2021/03/03 (Wednesday)
- Lab in-person: Derek
- Virtual partner: Matt
| Status | Run 74 in progress. |
|---|---|
| Setup: DIB1/2+acc → SL 41/43 → 3.2 MHz filters → cables 2/3 → nothing/nothing → DCRC50(3)/55(1). No lead/poly shield. | |
| 1145 | MB = 27.8% |
| 1205 | Tower = 92.0 mK |
| Yesterday we took some 7V data with the accessory diverter boards removed from DCRC1. Before that, we hadn't been able to see the 60keV line, and I wondered whether the Side2 electrode was not properly grounded, just floating. Partly because we see a muon bulge but the energy seems too low. By removing the diverter boards the Side2 electrode should be grounded by the DCRC because it is connected to a phonon return line. (or at least I think so - this raises a question, where are the multiple return lines for one channel connected to one another? Is it at the SQUET? We are bypassing the SQUET.) The data looks the same as before, so either Side2 was grounded fine with the diverters present, or it is still floating now with those boards removed. | |
| 1420 | Derek enters lab |
| 1422 | Tower/MC/Coldplate = 92.3/31.2/192 mK, Still = 1.49 K / 0.130 mbar / 0 mW, G1/G2= 206/189 mbar, 1K Pot = 1.67 K / 36±2 mbar. |
| 1423 | Fill LN2 cold trap bath. |
| 1424 | MB = 22.6% |
| Do some checks on a DCRC and the diverter boards. As it turns out, all of the QET A return lines are grounded in the DCRC. So, this rules out the theory that Side2 was left floating by the DCRC. (Verified that this is also true for DCRC55, the one we are using.) Check that everything is connected correctly on the HV diverter board - looks OK. So, we still have a mystery. As far as we can tell, we have indeed been grounding Side2 properly. | |
| 1530 | Reconnect the two diverter boards to DCRC55(1). Look at the channels with Pulse Viewer - noise looks OK (maybe a little higher than before). Try triggering on one channel at 0V - no pulses seen. Apply +5V - see pulses. Now try unplugging the shorting cable that we are using to ground Side2. We continue to see pulses. But hard to say whether they are smaller/less frequent, as we might expect with a floating Side2. So we should try a data series to compare. |
| 1546 | Start 31min series of +7V data (bias applied after 1 min), with HV lead left floating, with 1000 beginning randoms, trigger threshold 80/80/80/80 on DCRC3qI/qO/DCRC1qI/qO, no in-run randoms, with 1.6384 ms pulses (8192 length) and 400 us prepulse (500 length). Use sequence r74_takeandflash_dcrcbias.msl |
| Triggering looks OK | |
| Turns out this data looks very similar to what we had before with the HV lead grounded. Meaning we are seeing the same thing whether we ground Side2 or leave it floating. Which seems implausible. So that suggests that we are never successfully grounding Side2, it's always floating. What we should try next is to apply a bias to Side2, with the charge channels left at 0V. We should see pulses start to appear when the bias is applied, if we actually have a connection to Side2. |
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| 1620 | Start LHe transfer @ MB = 19.9% |
| 1655 | End LHe transfer @ MB = 88.0% |
| 1720 | Derek exits lab |