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2015/08/19 (Wednesday)

	Overnight status: 10 MHz C-filter on DIB1 at ebox, HV1/2 → DCRC50/55, DCRCs powered but no bias.
	Temperature excursions began around 6:00, tower rase to around 45 mK, spikes as high as 60 to 140 mK
0844	MC/Tower/Cold Plate = 32.5/50/158 mK, Still = 1.29K / 0.11 mbar, G1/G2 = 170 mbar, 1K Pot = 1.73 K / 24 mbar. Base, cold plate, and still T all elevated from normal. Other stuff looks normal.
	does the temperature problem have something to do with the low bath?? Something similar seemed to happen at the end of the last run. The bath was even lower two days ago, but we were baking the detector so we may not have seen the current problem.
0850	Main bath = 10.7%
note:	boiloff rate is still unusually high at 1.9%/hour (usually it's less than 1.7%/hour)
0928	Begin LHe transfer at 9.3%
0932	Tower cools to its normal base. I'm not 100% sure this is due to the transfer because I also did some things with the DCRC: HV1 charge pulses looked choppy so I turned the FETs on and off and normal pulses returned. It's possible the bad state of the charge channels was causing the heating.
0941	The tower temperature rose again, corresponding with choppy charge traces and no phonon pulses. Turning the FETs off caused the tower to cool again. So maybe the low bath wasn't the issue.
0953	Once again the charge channels went choppy, the phonon pulses disappeared, and the temperature rose. Power cycling the FETs caused cooling and restoration of pulses.
0955	Cease LHe transfer (55.1%).
1000	Prepare for cooling power test, to better analyze the HV current-versus-temperature data. First turn off HV1 FETs to avoid some heating issue.

Low-power cooling power curve
MC heater (μW)	Tower (mK)
0	32.1±0.2
0.5	34±0.3
1	36.7±0.3
1.5	37.5±0.4
2	39±0.4
2.5	39.6±0.4

1415	Move 10 MHz filter to DIB2. Now 10 MHz C-filter on DIB2 at ebox, HV1/2 → DCRC50/55. Note this means that 4 out of 8 channels on Side 2, the bias side, are now filtered.
1420	Leave Side1 charge bias at zero, increase HV in + direction. Above +15 V started losing phonons, but they would come back… slowly increased HV in ~0.5 V steps, which would cause HV1pA to rise 50 mV, then wait for it to relax again. Slowly raise HV…
1445	HV up to +26.3 V (49.6 nA), definitely higher than before…
1505	Reach Kepco 0-40V supply's maximum of +31.1 V (60.7 nA). Phonon pulses good, no change in tower temperature. Meter reads +31.03 V. Hence Vcrystal = +6.75 V.
1510	Apply opposite bias to Side1 charge channels, increase in -1 V steps. Reach -14 V with no problems.
1520	Try - HV now. First set all biases to 0. Then increase HV to -31 V (-60.4 nA) quickly - no problem at all with phonon pulses.
1525	Now increase Side1 charge bias to +14 V - phonon pulses disappear but begin to come back after a couple of minutes, but still small.
1530	HV1pA flat at its high-end baseline, HV1pB pulses very distorted, HV1pC seems OK. (This one behaves as if it has the highest Tc.) Return Side1 charge bias back to 0V, but pA still flatline, pB and pC pulse-less. HV had to be reduced to -28 V to make pulses return.
1540	Behavior different now, increasing HV seems to elevate temperature, raise baselines, kill pulses. Raising Side1 charge bias also raises baselines. At some voltages pulses return over time, but limiting voltages seem to be worsening.
1615	HV at -21.93/-22.22/-23.22 V (by multimeter), -39.1/-39.6/-41.5 nA, causes HV1pA baseline to increase to 0.275/0.3/0.34(max) V.
1645	Try the 0-1000 V Kepco DC supply. 60 Hz spikes in charge channels with ground side of HV plugged in to supply, 60 Hz sinusoid with bias side plugged in, if supply plugged directly into wall, or through Variac, or with groundless plug. But supply→Variac→groundless plug→wall works fine.
1654	HV = 35.00/45.41/50.00 V (by multimeter) , 69.8/93.5/103.8nA ⇒ V_crystal = 7.08/8.01/8.84V. Phonon pulses present.
1705	Fill LN2 cold trap full.
1705	Main bath = 47.1%. This is actually a very slow boiloff - only 1.1%/hour.
1735	HV = 55.48V, 116.2nA, V_crystal = 9V. Phonon pulses present.
1742	Cranked HV to 60V quickly. Lost phonons, charge pulses still good.
1756	Phonons beginning to return. HV to 70.00V (multimeter) causes MC temp to go from 31.6mK to 32.2mK, but seems stable. Charge pulses still okay.
1802	HV to 80.00V (multimeter), 169.9nA. MC temp increase to 32.6mK
1828	Fridge seems stable at 32.6 mK. Leaving 80V bias overnight to see if phonons return.