2019/05/19 (Sunday)
| Status: | Transferred LN2 yesterday |
|---|---|
| 1136 | MC(Cernox) = 77.3 K, Sorb = 132.7 K, IVC = 1.9 mbar, G1 (fridge) = 619 mbar, Level resistor removed last night, DIB4 pD SQUID = 1.366 kΩ |
| 1145 | Begin pumping exchange gas out of IVC with scroll pump, then with turbo. |
| 1148 | Going to skip leak checking the IVC this time since we've checked it a few times and the leak detector isn't working. |
| 1200 | Start blowing out LN2. Adjust He gas cylinder regulator to bring G3 below 350 mbar. |
| 1202 | Main bath (G3) = 288 mbar +1atm |
| 1205 | Main bath (G3) = 255 mbar +1atm |
| 1210 | Main bath (G3) = 233 mbar +1atm |
| 1212 | Quick electrical check, looks good. |
| 1220 | Main bath (G3) = 225 mbar +1atm, no more LN2 coming out of the hose, so I think we're done. Stop pressurizing main bath. |
| 1223 | Wait, no liquid has been blown out into the bomb dewar. Is the transfer stick not low enough or what? at this point the transfer stick and tubing are frozen in place, so we need to wait for them to warm up to try and either pump out or retry the blowout. |
| 1230 | While we wait, top off the LN2 cold trap using the Main LN2 dewar and another hose. This only fills the LN2 trap part way before the main LN2 dewar runs dry. |
| 1235 | Pump mixture out of both sides of fridge into dump and Cold Trap 1, in preparation for throughput test. |
| 1238 | There is still some pressure in the main bath and cold LN2 gas is coming out so the tube is still frozen. Actually, maybe I just wan't aggressive enough when pressurizing to get the flow started. Let's try starting the blowout again with slightly higher G3 pressure. |
| 1242 | Start blowing out LN2. Adjust He gas cylinder regulator to bring G3 to around 350 mbar. It sounds like there's some liquid going into the dewar now. |
| 1245 | Main bath (G3) = 382 mbar +1atm |
| 1246 | G1/P1 = 1.6/ 1.6 mbar. let's do the throughput test. |
| 1248 | Main bath (G3) = 384 mbar +1atm |
| 1249 | Main bath (G3) = 360 mbar +1atm, pressure is dropping and it just sounds like gas coming out the blowout tube. |
| Throughput test procedure, Cold Trap 1: |
- All mixture in dump, LN2 trap 1 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
| 1250 | Perform mixture throughput test at MC = 77 K using above procedure with 3He pump on. Let G1 rise to 577 mbar before Step 3, then it falls to 83 mbar, barely rises. Throughput ~ 42.5 mbar/min. Compare Run 68 where we got 35.7 mbar/min. [image not archived: cool.svg] |
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| 1255 | Stop throughput check and leave dump open to both sides of fridge via cold trap 1 by opening V3 and V12A + speedivalve. |
| 1256 | Main bath (G3) = 146 mbar +1atm. Stop LN2 blowout. |
| 1308 | Start pumping out main bath with scroll pump. Takes 15 minutes to fall to 1 mbar. |
| 1330 | Pressurize MB with helium to 122 mbar above 1 atm. Open 1K Pot speedivalve and needle valve (2 full turns) to repressurize pot as well. Notice MB pressure falls about 3 mbar. Close 1K Pot valves again. |
| 1335 | Let 46 μbar He exchange gas into IVC. |
| 1345 | Commence initial LHe transfer. |
| 1347 | MC(Cernox) = 77.3 K, Sorb = 136 K, IVC = 40 μbar, G1(fridge) = 609.7 mbar. G3(MB) = 673 mbar. |
| 1400 | MC(Cernox) = 77.2 K, Sorb = 132 K, IVC = 19 μbar, G1(fridge) = 599.6 mbar. G3(MB) = 225 mbar. |
| 1401 | Turn on LHe dewar heater to 4PSIg |
| 1415 | MC(Cernox) = 76.8 K, Sorb = 116 K, IVC = 86 nbar, G1(fridge) = 532.1 mbar. G3(MB) = 419 mbar. What? Why is the IVC pressure so low? |
| 1435 | MC(Cernox) = 75.7 K, Sorb = 99.6 K, IVC = 74 nbar, G1(fridge) = 482.3 mbar. G3(MB) = 388 mbar. MB = 41.3% |
| 1445 | MC(Cernox) = 75.1 K, Sorb = 91.6 K, IVC = 74 nbar, G1(fridge) = 477.6 mbar. G3(MB) = 372 mbar. MB = 56.7% |
| 1500 | MC(Cernox) = 73.8 K, Sorb = 78.2 K, IVC = 63 nbar, G1(fridge) = 470.8 mbar. G3(MB) = 360 mbar. MB = 85.2% |
| 1501 | It's clear things are cooling much slower than normal. Compare to 20190306 where we were around MC/sorb = 47.5/7.4 K at this point. |
| 1502 | MB = 89.5%, turn off LHe dewar heater. |
| 1510 | Cease LHe transfer. MB = 88.2% |
| 1515 | Okay, so it seems there is not enough exchange gas in the IVC since cooling is suuuper slow. Probably the IVC gauge is messed up and we didn't add enough initially? At any rate, we'll have to try to add it now, which is a little dicey. |
