2017/01/20 (Friday)
| Status: Second fridge blockage discovered yesterday, need to warm up. Currently LN2 in the bath. He gas in IVC. Small leak at top of stripline tube. Mixture is in dump, fridge evacuated. | |
| 0830 | MC(Cernox) = 77.5 K, Sorb = 131 K, IVC = 1.9 mbar. |
| 0840 | Begin pressurizing main bath with He gas to blow out LN2 |
| 0845 | G3 (bath pressure) begins to fall. Nearly finished already? |
| 0855 | G3 has fallen to 165 mbar overpressure, was at about 600 mbar originally. Stop blowout. |
| 0905 | Pump out main bath with scroll pump. After 7 minutes it falls below 1 mbar so it seems to be empty. |
| 0920 | Fill main bath with N2 gas |
| 1135 | Open Trap 2 (warm) to G1: pressure 148 mbar, pretty high after yesterday's cryocleaning. (Falls to 63 mbar after opening up to P2.) Pump out trap with scroll pump. |
| 1145 | Open Trap 1 (warm) to G1: pressure 176 mbar, even higher, surprising - this wasn't used for cryocleaning but rather just to let mixture through to the fridge. Pump out trap with scroll pump. |
| These high values may suggest that the blockages are occurring simply because the mixture got very dirty during the long Run 62. Will cryoclean more thoroughly now. Hopefully the amount of contamination removed will decrease in subsequent cleanings (if not then we'll have to assume something is leaky). | |
| 1310 | Put Traps 1 and 2 back in LN2 bath and fill bath. |
| 1315 | Begin cryocleaning mixture through LN2 Trap 2 |
Summary of trap contaminations (pressures measured at G1):
- TRAP 2:
- On Wednesday used to cryoclean for 110 minutes. 84 mbar removed
- On Thursday used to cryoclean for 230 minutes. 148 mbar removed
- TRAP 1:
- On Wednesday and Thursday use for a total of 4 throughput tests. 176 mbar removed.
These values are all high compared to a quick survey of cleanings from Run 50 and 59 (46 mbar, 12 mbar, 6 mbar etc)
| 1400 | Fridge temperature is creeping up MC(Cernox) = 87.5 K, Sorb = 160 K, IVC = 2.2 mbar. |
|---|---|
| 1405 | Let 2 hose-lengths of He gas into main bath vacuum jacket to speed warmup |
| 1505 | Stop cryocleaning. This is 110 minutes, just like on Wednesday. We'll see how much comes out this time. Pump mix to dump, remove Trap 2 from bath to warm up. |
| 1645 | MC(Cernox) = 132 K, Sorb ≥ 249 K (max), IVC = 4.0 mbar. |
| 1725 | Trap 2 open to G1, seems to be at room temperature: 20 mbar. Much better. Pump out with scroll pump. |