| Status | Run 74 in progress. Warmed the fridge to fix short and thermal touch. Helium gas in cryostat vacuum jacket, partially pumped out. Mixture cryocleaned four times. IVC sealed and pumping overnight. |
| | Yesterday we saw high leak detector signal in IVC. Maybe this is because there is leftover He trapped in the IVC. Flushed it with N2 twice yesterday and pumped overnight. |
| 1320 | Matt enters lab. |
| 1325 | Turbo on IVC = 22 nbar. With Turbo valved out for 1 minute, IVC = 340 nbar. |
| | this is worse than yesterday. It could be because the gauge reads differently for N2 versus He, and maybe yesterday there was residual He versus N2 today. Maybe. |
| 1335 | Check contents of warm LN2 Trap 1: 6.2 mbar. Pump out with Scroll Pump. |
| 1345 | Check contents of warm LN2 Trap 2: 5.1 mbar. Pump out with Scroll Pump. |
| 1345 | Pump on IVC with LD, close Turbo valve and wait 1 minute: 1290 pbarL/s. |
| | this is significantly better than yesterday but still way too high. What does this tell us? Again I'm trying to decide whether the problem is a bad IVC seal or just trapped helium in the IVC slowly getting pumped out. |
| 1355 | LD on IVC settles around 1490 pbarL/s. Try blowing He around IVC joint, also at a few other points. No increase seen, suggesting leak <10 pbarL/s. |
| 1400 | Open valve to Turbo Pump a little to reduce leak signal to around 800 pbarL/s. This way the last digit will show differences as low as 1 pbarL/s. Do some more squirt tests - again seeing no increase, suggesting leak<2 pbarL/s (although it may not be entirely fair considering that the Turbo is pumping in parallel). |
| 1405 | Start slowly filling IVC again with N2. We'll do some more flushes. We can check again between now and cooldown (in 4 days) to see whether it improves. |
| 1420 | IVC reaches 1atm of N2. Start gently pumping IVC with Scroll Pump |
| 1430 | Pump IVC down to about 12 μbar. Then start slowly filling with N2 again for a second flush. |
| 1445 | IVC reaches a bit over 1atm of N2. Start gently pumping IVC with Scroll Pump |
| 1500 | IVC < 0.1 mbar, switch to Turbo Pump |
| 1525 | Turbo on IVC = 25 nbar. With Turbo valved out for 1 minute, IVC = 340 nbar. |
| 1525 | Pump on IVC with LD, close Turbo valve and wait 1 minute: 1270 pbarL/s. |
| 1525 | Switch back to pumping out IVC with Turbo Pump |
| 1530 | Matt exits lab |