2021/07/26 (Monday)
- Lab in-personnel: Giulia and Pramod
| Status | Run 74 in progress. First cooldown after IVC rebuild. |
|---|---|
| Tower thermometer is reading high, probably this is a thermometer problem and the actual temperature is much lower. High noise in some of the charge channels. | |
| Setup: DIB1/2+acc → SL 41/43 → 3.2 MHz filters → cables 2/3 → nothing/Source_mover_board+HV_diverter_board → DCRC50(3)/55(1). Kepco 40V supplye → HV BNC. No lead/poly shield. Currently both DCRCs are on. | |
| 1103 | Tower/MC/Coldplate = 277.2/37.6/ 192 mK, Still = 1.41 K / 0.08 mbar / 0 mW, G1/G2= 281.5/258.3 mbar, 1K Pot = 1.62 K / 20±1 mbar. MB = 64.7%. |
| Tower particularly high today (but do we believe it?). It looks like it was around 150 mK up to 5pm yesterday but then rose, climbing to 280 mK in less than 1 hour then sorta fluctuating between 280 and 320 mK. | |
| Note: E-box purge has been off since Friday. | |
| 1107 | Fill LN2 cold trap bath. |
| 1152 | At 10kHz noise in DCRC3qI/qO/DCRC1qI/qO = 36/5.3/3.89/141 e-6. This is q3/q1/q4/q2 At 3kHz (peak) noise in DCRC3qI/qO/DCRC1qI/qO = 1122/160/98/4073 e-6 |
| These are more higher than last week. | |
| 1300 | Restart N2 flow for E-box purge. |
| 1355 | Start data then abort, overtriggering. |
| 1405 | Start 45 min series of 0V/-15V (bias applied after 60 sec), with 1000 beginning randoms, trigger threshold 200/70/75/600 on DCRC3qI/qO/DCRC1qI/qO, 5Hz in-run randoms, with 1.6384 ms pulses (8192 length) and 400 us prepulse (500 length). Start sequence with Start button. |
| 1454 | Dial bias down to 0V and flash detector for 60 seconds. |
| We expected this base-temperature series to show the same impact ionization pattern as we saw before, i.e. peaking around 80keV at around 6 minutes. But instead it peaks around 130keV, which is even higher than we saw in the 660 mK case. So what is happening? Something has changed in the detector. Of course we don't know what “base” temperature is, and today the Tower temperature is reading high. MC temperature is a few mK higher than usual too. Also worth noting that if we look back at the run summary, 0/-15V data early on, in an earlier cooldown, looked different too - it peaked at around 130keV. So hard to say whether there's any consistency. |
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| Looking back the detector showed consistent behavior on July 13,14,15 (a little higher on the 15th), then the 20th was actually kind of a high peak. But then the Na-22 tests the following days seem reasonably close to the normal pattern. | |
| 1635 | Turn off DAQ programs and unplug both DCRCs, for now. |
| 1645 | MC temperature is starting to fall, 38.0 → 37.0 mK. Tower @ 248 mK, which is a little lower than it has been in the last 24 hours. |
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| 07210726_1405 Detector is in a new “state”. Impact ionization is stronger than before. |