2016/08/03 (Wednesday)
| Setup: iZIP mode, DIB1/2/3 → cables → 3.2 MHz filters → DCRC55(1)/33(2)/50(3), Tower has been cooled below Al transition with mu-metal shield at standard position | |
| Circulation and 1K Pot suspended overnight to pump on IVC, mixture open to fridge and dump - also want to pump mixture to dump to make sure we haven't lost any | |
| Condenser Speedivalve, Still Gate valve, V1, V3, V12B, V9 all open | |
| 0650 | Tower = 4.46 K, 1K Pot = 4.25 K. G1/G2 (trap&fridge) = 560/510 mbar. MB = 69.0% Boiloff rate is bad. Looks like yesterday pressure was only released from bath once, 15 minutes after transfer. That doesn't work. |
| Turbo pump on IVC = 1.0 nbar. Close turbo pump valve, IVC = 7.4 nbar. | |
| 0655 | Close V13b, turn on 3He pump, open V6. Now pumping fridge and Trap 2 to dump. Tower and 1K Pot temperatures go down a little. |
| 0700 | Remove Trap 1 from LN2 bath to warm up. Fill LN2 cold trap bath. |
| 0720 | G2 (dump) has settled at 789.7 mbar. That seems OK. Should doublecheck recent measurements. |
| IVC pressure has not increased since closing the turbo pump valve 30 minutes ago, with fridge around 4 K. So leak to IVC is not super fast. | |
| 0725 | Begin pumping on 1K Pot with 4He pump. Needle valve is closed. 1K Pot → 1.30 K / 0.45 mbar |
| 0730 | Open 1K pot needle valve about 45 degrees, 1K Pot → 1.45 K / 3 mbar |
| 0740 | Close V6. G2 (dump) = 789.9 mbar. Turn off 3He pump. |
| Opened the 1K pot needle valve further a few times, currently 1K Pot = 1.66 K / 24 mbar | |
| 0745 | Start opening and closing V12B, V13B in cycles to let some mixture into fridge. V3 is open to let mixture in to both sides. Watching 1K Pot to keep it at lowish pressures, < 50 mbar. |
| note | It's hard to say but I may have mistakenly opened V13a at least once, which would let mixture into the (now warm) Trap 1. So we need to cool Trap 1 again and then get any mixture out of it. I'll wait till later to return the trap to the bath since it will overflow the LN2 - let some LN2 boil off. But probably we'll want to get that mix back after we have established circulation and dilution cooling. |
| 0755 | G2 (dump) is down to 500 mbar, G1 (fridge) around 100 mbar - Tower temperature falls to 2.27 K |
| 0810 | Leaving V12b and V13b open, mixture is open to pump/dump/fridge. G2 (dump) = 180 mbar, G1 (fridge) = 145 mbar, both falling. Tower/MC/Still = 2.06/2.42/3.02 K. 1K Pot = 1.63 K / 16 mbar. Tweak needle valve open a little more. |
| 1035 | P2 down at 2.8mbar. Tweak open 1K Pot needle valve. |
| 1040 | Tower temp = 1.51K. G1/G2 = 24/16 mbar. Close V3, V9, turn on He3 pump, and begin opening V6. |
| 1047 | V6 open to 13.1%. G1/G2 = 41/37 mbar and increasing slowly. |
| 1117 | V6 now open to 13.8%. G1/G2 = 376/355 mbar. P2 was at ~10mbar, but all of a sudden dropped quickly to 7.0mbar before I opened V6, so I tweaked open the needle valve to fill the 1K Pot more. |
| 1125 | P1 has begun falling. Currently at 150mbar, G1/G2 = 470/437 mbar. 1K Pot = 1.70K / 40mbar. |
| 1145 | Opening V6 no longer increases the pressures on G1/G2. Open V6 all the way. G1/G2 = 380/352 mbar. P1 = 0.22mbar and dropping. 1K Pot = 1.63K / 17mbar. Tower temp = 855mK and dropping. |
| 1155 | Tower temperature at 294mK and dropping. G1/G2 = 322/298 mbar. P1 = 0.15 mbar. 1K Pot = 1.61K / 13mbar. |
| 1205 | Open V14 to let remaining mixture from dump into circulation. P1 rises to 8mbar, then begins decreasing. G1 rises to 297mbar, then begins dropping. 1K Pot steady at 1.6K. Place Cold Trap 1 back into LN2 bath to cool down in preparation to pump whatever mixture is in there back into circulation. |
| 1208 | P2 has dropped to 11mbar. Tweak open 1K Pot needle valve. Tower temperature = 85mK. |
| 1335 | Tower temp = 36.1 mK. G1/G2 = 200/185 mbar, P1 = 0.15 mbar. Close V14. |
| 1425 | Now that Cold Trap 1 is cold, open V8 and V11A to pump out whatever mixture may remain in it. P1 began at 0.070mbar, rose to 0.17mbar, then began to pump down. |
| 1445 | Tweak open 1K Pot Needle Valve. |
| 1515 | Performing electrical check. Qo channels on DIB2 (i.e. Qo Feedback to QoDrain/QoSource) all show open circuits (>0.5nS) whereas Qi channels show conductance of ~18nS. Presumably this is why we were seeing such erratic noise on DIB2 Qo. I wonder if repowering DCRC2 will exacerbate the issue, and cause heating like we saw before. |
| 1518 | Tower Temp = 35.3mK. Power on DCRC1 and DCRC3 and see if the temp remains stable. |
| 1519 | Tower temp spikes to 39.6mK, then drops back down to 36.0mK, then begins rising slowly. |
| 1527 | Tower temp has risen to 37.5mK. |
| 1530 | Tower temp stabilizing around 37.5mK. Power on DCRC2. |
| 1533 | Tower temp has risen to 38.0mK, and is oscillating upward. |
| 1535 | Tower temp = 38.5mK. |
| 1540 | Tower temp = 39.2mK. |
| 1541 | Unpower DCRCs to see if this lowers the temperature. |
| 1542 | Tower temperature has spiked to 59mK then dropped again. |
| 1547 | Tower temp = 38.2mK and dropping. |
| 1720 | Tower temp = 36.4mK, though it does appear to be climbing slowly. About an hour ago, it was 36.0mK. P1 = 60ubar. Close V8 and V11A to isolate cold trap. All the mix should be pumped out of it by now. |
| 1722 | P1 drops to 55ubar. 1K Pot = 1.46K / 3.6mbar. All very low. Tweak open 1K Pot needle valve. |
| 1728 | Tower temp has fallen to 35.8mK and is still dropping. P1 has risen to 90ubar. 1K Pot = 1.76K / 280mbar, though it's still settling. Will come back before collaboration dinner to tweak open needle valve in preparation for overnight. |
| 1730 | Fill LN2 cold trap full. |
| 1815 | Tower = 35.1 K, on a slow increase - that may be just from falling still pressure. 1K Pot = 1.62 K / 15 mbar |
| 1820 | MB = 47.1%. Fill will need to be started very early tomorrow morning |
| 1845 | Tower temp = 35.5mK. P2 had dropped to 7.5mbar, so tweak open 1K Pot needle valve. |