Previous Day
| | Setup: DIB1/3/4 → 3.2 MHz filters → cables 1,2,3 → HV board inputs 1,3,2 → HV board outputs 1,2 → DCRC55(1)/50(3) |
| | The DAQ apparently crashed last night some time during the 19:32 series. Data is still being taken this morning but it has been one continuous series since 19:32 last night with no randoms taken. The DAQ web page is down. |
| 0835 | Tower/MC/Coldplate = 33.6/36.3/222 mK, Still = 1.20 K / 85 μbar, G1/G2 = 115/105 mbar, 1K Pot = 1.55 K / 5.0 mbar. MB = 37.5%.
Boiloff rate is close to slow-mode. |
| 0840 | Fill LN2 cold trap bath. |
| 0840 | Tweak 1K pot needle valve open a few more degrees |
| 0845 | Restarted DAQ using instructions Starting the MIDAS DAQ Website. Looks like the 19:32 series finally ended and a new one has begun. |
| 0850 | DCRC1pC seems to be railed. Stop data series. |
| 0855 | Forgot to turn off logger, started short series by mistake |
| 0900 | Adjust driver offsets of active channels to get them all near -0.5 V. The inactive channels are railed. |
| 1055 | Apply HV to detector using the 0-40 V Kepco power supply. Increase voltage and check leakage across test resistor. At each voltage the leakage starts out high then falls off over a couple of minutes. Also record the baseline of the DCRC1pA trace. |
| HV [V] | Vtest [mV] | Ileak [nA] | Vcrystal [V] | DCRC1pA baseline [V] |
| 2 | 2 | 2.2 | 1.12 | -0.5 |
| 2 | 1.1 | 1.21 | 1.516 | -0.5 |
| 5 | 4.6 | 5.06 | 2.976 | |
| 5 | 2 | 2.2 | 4.12 | -0.49 |
| 5 | 0.8 | 0.88 | 4.648 | -0.48 |
| 10 | 7.5 | 8.25 | 6.7 | -0.47 |
| 10 | 2.9 | 3.19 | 8.724 | -0.46 |
| 10 | 1.2 | 1.32 | 9.472 | -0.48 |
| 15 | 8 | 8.8 | 11.48 | |
| 15 | 1.3 | 1.43 | 14.428 | -0.42 |
| 20 | 8 | 8.8 | 16.48 | |
| 20 | 2.1 | 2.31 | 19.076 | -0.35 |
| 25 | 8.5 | 9.35 | 21.26 | |
| 25 | 2.9 | 3.19 | 23.724 | -0.28 |
| 30 | 8.5 | 9.35 | 26.26 | |
| 30 | 3.8 | 4.18 | 28.328 | -0.2 |
formulas:
No obvious “breakdown noise” observed throughout the process.
| 1105 | Dial the HV down from 30 to 25 V, then remeasure: |
| HV [V] | Vtest [mV] | Ileak [nA] | Vcrystal [V] | DCRC1pA baseline [V] |
| 25 | 0.6 | 0.66 | 24.736 | -0.34 |
Both the leakage and the phonon trace baseline are lower than before. So it would seem that overshooting then backing off helps, as seen in previous detectors.
| 1110 | Dial HV back to zero, short HV input. After a minute baseline falls back to -0.47, close to previous base. |
If we interpret the change in baseline as occurring due to leakage current through the crystal, what current is implied? The baseline increased by about 0.27 V when Vcrystal was 28 V. Applying the appropriate gain factors this corresponds to a TES current decrease of 1.3 μA. With a QET bias of 179 μA and shunt resistance of 20 mΩ the TES is biased at approximately 3.6 μV*, so the TES is absorbing an additional 4.7 pW of power. The phonon collection efficiency of the TES is unknown but let's estimate 1%, typical of a single channel. Then the additional power being dissipated in the crystal is 470 pW. Since we know Vcrystal we know that this implies a leakage current through the crystal of 16 pA.
*Actually since the operating TES resistance is not much higher than the shunt resistance, this is a poor approximation. On the following day we measured the TES resistance of HV1pA to be 44.1 mΩ, so the TES voltage is closer to 2.5 μV. So the parasitic power is closer to 3.2 pW, so the implied leakage current is a little smaller, 11 pA.
| 1335 | Repeat earlier test with negative HV Bias. |
| HV [V] | Vtest [mV] | Ileak [nA] | Vcrystal [V] | DCRC1pA baseline [V] |
| -5 | -7.6 | -8.36 | -1.656 | -0.48 |
| -5 | -1.5 | -1.65 | -4.34 | -0.48 |
| -10 | -9.3 | -10.23 | -5.908 | -0.47 |
| -10 | -3 | -3.3 | -8.68 | -0.43 |
| -15 | -10.2 | -11.22 | -10.512 | -0.4 |
| -15 | -3.6 | -3.96 | -13.416 | -0.37 |
| -20 | -10.7 | -11.77 | -15.292 | -0.31 |
| -20 | -3.8 | -4.18 | -18.328 | -0.26 |
| -25 | -11.6 | -12.76 | -19.896 | 0.05 |
| -25 | -5.1 | -5.61 | -22.756 | 0.06 |
| -30 | -11.6 | -12.76 | -24.896 | 0.54* |
| -30 | -5.7 | -6.27 | -27.492 | 0.37 |
| *NOTE: | Channel occasionally railed when there were many pulses in succession. |
No obvious “breakdown noise” observed throughout the process.
| 1408 | Dial the HV down from -30 to -25 V, then remeasure: |
| HV [V] | Vtest [mV] | Ileak [nA] | Vcrystal [V] | DCRC1pA baseline [V] |
| -25 | -0.7 | -0.77 | -24.692 | -0.28 |
Again the leakage and baseline are smaller when using the backing-off method.
 |
| The red points were taken after backing off the bias |
| 1410 | Dial HV to 0V, and ground detector. |
| 1445 | Commence LHe transfer (28.4%). |
| 1529 | Cease LHe transfer (91.1%) |
| 1552 | Release pressure from main bath. |
| 1608 | Fill LN2 cold trap full. |
| 1709 | Release pressure from main bath. |
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