2020/03/13 (Friday)
| Setup | Run 72. DIB 1/3/4 → Stripline 43/41/48 → Cable 3/2/1 → nothing/nothing/accessory_interposer → HV_Conn 1/3/2 → HV 1/2 → DCRCX(4)/DCRC55(1). DCRCs off overnight. Lead/poly shield erected (4 lead walls, 2 poly walls). |
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| Status | LN2 transfer yesterday. Second cooldown for Run 72. |
| 0935 | MC(Cernox) = 77.2 K, Sorb = 118.9 K, IVC = 2.2 mbar, G2/G1 = 531/586 mbar |
| 0940 | Turn on 3He pump and open V6 to 12.8%, reestablishing circulation like yesterday. G2/G1/P1 → 650/716/3.2 and settle. |
| 0945 | Close V12a speedivalve for 2 minutes to assess throughput. G1 falls at 63 mbar/min, good. |
| 0945 | Begin pumping out IVC with Scroll pump, then switch to Turbo pump when pressure falls below 0.1 mbar |
| 0950 | Pump mixture out of fridge and cold LN2 Trap 1 to dump. |
| Throughput test procedure, Cold Trap 1: |
- All mixture in dump, LN2 trap 2 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
| 0955 | Perform mixture throughput test at MC = 77 K using above procedure with 3He pump on. Let G1 rise to 520 mbar before Step 3, then it falls to 62 mbar, then rises. Throughput = 39.1 mbar/min. A little lower than last time, 2020 Feb 18 |
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| We will skip leak checking the IVC this time, presumably it is no more or less leaky than last time. | |
| 1005 | Begin blowing out LN2. Main bath (G3) = 629 mbar+1atm. |
| Helium cylinder pressure is very low, we'll need to swap it out before the blowout finishes. | |
| 1020 | MB (G3) has fallen to 430 mbar+1atm and doesn't go up much when you close V1a, looks like the cylinder is almost empty (gauge on regulator is on the peg). |
| 1025 | Switch helium cylinders. MB (G3) pops back up to 610 mbar+1atm |
| 1040 | MB (G3) starts to fall, looks like we've probably got all the LN2 out. |
| 1045 | Stop pressurizing MB |
| 1055 | Start pumping out main bath with scroll pump. Takes 10 minutes to fall to 1 mbar. |
| 1105 | Pressurize MB with helium to 262 mbar above 1 atm. |
| 1110 | Isolate MB by closing V1a. Then adjust the helium pressure at G3 to 180.3 mbar+1atm. Close V4a, then open 1K Pot speedivalve to check pressure: G3 falls to 170 mbar+1atm. Close to what it was last night. Close 1K Pot speedivalve again. |
| Let's modify procedure now, by pumping out the 1K Pot. The idea is that the helium we are using now is industrial grade, so not entirely clean. Pressurizing the Pot with helium at this stage will result in more frozen air in the Pot - if we pump it out now, a little dirty helium will leak in through the needle valve, but not much, and when we finally let in helium from the LHe bath it will of course be cleaner. | |
| 1120 | Pump out 1K Pot through speedivalve (needle valve closed) using Scroll pump. Then close 1K Pot speedivalve. Open V1a again to monitor bath pressure. |
| 1120 | Turbo on IVC = 22 nbar. With Turbo valve out for a couple minutes, IVC = 0.34 ubar |
| 1125 | Let 63 μbar He exchange gas into IVC. |
| 1133 | Open mixture to both sides of the fridge. |
| 1135 | Fill LN2 cold trap bath. |
| 1140 | MC(Cernox) = 77.3 K, Sorb = 126 K, IVC = 63 μbar, G1(fridge) = 598.5 mbar. G3(MB) = 244 mbar. |
| 1148 | Begin initial LHe transfer |
| 1150 | MC(Cernox) = 77.5 K, Sorb = 129 K, IVC = 63 μbar, G1(fridge) = 597.7 mbar. G3(MB) = 715 mbar. Bath pressure is a little too high, the 250L Dewar was more full than usual. We pushed the extender down farther than necessary. |
| 1200 | MC(Cernox) = 76.1 K, Sorb = 120 K, IVC = 25 μbar, G1(fridge) = 594.6 mbar. G3(MB) = 408 mbar. |
| Set Range on LakeShore bridge to 6.32 kΩ, so that Cernox thermometer readout doesn't peg. (2.0 kΩ is sufficient.) | |
| 1210 | MC(Cernox) = 66.7 K, Sorb = 87 K, IVC = 14 μbar, G1(fridge) = 565.8 mbar. G3(MB) = 494 mbar. |
| 1220 | MC(Cernox) = 61.3 K, Sorb = 60 K, IVC = ?(forgot to check) μbar, G1(fridge) = 523.4 mbar. G3(MB) = 472 mbar. MB = 7.0% |
| 1230 | MC(Cernox) = 55.8 K, Sorb = 19.6 K, IVC = 10 μbar, G1(fridge) = 471.7 mbar. G3(MB) = 471 mbar. MB = 21.6% |
| 1240 | MC(Cernox) = 50.9 K, Sorb = 7.4 K, 1K Pot = 6.0 K, IVC = 8.6 μbar, G1(fridge) = 461.5 mbar. G3(MB) = 448 mbar. MB = 41.2% |
| 1250 | MC(Cernox) = 45.3 K, Sorb = 7.2 K, 1K Pot = 5.8 K, IVC = 8.6 μbar, G1(fridge) = 456.6 mbar. G3(MB) = 436 mbar. MB = 61.1% |
| 1300 | MC(Cernox) = 40.3 K, Sorb = 7.0 K, 1K Pot = 5.71 K, IVC = 7.4 μbar, G1(fridge) = 453.6 mbar. G3(MB) = 421 mbar. MB = 81.8% |
| 1308 | End LHe transfer @ MB = 90.8% |
| 1315 | MC(Cernox) = 31.9 K, Sorb = 6.2 K, 1K Pot = 5.08 K, IVC = 7.4 μbar, G1(fridge) = 498.2 mbar. G3(MB) = 211 mbar. |
| 1355 | MC(Cernox) = 14.3 K, Sorb = 5.7 K, 1K Pot = 4.61 K, IVC = 4.0 μbar, G1(fridge) = 506.5 mbar. G3(MB) = 180 mbar. |
| 1414 | MC(Cernox) = 10.0 K, Sorb = 5.5 K, 1K Pot = 4.47 K, IVC = 3.0 μbar, G1(fridge) = 511.2 mbar. G3(MB) = 176 mbar. Start pumping out IVC with Turbo pump. |
| 1445 | MC(Cernox)/Sorb/1K Pot = 6.3/5.8/4.67 K |
| 1500 | MC(Cernox)/Sorb/1K Pot = 5.9/6.0/4.84 K |
| 1535 | MC(Cernox)/Sorb/1K Pot = 5.17/6.5/5.19 K |
| 1655 | MC(Cernox)/Sorb/1K Pot = 4.74/6.8/5.40 K |