | MC(Cernox)/Sorb/1K Pot = 4.26/5.8/4.70 K |
| 1450 | Turbo on IVC = 1.2 μbar after 15 minutes pumping. With Turbo valved out for 1 minute, IVC = 22 μbar. |
| | No significant difference here, so no indication that the leak is from the dilution unit. |
| 1455 | Let mixture back into fridge through cold LN2 Trap 1. Warming effect: MC/1K Pot/Sorb spike to 4.5/5.5/6.9 K then cool again. No measurable change in IVC pressure. |
| 1525 | Receive DCRC RevE SN 8 from Pat Lukens @ FNAL. Arrives in electrostatic bag in cushioned box. No minibob or anything arrived with it. |
| 1525 | IVC = 30 μbar |
| | For fun let's try to start the 1K Pot, see what happens. It won't work of course… |
| 1525 | Pump out line leading to 1K Pot with scroll pump. Then switch over to 4He pump. Turn on 4He pump then change pump exhaust to recovery and open valve to recovery lines. |
| 1530 | Check pressure in 1K Pot (open 1K Pot speedivalve with V4a closed): Mechanical gauge = 0.41 bar. 1K Pot temperature dips to 3.7 K then rises. Sorb dips to 4.5 K and rises. |
| 1535 | IVC = 30 μbar |
| 1540 | Pump out 1K Pot in steps, alternating between V4a and the 1K Pot speedivalve, keeping P2 below 10 mbar, opening V4a for short bursts when necessary. After a few speedivalve iterations leave V4a and 1K Pot speedivalve open. 1K Pot dips as low as 3.65 K, then returns to 4.73 K / 0.24 mbar. Sorb dips too, MC unaffected. |
| 1545 | IVC = 30 μbar |
| 1545 | Open 1K Pot needle valve → 10°. 1K Pot → 3.1 K / 7.5 mbar. |
| | This is surprisingly good. MC falls too, → 4.23 K. IVC pressure unchanged. |
| 1545 | Open 1K Pot needle valve → 20°. 1K Pot → 2.6 K / 17 mbar. MC → 4.16 K |
| 1550 | Open 1K Pot needle valve → 30°. 1K Pot → 2.4 K / 24 mbar. MC → 4.13 K |
| 1555 | IVC = 30 μbar, no change |
| 1600 | 1K Pot = 2.1 K / 24 mbar. MC(Cernox)/Sorb = 3.72/4.0 K, G1 (fridge) = 478 mbar (3He pump is off) |
| | MC started dropping relatively quickly. IVC pressure still flat. |
| 1610 | MC thermometer comparison: Cernox/H35 = 3.5/4.1 K. Big discrepancy - these usually read the same around this temperature, I'm pretty sure. Maybe and effect from the helium in the IVC?? |
| 1610 | 1K Pot = 2.1 K / 26 mbar. MC(Cernox)/Sorb = 3.52/4.0 K, G1 (fridge) = 479 mbar |
| | OK it doesn't look very good, as expected. Normally MC would be well below 3 K now, fridge below 300 mbar. What's more, not sure I can trust Cernox and its sudden drop at 15:57, because H35 seems to be close to the 15:57 temperature. So the Cernox dip over the last 15 minutes may be spurious. There was no dip in fridge pressure at that time - in fact, at that time the fridge pressure flattened and hasn't gone down since. |
| 1620 | IVC = 30 μbar, no change |
| 1620 | 1K Pot = 2.2 K / 24 mbar. MC(H35)/Sorb = 4.11?/4.0 K, G1 (fridge) = 476 mbar |
| 1625 | IVC = 30 μbar. Start pumping IVC with Turbo Pump |
| 1625 | H35/Cernox/Tower = 4.1/3.5/3.6 K |
| | huh, looks like maybe H35 is the one reading incorrectly |
| 1635 | 1K Pot = 2.2 K / 26 mbar. MC(Cernox)/Sorb = 3.48/4.0 K, G1 (fridge) = 472 mbar |
| 1635 | Open 1K Pot needle valve → 40°. 1K Pot → 1.9 K / 65 mbar. MC → 3.45 K. G1(fridge) → 456 mbar |
| 1640 | Turbo on IVC = 1.2 μbar after 15 minutes pumping. With Turbo valved out for 1 minute, IVC = 22 μbar. Same as before we started the 1K Pot. |
| 1640 | 1K Pot = 1.9 K / 70 mbar. MC(Cernox)/Sorb = 3.42/4.0 K, G1 (fridge) = 442 mbar |
| | OK this isn't interesting. Let's stop the 1K Pot |
| 1640 | Close 1K Pot needle valve. 1K Pot → 3.2 K / 4.5 mbar. Fridge pressure and MC temperature rise a bit. |
| 1645 | Close 1K Pot speedivalve and V4a, switch 4He pump outlet to Exhaust and close corresponding recovery valve, turn off 4He pump |
| 1645 | IVC = 25 μbar. |
| 1645 | MC(Cernox) rises suddenly to 4.1 K |
| 1645 | H35/Cernox/Tower = 5.07/4.15/4.05 K |
| 1655 | Insert LN2 fill stick for a few seconds then remove, to boil off some bath. IVC pressure falls, 25→16 μbar. We saw this before: the cool gas rising flowing out of the bath must cool down the upper parts of the IVC. |
| 1705 | Isolate IVC and switch pumping line over to Cryostat Vacuum Jacket, pump out line |
| 1710 | Recovery = 14 cuft/hr |
| 1710 | Let 4.6 mbar He gas into vacuum manifold. Then open cryostat vacuum jacket valve to let this into the vacuum jacket. Vacuum Jacket → 0.074 mbar. |
| 1710 | MB = 28.7% |
| 1715 | Recovery = 279 cuft/hr. MB = 25.5% |
| 1715 | MC(Cernox)/Sorb/1K Pot = 4.34/6.2/4.94 K, G1 (fridge) = 528 mbar |
| 1720 | Recovery = 279 cuft/hr. MB = 25.5% |
| 1720 | Recovery = 309 cuft/hr. MB = 23.0% |
| 1720 | Vacuum Jacket = 0.025 mbar. |
| 1725 | Isolate CVJ then move pumping line over to IVC port, pump out line. Open IVC to pump manifold |
| 1725 | IVC = 7.4 μbar. |
| 1730 | Recovery = 432717.5 cuft / 261 cuft/hr. MB = 18.0% |
| 1730 | IVC = 7.4 μbar. Start pumping IVC with Turbo Pump |
| 1735 | MC(Cernox)/Sorb/1K Pot = 4.34/6.2/4.95 K, G1 (fridge) = 512 mbar |
| 1740 | Recovery = 239 cuft/hr. MB = 14.9% |
| 1740 | Turbo on IVC = 40 nbar after 10 minutes pumping. With Turbo valved out for 1 minute, IVC = 1.0 μbar. |
| | This is a pretty big differences, as if the leak is gone now. Though the bath is still much higher than when the leak originally shows up… a tad confusing. |
| 1745 | MC(Cernox)/Sorb/1K Pot = 4.34/6.2/4.98 K, G1 (fridge) = 501 mbar |
| 1750 | IVC = 0.86 μbar. |
| 1750 | MB = 11.4% |
| 1750 | Matt exits lab |
| 1752 | Recovery = 432800 cuft / 207 cuft/hr. Forgot to turn on the light so this is the last reading. |
| 1930 | MC(Cernox)/Sorb/1K Pot = 4.91/8.1/6.36 K, G1 (fridge) = 512 mbar |
| 1930 | IVC = 1.6 μbar. |