2019/03/22 (Friday)
| Setup | DIB1/3/4 → 3.2 MHz filters 2/3/1 → cable 3/1/2 → gender changer 3/?/2 → HVConn 1/3/2 → HV 1/2 → DCRCX(4)/DCRC50(3) DCRC33(2) → 1kV power supply → HV input Lead poly shield is erected, N/E/W walls complete, no poly or lead on S wall. PuBe source present in paraffin barrel behind lead stack. |
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| 0935 | Tower/MC/Coldplate = 41.7/30.0/185 mK, Still = 1.7±0.2 K / 0.150 mbar, G1/G2 = 244/221 mbar, 1K Pot = 1.78 K / 15 mbar. MB = 38.9% |
| Tower falling 0.23 mK/day | |
| 0955 | All channels show good pulses. |
| 1025 | MIDAS has been freezing up during the sequences and I have a feeling that it's because they're too long (from past experience). So I generated a modified sequence with a faster ramp-up rate (1→2 V/s) and a longer drift update period (10→20 s). Also I reduced the prebias time from 2→1 minute. These changes will make the sequence file itself shorter. Also I'm reducing the amount of time between when we start applying bias and when data starts, so that the effective bias (applied minus counterbias) will be higher. New sequence is HVdrift_fast_300V_5p4VPM_prebias_15_1_dur_18min.msl. |
| 1035 | Adjust QET bias on DCRC4pC, it had been looking quite ringy when we were taking data at high HV. 450→430 uA, looks like a bit less oscillation there. |
| 1040 | Start PuBe series at HV = 300→400V @ 5.4 V/min (18 min duration) with 1 minute 15% prebias CDMS detector: Driver Gains = 1x, DCRC4/3 QET biases = (410/370/430)/(420/390/420) uA, Front-End Gains = (4/2/3)/(10/15/10) 1000 BOR randoms, trigger on DCRC3pB/D threshold = 7/7 use sequence HVdrift_fast_300V_5p4VPM_prebias_15_1_dur_18min.msl |
| 1046 | HV = 343.8 V, Vtest = 130 mV, prebias wait begins |
| 1048 | Data starts. All channels look OK. |
| 1049 | HV = 306.4 V, Vtest = 48 mV |
| 1051 | HV = 315.2 V, Vtest = 55 mV |
| 1055 | HV = 336.7 V, Vtest = 56 mV. All channels look OK. |
| 1102 | HV = 372.7 V, Vtest = 63 mV |
| 1106 | HV = 392.5 V, Vtest = 70 mV |
| 1109 | Data has stopped, bias is ramping down. |
| 1115 | Fill LN2 cold trap bath |
| 1115 | Tower = 42.0 mK. Stayed pretty flat during data series. |
| 1115 | Sequence has flashed the detector. Tower spikes up about 2 mK. |
| 1130 | Check channels: all still good. DCRC3pB baseline is close to the bottom though. Adjust driver offset on that channel. |
| Let's try negative bias. We'll try the same sequence but with the leads on the HV swapped. We haven't checked whether -400 V is OK, so we'll keep a close eye during the rampup and stop the sequence if things look bad. | |
| 1138 | Start PuBe series at HV = -300→-400V @ 5.4 V/min (18 min duration) with 1 minute 15% prebias CDMS detector: Driver Gains = 1x, DCRC4/3 QET biases = (410/370/430)/(420/390/420) uA, Front-End Gains = (4/2/3)/(10/15/10) 1000 BOR randoms, trigger on DCRC3pB/D threshold = 7/7 use sequence HVdrift_fast_300V_5p4VPM_prebias_15_1_dur_18min.msl |
| 1144 | HV = -343.8 V, Vtest = -155 mV, prebias wait begins. Vtest falls to -80 mV after 1 minute. |
| 1146 | Data starts. All channels look OK. |
| 1147 | HV = -304.4 V, Vtest = -52 mV |
| 1154 | HV = -340.3 V, Vtest = -63 mV |
| 1200 | HV = -370.9 V, Vtest = -67 mV. Unfortunately DCRC3pB is railed. Adjust its driver offset. |
| 1204 | HV = -390.8 V, Vtest = 71 mV |
| 1205 | Data has stopped, bias is ramping down. |
| A quick look at the data does not indicate any obvious improvement for negative bias versus positive. So we'll switch back to positive for now. | |
| 1210 | Tower temperature is rising, up about a mK, so maybe one of the channels is unhappy again. |
| 1325 | Tower is up about 2 mK. DCRC3pB looks like it's in pretty heavy oscillations, and it's driver offset is pretty far off. Messed with this a little, then decided to try zapping SQUIDs. |
| 1330 | Zap SQUIDs. |
| 1340 | Temperature going up. Let's just set all the QET biases to 0 for now. |
| 1348 | Begin LHe transfer @ MB = 32.8% |
| 1405 | Get all the channels back in transition and showing good pulses. Tower temperature coming down. |
| 1425 | End LHe transfer @ MB = 95.5% |
| 1510 | Fill LN2 cold trap bath This was the second time this was done today, not sure if that was intentional or not. |
| 1510 | Tower = 41.5 mK. Channels look OK. |
| Generated a sequence to do 300→400V data same as before, but repeat 4 times. (Hopefully it won't crash MIDAS, we'll see.) Don't know for sure that we have things stable enough for this to work but it's worth a try. | |
| 1536 | Start 4 PuBe series at HV = 300→400V @ 5.4 V/min (18 min duration) with 1 minute 15% prebias CDMS detector: Driver Gains = 1x, DCRC4/3 QET biases = (410/370/430)/(430/390/420) uA, Front-End Gains = (4/2/3)/(10/15/10) 1000 BOR randoms, trigger on DCRC3pB/D threshold = 7/7 use sequence HVdrift_fast_4X300V_5p4VPM_prebias_15_1_dur_18min.msl |
| 1550 | Several channels are railed, and Tower temperature is increasing. So we will abort this run. |
| 1555 | Take HV back down to ~0V by adjusting DCRC2qI bias step by step. |
| 1605 | Take all channels to 0 QET bias then back up to 800 or 500 uA, relock, etc. Tower temperature (which peaked at 45 mK) now coming down. |
| 1700 | Tower temperature has settled at ~41.9 mk. Resetting the channels into transition to try another run. |
| 1705 | Tower = 41.9 mk, channels look ok. Start sequence again from the same base as previously generated. |
| 1712 | Start 4 PuBe series at HV = 300→400V @ 5.4 V/min (18 min duration) with 1 minute 15% prebias CDMS detector: Driver Gains = 1x, DCRC4/3 QET biases = (410/370/430)/(430/390/420) uA, Front-End Gains = (4/2/3)/(10/15/10) 1000 BOR randoms, trigger on DCRC3pB/D threshold = 7/7 use sequence HVdrift_fast_4X300V_5p4VPM_prebias_15_1_dur_18min.msl |
| 1720 | Vtest seems surprisingly high, around 140.9 mV, peaked around 210 mV during the prebias step, going to watch closely to see if it jumps again. |
| 1730 | Vtest is still high and temperature continues to increase, channels are also railing. aborting this run as well |
| 1732 | Take HV back to ~0 |
| 1755 | Take all channels to 0 QET bias then back up to 800 uA and relock. Tower temperature is stabilizing and possibly dropping. |