2016/05/03 (Tuesday)

Previous Day

	Setup: HV mode, DIB1/2/3 → -/-/Phonon reroute board → cables → 3.2MHz Filters → HV board → HV1/HV2 → DCRC55/50, DCRCs powered overnight
	Temperature basically stable overnight, started out a bit warmer then cooled to a base of 47.5 mK
0910	Tower/MC/Coldplate = 47.7/45.8/277 mK, Still = 1.17 K / 0.110 mbar, G1/G2 = 100/100 mbar, 1K Pot = 1.65 K / 9.0 mbar, Main Bath = 63.6%
0920	Fill LN2 coldtraps full.
1115	Set up timing link between HV boards. Some high-frequency noise disappears.
1130	Set up 0-1000V power supply for HV tests.
	Set HV to 20 V. Monitor HV2pD. Pulses look fine. Baseline unchanged. Leakage current starts at 16 nA (16 mV on test resistor), decreases to 1.5 nA after about 4 minutes
	Set HV to 40 V. Phonon pulses disappear. Baseline rises about 40 mV. Leakage 23→4 nA over 4 minutes.
	at 40 V, leakage current begins to increase.
	Increase HV to 50 V then back off to 40 V. Pulses return after 20 s. After 2 minutes pulses disappear again. At 3 minutes there is a temperature spike to 76 mK
	Reduce HV to 0, then increase to 50 V, then back off to 40 V again. No pulses. Temperature spikes corresponding with increases in leakage current. Leakage goes up then down, followed closely by temperature rise and fall. Typical current peak is 50 nA, temperature spikes from 48 mK base to 70 mK
1210	Set HV to 30 V and leave it there a while. Over 10 minutes pulses do not return. Two temperature spikes occur, to about 58 mK.
1225	After turning HV back to 0, finally see pulses again, though there's a very regular low-frequency noise present on both HV2 pC & pD as seen below:

1240	Noise still present. No further temperature spikes, though. Unplug DCRCs to let them “calm down.”
1510	Plug DCRCs back in. Zap SQUIDs.
1530	Minor low frequency noise still occasionally present, but much less significant than before.
1535	Set HV to 30V slowly and monitor temperature and pulses. Pulses still currently visible.
1545	Leakage 3.2 nA
1553	Turn up HV to 35V and pulses disappear. Leakage current: 5.1nA. No temperature response.
1555	Pulses return (though smaller than before) after ~90s.
1600	Leakage 2.1 nA
1601	Temperature spikes by 1mK. A mini-spike for some reason.
1603	Raise HV to 40V. Pulses disappear after ~30s. Leakage current: 9nA.
1606	Leakage current: 4.6nA.
	Temperature spike to 66mK. Similar spikes happen ~90 and ~180 seconds after.
1615	No spikes since the third one at 16:08:30. Leakage current: 4.7nA.
1630	Very soon after checking the leakage current (just like at at 16:06) after ~ 7minutes of peace, the temperature begins spiking approximately every 2 minutes. This happens for 7 spikes. Turn down the HV to 0V. Pulses return after ~60 seconds. Temperature has ceased spiking. Leakage current 11nA and dropping.
1703	Fill LN2 cold trap full.
1710	Attach Cf source to mu-metal shield at detector level. Also set up photoneutron source (strong Y source with Be target in source holder) on stool with wood blocks pointing at detector level. Intent is to activate detector overnight.

USD1 wirebonding
1600	Repair the one broken DIB-to-detector wirebond. All 4 DIB-to-detector charge-channel wirebonds finished.
	For detector-to-detector bonds use these settings: bond1/bond2 powers 475/475, bond times 30/30, loop height 50 mils, drop before clamp 10 mils
	Complete detector-to-detector bonds for charge-channel side: hopscotch connections for channels 2,3,4 and jumper connection between separate halves of channel 2
	On “phonon side” (ground side) make wirebonds from DIB1pin3 and DIB1pin5 to ground electrode. Surface seems to be uniformly covered in Al rather than a grid.
	Spent about 45 minutes in wirebonding lab
	Interestingly the resistances between channels are much smaller now that the “hopscotch” bonds are in place. Apparently the near-DIB pads are more isolated from the substrate than the channels themselves.

USD1 resistance checks [Ω]
	q1	q2	q3	q4	g1	g2	chassis
q1	-	22.7	36.2	47.6	16.4	16.4	open
q2	-	-	32.9	45.0	11.9	11.9	open
q3	-	-	-	56.9	27.1	27.1	open
q4	-	-	-	-	36.2	36.2	open
g1	-	-	-	-	-	0.8	open
g2	-	-	-	-	-	-	open
resistances between four charge channels and two ground connections on opposite side

USD1 pinout map
q1	q3	q2	q4	g1	g2
DIB1qO	DIB1qI	DIB2qO	DIB2qI	DIB1pin3	DIB1pin5
Charge channels are numbered outer-to-inner
A “1” is scratched onto housing above DIB1 (a little hard to see)

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