2013/10/16

1127	Filled LN2 cold trap full.
1230	Performed measurements on mixing chamber temperature, still temperature and pressure, and cold plate temperature. Results below.

Still Heater Power [mW ± 0.05 mW]	H35 Thermometer [mK]	Still pressure [μbar]	Still Thermometer [kΩ ± 0.01 kΩ]	Cold Plate Thermometer [kΩ ± 0.01 kΩ]
0	76.6 ± 0.05	95 ± 2.5	4.67	19.61
1	80.7 ± 0.05	120 ± 5	4.56	18.90
2	82.2 ± 0.05	130 ± 5	4.53	18.57

1530	Start singleshot test.
1720	Stopped singleshot test, results posted below. Stop 1K Pot, turn off still heater,begin pumping from both sides of fridge and turned on mixing chamber heater to 10mW.
2225	Recovered 682 mbar of mixture, 1 K pot temperature >7 K, turn off mixing chamber heater.
2315	Stop mixture recovery. Start 1 K pot, temperature 1.82 K. Commence manual condensation procedure through nitrogen cold trap 1.
	Fill N2 cold trap full.

681 mbar Single Shot Test with He-3 in dump

The single shot test performed today gave results shown in Figure 1 below. From the figure, which shows pressure in G2 (mbar) and mixing chamber temperature (mK) as a function of time, it can be seen that the single shot test was started at 60 seconds which resulted in a rapid decrease in G2 due to V9 opening up to the nearly empty dump. This rapid increase subsided at 102 seconds with G2=68 mbar. Once the test has been started, the mixing chamber temperature began to decrease. This decrease is due to the He3 being pumped from the fridge to the dump. From 102 seconds (mixing chamber temperature of 79.9 mK) to 3365 seconds (mixing chamber temperature of 45.1 mK) the temperature in the mixing chamber decreases, allowing us to assume that the pressure increase during this time range is due to the accumulation of He3. During this total time of the single shot test (102 seconds to 3365 seconds) G2 increases from 68 mbar to 197 mbar, and thus 149 mbar if He3 was collected. This is roughly 19-21% He3 in the mixture. This is an estimate because we are not certain how much He-3 was removed in the previous single shot test. We predict that between 610 and 680 mbar of mixture remains in the fridge.

Figure 1: Single Shot Test Results