2021/09/21 (Tuesday)

Lab in-personnel: Giulia and Matt

Status	Run 74 in progress. First cooldown after IVC rebuild.
	Tower thermometer is reading high, probably this is a thermometer problem and the actual temperature is much lower. High noise in some of the charge channels.
	Setup: DIB1/2+acc → SL 41/43 → 3.2 MHz filters → cables 2/3 → nothing/~~Source_mover_board~~+HV_diverter_board → DCRC50(3)/55(1). Kepco 40V supplye → HV BNC. Lead shield erected, 4 walls. Currently both DCRCs are on.
	Position of Am source: y = 0.0 mm
0832	Tower/MC/Coldplate = 83.9/35.7/192.3 mK, Still = 1.38 K / 0.110 mbar / 0 mW, G1/G2= 306.2/276.1 mbar, 1K Pot = 1.56 K / 10±1 mbar. MB = 38.4%.
0839	Fill LN2 cold trap bath
0840	At 10kHz noise in DCRC3qI/qO/DCRC1qI/qO = 0.9/0.7/1.7/1.9 8e-6. This is q3/q1/q4/q2 At 3kHz (peak) noise in DCRC3qI/qO/DCRC1qI/qO = 2.1/0.8/2.5/4.1 e-6.
	Noise is even lower than yesterday.
0851	Start 45 min series of +9/0V data (bias applied after 60 sec), with 1000 beginning randoms, trigger threshold 55/40/25/55 on DCRC3qI/qO/DCRC1qI/qO, 5Hz in-run randoms, with 1.6384 ms pulses (8192 length) and 400 us prepulse (500 length). Use Sequencer script r74_takeandflash_dcrcbias.msl. This flashes for 30 seconds at end of series.

07210921_0851

1118	Start breakdown-test series
	Tested for breakdown with negative bias. Previously by applying +bias to Side 2 we were able to max out the supply (>30V or something) without any breakdown. This time I applied -10V to Side1 first, then started increasing +bias on Side2 while watching randoms. Breakdown occurred at -10/+7.6 V. Dialed down to -10/+2.6 and the choppy breakdown noise mostly went away, but there were occasional disturbances where the baseline jumped or sloped steeply, sometimes railing. Dial down to -10/0V, breakdown disappeared. Dial up to -10/+3.6 V, breakdown recurred.
1125	Dial down to 0V on Side 2 and set Side 1 to 0 V, flash DCRC1&3 LEDs for 60 seconds.
1145	Another breakdown test, leaving Side1 at 0V and increasing +bias on Side2. Dial all the way to 0/+31 V (max) without breakdown.
1150	Dial down to 0V, flash DCRC1&3 LEDs for 60 seconds.
1210	Another breakdown test. Set Side1 = -3V then dial up +bias on Side2. At -3/+19.6 V see breakdown. Dial down to -3/+12.74 V, breakdown disappears. Increase Side1 bias in small steps: at -4.5/+12.74 V see breakdown. Dial down Side2 to -4.5/9.61V, breakdown disappears.
1215	Dial down to 0V on Side 2 and set Side 1 to 0 V, flash DCRC1&3 LEDs for 60 seconds.
1230	Another breakdown test. This time start at 0/+20V, then reduce Side2 and increase Side1 in 0.5V steps (keeping the bias difference = -20V). At +18.5/-1.5 V it sorta looks like breakdown but not as strong as what we usually consider breakdown. At +18.0/-2.0 V definitely see breakdown. Dial down to +15.3/-2.0 V, breakdown disappears.
1235	Dial down to 0V on Side 2 and set Side 1 to 0 V, flash DCRC1&3 LEDs for 60 seconds.
1310	Positive bias breakdown test: start with +5/0 V, then dial up Side 2. Breakdown at +5/-14.4 V. Dial Side2 down, breakdown disappears at +5/-8.4 V.
1315	Dial down to 0V on Side 2 and set Side 1 to 0 V, flash DCRC1&3 LEDs for 60 seconds.
1405	Start at 0/0 V, then dial up Side2: breakdown at 0/-19.4 V. (Note this is identical to the last trial, same delta-V as +5/-14.4 V.) Dial down Side2, breakdown disappears at 0/-13.1 V (also nearly the same delta-V as last trial).
1425	Close V6 to stop circulation
1430	Still pressure rising, Condenser pressure falling, Tower temperature rising.
1430	Turn off 3He pump.
1430	Close 1K Pot needle valve. Temp&press fall, 1K Pot → 1.43 K / 3.4 mbar.
1440	Tower = 0.47 K, rising ~1.6 K/hr
1500	Tower = 0.67 K, rising ~0.66 K/hr
1501	Start 45 min series of +10/0V data (bias applied after 60 sec), at elevated temperature, with 1000 beginning randoms, trigger threshold 40/30/30/50 on DCRC3qI/qO/DCRC1qI/qO, 5Hz in-run randoms, with 1.6384 ms pulses (8192 length) and 400 us prepulse (500 length). Use Sequencer script r74_takeandflash_dcrcbias.msl. This flashes for 30 seconds at end of series.
1501	Tower = 0.71 K at beginning of series
1547	Tower = 0.99 K at end of series

07210921_1501

1555	1K Pot = 1.43 K / 3.0 mbar (4He pump is still on)
2153	Start 45 min series of +10/0V data (bias applied after 60 sec), at elevated temperature, with 1000 beginning randoms, trigger threshold 40/30/25/60 on DCRC3qI/qO/DCRC1qI/qO, 5Hz in-run randoms, with 1.6384 ms pulses (8192 length) and 400 us prepulse (500 length). Use Sequencer script r74_takeandflash_dcrcbias.msl. This flashes for 30 seconds at end of series.
2153	Tower = 1.27 K at beginning of series
2239	Tower = 1.28 K at end of series

07210921_2153

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