2015/03/27
Summary of mixture amounts:
| morning of | G2 (mbar) | Pbar (“Hg) | Pdump (mbar) | 3He (mbar) | 3He (%) |
|---|---|---|---|---|---|
| Mar 23 | 653 | 30.3 | 665.9 | 166.5 | 25% |
| Mar 24 | 700 | 30.1 | 706.1 | 166.5 | 23.6% |
| Mar 26 | 746.3 | 30.1 | 752.4 | 166.5 | 22.1% |
| Mar 27 | 789.5 | 30.3 | 802.4 | 166.5 | 20.8% |
The barometric pressure (Pbar) is from Weather Underground (wunderground.com) weather history for Minneapolis. This is Sea Level Pressure (so not the actual measured pressure but rather corrected to remove the elevation of the weather station). The original 25% is based on the mass spec measurement and has a +/- 3% error. The other percents are inferred from this original measurement.
| 0900 | fill LN trap dewar |
|---|---|
| 0918 | pump fridge contents to dump. Dump reads 789.5 mbar at G2. |
| Pbar = 30.3 “Hg, so corrected for barometric pressure, Dump = 802.4 mbar | |
| 0948 | Start 1KPot |
| 1000 | Begin condensing mixture |
| 1043 | Condensing, V12a open 100%. G1/G2 = 72/74 mbar, MC = 2.1 K |
| 1050 | Begin circulation. V6 open 13% |
| 1113 | V6 = 14.2%, MC/Still = 1.13/1.17 K |
| 1128 | Open V6 100% |
| 1130 | MC = 0.87 K, Still = 0.87 K / 0.22 mbar |
| 1131 | MC 776 mK, Still 921 mK / 0.20 mbar, G1/G2 131/124 mbar, 1KPot 1.77 K / 45 mbar |
| 1139 | Open V14 |
| 1144 | MC 593 mK, Still 896 mK / 5.0 mbar, G1/G2 106/107 mbar, 1KPot 1.77 K / 45 mbar |
| 1157 | MC 526 mK, Still 948 mK / 1.3 mbar, G1/G2 133/127 mbar, 1KPot 1.77 K / 45 mbar |
| 1208 | MC 474 mK, Still 986 mK / 0.65 mbar, G1/G2 134/127 mbar, 1KPot 1.76 K / 45 mbar |
| 1210 | With P1=0.6 mbar, close V14. |
| 1216 | MC 448 mK, Still 992 mK / 0.20 mbar, G1/G2 135/128 mbar, 1KPot 1.76 K / 45 mbar. |
| 1241 | MC 471 mK, Still 951 mK / 0.17 mbar, G1/G2 121/117 mbar, 1KPot 1.70 K / 22 mbar. |
| 1303 | MC 475 mK, Still 951 mK / 0.17 mbar, G1/G2 119/116 mbar, 1KPot 1.70 K / 22 mbar. |
| 1316 | MC 477 mK, Still 951 mK / 0.17 mbar, G1/G2 122/119 mbar, 1KPot 1.70 K / 22 mbar. |
| 1355 | MC 477 mK, Still 951 mK / 0.19 mbar, G1/G2 127/123 mbar, 1KPot 1.70 K / 22 mbar. |
| 1417 | MC 409 mK, Still 1.05 K / 0.24 mbar, Still heater 5mW, G1/G2 136/135 mbar, 1KPot 1.70 K / 22 mbar. |
| 1425 | MC 342 mK, Still 1.11 K / 0.32 mbar, Still heater 10mW, G1/G2 141/146 mbar, 1KPot 1.70 K / 22 mbar. |
| 1433 | MC 321 mK, Still 1.17 K / 0.38 mbar, Still heater 15mW, G1/G2 151/157 mbar, 1KPot 1.70 K / 22 mbar. |
| 1450 | Begin a series of single-shots to remove 3He to dump. Removed 87.0 mbar, measured at G1. Left still heater on at 15 mW. Still stayed below 1.2 K and MC below 450 mK during procedure. Restored circulation with reduced mix. |
| 1513 | MC 560 mK, Still 1.17 K / 0.34 mbar, Still heater 15mW, G1/G2 137/143 mbar, 1KPot 1.70 K / 22 mbar. |
| 1517 | MC 574 mK and relatively flat, begin applying more heat to still. |
| 1525 | MC 507 mK, Still 1.21 K / 0.38 mbar, Still heater 20mW, G1/G2 145/154 mbar, 1KPot 1.70 K / 22 mbar. |
| 1532 | MC 472 mK, Still 1.28 K / 0.40 mbar, Still heater 25mW, G1/G2 155/165 mbar, 1KPot 1.70 K / 22 mbar. |
| 1541 | MC 442 mK, Still 1.27 K / 0.50 mbar, Still heater 30mW, G1/G2 177/187 mbar, 1KPot 1.70 K / 22 mbar. |
| 1549 | MC 415 mK, Still 1.33 K / 0.60 mbar, Still heater 40mW, G1/G2 208/220 mbar, 1KPot 1.72 K / 28 mbar. |
| As before, with less 3He, we can still get dilution cooling, and improve MC temperature by increasing still heat. But both still and (more importantly) MC temperatures are higher. | |
| 1555 | Dialing still heat back to 15 mW in preparation of putting all the mix back in. Adding mix to circulation through V14. |
| 1629 | Close V14 when P1 reads 0.9 mbar |
| Performing Cooling Power Test with all mix in and still heater at 15 mW | |
| 1636 | MC heater = 0 uW, MC temp = 324.4 mK |
| 1640 | MC heater = 10 uW, MC temp = 327.4 mK |
| 1645 | MC heater = 20 uW, MC temp = 327.1 mK (wiggles between 327 and 328.5) |
| 1650 | MC heater = 30 uW, MC temp = 327.9 mK |
| 1656 | MC heater = 40 uW, MC temp = 330.0 mK (dip) |
| 1708 | MC heater = 50 uW, MC temp = 330.3 mK |
| 1712 | MC heater = 60 uW, MC temp = 331.9 mK (dip) |
| 1716 | MC heater = 70 uW, MC temp = 333.5 mK |
| 1720 | MC heater = 80 uW, MC temp = 332.7 mK (dip) |
| 1723 | MC heater = 90 uW, MC temp = 336.0 mK |
| 1726 | MC heater =100 uW, MC temp = 337.3 mK |
| The “dips” above are brief (~1 min) dips in the MC temperature, then a return. These came at the same time as spikes in the still pressure. | |
| 1731 | Turn off MC heater and Still heater. Preparing for Hassan's suggested test for the still. |
| 1748 | Still temperature drops to lower than even before we began heating |
| 1749 | Still = 881 mK, MC = 558 mK |
| 1751 | Starting one-shot. Still temp increases to 955 mK, then begins dropping |
| 1754 | Still = 900 mK / 0.14 mbar. Target is 771 mK (100 lower than when we began). G2 = 30 mbar and rising as we pump mix to dump. |
| 1755 | Still = 850 mK / 0.11 mbar. G2 = 34 mbar. |
| 1757 | Still = 796 mK / 0.08 mbar. G2 = 37 mbar. |
| 1757 | Still = 781 mK, cease one-shot, resume circulation. Still temperature begins to increase. |
| 1801 | Still = 861 mK / 0.13 mbar. |
| 1803 | Still = 900 mK / 0.15 mbar, MC = 817 mK |
| 1807 | Still temperature decreases again and flattens out at 881 mK / 0.19 mbar – same temperature as before the one-shot. MC = 1.09 K |
| 1810 | begin recovery |