| 1125 | Perform mixture throughput test at MC = 77 K using above procedure with 3He pump on. Let G1 rise to 550 mbar before Step 3, then it falls to 70 mbar, then rises. Throughput = 43.1 mbar/min. A little higher than last time, 2021 Apr 28 |
| 1130 | Open mixture to both sides of the fridge and cold LN2 Trap 1. |
| 1130 | Try Leak Detector on IVC, with Turbo still pumping in parallel. (We've been pumping out the helium for 2.5 hours.) LD = 358 pbarL/s. With Turbo valved out for a minute, LD → 1830 pbarL/s. Worse than last time, that's disconcerting. Open Turbo valve to continue pumping IVC. |
| 1200 | IVC = 1700 pbarL/s |
| 1200 | Begin blowing out LN2. Main bath (G3) → 569 mbar+1atm |
| 1205 | IVC = 2030 pbarL/s, MB = 579 mbar+1atm |
| 1215 | IVC = 1990 pbarL/s, MB = 562 mbar+1atm |
| 1225 | IVC = 1910 pbarL/s, MB = 219 mbar+1atm and falling. Close V1a for a second, G3 rises, proving we still have pressure in the feed. |
| 1230 | IVC = 1940 pbarL/s, MB = 191 mbar+1atm and flat |
| 1230 | Stop LN2 blowout |
| 1235 | Fill LN2 cold trap bath |
| 1235 | remove hose from MB LN2 fill pipe, remove fill pipe from cyostat and put stopper in port, for MB pumpout |
| 1240 | Start pumping out main bath with scroll pump. Takes 10 minutes to fall to 1 mbar. (Looks like it's a bit faster if you remove the LN2 fill pipe.) |
| 1240 | IVC = 1860 pbarL/s |
| 1250 | IVC = 1800 pbarL/s |
| 1250 | Pressurize MB with helium to 202 mbar above 1 atm. |
| 1250 | IVC = 1780 pbarL/s |
| 1255 | Isolate MB by closing V1a. Pump out line to the G3 volume with Scroll Pump. Isolate pump, then open 1K Pot speedivalve to check pressure: about 0.05 bar. Then pump out 1K Pot (needle valve closed) with Scroll Pump to 0.028 mbar on P2. Then close 1K Pot speedivalve and V4a. Open V1a again to monitor bath pressure. |
| 1305 | Let 63 μbar He exchange gas into IVC. |
| 1310 | Try to start LHe transfer, but I had a little trouble connecting and the o-ring froze up. So I disconnected the transfer line sections, removed the long one from the Dewar and I'm letting the ends warm up. |
| 1324 | Start LHe transfer |
| | a little worried that I got a little ice in the transfer tube. Dewar pressure is high, recovery meter is moving - that's good but not sure it's moving as fast as usual. OTOH we have the new valve in the hall with its smaller diameter, we may be dealing with higher pressures at the beginning of transfers from now on. |
| 1330 | Turn off 3He pump, we'll leave it off like last time. |
| 1335 | MC(Cernox)/Sorb = 77.1/138.5 K, IVC = 34 μbar, G1(fridge) = 607.4 mbar. G3(MB) = 465 mbar+1atm |
| 1345 | MC(Cernox)/Sorb = 69.4/114.9 K, IVC = 19 μbar, G1(fridge) = 596.7 mbar. G3(MB) = 430 mbar+1atm |
| 1350 | MC(Cernox)/Sorb = 65.6/98.1 K, IVC = 16 μbar, G1(fridge) = 586.3 mbar. G3(MB) = 403 mbar+1atm |
| 1355 | MC(Cernox)/Sorb = 62.5/83.6 K, IVC = 14 μbar, G1(fridge) = 575.2 mbar. G3(MB) = 425 mbar+1atm |
