2020/09/01 (Tuesday)
- Lab in-person: Matt
- Virtual partner: Michael
| 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 overnight. Lead/poly shield erected (4 lead walls, 2 poly walls). |
|---|---|
| 0643 | MB = 34.5%. Predict it will hit 20% at 15:07 |
| 1030 | Tower = 49.3 mK |
| 1030 | Turn on MC Heater → 1 uW. Tower → 51.7 mK. |
| 1050 | Tower has drifted down to 51.2 mK |
| 1130 | Tower settles around 51.1 mK with MC Heater at 1 uW |
| 1230 | Turn off MC Heater |
| 1315 | Matt enters lab |
| 1315 | Tower/MC/Coldplate = 49.2/30.4/172 mK, Still = 1.41 K / 0.095 mbar / 0 mW, G1/G2= 250/237 mbar, 1K Pot = 1.69 K / 45±2 mbar. |
| 1320 | Fill LN2 cold trap bath |
| 1320 | Turbo on Cryostat Vacuum Jacket = 3.4 nbar. With Turbo valved out for 1 min, Cryostat Vacuum Jacket = 0.10 ubar. Resume pumping. |
| 1320 | Swap HV leads to negative bias |
| 1330 | Stop pumping on Cryostat Vacuum Jacket, connect turbo pumping station to IVC port. |
| time | MB |
|---|---|
| 7:43 | 32.9 |
| 8:43 | 31.2 |
| 9:43 | 29.5 |
| 10:43 | 27.8 |
| 11:43 | 26.1 |
| 12:43 | 23.7 |
| 1353 | Start LHe transfer @ MB = 21.8% |
|---|---|
| 1420 | Start pumping out IVC with Turbo Pump. Meant to start this before the transfer but I forgot. |
| 1431 | End LHe transfer @ MB = 91.8% |
| 1450 | During transfer Tower temperature started to rise, peaking around 75 mK, then starting to cool. Looks like something similar happened after the last transfer too, according to the temperature log. |
| 1450 | MB = 91.7% |
| 1510 | Matt leaves lab |
| 1645 | Tower = 51.9 mK, still falling. |
| 1700 | Write sequence for -200V drifted 37.2 mV/s with prebias. HVdrift_neg200V_pre15_2min_37p2mVps_multiloop10_60min.msl |
| 2159 | Start a 60 min series at HV = -200V, drifting 0.0372 V/s, prebias 15% for 2min, CDMS detector: Driver Gains = 1x, DCRC4/1 QET biases = (0,320,370,0)/(0,360,420,410)uA, Front-End Gains = (3/3/3)/(5/5/5) 1000 BOR & 5 Hz in-run randoms, trigger on DCRC1pD threshold = 8 Use sequence HVdrift_neg200V_pre15_2min_37p2mVps_multiloop10_60min.msl |
| 2200 | Tower = 50.1 mK |
| 2200 | Vtest = -9.7 mV shortly after drift begins. Drift appears to start at -203.3 V. 1.9% HV loss. |
| 2309 | Vtest = -16.2 mV then falls, indicating drift has ended: Lag Ratio ~ 1.17, significantly higher than the usual 1.1. HV at end of drift should be 339.0 V according to sequence, indicating 1.9% HV loss. |
| 2310 | Tower = 50.0 mK |
| later look at data shows Lag Ratio = 1.16 |
 |
| Here is clear evidence of -bias showing much lower Luke gain than +bias |
| -200V Luke gain seems lower even than -150V |
| Similar time dependence, hard to know whether drift is right. |