Reduced mass persistent switches for large superconducting magnets in space

Superconducting magnets in space must operate in the persistent mode. The author describes the characteristics of low mass niobium titanium persistent switches for low mass superconducting magnets which were designed to quench protect themselves through the quench back process. The whole coil is driven normal shortly after the quench has started and the magnet stored energy is taken up by the coil and the persistent switch. The concept of using a resistor and diode in parallel with the persistent switch to reduce the overall mass of the persistent switch system and the helium consumption during magnet charging is discussed. A 1.4-m-diameter free-flyer version of the 11.6-MJ stored energy ASTROMAG magnet and its persistent switch is presented as an example.<>