2018/05/24 (Thursday)
| Status: LN2 transfer yesterday. Some mixture in fridge and LN2 Trap 1, some left isolated in dump. | |
| 0900 | MC(Cernox) = 77.3 K |
| 0915 | Fill LN2 cold trap full |
| 0918 | MC(Cernox)/Sorb = 77.3/121.8 K, IVC = 1.6 mbar, G1 (fridge) = 200 mbar |
| 0945 | Start pumping out IVC with scroll then turbo pump |
| 0950 | Turn off MC and Still heaters. Inadvertently had left them on since the warmup |
| 0955 | Try Mini-throughput check: close off Trap 1 and V3. Only V1, V9, condenser speedivalve, still gate valve open. Turn on 3He pump, then open V6 to 12.8%. This pumps mix out of the still side and we can see if the pressure goes down on the condenser side. G1 (condenser) starts out at 200 mbar, then falls steadily at 5.67 mbar/min. Similar to May 4 |
| 1015 | Complete electrical check. Things look good as before except some QETs to ground are ~1.5 nS. There is no pattern related to detector side/channels. Possibly related to high humidity (41% measured in lab). |
| 1155 | IVC leak = 107 pbarL/s |
| 1200 | Begin blowing out LN2 |
| 1205 | IVC leak = 105 pbarL/s, Main bath = 467 mbar above 1 atm |
| 1220 | IVC leak = 99 pbarL/s, Main bath = 447 mbar above 1 atm |
| 1230 | IVC leak = 95 pbarL/s, Main bath = 440 mbar above 1 atm |
| 1240 | IVC leak = 91 pbarL/s, Main bath = 437 mbar above 1 atm |
| 1255 | IVC leak = 87 pbarL/s, Main bath = 420 mbar above 1 atm, starting to fall |
| 1300 | IVC leak = 107 pbarL/s, Main bath = 172 mbar above 1 atm and falling |
| 1303 | IVC leak = 107 pbarL/s, Main bath = 160 mbar above 1 atm, flattening out |
| 1305 | Stop pressurizing main bath |
| Throughput test procedure, Cold Trap 1: |
- All mixture in dump, LN2 traps cold, condenser & still valves open (3He pump on - optional)
- Open V9, V13a, V12a+speedivalve, V3. Wait for G1 to be close to G2.
- Close V12a+speedivalve and V3, open V1
- monitor G1
| 1310 | Perform mixture throughput test at MC = 77 K using above procedure with 3He pump on. Let G1 rise to 228 mbar before Step 3, then it falls to 21 mbar and starts to rise. Throughput = 7.4 mbar/min. Something strange here, looks like not all the mixture was in the dump. Had left some in Trap 1 but that shouldn't really matter. |
|---|---|
| 1315 | IVC leak = 320 pbarL/s. It has risen some but it is low compared to typical IVC leaks. Probably just helium going in at the top of the fridge. |
| 1320 | Pump out main bath with scroll pump. Falls below 1 mbar in about 10 minutes |
| 1325 | IVC leak = 150 pbarL/s |
| 1325 | Pump mixture from fridge to dump, then from LN2 Trap 1 to dump. Dump pressure rises to 708 mbar and was still on its way up, so I guess we aren't missing any mixture. Let's do the throughput test again. |
| 1330 | Perform another mixture throughput test at MC = 77 K using above procedure with 3He pump on. Let G1 rise to 228 mbar before Step 3, then it falls to 20 mbar and starts to rise. Throughput = 7.6 mbar/min. |
| Still don't understand why these pressures are so much lower than normal e.g. May 15. What am I doing differently? | |
| 1340 | IVC leak = 87 pbarL/s |
| 1340 | Check pressure in 1K Pot: 150 mbar on P2. Pump out with scroll pump. |
| 1345 | 1K Pot pumps down to 0.080 mbar. Open needle valve 5 full rotations to pump it out too. Pot pressure does not change at all. This is a little concerning because the bath pressure is around 0.22 mbar, so I may have thought some gas would leak in through the needle valve. Maybe not enough to notice. |
| 1355 | Pressurize MB with helium to 180 mbar above 1 atm. |
| 1400 | Check 1K Pot pressure; 15.0 mbar. Rose slowly, 1 mbar/5 sec. Open needle valve 30 degrees, no change in rate. Open one full rotation, pressure rises more quickly - rises to 60 mbar / 5 sec then quickly rises offscale. |
| 1410 | Let some of the helium from the main bath into the 1K Pot. Pot/MB pressure = 135 mbar above 1 atm. |
| 1410 | IVC leak = 295 pbarL/s |
| 1415 | Let 63 μbar He exchange gas into IVC. |
| 1420 | Open mixture from dump to cold LN2 Trap 1 to both sides of fridge. Turn off 3He pump. Fridge pressure(G1) reads 216 mbar. Why is this so much lower than usual, e.g. May 15 when it was 596 mbar? Very confused here. |
| 1430 | investigating. Pump mixture out of Trap 1 to dump (fridge isolated). Dump pressure reaches 650 mbar. |
| Figured it out! Nick closed the manual valves on the dump! The dump has been isolated all day. He did it when he pumped out the main bath so it was also isolated during LN2 transfer. | |
| Throughput test procedure, Cold Trap 1: |
- All mixture in dump, LN2 traps cold, condenser & still valves open (3He pump on)
- Open V9, V13b, V12b+speedivalve, V3. Wait for G1 to be close to G2.
