2020/10/22 (Thursday)
- Lab in-person: Matt
- Virtual partner: Zach
| Setup | Run 73. DIB 1/3/4 → Stripline 43/48/41 → pi-filters 1/2/3 → Cable 3/1/2 → nothing/nothing/accessory_interposer → HV_Conn 1/3/2 → HV 1/2 → DCRCX(4)/DCRC55(1)-master; DCRC33(2) → HV control. DCRCs on. Lead/poly shield erected (4 lead walls, 2 poly walls). |
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| The Kepco power supply that provided HV bias for the detector is working intermittently. Currently it is not working, need to try to get it going again in the lab today. | |
| 1020 | Matt Fritts body temperature = 96.9 F |
| 1130 | Matt enters lab |
| 1135 | Tower/MC/Coldplate = 92.0/31.4/196 mK, Still = 1.50 K / 0.120 mbar / 0 mW, G1/G2= 246/223 mbar, 1K Pot = 1.63 K / 21±2 mbar. |
| 1150 | Troubleshooting the Kepco HV supply. It seems that we can set the HV just fine, if it is not connected to the HV box input to send the bias down the fridge lines. But if either the + or - lead on the Kepco is connected to the ground-side lead of the HV box input, the bias falls to 0V. When that connection is removed the bias goes back to normal. |
| We get the same effect - bias falls to zero - if we connect one of the HV leads to either of the DCRC1/4 grounds, specifically the connector shields on the DCRCs. Same effect if we connect it to DCRC2's ground shield. | |
| 1245 | Currently testing with DCRC2qI set to 11.8, which gives an output HV of 4.0 V. When one of the HV leads is grounded to DCRC2 ground, the HV falls to zero. The control voltage going into the back of the Kepco supply is 0.1 V normal, falls to 0.0V when grounded. The output voltage from the DCRC that goes to the opamp circuit stays at ~11 V whether the HV lead is grounded or not. |
| 1305 | Try disconnecting the relay part of the circuit that turns the Kepco on and off with DCRC2qO. This seems to produce a rather different HV calibration. But the grounding problem is still there. I'll reconnect the relay system. |
| 1325 | Connecting an HV lead to Input 5 at the back of the Kepco also causes HV to fall to zero. Not surprising since this is connected to DCRC2 ground. So - that may be normal behavior. But maybe DCRC2's ground should be isolated from DCRC1&4's grounds. Why isn't it? |
| 1330 | Breakthrough: DCRC2 was sitting on a pad of paper, but recently the pad moved so that part of DCRC2 was sitting directly on the GwINSTEK power supply housing. Now that I've moved it to be isolated from the housing, the output HV behavior is completely different… and the HV no longer falls to zero when the HV lead is connected to DCRC1/4 ground. (Although it does change a little - so the calibration should maybe be done with this ground connected.) |
| Lesson learned: make sure that the DCRC controlling the HV is sitting on an electrically isolated surface. | |
| 1400 | Recalibrate HV, and put this into the RootSequencer. |
| 1410 | Reconnect HV to HP meter. Also connect to the HV box, but the leads to the HV box are shorted together and plugged into the - output on the Kepco. Try changing the bias from the ODB - it works. |
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| 1420 | Hook up the HV to the HV box in positive polarity. Try dialing up to a couple of volts (DCRC2qI 11.58→11.5) - it works. good. |
| 1525 | Fill LN2 cold trap bath |
| 1425 | Channels look reasonable except DCRC1pB has some ugly noise. I turned off the DAQ programs earlier because something got stuck, so maybe I should zap. |
| 1425 | Zap DCRC1&4 SQUIDs |
| 1430 | Matt leaves lab |
| 1655 | Finish IbIs on DCRC1pD. Implied detector temperature = 59.3 mK. Tower thermometer varied withing 84.3-86.1 mK. This is not very consistent with the last few days; Detector temperature is about 1 mK lower than expected. |
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| 1705 | Do one more DCRC1pD IbIs, looks like the Tower thermometer calibration line is shifted a little downward. We'll use this as a new recalibration. |
| 1722 | Start a 60 min series at HV = +300V, drifting 0.0262 V/s, prebias 15% for 2min, CDMS detector: Driver Gains = 1x, DCRC4/1 QET biases = set automatically to track temperature, Front-End Gains = (3/3/3)/(5/5/5) 1000 BOR & 5 Hz in-run randoms, trigger on DCRC1pD threshold = 8 Use RootSequencer.c, function drift_sequence(300,0.0262) Use QETbias_update.c, function sequence_update_QETbiases(66,30,0,0.115,49.45) |
| 1722 | Vtest = 2.1 mV shortly after drift begins. Drift starts at 313.4 V according to RootSequencer. 0.27% HV loss. |
| Tower thermometer wandered between 85 and 89.5 mK during series. | |
| 1823 | Vtest = 2.5 V at end of drift. Final HV = +407.7 V according to RootSequencer. 0.25% HV loss. |
| 1910 | do another IbIs, refine the recalibration a little |
| 1924 | Start a 60 min series at HV = +100V, drifting 0.0274 V/s, prebias 15% for 2min, CDMS detector: Driver Gains = 1x, DCRC4/1 QET biases = set automatically to track temperature, Front-End Gains = (3/3/3)/(5/5/5) 1000 BOR & 5 Hz in-run randoms, trigger on DCRC1pD threshold = 8 Use RootSequencer.c, function drift_sequence(100,0.0274) Use QETbias_update.c, function sequence_update_QETbiases(66,30,0,0.16,45.8) |
| 1924 | Vtest = 0.7 mV shortly after drift begins. Drift starts at 106.2 V. 0.26% HV loss. |
| Tower swung between 79.1 and 85.4 mK during series. | |
| 2025 | Vtest = 1.1 V at end of drift. Final HV = +205.5 V. 0.21% HV loss. |
| 2035 | Arduino web page is still communicating with source mover. Do “rd dwell”, returns 40 ms, good. |
| 2040 | Move source -4×49 steps with 4 minute pause after each move, mvNwait -4 240 49 This should move the source to y = -39.357 mm warm (-39.206 mm cold, after correction for differential contraction). This is right between pD and pB. Total sequence should take 3hr 16min, ending at 11:56 pm |