| 1520 | Close valve connecting pump manifold to IVC lines. Then let in just 4.6 ubar of He into the pump manifold. |
| 1525 | MC(Cernox) = 71.9 K, Sorb = 58.1 K, |
| 1526 | Slowly open valve to connect pump manifold to IVC. No real change in cooling or recovery rate. IVC pressure falls to 74 nbar. |
| 1530 | Close valve connecting pump manifold to IVC lines. Then let in just 12 ubar of He into the pump manifold. Then open that to the IVC. IVC pressure falls to 86 nbar. |
| 1535 | Close valve connecting pump manifold to IVC lines. Then let in just 19 ubar of He into the pump manifold. Then open that to the IVC. IVC pressure falls to 74 nbar. |
| 1543 | Close valve connecting pump manifold to IVC lines. Then let in just 190 ubar of He into the pump manifold. Then open that to the IVC. IVC pressure falls to 0.14 ubar. |
| 1545 | Fill LN2 cold trap full. |
| 1543 | Close valve connecting pump manifold to IVC lines. Then let in just 400 ubar of He into the pump manifold. Then open that to the IVC. IVC pressure falls to 0.46 ubar. |
| 1556 | Just noticed that the Sorb is 14 K |
| 1600 | MC(Cernox) = 66.3 K, Sorb = 11.2 K, IVC = 0.34 ubar, G1(fridge) = 487 mbar. G3(MB) = 197 mbar. MB = 77.9% |
| 1605 | Close valve connecting pump manifold to IVC lines. Then let in just 860 ubar of He into the pump manifold. Then open that to the IVC. IVC pressure falls to 1.9 ubar. |
| 1610 | MC(Cernox) = 62.0 K, Sorb = 8.1 K, IVC = 1.6 ubar, G1(fridge) = 482 mbar. G3(MB) = 197 mbar. MB = 74.7% Looks like we've got a substantially faster cooling rate of 0.5 K/min now, should hit 10 K around 6 PM. |
| 1630 | MC(Cernox) = 51.9 K, Sorb = 7.3 K, IVC = 1.4 ubar, G1(fridge) = 484 mbar. G3(MB) = 173 mbar. |
| 1635 | Okay, my bus only comes every hour, let's speed this up a little more to be sure it's ready to pump out by 1800. Close valve connecting pump manifold to IVC lines. Then let in just 340 ubar of He into the pump manifold. Then open that to the IVC. IVC pressure falls to 6.3 ubar. |
| 1644 | Cooling rate didn't change much. |
| 1645 | Close valve connecting pump manifold to IVC lines. Then let in just 740 ubar of He into the pump manifold. Then open that to the IVC. IVC pressure falls to 8.6 ubar. |
| 1646 | MC(Cernox) = 44.6 K, Sorb = 7.2 K, IVC = 8.6 ubar, G1(fridge) = 483 mbar. G3(MB) = 172 mbar. |
| 1652 | Close valve connecting pump manifold to IVC lines. Then let in just 540 ubar of He into the pump manifold. Then open that to the IVC. IVC pressure falls to 10 ubar. |
| 1655 | MC(Cernox) = 39.2 K, Sorb = 7.0 K, IVC = 10 ubar, G1(fridge) = 482 mbar. G3(MB) = 168 mbar. |
| 1700 | MC(Cernox) = 36.7 K, Sorb = 6.8 K, IVC = 8.6 ubar, G1(fridge) = 483 mbar. G3(MB) = 163 mbar. Estimate that MC will hit 10 K around 1745 now. |
| 1717 | MC(Cernox) = 27.7 K, Sorb = 6.4 K, IVC = 8.6 ubar, G1(fridge) = 492 mbar. G3(MB) = 150 mbar. Estimate that MC will hit 10 K around 1750. |
| 1730 | MC(Cernox) = 22.5 K, Sorb = 6.1 K, IVC = 7.4 ubar, G1(fridge) = 494 mbar. G3(MB) = 142 mbar. Estimate that MC will hit 10 K around 1753. These were all linear estimates, but Newton and his Law of Cooling might screw me here… Let's give it one more bump. |
| 1740 | Close valve connecting pump manifold to IVC lines. Then let in just 540 ubar of He into the pump manifold. Then open that to the IVC. IVC pressure falls to 8.6 ubar. |
| 1742 | Close valve connecting pump manifold to IVC lines. Then let in just 740 ubar of He into the pump manifold. Then open that to the IVC. IVC pressure falls to 10 ubar. |
| 1750 | MC(Cernox) = 17.3 K, Sorb = 5.9 K, IVC = 10 ubar, G1(fridge) = 501 mbar. G3(MB) = 135 mbar. |
| 1757 | Increase resistance range on LakeShore bridge |
| 1800 | MC(Cernox) = 13.7 K, Sorb = 5.7 K, IVC = 8.6 ubar, G1(fridge) = 504 mbar. G3(MB) = 129 mbar. MB=53.8% (this is quite low already, this must be an inefficient way to cool) Note from Matt: maybe not. It takes a certain amount of LHe to cool the guts of the fridge, and you did an entire transfer without even starting to cool the guts of the fridge. Once you finally established a thermal connection, you got the rest of the boiloff. You could compare how much LHe you removed from the Dewar to a normal initial transfer - could be it's significantly less. |
| 1808 | MC(Cernox) = 9.7 K, Sorb = 5.5 K, start pumping out IVC with turbo pump. |
| 1935 | MC(Cernox) = 9.6 K, Sorb = 6.6 K, G1(fridge) = 537 mbar. |