2019/03/13 (Wednesday)
| 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) manual kepco 1kV power supply → HV input |
|---|---|
| 0910 | Tower/MC/Coldplate = 51.7/32.3/199 mK, Still = 1.74±0.06 K / 0.160 mbar, G1/G2 = 199/199 mbar, 1K Pot = 1.78 K / 17 mbar. MB = 65.2% |
| Tower cooling at a rate of 1.94 mK/day | |
| 0920 | Fill LN2 cold trap bath |
| 1010 | He recovery: between transfers we've found the reco meter running backwards. Yesterday I isolated the 4He pump exhaust from the recovery system and it started running forward again. Overnight we recovered at a rate of 11.2 L/day, and boiled off the bath at a rate of 17.6 L/day, 63% recovery. |
| 1017 | Cap off the end of the hose that leads to the 4He pump exhaust, then open the line up to recovery. This is just to see whether the hose itself leaks. We'll see whether the recovery rate changes. |
| 1100 | Recovery rate unaffected by opening to capped exhaust line. |
| 1108 | Connect 4He pump exhaust to recovery with oil filter removed. |
| 1230 | MB = 60.5% |
| 1235 | Since connecting the 4He exhaust to recovery with the oil filter removed, recovery rate has increased slightly, from 12.0 L/day to 12.5 L/day. Currently the bath boiloff rate is about 17.9 L/day. So recovery efficiency only increased from 67.0% to 69.8%. |
| 1242 | Add more oil to the 4He pump, raising the level from around 20% to around 50% between the marks. (Lebyonol LVO 100 mineral oil added to center port in back of pump.) |
| 1250 | At 10:35, Tower temperature began to rise, from 51.5 mK reaching about 55.1 mK by 11:00. I suspect one of our channels has gone bad again like yesterday… |
| 1310 | Channels are all flatlined, probably because a bad channel is heating everything. Try turning off QET bias on DCRC3pC which was yesterday's culprit: no change. Start turning off biases one by one. When DCRC4pA is turned off, temperature starts falling. (Or maybe it was DCRC3pD.) Now channels start to show pulses again. |
| 1325 | Get all 6 channels back into a reasonable place in transition, all show decent pulses. |
| 1410 | Tower = 51.1 mK |
| Yesterday's data gives an idea of how quickly counter bias develops in the detector at the current energy deposition rate. About 15 seconds per volt. Plan today is to test a time-varied applied HV. | |
| 1513 | Start dialing up HV to target 150 V |
| 1517 | See a little jagged noise. Dial up to 160, wait for leakage to settle, then we'll dial back to 150. |
| 1520 | Start background series at HV = 150 V but increasing by 4 V every minute CDMS detector: Driver Gains = 1x, DCRC4/3 QET biases = (405/370/420)/(400/370/410) uA, Front-End Gains = (4/2/3)/(10/15/10) 1000 BOR randoms, trigger on DCRC3pB threshold = 7 |
| 1539 | At HV=222V, power supply is maxed out at this coarse setting. Let's leave it sit like this for a bit longer. |
| 1600 | Dial HV down to 0 V. First big knob 1 click, then shortly after dial down little knob. |
| 1603 | Switch HV bias and begin increasing voltage by -4 V / min |
| 1610 | Not sure we are still getting pulses because pulse viewer isn't showing anything, maybe the triggering channel railed. |
| 1611 | Enable DCRC3pC threshold = 15. seeing pulses now, but not sure, I had to click a couple of channels, so maybe it was OK before. OK no - DCRC3pB is mostly railed. |
| 1615 | Adjust driver offsets on DCRC3pB and pC |
| 1625 | Fill LN2 cold trap bath |
| 1625 | MB = 54.8% |
| 1628 | HV = -100 V |
| 1629 | Dial HV back down to 0 V |
| 1650 | It's difficult to see any change in recovery between 1) isolating 4He pump from reco 2) connecting pump to reco with no filter 3) adding more oil to pump. The recovery rate has just been wavering around a pretty steady average. |
| 1652 | Stop data |
| 1655 | Looks like once again LazyLogger stopped. Restart MIDAS to restart LazyLogger. |
quick look at data:
looks like we did a decent job of canceling the counter bias.
A quick calibration of the first 10 minutes suggests a noise sigma = 41 eV.