2017/12/18 (Monday) · UMN CDMS Wiki archive

	Setup: DIB1/3/4 → SL 27/19/20 → 3.2 MHz filters → cables 2,1,3 → HV board inputs 1,3,2 → HV board outputs 1,2 → DCRC55(1)/50(3). DCRC4 → HV power supply.
0912	Tower/MC/Coldplate = 21.5/25.4/148 mK, Still = 1.3 K / 0.100 mbar, G1/G2 = 239/226 mbar, 1K Pot = 1.62 K / 26 mbar, MB = 73.4%
0917	Fill LN2 cold trap full.
	Let's experiment with heating the MC. We'll get a cooling curve. Then we'll try running the detector at an elevated temperature.
0930	Tower/MC = 21.3/24.9 mK
0935	Set MC heater to 0.5 μW
0940	Tower rose to 26 mK but is now falling again, down to 25 mK
1000	Tower/MC = 23.2/26.8 mK, 0.5 μW. Mostly flat.
1005	Set MC heater to 1.0 μW
1010	Tower jumped up to 40 mK but is now falling again.
1050	Tower/MC = 34.6/38.0 mK, 1.0 μW. Mostly flat.
1050	Set MC heater to 2.0 μW
1110	Tower/MC = 38.2/41.0 mK, 2.0 μW. Flat.
1115	Set MC heater to 4.0 μW
1125	Tower/MC = 44.5/46.8 mK, 4.0 μW. Flat.
1200	Do a quick manual IbIs on DCRC1pA. Plotted both Is:Ib and 13kHz oscillation versus Ib. It actually hasn't shifted much at this temperature.
1130	Set MC heater to 8.0 μW
1310	Tower/MC = 55.7/57.2 mK, 8.0 μW. Flat.
1320	Do a quick manual IbIs on DCRC1pA. Now it's definitely shifted.
1525	Finish manual IbIs on all channels. All are shifted with respect to the 21 mK measurements. As seen in Run 61 the strong oscillation peaks are now much weaker. Chose QET biases for each channel at this temperature, roughly matching the same point in transition (and away from oscillation regions) as with the colder case.

chan	Original QET bias (21 mK)	New QET bias (55 mK)
DCRC1pA	480	430
DCRC1pB	360	340
DCRC1pC	440	380
DCRC3pB	480	400
DCRC3pC	380	350
DCRC3pD	490	430

1540	Dial HV up to 70 V with 15% 5-minute prebias, using changeHV_0_70_preBias15_5.msl
1545	Tower = 54.7 mK, pretty stable
1545	HV = 69.86 V, V_leak = 3.28 mV
1550	Start sequence of 4 60-minute background data series at HV = 70V, Driver Gains = 2x, QET biases = (430/340/380)/(400/350/430) uA, Front-End Gains = 10/5 on DCRC1/3, 1000 initial randoms, trigger on DCRC3pD threshold 14, MC heater = 8.0 μW, Tower = 54.7 mK
1559	Reduce trigger threshold from 14 to 12. It looks like we are only triggering on strong pulses. Also it looks like we are avoiding the trigger bursts that we got before, caused by driving DCRC3pD into the strong oscillations after a muon.
1605	Reduce trigger threshold from 12 to 11. This looks good - it occasionally triggers in the noise. No trigger bursts, looks like.
1721	Fill LN2 cold trap full.
2118	Tower = 55.5 mK
2119	Dial down HV bias to 0V and flash using changeHV_70_0_thenflash.msl
2203	Tower peaked at 550mK, fell to 60mK after 10min, 56mK after 20min, and 55mK after 34min
2223	Start 5 min long trace randoms transition data series at HV=0V, Driver Gains = 2x, QET biases = (430/340/380)/(400/350/430) uA, Front-End Gains = 10/5 on DCRC1/3, DCRC1,3 trace length = 13.1072ms, Trigger on 20Hz randoms
2230	Start 5 min long trace randoms SC/transition data series at HV=0V, Driver Gains = 2x, QET biases = (0/340/380)/(400/350/430) uA, Front-End Gains = 10/5 on DCRC1/3, DCRC1,3 trace length = 13.1072ms, Trigger on 20Hz randoms
2242	Start 5 min long trace randoms SC data series at HV=0V, Driver Gains = 2x, QET biases = (0/0/0)/(0/0/0) uA, Front-End Gains = 10/5 on DCRC1/3, DCRC1,3 trace length = 13.1072ms, Trigger on 20Hz randoms
2250	Ooops! Was actually trying to take randoms at 2000 Hz! Given the readout bottleneck, the above series are probably at something like 65Hz really.
2251	Restore 55mK QET bias setting from table above.