2018/03/07 (Wednesday)
| Status: started 1K Pot yesterday, it kept running dry. DIB1/2 connected to DCRC50(3)/DCRC55(1). | |
| 0845 | MC(Cernox) = 3.44 K, Sorb = 4.0 K, Turbo (on IVC) = 3.4 nbar, G1 (fridge) = 330 mbar, Main bath = 70.7% |
| 0845 | 1K Pot = 2.26 K / 5.5 mbar |
| overnight, there was one period a couple hours long where the 1K Pot and Tower temperatures and the fridge pressure were all elevated. Then they all came back down. | |
| 0850 | Open Needle Valve a few more degrees. 1K Pot → 1.8 K / 200 mbar |
| 0855 | Fill LN2 cold trap bath |
| 0855 | Tower = 3.25 K, Fridge (G1) = 236 mbar. Both are falling. Tower is lower than at any time yesterday. |
| 0905 | Tower = 3.15 K, Fridge (G1) = 186 mbar |
| 0905 | 1K Pot = 1.69 K / 26 mbar Open Needle Valve a few more degrees, couple times. 1K Pot → 1.7 K / 36 mbar |
| 0940 | Start 5 min series of 5V data (DCRC bias), with 1000 beginning randoms, and a 700/100/150/150 bin threshold trigger on DIB1qI/qO/DIB2qI/qO, with 1.6384 ms pulses (8192 length) and 400 us prepulse (500 length). |
| 0944 | Logger seems not be to be running. Stopped run. Restart midas. |
| 0947 | Start 30 min series of 5V data (DCRC bias), with 1000 beginning randoms, and a 700/100/150/150 bin threshold trigger on DIB1qI/qO/DIB2qI/qO, with 1.6384 ms pulses (8192 length) and 400 us prepulse (500 length). |
| 0950 | Tower = 3.14 K, Fridge (G1) = 162 mbar |
| 0955 | 1K Pot = 1.61 K / 8.5 mbar Open Needle Valve a few more degrees, couple times. 1K Pot pressure rises off scale, but comes back down again. |
| 1023 | Start 30 min series of 10V data (DCRC bias), with 1000 beginning randoms, and a 700/100/150/150 bin threshold trigger on DIB1qI/qO/DIB2qI/qO, with 1.6384 ms pulses (8192 length) and 400 us prepulse (500 length). |
| 1033 | 1K Pot = 1.61 K / 8.0 mbar Open Needle Valve a few more degrees. 1K Pot pressure rises to 30mbar. |
| 1110 | Tower = 3.11 K, Fridge (G1) = 158 mbar |
| 1110 | 1K Pot = 1.6 K / 7.5 mbar Open Needle Valve a few more degrees. 1K Pot → 1.74 K / 50 mbar. |
| 1130 | 1K Pot = 1.61 K / 9.0 mbar Open Needle Valve a few more degrees. 1K Pot → 1.74 K / 50 mbar. |
| 1200 | 1K Pot = 1.58 K / 6.5 mbar. Fridge pressure has been decreasing but now leveling out. Open Needle Valve a few more degrees. 1K Pot → 1.69 K / 24 mbar. |
| We got the best decrease in fridge pressure at 11:30. At that time the needle valve was opened enough to cause the 1K Pot pressure to go off scale temporarily | |
| 1220 | 1K Pot = 1.59 K / 7.0 mbar Open Needle Valve further several times, until 1K Pot pressure goes off scale. 1K Pot → 1.80 K. |
| OK, we'll start trying to circulate. Will open needle valve occasionally to keep 1K Pot pressure above 20 mbar. | |
| 1330 | Close V9 leaving 143 mbar in dump. Close V3. Turn on 3He pump, which will push a little more mix into condenser. |
| 1335 | Start circulation through Trap 2. V6 → 12.8%. Condenser peaks at 300 mbar. 1K Pot pressure spikes off scale then falls. Tower temperature falling quickly, <2.6 K. |
| 1340 | V6 → 13.2%. Condenser peaks at 170 mbar. Tower temperature seems to be varying with 1K Pot - hit a low of 2.1 K but came back up to 3.4 K |
| 1350 | Condenser pressure increasing apparently because 1K Pot ran dry. Open needle valve more. Wait for condenser to come down, currently at 345 mbar |
| 1355 | Spike in 1K Pot causes Condenser pressure and Tower temperature to start falling again. Condenser → 304 mbar. |
| 1355 | V6 → 13.5%. Condenser → 500 mbar. Tower → 3.05 K. Condenser plateaus. |
| 1355 | V6 → 13.8%. Condenser → 630 mbar. Tower → 3.10 K. |
| 1405 | While I was away from the fridge, Still pressure fell as low as 50 mbar and Tower temperature fell to 1.5 K. But then the 1K Pot ran dry and became hot, then Still & Condenser pressures rose and Tower temperature rose. |
| 1410 | Open 1K Pot needle valve some more to get it going again |
| 1415 | Condenser is pretty high, 856 mbar, but 1K Pot is working and Tower is cooling again. Hopefully condenser will start falling. |
| 1420 | Condenser = 823 mbar and falling. |
| 1420 | V6 → 14.0%. Condenser peaks at 875 mbar. |
| 1430 | V6 → 14.2%. Condenser peaks at 920 mbar. Still pressure falls, → 200 mbar |
| 1435 | V6 → 14.4%. Condenser peaks at 930 mbar. Still pressure falls, → 60 mbar |
This is beginning to feel like a losing battle. We have to keep opening the needle valve more and more - the pot cools to 1.8 K, stays there for a few minutes, then rises immediately to around 2.5 K accompanied by a falling pressure. When the pot goes dry the condenser pressure goes up too, not surprisingly. Tower has been pretty flat at 2.6 K.
