2022/04/14 (Thursday)
- Lab in-personnel: Matt, Nikki
| Status | Run 76 in progress |
|---|---|
| Setup | Cable 2/1/3 → diverter/nothing/nothing → HV CONN1/2/3 → HV 1/2 → DCRC50(3)/DCRC55(1), DCRC33(2)→HV control, NaI trigger signal → DCRC52(6) actually discovered later that Cables 1&3 were swapped. |
| 0900 | Pulses look good |
| 0905 | Use Root Sequencer to increase HV to 32 V. TESs go normal, pulses gone, baselines elevated. Step HV down… TESs are still normal down to 4V. Set HV back to ~0V, pulses return. |
| 0915 | Flash LEDs for 30 seconds (these are connected to DCRC3). MC peaks at 38 mK, then cools again. |
| 0945 | Try HV = 0.7 V. Pulses still present but it looks like baselines are elevated, somewhat noisy. Bring HV back to zero, pulses return. Try 2.8 V, channels go normal; back to 0V, pulses return. |
| 1426 | Begin LHe transfer @ MB = 30.4% |
| Some tweaks to procedure. We tried turning off the heater on the 250L Dewar early; we found that if the pressure falls below 3PSI on the Dewar gauge the transfer gets very slow. At the end we raised both ends of the transfer line as high as possible and waited for the pressure to fall as usual. But this time we also connected the extra recovery hose with the quick-connect to the Dewar exhaust. We had the wrong kind of connector so we had to replace it - that took a little while. In the end the pressure was < 2.5 PSI when we finally removed the transfer line. Maybe it would have gotten lower if we could have connected the Dewar exhaust sooner. |
|
| 1538 | End LHe transfer @ MB = 92.5% |
| 1610 | MC/Coldplate = 27.4/140 mK, Still = 1.04 K / 0.100 mbar / 0 mW, G1/G2= 128/138 mbar, 1K Pot = 18° / 1.57 K / 13±2 mbar |
| 1615 | Goldman = 71.6 mK @ 632 uV excitation |
| 1620 | Fill LN2 cold trap bath |
| 1625 | Connect HV test resistor to Keithley meter. At first this causes a disturbance in the phonon channels but it goes away after a couple minutes. |
| 1630 | Try a couple of biases: HV = 2.76 V → Vtest = 6.52 mV. HV = 7.07 V → Vtest = 17.07 mV. These are very high - they imply Ileak = 1.2/18.8 nA and suggest that essentially 0 bias is reaching the detector, the voltage is dropping entirely across the test resistor. |
| Could there be a TES shorted to chassis? Recall that we had an intermittent short during tower installation: Face5pin7 in the tower was shorting to the tower chassis. It went away but maybe it returned. This is Face5pD = Side2pE. A side2 channel - so this would short out the HV. | |
| 1640 | Unplug HV connector from HV board and instead measure the resistance at the HV connector on the board with the Fluke multimeter. 2.4 nS, which is 420 MOhm, which is close to the 400 MOHm ballast resistor. So this suggests a low resistance at the cold end - possibly a short. |