2018/03/03 (Saturday)
| Status: Warmed up after a blockage, also removed and reinstalled tower. Pumping IVC overnight. Helium in cryostat vacuum jacket from warmup. | |
| 0750 | IVC pumping pressure = 40 nbar, IVC = 1.6 ubar with pump valved out |
| Cryocleaning log | |||
|---|---|---|---|
| date | trap | duration (minutes) | contaminants removed (mbar) |
| Feb 27 | 2 | 55 | 13.5 |
| Feb 27 | 1 | 55 | 0.2 |
| Feb 28 | 2 | 140 | 4.5 |
| try to cool down, discover blockage | |||
| Mar 1 | 2 | 75 | 6.7 |
| Mar 2 | 2 | 115 | 4.6 |
| Mar 2 | 1 | 75 | 10.0 |
| Mar 3 | 2 | 83 | 2.8 |
| Mar 3 | 1 | 90 | 5.5 |
| 0800 | Put LN2 cold traps in bath and fill bath |
|---|---|
| 0810 | Close IVC valves at top of fridge, then connect pumping hose to cryostat vacuum jacket. |
| 0815 | Start pumping cryostat vacuum jacket with scroll pump. Had 4.6 mbar in it before pumping. |
| 0820 | Start cryocleaning mixture through LN2 Trap 2, V6 = 12.5% |
| 0830 | Switch to turbo pump to pump out cryostat vacuum jacket |
| 0830 | Increase V6 → 12.9% to reestablish flow |
| 0835 | Cryostat vacuum jacket pumping pressure = 0.86 ubar |
| 1003 | Stop cleaning through trap 2 and pump mixture to dump. |
| 1004 | Cryostat vacuum jacket pumping pressure = 0.19 ubar |
| 1038 | Remove LN2 Cold Trap 2 from bath to let warm up |
| 1045 | Start cryocleaning mixture through LN2 Trap 1, V6 = 13.0% |
| 1057 | Increase V6 → 13.2% to reestablish flow |
| 1215 | Stop cleaning through trap 1 and pump mixture to dump. |
| 1230 | Remove Trap 1 from LN2 bath to let warm up |
| 1235 | Check warm Trap 2: around 2.8 mbar. Pump this out with scroll pump. |
| 1250 | Cryostat vacuum jacket pumping pressure = 0.12 ubar. Pressure with pump valve out = 14 ubar |
| 1310 | Noticed that the LN2 Dewar is low. Took it to the fill station but have to wait for another Dewar being filled right now. |
| 1315 | Trap 1 is mostly warmed up (put it in a bucket of hot water to warm it faster). Remove from bucket and check the pressure: 7.8 mbar, but it's falling now, maybe it was a bit warmer than room temp, not sure - should wait for it to stabilize |
| 1355 | Trap 1 feels like room temperature, now the pressure reads 5.5 mbar. Pump out trap with scroll pump. |
| 1405 | Check pressure in 1K Pot: 28 mbar on P2. Pump out with scroll pump. |
| 1420 | LN2 Dewar is now full |
| 1430 | Check fridge pressures: about 0.025 mbar in LHe cold trap. No noticeable amount in Still or Condenser. Pump on fridge a few minutes with scroll pump. |
| 1435 | Cryostat vacuum jacket pumping pressure = 0.10 ubar. Pressure with pump valve out = 12 ubar |
| 1440 | Open fridge lines up to (cold) Trap 1. |
| 1440 | Let mixture from pump into fridge through Trap 1, leaving most mixture in the dump. 3He pump off, V13a, V12a+speedi, V3, V1, condenser & still valves all open |
| 1450 | Stop pumping on cryostat jacket. Reconnect pumping manifold to IVC pumping line. |
| 1500 | Pump out main bath |
| 1500 | Connect Leak Detector to IVC. Background = 14 pbarL/s. |
| 1505 | Pressurize main bath with He to 255 mbar above 1atm on G3. LD signal goes up slightly, to 30 pbarL/s. Tolerable. |
| 1510 | Let 5.4 mbar He exchange gas into IVC |
| 1515 | Begin LN2 transfer |
| 1515 | MC(Cernox) = 295.0 K, Sorb = >249 K (max), IVC = 5.4 mbar, G1 (fridge) = 218 mbar, Level resistor = 1.030 kΩ. |
| 1525 | MC(Cernox) = 293.0 K, Sorb = >249 K (max), IVC = 4.6 mbar, G1 (fridge) = 217 mbar, Level resistor = 1.084 kΩ. |
| 1530 | Mini-throughput check: close off Trap 1 and V3. Only V1, condenser speedivalve, still gate valve, and V9 open. Turn on 3He pump, then open V6 to 12.8%. This pumps mix out of the still side and we can see if the pressure goes down on the condenser side. G1 (condenser) started out at 217 mbar, then started falling at about 1.0 mbar/s. Restore GHS to previous state. |
| 1535 | MC(Cernox) = 280.5 K, Sorb = >249 K (max), IVC = 4.0 mbar, G1 (fridge) = 217 mbar, Level resistor = 1.153 kΩ. |
| 1545 | MC(Cernox) = 264.3 K, Sorb = >249 K (max), IVC = 3.4 mbar, G1 (fridge) = 216 mbar, Level resistor = 1.208 kΩ. |
| 1550 | Another mini-throughput check as before. G1 (condenser) starts out at 215 mbar, then falls at about 2.0 mbar/s. Good sign. We'll keep our fingers crossed. Restore GHS to previous state: most mixture in dump, some in fridge, both sides open to Cold Trap 1. |
| 1600 | MC(Cernox) = 222.6 K, Sorb = >249 K (max), IVC = 2.5 mbar, G1 (fridge) = 215 mbar, Level resistor = 1.339 kΩ. |
| 1615 | MC(Cernox) = 185.0 K, Sorb = 215.3 K, IVC = 2.2 mbar, G1 (fridge) = 213 mbar, Level resistor = 1.339 kΩ. |
| 1630 | MC(Cernox) = 162.5 K, Sorb = 174.0 K, IVC = 2.2 mbar, G1 (fridge) = 211.5 mbar, Level resistor = 1.339 kΩ. |
| 1634 | MC(Cernox) = 158.0 K, Sorb = 166.9 K, IVC = 2.2 mbar, G1 (fridge) = 214 mbar, Level resistor = 1.339 kΩ. |
| 1634 | Stop LN2 transfer |