2021/09/24 (Friday)
- Lab in-personnel: Giulia and Matt
| Status | Run 74 in progress. First cooldown after IVC rebuild. |
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| 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/ |
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| Position of Am source: y = 0.0 mm | |
| Refilled main bath yesterday after letting it run dry, to take some more ~4K measurements. | |
| 1006 | Tower/MC/Coldplate = 1139/5976/11000N mK, Still = 8.513 K / 10000 mbar / 0 mW G1/G2 = 554.0/508.6 mbar, 1K Pot = 6.44 K / |
| 1014 | Fill LN2 cold trap bath. |
| 1004 | At 10kHz noise in DCRC3qI/qO/DCRC1qI/qO = 1.3/1/12/1.5 8e-6. This is q3/q1/q4/q2 At 3kHz (peak) noise in DCRC3qI/qO/DCRC1qI/qO = 2.1/1.3/2.8/2.8 e-6. |
| Noise is lower than yesterday. | |
| 1041 | Start 45 min series of +10/0V data (bias applied after 60 sec), at elevated temperature, with 1000 beginning randoms, trigger threshold Use Sequencer script r74_takeandflash_dcrcbias.msl. This flashes for 30 seconds at end of series. |
| Oops - noticed that DCRC3qI trigger was not enabled | |
| Like last time (at 3.5 K) it seems to be triggering a lot on non-pulses. Maybe should try again with higher thresholds. | |
| Tower = 4.68-4.72 K during series |
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| 07210924_1041 |
| 1139 | Start 45 min series of +10/0V data (bias applied after 60 sec), at elevated temperature, with 1000 beginning randoms, trigger threshold 50/40/30/60 on DCRC3qI/qO/DCRC1qI/qO, Use Sequencer script r74_takeandflash_dcrcbias.msl. This flashes for 30 seconds at end of series. |
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| Tower 4.73-4.77 K during series. |
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| 07210924_1139 |
| 1240 | Turn on 4He pump to pump out line leading to 1K Pot but notice P2 does not fall below 0.6 mbar. Check oil level in pump, looks like it's at bottom of gauge. Fill to about 30% with Leybold LVO100 (LVO 100) pump oil. With pump on level falls to about 20%. Now it pumps down the line fine, P2 → 0.013 mbar. |
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| 1245 | Check pressure in 1K Pot: Mechanical gauge = 0.17 bar. (Note: V4a was closed during this check.) 1K Pot temperature dips to ~ 5 K |
| 1245 | Pump out 1K Pot in steps, alternating between V4a and Speedivalve. Throttle valves to keep pressure at P2 below around 10 mbar. After several iterations, leave both valves open. |
| 1250 | MC(Cernox)/MC(H35)/Tower = 4.96/6.08/4.77 K. |
| 1250 | Sorb = 4.2 K. G1 (fridge) = 536 mbar and falling. 1K Pot = 3.34 K / 2.0 mbar |
| 1255 | Open 1K Pot needle valve → 10°. No change… hmm. Open 1K Pot needle valve → 30°. No change. Crap - looks like the inlet is blocked. |
| 1300 | Open 1K Pot needle valve → 90°. 1K Pot → 3.85 K / 4.5 mbar. Strange, pressure goes up a little but temperature rises instead of falling. After a minute pressure spikes to 130 mbar. Close needle valve, pressure comes down. Temperature hit 4K, then started falling a little, → 3.4 K |
| so it seems more like maybe the outlet is blocked. Or maybe the pot is partially full of ice. Lame. | |
| 1305 | 1K Pot needle valve closed. 1K Pot = 3.43 K / 2.2 mbar. |
| 1315 | 1K Pot = 0° / 3.22 K / 1.5 mbar |
| 1315 | Tower = 4.66 K and falling. So pot is having some effect at least. |
| 1335 | Tower = 3.65 K and falling rapidly. Should we try to stabilize it for another data series? Would closing the 1K Pot speedivalve work? 1K Pot = 3.14 K. Tower won't get colder than the pot, presumably. |
| 1355 | Tower = 3.26 K, falling slowly. Turn on MC heater → 4000 uW, try to flatten the temperature (later reduce to 1000 uW) |
| 1358 | Start 45 min series of +10/0V data (bias applied after 60 sec), at elevated temperature, with 1000 beginning randoms, trigger threshold 50/40/30/60 on DCRC3qI/qO/DCRC1qI/qO, 5Hz in-run randoms, with 1.6384 ms pulses (8192 length) and 400 us prepulse (500 length). Use Sequencer script r74_takeandflash_dcrcbias.msl. This flashes for 30 seconds at end of series. |
| Tower = 3.27-3.28 K during series |
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| 07210924_1358 |
| 1445 | Turn off MC heater |
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| 1450 | 1K Pot is oscillating every 15 minutes, min 3.1 K / 1.0 mbar, max 3.4 K / 2.5 mbar. |
