2016/11/18 (Friday)
| Setup: DIB1/3/4 → 3.2 MHz filters → cables1/2/3 → DCRC55(1)/33(2)/50(3) | |
| 1015 | Tower/MC/Coldplate = 33.1/36.0/212 mK, Still = 1.3 K / 110 μbar, G1/G2 = 188/191 mbar, 1K Pot = 1.69 K / 28 mbar. MB = 23.5%. Boiloff rate: close to slow-mode. |
| 1040 | Start LHe transfer (22.3%) |
| 1125 | Finish LHe transfer (92.6%) |
| 1140 | Released pressure from MB. |
| 1230 | Re released pressure from MB. |
| 1235 | Try test signals on DCRC1 and DCRC3. Able to connect to all the active channels, unlike two days ago. There is still the bug that on DCRC1, turning on the test signal automatically seems to connect it to pB. Will avoid DCRC2 entirely for fear of screwing things up. |
| 1245 | Re released pressure from MB. MB = 92.1% |
| 1255 | Yesterday DCRC1pC QET bias had been adjusted to a higher value, 192 uA. Two days ago it was set to 187, which was an adjustment from the previous 185. Today, I adjusted downward, saw the 10kHz oscillations, kept going below the oscillatory regime, and 185 again looks like a good value. |
| 1530 | Trying to do some IbIs, dIb/dIs, having some difficulty. DCRC1 pB has lost its pulses, snapping doesn't seem to help. DCRC1 pC had unusually weak pulses. Also something I did seems to have caused a mass railing on multiple DCRCs. Tired of trying to fix them - try zapping the SQUIDs. |
| 1600 | After zap, DCRC1 pC looks much improved. But DCRC1 pB is still totally pulseless. Snapping the QET bias to 800 uA seems to push it into normal, but anything much lower than that looks choppy, like s/c sorta. Maybe the SQUID settings are out of whack |
| 1615 | While playing around, I looked at the test signal connected to feedback on DCRC1pB, then changed the polarity to “open”. I think this is what Bill P suggested as a method to look directly at the test signal. I find that the peak-to-peak voltage output is systematically higher than the amplitude setting. At 12 mVpp setting, the output is 15 mVpp. At 50 mVpp setting, the output is 59.7 mVpp. |
| 1650 | Played a little with SQUID settings, to see if DCRC1pB could be fixed. Found that its lockpoint seemed way off, not even within the modulation curve - but this was also true for a couple of other channels whose pulses were just fine. So that's weird. Adjusting DCRC1pB's SQUID settings didn't help the situation. It's weird, but DCRC1pB's baseline and noise pattern don't change at all when you scan between 400 and 0 uA on the QET bias. And yet there is a change when you get around 800. I don't get it. |
| 1655 | DCRC1pB is back(?!?). Just tried the snap procedure again (set QET bias to 800, then step down slowly) and the pulses returned. Reset it to 185 uA. Now all DCRC1 channels are set to the Nov 15 values and all are working. |
| 1905 | DCRC1 channels set back to data-taking mode, done with IbIs measurements for the evening. During IbIs, noticed that DCRC1pB with no QET bias had low-frequency baseline shifts on the order of +/- 0.001V. All DCRC1 channels are set to the Nov 15 QET bias values and all are working. |