Cryogenic magnet structure with integral maintenance boot

A method for cryogenically refrigerating a magnet structure, the method comprising:

• cooling at least two superconducting coils with at least one cryogenic refrigerator via thermal conduction through at least one integral maintenance boot assembly, wherein the at least two superconducting coils that are (a) substantially symmetric about a central axis, (b) on opposite sides of a median plane, (c) contained in at least one cryostat sealed with the at least one integral maintenance boot assembly, and (d) surrounded by a magnetic yoke, and wherein the at least one cryogenic refrigerator cools the superconducting coils to a temperature at which the coils are superconducting;
• generating a vacuum in the at least one cryostat;
• and
• removing the at least one cryogenic refrigerator from thermal and physical contact with the at least one integral maintenance boot assembly and preserving the vacuum after that removal with a seal provided by the integral maintenance boot assembly.