2019/05/08 (Wednesday)
| Status | Cooling to 77K overnight. Third attempt after two fridge impedance blockages. |
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| Setup | DIB1/3/4 → 3.2 MHz filters 2/3/1 → cable 3/1/2 |
| 0905 | MC(Cernox) = 77.3 K, Sorb = 131.7 K, IVC = 1.4 mbar, G1 (fridge) = 622.1 mbar, Level resistor = 1.202 kΩ. DIB4 pD SQUID = 1.314 kΩ. |
| 0906 | Begin pumping out IVC with scroll pump. After a few minutes switch to turbo pump. |
| 0920 | Start leak detector with scroll pump as forepump instead of the internal pump. |
| 0935 | Quick electrical check of phonon-related channels and LEDs - looks good, no opens or leaks seen. |
| 0935 | Leak detector on IVC = 176 pbarL/s with turbo pumping, = 1200 pbarL/s with turbo valved out. Switch back to turbo only to pump on it further. |
| 1005 | Leak detector on IVC = 146 pbarL/s with turbo pumping, = 1000 pbarL/s with turbo valved out. Switch back to turbo only to pump on it further. |
| 1035 | Leak detector on IVC = 132 pbarL/s with turbo pumping, = 920 pbarL/s with turbo valved out. Switch back to turbo only to pump on it further. |
| 1100 | Leak detector on IVC = 120 pbarL/s with turbo pumping, = 860 pbarL/s with turbo valved out. |
| 1110 | Begin blowing out LN2. Main bath (G3) = 413 mbar above 1atm. |
| 1115 | Main bath (G3) = 428 mbar +1atm, IVC = 843 pbarL/s. |
| 1125 | Main bath (G3) = 414 mbar +1atm, IVC = 812 pbarL/s. |
| 1130 | Main bath (G3) = 280 mbar +1atm and falling, IVC = 797 pbarL/s. |
| 1135 | Main bath (G3) = 135 mbar +1atm and flat, IVC = 777 pbarL/s. I think we're done. Stop pressurizing main bath. |
| 1140 | Stop leak detector because we need to disconnect the scroll pump to pump out the main bath. |
| 1142 | Start pumping out main bath with scroll pump. Takes 10 minutes to fall to 1 mbar. |
| 1150 | Fill LN2 cold trap bath |
| 1155 | Pressurize MB with helium to 310 mbar above 1 atm. Open 1K Pot speedivalve and needle valve (2 full turns) to repressurize pot as well. No noticeable drop in pressure when I do this. Close 1K Pot valves again. |
| 1200 | Pump mixture out of both sides of fridge into dump and Cold Trap 1, in preparation for throughput test. |
| 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
| 1205 | Perform mixture throughput test at MC = 77 K using above procedure with 3He pump on. Let G1 rise to 560 mbar before Step 3, then it falls to 32 mbar, barely rises. Throughput ~ 0.05 mbar/min. Worse even than last time. Compare Run 68 where we got 35.7 mbar/min. |
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| another blockage. this is getting tedious. | |
| 1210 | Turbo on IVC: 1.4 nbar. Stop pumping out IVC. IVC → 14 nbar after a few minutes. |
| 1225 | Let about 0.18 bar nitrogen into IVC. MC temperature rises, 77.4→77.7 K and climbing. Close off IVC. |
| 1225 | Let mixture into both sides of fridge. G1(condenser) settles. Try forward throughput test - close V3 to isolate the condenser from the still, then pump on the still with V6 open to 12.8%. After a few minutes P1(still) falls. But G1(condenser) stays flat. |
| 1235 | Pump mixture from fridge to dump. |
| 1235 | Connect vacuum hoses to cryostat vacuum jacket and pump them out. |
| 1240 | MC(Cernox)/Sorb = 78.0/141.7 K and rising |
| 1240 | Let 220 mbar (on digital gauge) N2 gas into vacuum manifold. Then open cryostat vacuum jacket valve to let this into the vacuum jacket. Vacuum jacket → 19 mbar. (That's higher than before - what did I do differently? Must not have been 200 mbar in the vacuum manifold last time. |
| 1250 | Isolate fridge and LHe cold trap, then pump Cold Trap 1 to dump. 2 days later, removed 8.5 mbar from this trap. |
| 1325 | Main bath = 860 mbar +1atm. Let the pressure out. Cover port with plastic cap weighted with KF o-ring. |
| 1325 | MC(Cernox)/Sorb = 81.9/173.8 K and rising |
| 1545 | MC(Cernox)/Sorb = 108.7/>249 K (max) and rising |
| 1635 | MC(Cernox)/Sorb = 118.3/>249 K (max) and rising |
| 1636 | Put cold trap 2 in LN2 bath and top off LN2 bath. |
| Throughput test procedure, Cold Trap 2: |
- All mixture in dump, LN2 trap 2 cold, condenser & still valves open (3He pump on - optional)
- Open V9, V13b, V12b+speedivalve, V3. Wait for G1 to be close to G2.
- Close V12b+speedivalve and V3, open V1
- monitor G1
| 1645 | Perform mixture throughput test at MC = 120 K using above procedure with 3He pump on. Let G1 rise to 573 mbar before Step 3, then it falls to 34 mbar, doesn't rise. Throughput < 0.1 mbar/min. Still blocked. |
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| 1652 | Pump mix out of fridge to dump. |
| 1706 | Isolate fridge and LHe trap by closing Still gate valve, Condenser speedivalve, and V1. |
| 1708 | Pump mix from LN2 trap 2 to dump. 2 days later, removed more than 2.5 mbar from this trap |