Is there too much helium in the IVC? The temperatures are bouncing aroudn the lambda point, roughly. Maybe superfluid He climbs up to the pot, warms it, then gets heated above superfluid and goes away again.
| 1450 | Still = 3.3 K, Coldplate = 3.1 K. Not good… |
|---|---|
| 1450 | Condenser = 971 mbar. Too high, can't keep it down. Close V6 to let mixture expand into Still. |
| The Turbo pump on the IVC has generally been around 3 nbar. But watching it while the 1K Pot warmed up again, it rose to 5.4 nbar. Should close the Turbo valve, then turn off the pump and let things warm to 4K, see how high the IVC pressure goes. | |
| 1455 | Open needle valve more to get pot working again, 1K Pot → 1.8 K as usual |
| 1455 | Turbo on IVC → 4.6 nbar. Close valve to turbo pump. |
| 1500 | IVC = 86 nbar. 1K Pot = 1.71 K. Close V4a to stop pumping on 1K Pot. |
| 1505 | 1K Pot has risen to 3.1 K. Tower = 3.5 K. IVC = 120 nbar, not a dramatic increase. |
| 1505 | 1K Pot = 3.7 K. Tower = 3.76 K. IVC = 160 nbar. |
can compare with Run 59. In that run we were repeatedly warming the tower to test the mu-metal shield, and we also had a leak from bath to IVC, which we could see when we warmed up - accumulated He in the IVC would be seen at the pressure gauge when we were warm. We have a similar amount of gas in the IVC now. One difference with Run 59 is that then we were leaving the 1K Pot on when we warmed up.
| 1515 | 1K Pot = 3.9 K. Tower = 3.90 K. IVC = 220 nbar. Pump out IVC with turbo pump. |
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| 1520 | Close 1K Pot needle valve. We don't want the pot too full if/when we start pumping on it again. |
| 1520 | Turbo = 10 nbar. Close turbopump valve to check IVC pressure. IVC = 140 nbar. A bit lower. Open turbopump again to continue pumping on IVC. |
| 1540 | 1K Pot = 4.1 K. Tower = 4.25 K. Turbo = 5.4 nbar. Open V4a to pump on 1K Pot. (Needle valve is closed.) 1K Pot falls quickly to 1.8 K then rises when it empties - Tower and Fridge pressures fall too. |
| 1545 | Open needle valve enough to get 1K Pot pressure up to 50 mbar. Then adjust to keep temperature ⇐ 1.8 K. |
| 1610 | Have been increasing the needle valve periodically to keep the 1K Pot above 10 mbar. Meanwhile mixture in fridge is condensing again and Tower temperature is coming down. But it doesn't look like any improvement over this morning. |
| 1635 | Situation is similar to earlier before we started circulation: Fridge (G1) = 165 mbar, Tower = 3.12 K, Pot pressure keeps running low. I don't think things are getting better… |
| … so let's stop the 1K Pot and let things settle to 4K, and also stop pumping on the IVC to see how high the pressure goes up overnight. | |
| 1640 | Close turbo pump valve. IVC = 74 nbar. |
| 1645 | Close 1K Pot needle valve and speedivalve. Close V4a and 4He pump valve, turn off 4He pump. |
| 1650 | Fill LN2 cold trap bath |
| 1655 | 1K Pot = 3.0 K, Tower = 3.5 K, IVC = 120 nbar |