2018/07/31 (Tuesday)
| status: room temperature. Turbo pumping cryostat vacuum jacket overnight. | |
| Conclusions from yesterday: no leak to the IVC was measured from the main bath, or from the dilution unit, or even from the top of the fridge. Some slow increase in signal was seen after blowing around the top but it was small. Surprising that no noticeable leak around the stripline tubes was seen, but the background was a bit higher than before. (Could try again to see if background is lower, but at any rate the leak is small, <10 pbarL/s.) It is of course still possible that an indium seal leak will show up when we get to 77K. | |
| Plan for today: try 77K cooldown again. As usual we should first start cleaning mixture and do several cleanings, then transfer LN2 later in the day. | |
| 0947 | Put both LN2 cold traps back into LN2 dewar. Fill LN2 cold trap dewar full. |
| 1130 | Turbo on cryostat vacuum jacket = 22 nbar. Vacuum jacket with turbo valved out = 250 nbar. Stop pumping cryostat vacuum jacket. |
| 1145 | Check pressure in IVC: 19 ubar. That's after a day without pumping, 2 orders of magnitude higher than yesterday. Start pumping IVC with turbo pump. |
| 1155 | Check IVC pressure after 10 minutes of pumping: 2.2 ubar. Continue pumping. |
| 1215 | Check IVC pressure after 30 minutes of pumping: 250 nbar. Continue pumping. |
| 1300 | Leak detector on IVC, background 16.6 pbarL/s Try squirting a few blasts of He at the top of the Wizard Staff (stripline tube) connections. No leak seen. |
| 1305 | Let 2.5 mbar of N2 into IVC. Then pump it out again with scroll and turbo. A sort of gentle flush. |
| 1310 | Leak detector on IVC, background 13.1 pbarL/s. A little better. Again blast all over the top of the fridge with He gas, no leaks seen. |
| Cryocleaning mixture | |
|---|---|
| 1015 | Start cleaning mixture through cold LN2 Trap 1, V6 = 12.6% |
| 1032 | Increase V6 = 12.8% to speed up cleaning |
| 1048 | Increase V6 = 13.0% to speed up cleaning |
| 1115 | Stop cleaning through cold trap 1 after 60 min. Pump mix to dump. |
| 1242 | Start cleaning mixture through cold LN2 Trap 2, V6 = 12.8%. Take cold trap 1 out to warm. |
| 1148 | Increase V6 = 13.0% to speed up cleaning |
| 1242 | Stop cleaning through cold trap 2 after 60 min. Pump mix to dump. |
| 1314 | 42.2 mbar in warm trap 1. Pump out trap 1. |
| 1330 | Take trap 2 out of LN2 dewar to warm, put trap 1 back in LN2 dewar to cool. |
| 1340 | Start cleaning mixture through cold LN2 Trap 1, V6 = 12.8% |
| 1346 | Top off LN2 cold trap. |
| 1347 | Increase V6 = 13.0% to speed up cleaning |
| 1445 | Stop cleaning through cold trap 1 after 65 min. Pump mix to dump. |
| 1511 | Remove cold trap 1 from LN2 dewar to warm up. 9.4 mbar in warm trap 2. Pump out trap 2. |