2018/06/25 (Monday)
| overnight: Tower rose yesterday after LN2 transfer to about 86 mK, drifting down since then. G2 slowly rising, G1 plateaued (actually both are close to what they were when checked yesterday). | |
| 0825 | Tower/MC/Coldplate = 80.4/78.0/246 mK, Still = 1.28 K / 0.036 mbar / 0.3 mW, G1/G2 = 246/222 mbar, 1K Pot = 1.45 K / 3.8 mbar. MB = 36.5% |
| 1026 | Fill LN2 cold trap full |
| 1220 | Preparing to try adding some 4He to the mixture. Will use procedures from 2015 March 25, the last time that we added mixture. |
| 1225 | Switch to one-shot mode by closing V13a, opening V9, so that mixture is being pumped to dump |
| 1235 | During one-shot G2 (dump) fell to 157 mbar, then began rising, about 3mbar/min. Tower temperature holding steady so far. Still pressure fell a little, .036 → .032 mbar. |
| 1300 | Tower temperature has an uptick, 94→101 mK over a few minutes. G2 (dump) = 180 mbar and rising steady. G1 (condenser) 63 mK and falling. |
| 1320 | Begin filling HPGe dewar from large LN2 dewar. |
| 1400 | Tower = 165 mK and rising, G1(condenser) = 22mbar and falling, G2(dump) = 199 mbar and rising, Still = 0.022 mbar. |
| 1400 | Open V3 to pump directly from condenser + LN2 Trap 1 to dump (also pumping from still to dump) |
| 1410 | G1/P1 = 2.0/0.75 mbar and flattening. Close Condenser speedivalve and Still gate valve, leaving some mix in the fridge. Tower = 179 mbar, rising slowly. 1K pot stable. |
| 1415 | G1/P1 = 2.7/0.24 mbar as we continue to pump out LN2 Trap 1. Tower has risen to 210 mK. |
| 1420 | Check pressure in manifold and vent by opening V7 and V2 (all other valves to G1 closed). Several mbar. Close V4a, temporarily not pumping pot, then open V5a and V2a to pump out manifold and vent with 4He pump. |
| 1420 | Start pumping 1K Pot again. Pot rose to 2.1 K, now falling back to 1.4 K. Tower = 275 mK. |
| 1425 | Open V12B+speedi and V11B. This opens LN2 Trap 2 to G1 and to manifold. |
| 1430 | Let He into vent through wall valve and vent speedivalve. Close wall valve, then pump out with 4He pump through V2a, V5a (close V4a temporarily). Repeat this to flush hose again, then leave wall valve and vent speedivalve open. |
| 1435 | G1 (Trap 2) = 0.6 mbar. G2 (dump) = 203.3 mbar |
| 1435 | Open V7 for 0.5 sec or so, letting He into Trap 2. G1 (Trap 2) → 229.2 mbar. According to notes from 2015, this should correspond to a 13.7 mbar increase in dump pressure when we pump it to the dump. |
| 1440 | Open V5 to pump from Trap 2 to dump. |
| 1455 | G1 (Trap 2) = 0.7 mbar. G2 (dump) = 217.0 mbar. So we've added 13.7 mbar of 4He to mixture. |
| 1510 | Attempt transfer with new method - use extender on storage-Dewar side from old transfer tube so that we can lower that end into the LHe then immediately lower the other end into the cryostat, but just barely in at the beginning, so that warm gas is not being blown into the bath itself. Then the idea is to lower it after we are convinced that liquid is flowing. Failed to make it work - pressure was very high, and extender on cryostat side is not vacuum jacketed so it got cold and o-ring froze to it, couldn't lower the cryostat side. Aborted to let the transfer tube warm up. |
| 1520 | Begin cryocleaning mixture through cold LN2 Trap 2, V6 = 13.1%. After 10 min increase V6→13.2% to restart flow. After another 10 min increase V6→13.3% to speed up flow. |
| 1535 | Tower = 417 mK, 1K Pot = 1.48 K |
| 1556 | Begin LHe transfer @ MB = 27.2% |
| 1600 | Stop cryocleaning mixture, pump back to dump |
| 1615 | Begin cryocleaning mixture through cold LN2 Trap 1, V6 = 13.2%. After 5 min increase V6→13.3% to speed up flow. After another 5 min increase V6→13.4% to speed up flow. After another 5 min increase V6→13.5% to speed up flow. |
| 1700 | Stop cryocleaning mixture. Pump mixture to dump. |
| 1700 | Tower = 603 mK, 1K Pot = 1.42 K |
| 1715 | End LHe transfer @ MB = 92.9% |
| 1725 | Let mixture from dump into condenser through LN2 Trap 1. |
| 1730 | Open Still gate valve and V3, letting mixture into both sides of fridge. This caused Tower to spike up to 3 K. |
| 1735 | G1 = 90 mbar and rising, G2 = 107 mbar and falling, coming to equilibrium |
| 1735 | Close V9 leaving 103 mbar in dump |
| 1735 | Start circulation through Trap 1. V6 → 12.8%. Condenser peaks at 240 mbar. |
| 1740 | V6 → 13.2%. Condenser peaks at 285 mbar. Tower → 2.16 K. |
| 1750 | V6 → 13.5%. Condenser peaks at 460 mbar. Tower → 1.62 K. Still → 34 mbar. 1K Pot spikes to 1.6K/30mbar as He reaches lambda point |
| 1800 | V6 → 13.8%. Condenser peaks at 490 mbar. Tower → 1.44 K. Still → 5.0 mbar. |
| 1805 | V6 → 14.2%. Condenser peaks at 500 mbar. Tower → 1.25 K. Still → 1.1 mbar. |
| 1810 | V6 → 15.0%. Condenser falling. Tower → 1.11 K. Still → 0.28 mbar. |
| 1815 | Still power had been left on, turn it off now. |
| 1815 | V6 → 100%. Condenser → 460 mbar. Tower → 1.09 K. Still → 0.055 mbar. |
| 1820 | Open V14 to let mix from dump into circulation. Condenser peaks at 760 mbar. Still rises off scale then falls. |
| 1825 | Condenser = 755 mbar, Tower = 0.86 K, Still = 28 mbar |
| We'll leave like this, later can close V14 remotely | |
| 1835 | Condenser = 720 mbar, Tower = 0.64 K, Still = 11 mbar |
| 1920 | Condenser = 463 mbar, Tower = 0.20 K, Still = 0.34 mbar. Close V14. |