The leak‐checking and testing of the first yin–yang magnet for the Mirror Fusion Test Facility (MFTF) Available to Purchase

Leak‐testing and leak‐reporting techniques used on the MFTF yin–yang magnet for the world’s largest superconducting coil are reported. Based on this experience, techniques will be developed for leak‐testing techniques to be employed on the 24 MFTF‐B coils. Additional information is presented on MFTF magnet operation after the completion of these tests. Also described are the leak‐hunting techniques and their results when applied to the two liquid‐helium circuits (the coil bundle and guard vacuum: both require helium flow for magnet cooldown), their associated piping, liquid‐nitrogen radiation shield, and piping. Leak hunting and repair was started in July 1981, when the installation of the magnet liner radiation shields was completed and continued until acceptable leak‐rate requirements were met in December 1981. Cooldown and acceptance testing of the magnet was accomplished in January and February 1982.