Microgravity annealing system for thin‐film superconductors

A mirror furnace system for annealing of superconducting thin films, which is adapted for the world’s longest dropshaft completed at Kamisunagawa, Japan, is described. The system must be designed for completing both melting and solidification processes during a short 10‐s microgravity period, and also for withstanding the deceleration of a drop capsule in which the furnace system is contained. All moving components must be operated so as not to disturb the microgravity environment. A random vibration test for the entire system was carried out before the microgravity experiment, and structural compatibility was verified. The furnace system worked well, and the accumulated number of free falls was 19. Results of annealing of the superconducting material at one gravity and microgravity were compared using scanning electron microscopy and x‐ray microanalysis.