2018/06/19 (Tuesday)

Previous Day

	overnight: Tower temp, 1K pot steady
0930	Tower/MC/Coldplate = 40.5/40.3/181 mK, Still = 1.2 K / 0.055 mbar, G1/G2 = 251/230 mbar, 1K Pot = 1.46 K / 4.0 mbar. MB = 38.2%
0940	Fill LN2 cold trap full.
0952	Yesterday we couldn't even hold this 40mK base with the detector running. Let's play a bit with still heating and the 1K pot today to see if we can get more cooling power.
0954	Open 1K pot needle valve +10 degrees. P2 peaks at 300 mbar, but quickly falls. 1K pot oscillating about 1.61 K / 25 mbar.
1020	Tower temp has fallen slightly to 39.8 mK. 1K pot = 1.57 K / 12 mbar and falling.
1022	Open 1K pot needle valve +10 degrees. P2 peaks at 85 mbar, but quickly falls. 1K pot oscillating about 1.62 K / 25 mbar.
1043	Tower has risen again to 40.1 mK and 1K pot = 1.57 K / 12 mbar and falling. So tweaking the 1K pot didn't seem to help much.
1044	Tower = 40.2 mK, Still = 1.10±0.05 K / 0.055 mbar / 1 mW
1050	Set Still heat = 0.5 mW. Tower temp starts to rise.
1105	Tower = 43.7 mK and increasing, Still = 1.02±0.05 K / 0.045 mbar / 0.5 mW. 1 K pot = 1.56 K / 9.5 mbar.
1109	Set Still heat = 1 mW. Tower temp starts to decrease.
1139	Tower = 40.8 mK and cooling slowly, Still = 1.10±0.05 K / 0.055 mbar / 1 mW.
1148	Set Still heat = 1.2 mW. Tower temp seems unaffected.
1204	Tower = 40.0 mK, Still = 1.15±0.05 K / 0.060 mbar / 1.2 mW.
1212	Set Still heat = 1.5 mW. Tower temp decreasing slowly.
1228	Tower = 38.6 mK, Still = 1.11±0.05 K / 0.065 mbar / 1.5 mW.
1237	Set Still heat = 1.8 mW.
1255	Tower = 43.5 mK and rising, Still = 1.04±0.05 K / 0.070 mbar / 1.8 mW.
1301	Tower = 48.2 mK. Set Still heat = 1.0 mW.
1356	Tower = 44.7 mK and cooling slowly. 1K pot = 1.51 K / 6.0 mbar and falling slowly.
1358	Open 1K pot needle valve +10 degrees. P2 peaks at 500 mbar, but quickly falls. 1K pot oscillating about 1.65 K / 35 mbar.
1420	1K pot = 1.57 K / 11 mbar and falling
1430	Commence LHe transfer (MB = 31.0%)
1523	Ceace LHe transfer (MB = 90.7%)
1558	Tower has slowly risen from 40.6 to 44.7 mK since 1445. 1K pot = 1.49 K / 6.0 mbar
1605	G1/G2 = 274/252 mbar. Try to assess flow rate by closing V13A and watching G2 rise for ~1 min. G2 rises at rate of 12.0 mbar/min, G1 falls at rate of 13.0 mbar/min. Not sure what to compare this to.

Assume the G2 volume is primarily the hose from 3He pump to IGH. Said hose is 2.5M long with ID~1 cm, which gives a G2 volume = 2e-4 m^3. This gives a flow rate of dn/dt=(dP/dt)*V/RT= 480*(1K/T) umol/s. I'm not sure how to estimate the correct temperature, but it is somewhere between the Still temp (~1K) and room temp. This matters a lot, as it gives us a range of between dn/dt = 1.6 - 480 umol/s for the true flow rate. It is also unclear what the 3He/4He ratio is in this volume.

1642	Fill LN2 cold trap full.

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