2019/05/15 (Wednesday)
| Status | LN2 transfer yesterday, 4th attempt. |
|---|---|
| Setup | DIB1/3/4 → 3.2 MHz filters 2/3/1 → cable 3/1/2 |
| Mixture has been open to cold LN2 Traps 1 and 2 overnight | |
| 0805 | Pump mixture out of Traps 1 and 2 to dump. After pumping them out, take them out of the bath to warm up. Removed 5.8 mbar from Trap 1 Removed 2.1 mbar from Trap 2 Along with the G1/G2 behavior during cleanings, this is good evidence that Trap 2 is not as efficient at cleaning as Trap 1. |
| 0810 | MC(Cernox) = 77.4 K, Sorb = 132.3 K, IVC = 1.4 mbar, Level resistor = 1.209 kΩ. DIB4 pD SQUID = 3.01 kΩ. |
| 0810 | Begin pumping out IVC with scroll pump. After a couple of minutes switch to turbo pump. |
| 0930 | LN2 Trap 1 is mostly warm. Check contents: 5.8-0.0 = 5.8 mbar on G1. Pump out with scroll pump. |
| 0945 | LN2 Trap 2 is mostly warm. Check contents: 2.1-0.0 = 2.1 mbar on G1. Pump out with scroll pump. |
| 0955 | Let mixture into cold LN2 Trap 1 through V13a. (V9 also open, 3He pump is on.) Open Still Gate Valve to monitor Still pressure on P1. P1 falls slightly, 0.019→0.018 mbar. Open V1 (LHe trap) - G1 goes up maybe 0.1 mbar. Open Condenser speedivalve, G1 either flat or slight increase. |
| 1000 | Open speedivalve for V12a. Even with V12a closed, G1 rises quickly. No increase seen on P1, which is troubling. This is a mini- throughput test. |
| 1005 | Pump mixture out of condenser and into the dump and LN2 Trap 1 using V5. |
| Throughput test procedure, Cold Trap 1: | |
| 1030 | Begin blowing out LN2. Main bath (G3) = 430 mbar above 1atm. |
- 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
| 1010 | 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 31 mbar, doesn't rise, or just barely. Throughput ~ 0.02 mbar/min. Worse even than last time. Compare Run 68 where we got 35.7 mbar/min. |
|---|---|
| another blockage | |
| 1030 | Begin blowing out LN2. Main bath (G3) = 413 mbar above 1atm. |
| 1040 | 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. G1(condenser) decreases but very slowly, 0.23 mbar/min. compare 33 mbar/min in Run 69. After 7 minutes, G1(Condenser starts rising for some reason. Maybe a temperature increase from the LN2 blowout? |
| 1055 | Main bath (G3) has fallen to 145 mbar +1atm and flat. Looks like LN2 blowout is finished. Stop pressurizing main bath. |
| 1120 | Start pumping out main bath with scroll pump. Takes 13 minutes to fall to 1 mbar. |
| G1 pressure falls a little, so the variations in the Condenser pressure probably have to do with temperature changes. | |
| 1125 | Pump mixture out of both sides of fridge to dump and Trap 1 |
| 1145 | Pressurize MB with helium to 210 mbar above 1 atm. (SKIP THIS: 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.) |
| 1315 | Turbo on IVC: 1.6 nbar. Stop pumping out IVC. IVC → 63 nbar after a few minutes. |
| 1320 | Perform mixture throughput test at MC = 77 K using the same procedure as 10:10 with 3He pump on. Let G1 rise to 560 mbar before Step 3, then it falls to 31 mbar, doesn't rise. Throughput <0.01 mbar/min. |
| We'll leave this sit as we start to warm up, maybe we can catch when it starts to rise. | |
| 1330 | Let about 0.6 bar nitrogen into IVC. (This is too much, wasn't paying attention.) MC and Sorb temperatures rise. |
| 1350 | MC(Cernox)/Sorb = 79.4/152.8 K. G1(condenser) = 31.3 mbar, flat. |
| 1355 | IVC pressure is too high, so pump it down lower with scroll pump, down to 0.18 bar on mechanical gauge, 0.14 bar on Pfeiffer gauge. |
| 1405 | Connect vacuum hoses to cryostat vacuum jacket and pump them out. |
| 1415 | Let 160 mbar on digital gauge, about 0.27 bar on mechanical gauge, N2 gas into vacuum manifold. Then open cryostat vacuum jacket valve to let this into the vacuum jacket. Vacuum jacket → 8.6 mbar. |
| 1420 | MC(Cernox)/Sorb = 80.8/159.4 K. G1(condenser) = 31.4 mbar, flat. Since beginning of throughput test an hour ago, throughput < 0.003 mbar/min. |
| 1425 | Main bath = 445 mbar +1atm. Let the pressure out. Cover port with plastic cap weighted with KF o-ring. |
| 1530 | MC(Cernox)/Sorb = 88.8/199.7 K. G1(condenser) = 32.6 mbar, going up slightly probably just from the temperature increase. |
| 1700 | MC(Cernox)/Sorb = 105.4/246.0 K. G1(condenser) = 33.1 mbar, pretty flat. |