2021/06/15 (Tuesday)
- Lab in-personnel: Matt
| Status | Run 74 in progress. First cooldown after IVC rebuild. Started circulation last week. |
|---|---|
| Tower thermometer is reading high, probably this is a thermometer problem and the actual temperature is much lower. | |
| Setup: DIB1/2+acc → SL 41/43 → 3.2 MHz filters → cables 2/3 → nothing/HV_diverter_board → DCRC50(3)/55(1). HV BNC not connected. No lead/poly shield. | |
| 0945 | Tower/MC/Coldplate = 208/33.7/198 mK, Still = 1.44 K / 0.085 mbar / 0 mW, G1/G2= 147/133 mbar, 1K Pot = 1.65 K / 28±2 mbar. MB = 32.6% |
| 0950 | Fill LN2 cold trap bath |
| 1015 | Looking at noise in charge channels with BatViewer. Bad in some channels: |
| At 10kHz noise in DCRC3qI/qO/DCRC1qI/qO = 36/8.9/6.1/101 e-6. This is q3/q1/q4/q2 | |
| So the worst is DCRC1qO which is q2. Maybe this channel is the source of the noise - the amplitude of the noise falls off in either direction, geometrically speaking. | |
| 1025 | Power down DCRC55(1). Plug Cable 3 into breakout box, check for shorts. Feedback/Drain/Source on both channels look OK, around 0.2 nS to chassis. |
| 1030 | Start DAQ programs with DCRC3 only. At 10kHz noise in DCRC3qI/qO = 88/28 e-6. More than twice as bad as before! Is it because Side2 is now floating? Try grounding Side2 at breakout box - no change. |
| 1040 | Power down DCRC50(3), plug cable into DCRC55(1) again. At 10kHz noise in DCRC1qI/qO = 48/101 e-6. So DCRC1qI is worse than before, qO is about the same. |
| 1100 | Repower both DCRCs and set back to standard setup. Try applying bias with Kepco 0-40V supply - some pulses seen. Ground Side 2 then check noise again: |
| At 10kHz noise in DCRC3qI/qO/DCRC1qI/qO = 77/9.0/88/103 e-6. q3/q1/q4/q2. Basically the same as when we started except q4 which is apparently much noisier now. But the noise in the other channels is oscillatory, a few kHz - in q4 it looks like white noise plus some choppiness. Surprised that its as high as it is. Stressing the DSub connection for DCRC1 improved q4 noise, drops to 13e-6. |
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| 1110 | Flash detector for 10 seconds. MC(H35) peaks at 58 mK. No improvement in noise. |
| 1302 | Begin LHe transfer @ MB = 27.5% |
| 1340 | End LHe transfer @ MB = 90.8% |
| 1400 | At 10kHz noise in DCRC3qI/qO/DCRC1qI/qO = 60/7.8/41/88 e-6. All are a bit lower than before the transfer. Note that MC temperature is a little lower, 33.6→33.0 mK |
| 1405 | Tower/MC = 199/33.0 mK |
| 1411 | Start 44min series of 0V/-15V data (bias applied after 1 min), with 1000 beginning randoms, trigger threshold none/none/600/none on DCRC3qI/qO/DCRC1qI/qO, 5Hz in-run randoms, with 1.6384 ms pulses (8192 length) and 400 us prepulse (500 length). Start sequence with Start button. |
| 1414 | Adjust trigger threshold down to 400, 3 minutes into the series |
| Temperature excursions: strange. At 14:07 MC fell quickly, 33.0→31.8. Then at 14:14 it rose pretty quickly to 36.5 mK, then started to settle gradually. | |
| 1455 | Dial HV down to 0V, then short detector bias leads together. |
| Note - probably should be N2-purging ebox, haven't set that up yet. | |
| 1455 | Flash detector with DCRC1,3 LEDs for 30 seconds |