Maintaining Ultra High Vacuum Integrity Through Leak Chasing

At the Multicharged Ion Research Facility at Oak Ridge National Laboratory, the measurement of charge transfer induced soft X-Rays [1] in a new merged-beams configuration requires ultra-high vacuum to reduce backgrounds. A systematic, reproducible approach to finding and eliminating leaks is vital. Major leaks due to improperly sealed flanges were found by spraying ethyl alcohol on the sealing surfaces and observing fluctuations in pressure using a Pirani gauge. Then, at a vacuum at 10^-5 Torr and below, we sprayed helium gas outside the beam lines and observed vacuum fluctuations in the helium levels using a residual gas analyzer (RGA). Ultimate pressures inside a tube held at 1.8 K  temperatures where H and ion beams will be merged is expected to be around 10^-13 Torr.

This research is supported by a NASA Astrophysics Research and Analysis Grant No. NNH18ZDA001N.

[1] R. T. Zhang, D. Wulf, D. McCammon, D. Seely, V. Andrianarijaona, and C. C. Havener, AIP Conference Proceedings, 2160, 070004 (2019)