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| 0905 | Tower/MC/Coldplate = 76.0/57.7/380 mK, Still = 1.2 K / 0.15 mbar, G1/G2 = 148/137 mbar, 1K Pot = 1.66 K / 40 mbar. MB = 67.0% |
| 0915 | Fill LN2 cold trap bath. |
Cryo observations: the tower base temperature is apparently somewhat wavy. Currently for example there's a 4mK peak-to-peak oscillation, with a period of say 3 minutes. It's not a good sine curve but there are clear ups and downs. This wiggly behavior is generally not seen when running with the standard stack and the 600mK rod. Still pressure also seems oscillatory, not sure how unusual that is.
| Tower temperature over 30 minutes | Still pressure (upper left) over 30 minutes |
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The MC temperature oscillates too. Seems to be more regular, a sawtooth. Coldplate temperature oscillates too, 380 mK mean with 30 mK pp oscillations. Looks like faster frequency more like the still than the MC. In fact close examination suggests coldplate temperature is approximately tracking still pressure.
| Tower (left) then MC (right) temperatures, 30 minute window | Coldplate temperature over 30 minutes |
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A little later the Still pressure fluctuations looked a little more regular and they actually seem to track with MC temperatures, both with a frequency around 2 minutes or so. So maybe all the temperatures are fluctuating together.
| 1210 | Apply 1 mW power to still heater. Still: 0.14→0.15 mbar. MC temperature doesn't change much. The most noticeable change is that the frequency of oscillations has increased and become more regular, and the amplitude is a bit smaller. Frequency is about 1.7 minutes, both in MC temperature and still pressure, and they are nearly in phase. |
| 1245 | Set still heater to 2 mW. Still: 0.15→0.16 mbar. MC falls maybe 2 mK, oscillation pattern changes a little. |
| 1305 | Set still heater to 4 mW. Still: 0.16→0.19 mbar and much more stable (flat). MC falls to 56.5 mK and is also more stable, but slowly rising, approaching 58 mK. |
| 1320 | Set still heater to 6 mW. Still: 0.19→0.20 mbar and stable. MC falls to 56.0 mK without oscillations. Drifts up to 57 mK after a few minutes. |
| 1455 | Investigating charge baseline noise. In 2 dcrc data it is almost completely ~400kHz sinusoidal noise with a ~22kHz beat. Played around with holding shielding around dcrcs and switchboards without any real change in noise level. Then tried looking at DCRC1QI psd with DCRC2 running and turned off. The comparison of psds from single 0.1768 s traces are shown below. With only DCRC1 powered, there is a clear 400kHz excess. Once DCRC2 is powered on (and connected via timing link) a second peak comes in near 400kHz. Another peak at ~200kHz also appears. Though the ~22kHz beat is not clear in this psd, it becomes very obvious in the time-domain trace once the second DCRC is powered on. |
| DCRC2 off | DCRC2 on |
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