2020/08/21 (Friday)
- Lab in-person: Zach
- Virtual partner: Matt
| 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 off overnight. Lead/poly shield erected (4 lead walls, 2 poly walls). |
|---|---|
| Status: Added more 4He to the mixture four days ago, boiled off bath and warmed fridge to 12 K to pump out helium from IVC, then started circulation yesterday. | |
| Note: I may have inadvertently left the valve to the turbo pump closed yesterday. If so then today we should make a note of the IVC pressure, then open the valve again to pump on the IVC continuously. | |
| 0805 | MC(H35) = 28.7 mK, Still = 0.095 mbar, G1/G2 = 129/130 mbar. MC temperature flat overnight. |
| 0935 | Zach body temp = 98.8 |
| 0955 | Zach arrives at lab. |
| 1000 | Tower/MC/Coldplate = 45.7/28.6/187 mK, Still = 1.39 K / 0.095 mbar / 0 mW, 1K Pot = 1.70 K / 55±2 mbar. |
| I realize now that in all previous MC temps that I've recorded I used “MC Sensor” instead of “H35” - Zach. | |
| 1005 | MB = 58.2% |
| 1006 | Turbo was valved off overnight, IVC = 63 nbar, opened turbo on IVC, pressure went to 5.4 nbar. |
| 1030 | Power DCRCs 1&4. Had trouble powering DCRC1, lights would not go on when ethernet plugged in. But it worked when plugged into minibob. Turns out that the connection to the HV box affects whether it goes on or not, pushing it in more firmly the lights go on. Trying to adjust the height of the cardboard holding up the DCRCs to make this connection better. |
| 1040 | G1/G2= 134/133 mbar. |
| 1055 | Filled LN2 cold trap bath. |
| 1056 | Zach leaves lab. |
| 1923 | Zach body temp = 99.3 |
| 1105 | Zap SQUIDS on DCRCs1&4 |
| 1140 | Tower = 47.2 mK |
| the Tower temperature seems unaffected by the LN2 transfer - that's great! Looks like maybe it will be more stable now that we are running with more mixture. But it is lower than we had before, so we are going to have to adjust the QET biases. |
| QET bias table | |||
|---|---|---|---|
| Temperature range | |||
| 50.9 to 54.1 | 54.2 to 57.4 | 57.5 to 60.7 | |
| DCRC4pB | 320 | 310 | 300 |
| DCRC4pC | 370 | 360 | 350 |
| DCRC1pB | 360 | 360 | 350 |
| DCRC1pC | 420 | 410 | 400 |
| DCRC1pD | 420 | 410 | 400 |
| 1150 | Extrapolating from this table we can guess that good values at 47.2 mK are 340, 390, 370, 440, 440 uA. Let's start with these. |
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| 1240 | Do IbIs for DCRC4pB. Check to see what QET bias we want to match the dP/dI that we got when we measured IbIs at 52 mK (first column in table). Turns out we want almost exactly the same, 320 uA. So likely we can continue to use the first column values above. |
| 1300 | Write new sequence for +75V at 30.1 mV/s with 15% prebias for 2 minutes: HVdrift_pos75V_pre15_2min_30p1mVps_multiloop10_15min.msl |
| 1313 | Start a 15 min series at HV = +75V, drifting 0.0301 V/s, prebias 15% for 2min, CDMS detector: Driver Gains = 1x, DCRC4/1 QET biases = (0,320,370,0)/(0,360,420,420)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_pos75V_pre15_2min_30p1mVps_multiloop10_15min.msl |
| 1309 | Tower = 47.7 mK |
| 1314 | Vtest = 10.9 mV shortly after drift begins. Drift appears to start at +77.9 V. 5.6% HV loss. |
| This leakage is kinda high. Maybe we need to check the Ebox purge, increase the flow rate a little. | |
| 1330 | Vtest = 14.7 mV, HV = 104.7 V, drift ends. 5.6% HV loss. Lag ratio = 1.1ish. |
| 1330 | Tower = 47.8 mK. |
| Looking at data with BatViewer, looks like we were triggering much too often. Is there spiky junk? |
 |  |
| Gain&drift look the same as before | No second “spiky” peak seen here. But peak-to-peak of randoms is higher. Suggests we need to increase trigger threshold →10 or 11 |
| 1440 | Looked at the DCRC1pD QET bias settings. Made a quick plot of the amplitude of the oscillation noise (the height of the peak in the PSD seen at 13 kHz) versus QET bias. This seems to peak at 430 uA and gets smaller at greater and lesser QET biases. Trying 410 uA instead of 420 uA, it looks better - looks like you can trigger with threshold=8 and mostly get good pulse. This QET bias will significantly increase the TES gain of this channel, by I think about a factor of 1.5, so we'll probably see higher gain in the 60keV line. |
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| 1445 | Tower = 48.5 mK. It seems to be settling here, a little higher than before the flash. |
| Try to lower drift by 0.002 V/s. | |
| 1537 | Start a 15 min series at HV = +75V, drifting 0.0281 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_pos75V_pre15_2min_28p1mVps_multiloop10_15min.msl |
| 1540 | Tower = 48.3 mK |
| 1540 | Vtest = 10.8 mV shortly after drift begins. Drift appears to start at +77.7 V. 5.6% HV loss. |
| 1555 | Vtest = 14.5 mV, HV = 103.0 V, drift ends. 5.6% HV loss. Lag ratio = 1.1ish. |
| 1555 | Tower = 48.3 mK. |
| Seems like drift still isn't low enough, try lowering again by 0.002 V/s. | |
| 1716 | Start a 15 min series at HV = +75V, drifting 0.0261 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_pos75V_pre15_2min_26p1mVps_multiloop10_15min.msl |
| 1711 | Tower = 48.6 mK |
| 1717 | Vtest = 11.9 mV shortly after drift begins. Drift appears to start at +77.4 V. 6.1% HV loss. |
| 1733 | Vtest = 15.3 mV, HV = 100.5 V, drift ends. 6.1% HV loss. Lag ratio = 1.1ish. |
| 1735 | Tower = 48.5 mK. |
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| Now the drift is good, take a 60min series. | |
| 1815 | Start a 60 min series at HV = +75V, drifting 0.0261 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_pos75V_pre15_2min_26p1mVps_multiloop10_60min.msl |
| 1815 | Tower = 49.5 mK, ~1mK above base. |
| 1820 | Vtest = 11.8 mV shortly after drift begins. Drift appears to start at +77.4 V. 6.1% HV loss. |
| 1826 | Vtest = 29.2 mV, HV = 170.9 V, drift ends. 6.8% HV loss. Lag ratio = 1.1ish. |
| 1826 | Tower = 48.5 mK |
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| Looks like the drift rate was good at first, but as the fridge cooled by ~1mK the rate was not high enough. There is also a strange drop in gain at around 46min in, after which it is flat again. |