- Close V12b+speedivalve and V3, open V1
- monitor G1
| 1501 | Perform mixture throughput test at MC = 77 K using above procedure with 3He pump on. Let G1 rise to 590 mbar before Step 3, then it falls to 88 mbar and starts to rise. Throughput = 46.6 mbar/min. |
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| 1507 | Turn off 3He pump. Leave dump open to both sides of fridge via cold trap 1. |
| 1510 | MC(Cernox) = 77.6 K, Sorb = 130.8 K, IVC = 63 μbar, G1(fridge) = 597 mbar. |
| 1528 | Begin initial LHe transfer |
| 1538 | MC(Cernox) = 77.7 K, Sorb = 129.8 K, IVC = 46 μbar, G1(fridge) = 594 mbar. |
| 1600 | MC(Cernox) = 64.1 K, Sorb = 78.7 K, IVC = 14 μbar, G1(fridge) = 563 mbar. |
| 1610 | MC(Cernox) = 58.5 K, Sorb = 48.6 K, IVC = 14 μbar, G1(fridge) = 518 mbar. |
| 1621 | MC(Cernox) = 52.8 K, Sorb = 9.0 K, IVC = 10 μbar, G1(fridge) = 470 mbar, MB=8.2% |
| 1631 | MC(Cernox) = 47.5 K, Sorb = 7.6 K, IVC = 10 μbar, G1(fridge) = 462 mbar, MB=13% |
| 1645 | MC(Cernox) = 38.2 K, Sorb = 7.1 K, IVC = 7.4 μbar, G1(fridge) = 456 mbar, MB=26.8% |
| 1705 | MC(Cernox) = 22.6 K, Sorb = 6.2 K, IVC = 6.3 μbar, G1(fridge) = 451 mbar, MB=48.7% |
| 1711 | MC(Cernox) = 9.6 K, start pumping with turbo pump. MB = 54.4% |
| 1722 | MC(Cernox)/1K pot = 4.45/4.56 K, Sorb = 5.8 K, IVC = 2.2 μbar(?? probably nbar), G1(fridge) = 437 mbar, MB=72.3% |
| 1730 | MC(Cernox)/1K pot = 4.39/4.55 K, Sorb = 5.8 K, IVC = 2.2 μbar(?? probably nbar), G1(fridge) = 436 mbar, MB=79.7% |
| 1733 | MC(Cernox)/1K pot = 4.32/4.57 K, Sorb = 5.8 K, IVC = 1.6 μbar(?? probably nbar), G1(fridge) = 435 mbar, MB=83.7% |
| 1742 | MC(Cernox)/1K pot = 4.33/4.66 K, Sorb = 5.9 K, IVC = 1.6 μbar(?? probably nbar), G1(fridge) = 433 mbar, MB=93.6% |
| 1746 | Cease LHe transfer (90.2%) |
| 1747 | MC(Cernox)/1K pot = 4.43/4.86 K, Sorb = 6.2 K, IVC = 4.0 μbar(?? probably nbar), G1(fridge) = 478 mbar, MB=90.2% |
| 1758 | Fill LN2 cold trap full |