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| | Current setup: iZIP mode, DIB1/2/3 → cables → 3.2 MHz filters → DCRC55/33/50. |
| | Overweekend: activating source with Cf source in shield at detector level |
| 0900 | Fill LN cold trap Dewar |
| 0900 | Tower/MC(H35)/MC sensor/Cold Plate = 31.0/25.3/41.3/160 mK, Still = 1.38 K / 0.085 mbar, G1/G2 = 155 mbar, 1K Pot = 1.74 K / 22 mbar, Main bath = 44.7%. |
| 0915 | Remove Cf source from fridge |
| 0935 | Pulses on DCRC55 look fine, the 80Hz noise on DCRC55pB has not reappeared. |
| 1050 | DCRC55 pB still looks good. Disconnect all DCRCs for HV setup. |
| | New Current Setup: HV Mode, DIB1/2/3 → cables → 3.2MHz filters → HV Box → DCRC50/55. Now all LED lines are grounded in the HV box |
| 1115 | Zap SQUIDs. Current HV QET biases in uA (estimates originally chosen during first round of HV tests): |
| QET biases (μA) |
| | HV1 (DCRC50) | HV2 (DCRC55) |
| A | 93.2 | - |
| B | 114.2 | 88.7 |
| C | 88.5 | 110.9 |
| D | - | 88.5 |
| 1130 | Repeat HV versus Ileak study monitoring HV1 pulses: |
| HV (V) | Ileak (nA) |
| 0.004 | -0.1 |
| 5.001 | 8.0 |
| 10.00 | 15.5 |
| 11.5 | 16.3 |
| 11.8 | 16.8 (pulses start disappearing) |
| 11.9 | 16.8 (pulses gone except very rough HV1pC) |
| 12.0 | 17.0 (pulses completely gone) |
| 1217 | Zero HV bias and commence negative bias sweep. |
| HV(V) | Ileak (nA) |
| 0.001 | -0.3 |
| -5.002 | -8.0 |
| -10.00 | -15.7 |
| -11.00 | -17.2 |
| -11.50 | -17.7 |
| -12.00 | -18.4 |
| -13.00 | -20.0 |
| -14.00 | -21.6 |
| -14.50 | -22.3 (pulses almost gone) |
| -15.00 | -23.1 (pulses gone except HV1pB) |
| -15.50 | -24.0 (pulses completely gone) |
| 1405 | Start IbIs on DCRC50 (HV1) with Frontend Gain=1, Output Gain=0, and Qbias=0. |
| 1430 | Start IbIs on DCRC55 (HV2) with Frontend Gain=1, Output Gain=0, and Qbias=0. |
| 1630 | Set Frontend Gain=1, Output Gain=3. Set HV1 pA & pB to QET bias = 0. Keep pC at QET bias = 88.5uA. Scan HV. |
| HV(V) | Ileak(nA) | pAbaseline (V) | pBbaseline (V) | pCbaseline (V) |
| 0 | 0 | -0.58 | 0.900 | -0.295 |
| 4.998 | 7.7 | -0.58 | 0.900 | -0.295 |
| 10.00 | 15.1 | -0.578 | 0.900 | -0.26 |
| 11.00 | 16.0 | -0.576 | 0.900 | 0.325 |
| 11.50 | 16.3 | -0.576 | 0.900 | Railed† → -1.2 |
| 12.00 (pulses on HV1pC gone) | 16.6 | -0.478 | 0.370 | -0.172 |
| † After railing, Driver Offset was changed from 0.40 to -0.04, which brought the baseline back at -1.2V. |
| NOTE: | Dialling up the HV quickly, you can go well past 12V with no change in baseline, but after waiting ~1 minute, pC pulses disappear and pA/pB baselines change to their new values. Further increase in HV doesn't change baselines. (Bimodal) |
This was intended as a double check to eliminate the hypothesis that current from the HV box was leaking into the QET lines and causing heating in that way. The sudden change in baselines for channels with QET bias set to zero is surprising. But a change would be expected if the QET bias was not zero, because as the TES transitions from s/c to normal the current would suddenly be diverted through the shunt resistor. In the test below we try different small QET biases on pA and pB, then increase HV to drive them to normal and observe the baseline shift:
| HV1pA | HV1pB |
| QET bias (μA) | s/c baseline (V) | norm. baseline (V) | baseline change (V) | QET bias (μA) | s/c baseline (V) | norm. baseline (V) | baseline change (V) |
| 0 | -0.585 | -0.478 | 0.107 | 0 | 0.900 | 0.371 | -0.529 |
| 5 | -1.10 | -0.506 | 0.594 | 5 | 0.22 | 0.371 | 0.151 |
| -5 | 0.055 | -0.447 | -0.502 | -5 | 0.185* | -0.958* | -1.143 |
| -0.6 | -0.505 | -0.472 | 0.033 | 4.1 | -1.013 | -1.015 | -0.002 |
| Output gains = 3. *: offset was adjusted to see shift. |
Plotting the baseline shift versus applied QET bias suggests that the true 0 of the QET bias is offset. Linear fits suggests that true zero is achieved at nominal settings of -0.67 / 4.11 μA for DCRC50pA/pB. As shown above applying QET biases close to these values produces smaller shifts in baseline between s/c and normal.
| 1530 | Commence LHe transfer (34.7%). |
| 1700 | Cease LHe transfer (89.1%). |
| 1740 | Fill LN2 cold trap full. |
| 1750 | Reset QET biases to standard values and output gains to 0. Take baseline versus HV data: |
| HV1pA baseline (std. QET bias, 93.2 μA) |
| HV (V) | I_leak (nA) | Baseline (V) | notes |
| 10 | 13.1 | 0.07 | |
| 11 | 14.8 | 0.07 | |
| 11.5 | 15.7 | 0.08 | |
| 11.8 | 16.4 | 0.12 | |
| 12 | 16.6 | 0.17 | |
| 12.1 | 16.7 | 0.2 | |
| 12.2 | 16.9 | 0.27 | |
| 12.3 | 17.1 | 0.34 | |
| 12.4 | 17.4 | 0.34 | pulses almost gone |
| 12.5 | 17.1 | 0.34 | pulses completely gone |
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