| 0900 | Turbo pump pumping on IVC overnight, now reads 7.4e-5 mbar. (With pump valved off, pressure rises to 2e-3 mbar.) |
|---|---|
| 0905 | Turn on leak checker and check calibration. Background with leak checker valve closed <2e-10 mbarL/s |
| with valve open and turbo pumping bkg even lower, 7e-11 mbarL/s. | |
| valve out turbo pump. leak checker bkg rises to 2.6e-9 mbarL/s. | |
| 0935 | With background leak rate of 2.7E-9 mbarL/s, conduct leak check on bellows/flanges above fridge. Leaks detected at wizard's staff flange (flange connecting Ebox bellows to stripline tube) with a leak rate as high as 1E-7 mbarL/s, and at the flange connecting the two bellows that lead to the Ebox from the wizard staff with a leak rate as high as 5E-7 mbarL/s. Some other spikes were detected, including a 5.3E-8 mbarL/s leak on the bellows leading to the wizard staff, but these could be due to close proximity to the other leak. Allow leak rate to fall before proceeding. |
| 0945 | Fill LN2 cold trap full. |
| 0955 | Conduct leak check again with background of 3.4E-9 mbarL/s. Wizard staff flange shows a leak rate of 3.8E-8 mbarL/s, and flange connecting bellows leading to Ebox shows a leak rate of 3.2E-7 mbarL/s. Vent to atmosphere before opening flanges to clean and re-tighten them. |
| 1040 | Adjust wizard staff flange and flagne connecting bellows leading from Ebox. Starting with a 6.8E-9 mbarL/s background, conduct another leak check on fridge flanges. No leak seen between bellows leading to Ebox, leak of 9.0E-7 mbarL/s seen on wizard staff flange. flange connecting wizard staff to T-pipe has a leak rate of 2.0E-6 mbarL/s. Vent to atmosphere before opening flanges to clean and re-tighten them. |
| 1111 | Checked pressures in IGH. Turned the 3He pump on to pump IGH contents to dump. Reading the dump at G2 (through V9) the pressure increased slowly for a couple of hours, suggesting it takes a while to pump everything out from that back of the pump. Final pressure at G2 was 794.4 mbar (barometric sea-level pressure = 30.21 “Hg, so corrected dump pressure = 803.8 mbar). |
| 1130 | Loosen and re-tighten wizard staff flange, and clean/reset T-pipe flange. Conduct another leak check with an initial background of 6.8E-9 mbarL/s. No significant leak found when spraying T-pipe flange or wizard staff flange (some oscillations, but stayed under 7E-9 mbarL/s). Leak rate of 4.1E-8 mbarL/s was found when spraying front Ebox flange. Vent to atmosphere before opening cover to clean and re-tighten. |
| 1225 | Clean and re-tighten Ebox front cover. Conduct leak check with initial background of 7.3E-9 mbarL/s. No leak detected for Ebox front panel. Spray test of wizard staff and IVC flanges also resulted in no significant rise or sign of leak. Commence pumping on IVC with turbo pump and isolate leak checker. |
| To clean the seals we cleaned the metal surfaces with methanol and brushed off the o-rings, then applied a little vacuum grease to the o-rings. The top seal of the wizard staff is not directly accessible, so for this simply reseated the elbow at atmospheric pressure and retightened the compression ring. | |
| 1235 | Conduct room temperature throughput test. With G2= 794 mbar, open V13A, V12A and coldtrap 1 speedivalve, V3 and gate and condenser line valves. Allow mixture to flow to both sides of fridge until G1 stabilizes at 678 mbar. Then close V12A and coldtrap 1 speedivalve and open V1. G1 drops to 55 mbar before beginning to rise. Throughput test results in a flow rate of 9.2 mbar/min for G1. Pump mixture to dump. |
| 1306 | Pumping out IVC. Turbo at 3.4e-4 mbar |
| 1310 | Commence cryocleaning mixture through Cold Trap 1. |
| 1450 | Raise dewar and switch from external pressure sensor (reading 1.2E-4 mbar) to leak checker. |
| 1510 | Evacuate main bath and 1 K pot. Background helium leak rate 2.6E-9 mbar l/s. Overpressurise main bath with He-4 gas. Helium leak rate rises to 8.0E-8 mbar l/s before falling again (to 1.0e-8 mbarL/s after 10 minutes or so). This is very similar to the differential pressure leak witnessed on 2014/03/11, and thus not cause for much concern. Proceed with nitrogen transfer. |
| 1517 | Add 5.4 mbar He exchange gas. Isolate IVC. Commence LN2 transfer. |
| 1713 | Finish LN2 transfer. Currently mixing chamber temperature at 105 K. |