2020/03/15 (Sunday)
| Setup | Run 72. DIB 1/3/4 → Stripline 43/41/48 → Cable 3/2/1 → nothing/nothing/accessory_interposer → HV_Conn 1/3/2 → HV 1/2 → DCRCX(4)/DCRC55(1). DCRCs off overnight. Lead/poly shield erected (4 lead walls, 2 poly walls). |
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| Status | Started circulation yesterday. Second cooldown for Run 72. |
| Overnight: 1K Pot and circulation look fine. But baseline temperature is doing interesting things. Interesting=bad. MC is wandering around, and it looks a lot like it's from helium films. So there's too much helium in the IVC. |
| Wacky MC temperature behavior |
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| Looks like an illustration from a book about chaos. |
| 1340 | MB = 16.5% |
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| 1400 | MC(H35) = 70±20 mK, oscillating wildly. Still = 0.140 mbar / 0 mW, G1/G2 = 77/62 mbar, 1K Pot = 1.73 K / 125±25 mbar. |
| 1445 | Tower/MC/Coldplate = 75.7/70±15/195 mK, Still = 1.44 K/ 0.140 mbar / 0 mW, G1/G2= 77/63 mbar, 1K Pot = 1.73 K / 125±25 mbar. |
| Tower is much more stable than MC. But it's not very low. It's not as cold as it was at this time after the first cooldown. And last time the MC was much cooler. We didn't look at it for long periods so it's possible it was oscillating and we didn't know it, but probably not since the temperature was pretty low. | |
| 1510 | Looks like the Tower temperature is oscillating too, interestingly at half the frequency of the MC temperature oscillations. MC period is 170 seconds, Tower period is 390 seconds. Tower = 76.1±0.6 (variation is much smaller than MC variation). |
| 1515 | Set Still heater to 7 mW, just for fun. After 10 minutes this does not seem to have improved the base. |
| 1515 | Turbo on IVC = 4.6 nbar. With Turbo valved out for a minute, IVC = 63 nbar. Leave Turbo valved out for now. |
| 1525 | Stop circulation: close V6. |
| 1530 | Still pressure rises, Condenser pressure falls, Tower temperature rises rapidly to 0.3 K |
| 1530 | Stop 1K Pot: close 1K Pot speedivalve, V4a, and valve at pump. Switch 4He pump exhaust valve to Exhaust, close 4He pump recovery valve, turn off 4He pump. |
| 1535 | Tower = 0.45 K and rising. 1K Pot = 2.17 K and rising. |
| 1540 | Tower rises quickly to 1 K. IVC pressure rising, 240 nbar, 460 nbar, 540 nbar… Tower → 3.1 K. IVC = 540 nbar. Fridge pressures rising. |
| 1545 | MC(Cernox) = 2.98 K. Set LakeShore to Autorange, let's see how that works out. Set excitation to 63 uV. |
| 1550 | MC(Cernox)/1K Pot = 3.32/3.22 K, Condenser (G1) = 420 mbar and rising, IVC = 740 nbar |
| 1550 | Helium recovery rate: 14 cuft/hour |
| 1550 | Fill LN2 cold trap bath from 5L Dewar |
| 1550 | MC(Cernox)/1K Pot = 3.71/3.58 K, Condenser (G1) = 660 mbar and rising, IVC = 860 nbar |
| 1600 | MC(Cernox)/1K Pot = 3.87/3.79 K, Condenser (G1) = 785 mbar and rising, IVC = 860 nbar |
| 1600 | Let a little helium into IVC. IVC → 1 ubar |
| 1605 | Let a full hose-length of helium into IVC. IVC → 46 ubar. |
| 1610 | MC(Cernox)/1K Pot = 3.98/4.01 K, Condenser (G1) = 835 mbar, IVC = 46 ubar Isolate IVC. |
| 1620 | Helium recovery rate: 17 cuft/hour. MB = 12.5% |
| 1620 | MC(Cernox)/1K Pot = 4.02/4.18 K, Condenser (G1) = 897 mbar. Open V9 to release mixture into dump. Note: V3 is open, 3He pump is on. This causes MC temperature to fall. |
| 1620 | Let 1.0 mbar He gas into vacuum manifold. Then open cryostat vacuum jacket valve to let this into the vacuum jacket. Vacuum Jacket → 0.034 mbar. |
| 1625 | MC(Cernox)/1K Pot = 3.60/4.17 K, Condenser (G1) = 518 mbar. Recovery rate = 88 cuft/hour |
| Tower temperature rises again when recovery speeds up | |
| 1630 | MC(Cernox)/1K Pot = 4.27/4.26 K, Condenser (G1) = 517 mbar. Recovery rate = 99 cuft/hour |
| 1632 | Recovery meter = 343300 cuft |
| 1635 | MB = 10.9%. |
| 1645 | Recovery rate = 50 cuft/hour |
| 1650 | MB = 9.8%. |
| 1650 | Pump mixture out of cold LN2 Trap 1 into dump (after isolating fridge) |
| 1655 | Recovery rate = 47 cuft/hour |
| 1655 | Cryostat vacuum jacket = 1.9 ubar |
