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2015/03/05

0930 G1=116 mbar, G2=103 mbar, P1=.22 mbar, and mixing chamber temperature is at 522 mbar. Although the mixing chamber temperature has dropped since we left the lab last night, as of 2130 last night the mixing chamber was at 520 mK and rising slightly. As the night progressed it also began some oscillations, reaching minimums of 515 mK and maximums of 530 mK. Pressures have also been rising overnight, increasing by roughly 20 mbar in G1 and G2 since midnight. Fill LN2 cold trap full.
1215 With 1K Pot stable at 1.610 K and mixing chamber temperature at 530 mK, commence test to determine if Still is running dry. Incrementally increase Still Heater and record pressure and temperature results. Results included in table below.
Time G1 (mbar) G2 (mbar) P1 (ubar) Still (K) Additional Comment
1215 124 111 220 0.964 Commence test. Turn on Still Heater to 0.5 mW.
1221 124 111 240 0.975 Increase Still Heater to 1.0 mW. Mixing chamber temperature at 513 mK.
1225 105 99 220 0.967 Increase Still Heater to 2.0 mW.
1230 102 96 240 0.980 Mixing Chamber temperature at 477 mK and dropping.
1236 102 96 260 0.985 Increase Still Heater to 2.5 mW.
1240 105 99 260 0.990 Mixing Chamber temperature at 468 mK and dropping.
1247 107 101 260 0.990 Increase Still Heater to 3.0 mW.
1249 109 103 260 0.997 Mixing Chamber temperature at 458 mK and dropping.
1304 113 107 260 0.997 Increase Still Heater to 4.0 mW.
1311 118 112 280 1.010 Mixing Chamber temperature at 438 mK and dropping.
1317 119 113 280 1.005 Increase Still Heater to 5.0 mW. P1 initially rises to 300 ubar and then settles to 280 ubar.
1324 123 111 280 1.018 Mixing Chamber temperature at 421 mK and dropping.
1330 126 118 280 1.017 Increase Still Heater to 6.0 mW. P1 initially rises to 300 ubar.
1341 134 126 300 1.028 Mixing Chamber temperature at 406 mK and dropping.
1347 139 131 300 1.024 Increase Still Heater to 7.0 mW. P1 initially rises to 320 ubar.
1353 145 136 320 1.035 Mixing Chamber temperature at 394 mK and dropping.
1400 130 127 320 1.037 Increase Still Heater to 8.0 mW. P1 initially rises to 340 ubar and then settles to 320 ubar.
1405 131 127 320 1.049 Mixing Chamber temperature at 384 mK and dropping.
1408 135 131 320 1.051 Increase Still Heater to 9.0 mW.
1420 152 145 340 1.087 Mixing Chamber temperature at 373 mK and dropping. Still temperature is rising more quickly.
1423 158 150 360 1.100 Increase Still Heater to 10.0 mW. P1 initially rises to 380 ubar.
1435 317 291 500 1.332 Turn off Still Heater to avoid G1 and G2 rising higher. Mixing Chamber temperature at 333 mK and rising, though that is likely because the heater has been shut off. End test.
1435 During Still heater tests, 1K Pot rose to 2.48 K, though P2 was only at 6.0 mbar. Open the 1K Pot needle valve more to allow in more He, causing G1 and G2 pressures to drop from 430 mbar and 396 mbar, respectively. 1K Pot temperature reached a stable temperature of 1.78 K.
1535 Commenced LHe transfer (34.8%).
1622 Pause LHe transfer since dewar is “empty”. Return with a new dewar and start transfer again (39.5%).
1700 End LHe transfer (92.6%).
2125 Fill N2 cold trap full.
Pressures in G1 and G2 are quite high at 190 mbar and 168 mbar respectively. Would indicate possible blockage in helium cold trap.
2355 It looks as though helium cold trap may be partially blocked. G1 pressure is 200 mbar, G2 lies at 182 mbar and mixing chamber temperature is 466 mK. All values have been gradually increasing over the last few hours. Let's pull mixture out of fridge. Can use this opportunity to conduct single-shot test.