| 1400 | MC(Cernox)/Sorb = 59.3/68.7 K, IVC = 12 μbar, G1(fridge) = 546.4 mbar. G3(MB) = 1.9% / 471 mbar+1atm |
| 1402 | MC(Cernox)/Sorb = 58.0/62.1 K, IVC = 12 μbar, G3(MB) = 3.1% |
| 1405 | MC(Cernox)/Sorb = 56.1/51.6 K, IVC = 12 μbar, G1(fridge) = 530.5 mbar. G3(MB) = 2.2% / 505 mbar+1atm |
| 1410 | MC(Cernox)/Sorb = 52.6/25.4 K, IVC = 12 μbar, G1(fridge) = 503.3 mbar. G3(MB) = 5.5% / 488 mbar+1atm |
| 1415 | MC(Cernox)/Sorb/1K Pot = 49.4/7.7/6.5 K, IVC = 8.6 μbar, G1(fridge) = 480.1 mbar. G3(MB) = 7.5% / 463 mbar+1atm |
| | good! At close to this point in the last two cooldowns, IVC pressure started to rise. Fingers crossed that that won't happen this time… |
| 1420 | MC(Cernox)/Sorb/1K Pot = 47.0/7.2/5.8 K, IVC = 8.6 μbar, G1(fridge) = 476.6 mbar. G3(MB) = 6.9% / 451 mbar+1atm |
| | looks like if you check MB this often it kinda fluctuates. Either that or something is wrong with the transfer |
| 1424 | MC(Cernox)/Sorb/1K Pot = 44.6/6.9/5.8 K, IVC = 14 μbar, G3(MB) = 8.6% |
| | IVC PRESSURE IS RISING AGAIN. sigh. |
| 1430 | MC(Cernox)/Sorb/1K Pot = 40.7/7.1/5.7 K, IVC = 34 μbar, G3(MB) = 12.6% |
| 1435 | MC(Cernox)/Sorb/1K Pot = 37.0/7.1/5.7 K, IVC = 54 μbar, G3(MB) = 18.6% |
| 1440 | MC(Cernox)/Sorb/1K Pot = 33.3/6.9/5.6 K, IVC = 74 μbar, G1(fridge) = 470.0 mbar. G3(MB) = 26.3% / 399 mbar+1atm |
| 1445 | MC(Cernox)/Sorb/1K Pot = 29.2/6.8/5.5 K, IVC = 100 μbar, G1(fridge) = 467.7 mbar. G3(MB) = 35.7% / 391 mbar+1atm |
| 1455 | MC(Cernox)/Sorb/1K Pot = 23.2/6.4/5.2 K, IVC = 120 μbar, G1(fridge) = 465.0 mbar. G3(MB) = 51.0% / 379 mbar+1atm |
| 1500 | MC(Cernox)/Sorb/1K Pot = 20.8/6.2/5.0 K, IVC = 120 μbar, G1(fridge) = 463.8 mbar. G3(MB) = 59.8% / 374 mbar+1atm |
| 1505 | MC(Cernox)/Sorb/1K Pot = 18.1/6.1/4.9 K, IVC = 120 μbar, G1(fridge) = 463.8 mbar. G3(MB) = 65.4% / 359 mbar+1atm |
| 1510 | End LHe transfer early @ MB = 59.9% |
| | Note: recommend letting a lot of pressure out of MB at end of transfer. I let pressure out of Dewar, but also removed the stopper from the second port, could see the pressure fall on the wall gauge. Then put the stopper back in, you need a wrench to hold it down. Much easier to put cap on transfer stick with the pressure low. |
| 1518 | MC(Cernox) = 5.86 K, IVC = 740 μbar, start pumping out IVC with Scroll Pump, a bit late. |
| 1520 | MC(Cernox)/Sorb/1K Pot = 4.41/5.4/4.34 K |
| 1525 | Scroll on IVC = 860 μbar. It's not going down. Oh well. |
| 1610 | Scroll on IVC = 300 μbar. Down a bit. Let's see if we can valve in the Turbo, gently. Nope - can get it down 1 click but then the Turbo shuts off, comes back on after I close the valve. |
| 1630 | Scroll on IVC = 160 μbar. Try again to valve in the Turbo, gently. It's working this time |
| 1645 | Turbo+Scroll on IVC = 25 μbar. Valve out Scroll, stays at 25 μbar. |
| 1715 | Turbo on IVC has crept up to 340 μbar and Turbo shut off. Valve out Turbo (which restarts) and pump IVC with Scroll |
| 1725 | Scroll on IVC = μbar. Stop pumping on IVC. |
| 1740 | IVC = 0.54 mbar. |
| 1740 | Matt exits lab |