2016/09/09 (Friday)
| Status: fridge at room temperature, cryostat Dewar is down, IVC is entirely removed. Pumping on still with leak detector, attached at top of fridge. Mixture is in dump and 3He pump, manual dump valves are closed. |
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| Yesterday the leak in the dilution unit could not be located. We considered the mixing chamber indium seal to be the most likely location so we replaced it. | |
| 0835 | Leak = 2.6 pbarL/s, a little lower than yesterday, which is slightly encouraging. |
| 1515 | Retighten MC screws |
| 1741 | Reattach top IVC (copper) can, IVC can, and bottom of IVC can for leak test. |
| 1753 | Background leakrate is currently 2.6 pbarL/s. Commence pumping out IVC cans (now sealed) with scroll pump. |
| 1811 | With IVC pressure at 0.14 mbar, stop pumping out IVC and start to add He gas. Add He to IVC in steps until there is more than one atmosphere. Background leak rate of fridge lines remained at 2.6 pbarL/s while IVC was being filled. |
| 1835 | Leak checker remained at 2.72 ± 0.03 pbarL/s with IVC full of He. Commence pumping out IVC He with scroll pump. |
| 1840 | Leak rate = 2.82 ± 0.03 pbarL/s. |
| Cease pumping out IVC. Now let's hook up the turbopump to the fridge lines for over the weekend pumping. IVC currently at vacuum. | |
| When removing speedivalve from top of leak checker, the bellows between it and the Gate valve act like a damn spring and contract as soon as the flange clamp is removed. This can't have been good for that particular seal, so perhaps that was contributing to the ambient leaks we were seeing. | |
| 1855 | Connect turbopump to fridge lines and begin pumping from still side for over the weekend. |