2018/05/18 (Friday)
| Status: 1K Pot is not working. Warming up to examine it. Helium in cryostat vacuum jacket. | |
| 0850 | MC(Cernox) = 279.3 K |
| 0850 | Begin pumping out cryostat vacuum jacket with scroll pump, then turbo pump |
| 1035 | Check pressure in 1K Pot: 30 mbar. Pump out with scroll pump |
| 1035 | Stop pumping on 1K Pot, leave speedivalve open to watch pressure on P2: |
| minutes | mbar (P2) |
|---|---|
| 0 | 0.08 |
| 0.5 | 0.6 |
| 1.0 | 1.5 |
| 1.5 | 2.3 |
| 2.0 | 3.4 |
| 3.0 | 4.5 |
| 4.0 | 5.5 |
| 5.0 | 7.0 |
| 1045 | With needle valve open 10 degrees, stop pumping on 1K Pot, leave speedivalve open to watch pressure on P2: |
|---|
| minutes | mbar (P2) |
|---|---|
| 0 | 0.08 |
| 0.5 | 0.58 |
| 1.0 | 1.5 |
| 1.5 | 2.7 |
| 2.0 | 3.7 |
| 3.0 | 5.0 |
| 1050 | With needle valve open 30 degrees, stop pumping on 1K Pot, leave speedivalve open to watch pressure on P2: |
|---|
| minutes | mbar (P2) |
|---|---|
| 0 | 0.09 |
| 0.5 | 0.8 |
| 1.0 | 2.2 |
| 1.5 | 3.6 |
| 2.0 | 4.5 |
| 3.0 | 7.0 |
| 4.0 | 11.0 |
| 5.0 | 17.0 |
| 1105 | Open needle valve 18.5 full rotations - this is enough to disconnect the shaft so that it can be pulled out. Pressure approaching 1 bar on mechanical gauge |
|---|---|
| 1120 | Remove needle valve shaft. The two o-rings near the top that seal the shaft from the lab atmosphere are intact but do seem a little worn out. Replace with new ones purchased from Chem store, o-ring size 1-010 (ID 1/4 OD 3/8 thick 1/16). First clean off surfaces on shaft and insert tube. Apply some vacuum grease, then reinsert needle valve shaft. |
 |  |  |
| Unscrewing needle valve | Needle valve is worn and slightly bent | Full valve |
| 1310 | Close needle valve completely, then pump out 1K Pot, then stop pumping on 1K Pot, leave speedivalve open to watch pressure on P2: |
|---|
| minutes | mbar (P2) |
|---|---|
| 0 | 0.065 |
| 0.5 | 0.45 |
| 1.0 | 1.1 |
| 1.5 | 2.0 |
| 2.0 | 2.7 |
| 3.0 | 4.0 |
| 4.0 | 5.0 |
| 5.0 | 6.0 |
| This is a little slower than before we replaced the o-rings | |
| 1335 | As a test, remove the o-rings, then close the needle valve, then pump out the pot, then stop pumping and watch the pressure rise. Rises equally fast as when the o-rings are present. So closing the needle valve apparently isolates the shaft from the pot. |
| 1630 | Stop pumping out cryostat vacuum jacket |
| 1635 | Check pressure in IVC: 16 mbar. Pump out with scroll, then turbo pump. |