| 1450 | Open 1K Pot needle valve → 30°. 1K Pot → 3.61 K / 15 mbar |
| 1505 | Tower flat at 3.28 K |
| 1510 | 1K Pot = 30° / 3.79 K / 9.5 mbar |
| 1510 | Open 1K Pot needle valve → 60°. 1K Pot → 4.0 K / 45 mbar |
| 1515 | 1K Pot = 60° / 3.99 K / 30 mbar |
| Tower hasn't budged. I guess this is maybe the coldest we can get with the 1K Pot in its current state. | |
| 1515 | Close 1K Pot needle valve |
| We have pretty good coverage of temperatures from 1 to 3.5 K. And one series at 4.8 K. Let's try to warm to somewhere above 3.5 K | |
| oh - actually we may be able to cool further by pumping mixture out of fridge. Depends on whether it is condensed, that's not clear. Let's try. | |
| 1520 | Close off LN2 Trap 2, then pump on both sides of fridge to dump, V6 = 12.8%. Yep! Tower temperature is falling. |
| 1525 | Tower = 2.3 K and falling |
| 1530 | Tower = 1.54 K and falling. G1/P1(fridge) = 1.6/0.45 mbar |
| 1535 | Tower = 1.28 K and falling. G1/P1(fridge) = 1.5/0.40 mbar |
| Start applying MC heat, try to get to a constant temp | |
| 1547 | Start 45 min series of +10/0V data (bias applied after 60 sec), at elevated temperature, with 1000 beginning randoms, trigger threshold 50/40/30/80 on DCRC3qI/qO/DCRC1qI/qO, 5Hz in-run randoms, with 1.6384 ms pulses (8192 length) and 400 us prepulse (500 length). Use Sequencer script r74_takeandflash_dcrcbias.msl. This flashes for 30 seconds at end of series. |
| Tower = 1.19-1.24 K during series, oscillating up and down as I tried to control it with the heater. |
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| 07210924_1547 |
| 1640 | Tried to warm Tower to around 2.0 K, but got a runaway effect and it climbed to 3.7 K. Maybe the fridge ran out of mixture. |
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| 1650 | Close V6 then let some mixture from Trap 2 into fridge, we can try cooling by pumping it out again |
| 1655 | Open V6 again to pump mixture out of both sides of fridge to dump |
| 1705 | Tower is cooled back down to 2.7 K. Start adjusting MC heat to try to stabilize it. |
| 1717 | Start 45 min series of +10/0V data (bias applied after 60 sec), at elevated temperature, with 1000 beginning randoms, trigger threshold 50/40/35/60 on DCRC3qI/qO/DCRC1qI/qO, 5Hz in-run randoms, with 1.6384 ms pulses (8192 length) and 400 us prepulse (500 length). Use Sequencer script r74_takeandflash_dcrcbias.msl. This flashes for 30 seconds at end of series. |
| Tower = 2.64-2.68 K during series |
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| 07210924_1717 |
| So the data today are pretty consistent with the previous 1-3.5 K data points, except that the detector seems to be in a “weak state”. Today's 3.28 K data shows a little impact ionization so we should target a temperature a little above that. | |
| P1(Fridge) = 0.75 K. Close V6 to stop pumping on fridge, we'll let the mixture expand. Turn off MC heater for now, I'll continue messing with it from home. 1K Pot = 3.34 K so I don't expect the Tower to rise higher than that |
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| 2003 | Start 45 min series of +10/0V data (bias applied after 60 sec), at elevated temperature, with 1000 beginning randoms, trigger threshold 50/40/30/60 on DCRC3qI/qO/DCRC1qI/qO, 5Hz in-run randoms, with 1.6384 ms pulses (8192 length) and 400 us prepulse (500 length). Use Sequencer script r74_takeandflash_dcrcbias.msl. This flashes for 30 seconds at end of series. |
| Tower = 3.95-4.02 K during series |
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| 07210924_2003 |
| 2200 | Start 45 min series of +10/0V data (bias applied after 60 sec), at elevated temperature, with 1000 beginning randoms, trigger threshold 60/50/30/80 on DCRC3qI/qO/DCRC1qI/qO, Use Sequencer script r74_takeandflash_dcrcbias.msl. This flashes for 30 seconds at end of series. |
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| Tower = 4.47-4.50 K during series |
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| 07210924_2200 |
| 2250 | 1K Pot is zigzagging regularly with a 12-minute period, 3.1-3.5 K, 1.5-4.0 mbar. Kinda interesting. |
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| 2250 | Close V6, turn off 3He pump, let mixture from dump through cold LN2 Trap 2 into fridge |