2019/05/02 (Thursday)
| Status | Warming up after a second blockage. Nitrogen in IVC and cryostat vacuum jacket. |
|---|---|
| Setup | DIB1/3/4 → 3.2 MHz filters 2/3/1 → cable 3/1/2 |
| 0935 | MC(Cernox)/Sorb = 227.5/>249 K (max) warming time constant around 15 hours, should hit 10 celsius 11:15am tomorrow. |
| Throughput test procedure, Cold Trap 1: |
- All mixture in dump, LN2 trap 1 cold, condenser & still valves open (3He pump on - optional)
- Open V9, V13a, V12a+speedivalve, V3. Wait for G1 to be close to G2.
- Close V12a+speedivalve and V3, open V1
- monitor G1
| 0940 | Perform mixture throughput test at MC = 228 K using above procedure with 3He pump on. Let G1 rise to 560 mbar before Step 3, then it falls to 43 mbar, then rises. Throughput 7.5 mbar/min. So significantly better - the blockage may be gone. Is the still above 0 Celsius? The MC is still -45 Celsius. This can be compared to room temperature and somewhat cooler throughput tests from Run 68 and earlier. Varied between 7.1 and 8.9 mbar/min. Should be better when cooler, so we can consider the above throughput a little low. |
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| 1205 | LN2 Trap 2 is warm. Check contents: 3.1-0.7 = 2.3 mbar on G1. Pump out with 4He pump. |
| Removed 2.3 mbar from Trap 2, which had the mixture open to it during the last LN2 transfer and overnight. | |
| 1220 | Start cryocleaning mixture through LN2 Cold Trap 2, V6 = 13.0% |
| 1225 | Increase V6 → 13.1% to restart flow |
| 1235 | Increase V6 → 13.3% to restart and speed up flow |
| 1250 | Increase V6 → 13.4% to speed up flow |
| 1305 | Reduce V6 → 13.3%, because it looks a little concerning. G2 went up to 860 mbar and didn't fall as usual, instead started rising again. And G1 rose significantly when G2 rose, which is different than yesterday and before - back then, when I increased the rate a lot, G2 went up but G1 went down a little. Also the one metal tube from Trap 2 is frosty pretty far up. Are we leaking in air from the cold o-ring? |
| 1310 | Stop cleaning through Trap 2 after 50 min. G2 flow pressure was 570-860 mbar. Pump mixture to dump. Removed 5.0 mbar. Not bad, I guess this cleaning didn't cause much of a problem. |
| 1330 | LN2 Trap 1 is warm. Check contents: 6.4-0.4 = 6.0 mbar on G1. Pump out with 4He pump. |
| 1345 | Start cryocleaning mixture through LN2 Cold Trap 1, V6 = 13.1% |
| 1400 | Increase V6 → 13.3% to restart flow |
| 1425 | Stop cleaning through Trap 1 after 50 min. G2 flow pressure was 575-595 mbar. Pump mixture to dump. Removed 3.4 mbar |
| 1530 | LN2 Trap 2 is warm. Check contents: 5.2-0.2 = 5.0 mbar on G1. Pump out with 4He pump. |
| 1550 | Start cryocleaning mixture through LN2 Cold Trap 2, V6 = 13.0% |
| 1625 | Increase V6 → 13.3% to restart flow |
| 1635 | Increase V6 → 13.4% to speed up flow. As usual G2 rises sharply, but again G1 rises as well, didn't do that yesterday. Maybe it was a lot dirtier yesterday. Tube got frosty again but this time G2 is falling off normally, not rising. |
| 1650 | Stop cleaning through Trap 2 after 60 min. G2 flow pressure was 575-?800 mbar. Pump mixture to dump. Removed 3.3 mbar |
| 1710 | LN2 Trap 1 is warm. Check contents: 4.0-0.6 = 3.4 mbar on G1. Pump out with 4He pump. |
| 1735 | MC (Cernox) = 255.6 K. Warming time constant is around 15.0 hours, should hit 10 Celsius tomorrow at 11:07 am |