| 1400 | Remove wizard staff and attach top end to it using viton O-ring and assembly. Push tube as far as possible into top end to ensure as good a seal as possible. Evacuate with scroll pump and conduct leak check. Background helium leak rate 3E-10 mbar l/s. Spraying around the O-ring does not affect leak rate. However, moving the wizard staff back and forth in relation to top end did result in a gradual increase in leak rate by about 1E-11 mbar l/s to 2E-11 mbar l/s when no helium was being sprayed around the O-ring. All of a sudden, the leak rate increased very rapidly, reaching 1E-9 mbar l/s within roughly half-a-minute. Leaving the pipe alone, the leak rate reached 8.6E-9 mbar l/s before falling again. |