| 1700 | Let 1.2 mbar He gas into vacuum manifold. Then open cryostat vacuum jacket valve to let this into the vacuum jacket. Vacuum Jacket → 0.034 mbar. |
| 1705 | Recovery rate = 117 cuft/hour |
| 1710 | Open fridge to dump through V4, V1, V3. V9 is also open and 3He pump is on. |
| 1710 | Recovery rate = 130 cuft/hour |
| 1715 | MB = 6.8%. |
| 1715 | MC(Cernox)/1K Pot = 4.35/4.32 K, Condenser (G1) = 559 mbar and falling. |
| 1720 | Recovery rate = 110 cuft/hour |
| 1725 | Recovery rate = 102 cuft/hour. MB = 5.8%. Cryostat vacuum jacket = 6.3 ubar. |
| 1730 | Let 1.2 mbar He gas into vacuum manifold. Then open cryostat vacuum jacket valve to let this into the vacuum jacket. Vacuum Jacket → 0.046 mbar. |
| 1725 | Recovery rate = 160 cuft/hour. MB = 3.5%. Cryostat vacuum jacket = 14 ubar. |
| 1739 | Recovery meter = 343400 cuft (at 17:38:38) |
| 1745 | Recovery rate = 164 cuft/hour. MB = 1.3%. Cryostat vacuum jacket = 12 ubar. |
| 1745 | MC(Cernox)/1K Pot = 4.38/4.33 K, Condenser (G1) = 523 mbar. |
| 1750 | Start pumping mixture from fridge to dump. MC temperature falls to 4.2 K but then rises again. Set Still/MC heaters to 200/20 mW. MC temperature rises to 5.0 K |
| 1755 | Recovery rate = 152 cuft/hour. MB = -0.7%. |
| 1757 | Recovery meter = 343450 cuft (at 17:57:43) |
| 1800 | MC(Cernox)/1K Pot = 5.08/4.39 K, MC/Still = 20/200 mW |
| 1805 | Recovery rate = 143 cuft/hour. MB = -1.0 |
| 1810 | MC(Cernox)/1K Pot = 5.15/4.41 K, MC/Still = 20/200 mW |
| 1819 | Recovery meter = 343500 cuft (at 18:19:10) |
| 1820 | MC(Cernox)/1K Pot = 5.22/4.47 K, MC/Still = 20/200 mW P1 down to 0.020 mbar as we continue to pump out fridge. G2(dump) = 690.2 mbar, seems kinda low. |
| 1820 | Close V6 to stop pumping out fridge. We'll see if/how fast the fridge pressures go up. |
| 1K Pot temperature climbs fast - that probably means there was still some cooling happening from the pumping, so still some helium in there? | |
| 1825 | MC(Cernox)/1K Pot = 5.28/5.42 K, MC/Still = 20/200 mW. Not pumping on fridge. |
| 1830 | MC(Cernox)/1K Pot = 5.29/5.86 K, MC/Still = 20/200 mW. Not pumping on fridge. Fridge pressures have not risen much, P1 = 0.022 mbar. |
| 1830 | Try opening V6 again to see if the 1K Pot temperature falls. MC falls a little. Annoying. Probably a little helium still in there. Well… I guess I can go home, won't be able to close the manual fridge valves, but can close V1 and V6, that will isolate the fridge. |
| taking photos of recovery meter every 10 seconds, in /data/chocula/k100/webcam/webcamAutomater/images. Will need to delete these frequently. | |
| 1843 | Recovery meter = 343550 cuft (at 18:42:46) |
| 1910 | Recovery meter = 343600 cuft (at 19:09:46). Rate = 111 cuft/hour |
| 1910 | MC(Cernox)/1K Pot = 5.97/>7 K, MC/Still = 20/200 mW. Pumping on fridge. P1 = 0.017 mbar. G1(dump) = 691.2 mbar, flat. |
| 1910 | Close V6 to stop pumping out fridge to dump. |
| 1925 | MC(Cernox) = 6.66 K, MC/Still = 20/200 mW. Not pumping on fridge. P1 = 0.034 mbar. G2 (condenser) is not rising. MC temperature is rising at the same rate. Looks like all the mixture is out. |
| 1925 | Turn off Still and MC heaters. This causes MC to fall to 6.4 K then start rising again. Did not cause a change in fridge pressure. |
| 1943 | Recovery meter = 343650 cuft (at 19:42:47). Rate = 91 cuft/hour |
| 1950 | G1(dump) = 691.6 mbar. Close V9: G1 rises a bit, to 693 mbar. Is that because the mixture in the dump is cold? Of course the pump itself is pretty hot. Turn off 3He pump. |
| I'll just leave V1 and V3 open. We can watch the fridge pressure rise as the temperature rises. | |
| 2026 | Recovery meter = 343700 cuft (at 20:26:17). Rate = 69 cuft/hour |
| 2100 | Around this time the recovery curve bends sharply, probably all the LHe is now boiled away. MC/Sorb = 12.3/20.8 K |
| 2139 | Recovery meter = 343750 cuft (at 21:38:38). Rate = 41 cuft/hour |
| 2238 | Recovery meter = 343760 cuft (at 22:38:29). Rate = 10 cuft/hour |
| 2320 | Recovery meter = 343763 cuft (at 23:20:09). Rate = 4.3 cuft/hour |
| 2330 | MC(Cernox)/Sorb = 39.8/60.7 K. No increase in fridge pressure yet. |
| 2341 | Recovery meter = 343764 cuft (at 23:41:20). Rate = 2.8 cuft/hour |