Automatic current lead retractor system for superconducting magnets

A system for automatically and safely retracting current leads feeding current to a superconductor-type magnet operating within a pool of liquid helium or the like, after a persistent mode is achieved, so as to minimize heat flow into such pool, which comprises:

• an elongated thimble unit fabricated from a material of low thermal conductivity, said thimble unit having a first end proximate said pool and a further end substantially removed from said pool;
• a first pair of concentric annular inner and outer magnet current contacts mounted within said first end of said thimble unit, said inner and outer contacts insulated from each other and each electrically connected to such magnet;
• an annular shorting switch contact mounted within said first end of said thimble unit concentric with said outer contact of said first pair of contacts electrically connected to said inner contact and insulated from said outer contact;
• a further pair of concentric annular magnet current contacts within said thimble unit proportioned for current carrying engagement with respective of said first pair of magnet current contacts and adapted for axial movement within said thimble unit from a position of engagement with said first pair of magnet current contacts to a position substantially removed from said first pair of magnet current contacts;
• a shorting switch blade within said thimble unit axially from a position joining said shorting switch contact to said outer magnetic current contact for shorting such magnet to a position removed from said shorting switch contact;
• a pair of coaxial current conductive support members each having a first end attached to respective of said contacts of said further pair of magnet current contacts and a further end, said support members insulated from each other;
• individual current cable lugs attached to each of said support members proximate said further ends for attachment to a magnet power supply;
• a first fluid-operated cylinder attached to said further ends coaxial support members for effecting axial movement of said coaxial support members to effect axial movement of said further pair of magnet current contacts;
• a switch blade support member having a first end attached to said shorting switch blade and a further end;
• a further fluid-operated cylinder attached to said further end of said switch blade support member for effecting axial movement of said switch blade support member for effecting movement of said shorting switch blade relative to said shorting switch contact;
• a fluid controller interposed between a source of fluid and said first and further fluid operated cylinders;
• signal generating means for producing signals corresponding to such persistent mode of such magnet, operability of said source of fluid, position of said shorting switch blade, and absence of current flow from said magnetic power supply;
• an electronic system controller for receiving signals from at least said signal generating means and for processing said signals to produce an output signal to said fluid controller for effecting automatic and safe retraction of such current leads to such magnet.