2018/05/09 (Wednesday)
| Status: Can't cool below around 3.5 K, suspect a touch somewhere to the 4K stage. Turned off 1K Pot yesterday and added a little He exchange gas to the IVC | |
| 1030 | Tower/MC(Cernox)/Coldplate/Still/1K Pot = 4.34/4.34/6.98/4.80/6.17 K, Fridge (G1) = 542 mbar, IVC = 40 nbar, MB = 35.3% |
| 1030 | Turn on MC and Still heaters to 20 mW each |
| MC temperature is going up of course, but 1K Pot temperature falls, interesting. | |
| 1035 | Fill LN2 cold trap bath |
| 1045 | Tower/MC(Cernox)/Coldplate/Still/1K Pot = 5.03/5.13/8.3/7.36/5.56 K, Fridge (G1) = 542 mbar, IVC = 86 nbar |
| 1050 | Let more He into IVC, one hose-length. MC & 1KPot temperatures fall. IVC→34 μbar |
| 1055 | Disconnect vacuum manifold from IVC and connect to cryostat vacuum jacket |
| 1100 | MB = 34.5%, recovery = 249 sec/sqft |
| 1105 | Let 1.6 mbar He gas into vacuum manifold. Then open cryostat vacuum jacket valve to let this into the vacuum jacket. Vacuum jacket → 34 μbar |
| 1110 | Recovery = 21 sec/sqft |
| 1115 | MB = 32.4%, recovery = 22 sec/sqft |
| 1125 | MB = 29.6%, recovery = 29 sec/sqft |
| 1145 | MB = 26.2%, recovery = 39 sec/sqft |
| 1145 | Let 1.9 mbar He gas into vacuum manifold. Then open cryostat vacuum jacket valve to let this into the vacuum jacket. Vacuum jacket → 63 μbar |
| 1245 | MB = 10.1%, recovery = 20 sec/sqft |
| 1300 | MB = 6.6%, recovery = 20 sec/sqft |
| 1315 | MB = 3.9%, recovery = 25 sec/sqft |
| 1330 | MB = 1.2%, recovery = 27 sec/sqft |
| 1345 | MB = -1.0% (min), recovery = 27 sec/sqft |
| 1350 | MC warming rate sharply increases, LHe level probably has fallen below IVC |
| 1400 | recovery = 27 sec/sqft |
| 1410 | Start pumping mixture back to dump. This causes a temporary drop in MC and 1K Pot temperatures. |
| 1430 | recovery = 29 sec/sqft |
| 1445 | recovery = 35 sec/sqft |
| 1500 | recovery = 36 sec/sqft |
| 1500 | MC(Cernox)/1K Pot = 5.62/7 K |
| 1505 | Cryostat vacuum jacket = 14 μbar. Add one hose-length of He gas. Settles at 86 μbar. sharp increase in MC warming rate. Recovery rate increases too, must still be some LHe (or it's just heating the gas a lot) |
| 1510 | recovery = 7.7 sec/sqft |
| 1510 | MC(Cernox)/Sorb = 6.8/12.9 K |
| 1515 | recovery = 8.9 sec/sqft |
| 1515 | MC(Cernox)/Sorb = 7.9/15.4 K |
| 1520 | recovery = 10.9 sec/sqft |
| 1530 | Another uptick in the MC warming rate. Maybe the last of the LHe is boiled away. |
| 1535 | recovery = 39 sec/sqft |
| 1535 | MC(Cernox)/Sorb = 19.0/31.8 K |
| 1555 | recovery = 200 sec/sqft, LHe must be gone |
| 1555 | MC(Cernox)/Sorb = 33.7/54.0 K |
| 1600 | Cryostat vacuum jacket = 190 μbar. Add five hose-lengths of He gas. Settles at 1.4 mbar. |
| 1605 | Turn heat gun on pointed up at bottom of cryostat |
| 1610 | MC(Cernox)/Sorb = 40.9/68.9 K |
| 1630 | MC(Cernox)/Sorb = 48.5/94.7 K |
| 1640 | MC(Cernox)/Sorb = 52.0/104.2 K |
| 1650 | MC(Cernox)/Sorb = 55.7/114.5 K |
| 1700 | MC(Cernox)/Sorb = 59.5/125.5 K |
| the Newton warming time constant appears to be 10.5 hours. But this is with the heatgun and the MC heater so probably it will not stay at this value. If it did stay at this value we'd hit 273 K at the end of the day tomorrow. Probably we'd be able to start pumping out the vacuum jacket but wouldn't get to the point of dropping the main bath. | |
| 1705 | Turn off heat gun |
| 2100 | MC(Cernox) = 153.4 |
| 2130 | MC(Cernox) = 162.6 |
| this is a fast warming trend, time constant around 7.5 hours. At this rate it will hit 273 K tomorrow morning before 11:00 |