Persistent protective switch for superconductive magnets

A high-field superconducting magnet system having a persistent switch system for permitting removal of current leads when not operating in a charge Or discharge mode, which comprises:

• a main high-field magnet coil having first and second charge/discharge terminals:
• a persistent switch system connected across said terminals;
• said persistent switch system comprising:
• a first switch coil formed from superconducting material connected to a first said charge/discharge terminals;
• a first quench heater in physical contact with said first switch coil;
• a second switch coil formed from a superconducting material connected in series with said first switch coil and connected in series with the second of said terminals;
• a second quench heater in physical contact with said second switch coil;
• a shunt coil wound with resistive wire, connected in parallel with said second switch coil in contact with said main coil to heat an area of said main coil to the normal state;
• and
• means for refrigerating said main coil and said first and second switch coils to temperatures at which said first and second switch coils are in a superconducting state.

The method of protecting a main high-field superconducting magnet coil while permitting Current leads to be removed when not in a charge or discharge mode which comprises the steps of:

• connecting a first switch coil formed from superconducting material to the first of two charge/discharge terminals of a high field superconducting magnet coil;
• bringing a first heater into close physical contact with said first switch coil;
• connecting a second switch coil formed from superconducting material in series between said first switch coil and the second of said two charge/discharge terminals;
• bringing a second heater into close physical contact with said second switch coil;
• connecting a shunt coil wound with resistive wire in parallel with said second switch coil;
• mounting said shunt coil in physical contact with, but electrically insulated from, said main high-field superconducting magnet coil;
• and
• refrigerating said main coil and said first and second coils to temperatures at which said coils are in a superconducting state.