Patent GB-1472919-A (GB)
Title: Magnet coil assembly
IPC: H01F6/00
Filed: 1974-07-05
Abstract: 1472919 Superconductive electromagnets SIEMENS AG 5 July 1974 [5 July 1973] 29993/74 Heading H1P A superconductor magnetic oil structure for, e.g. confinement or thermal isolation of hot gaseous plasma in a thermo nuclear reactor comprises plural electromagnetic units assembled in a torus with intervening bearing means therebetween to take up the mechanical forces developed between the units; a magnet coil unitary assembly from two or more of which a magnet coil structure may be provided and in which magnetic forces may be developed between the adjacent coils comprising a magnet coil disposed in a container, means for cooling the magnet coil and a vacuum housing enclosing the container to avoid heat transfer; the assembly enabling force transmission between the container and that of an adjacent magnet coil assembly by means extending through the vacuum housing in a sense parallel to the direction of the force and defined for each assembly by a pair of movable bearing elements transmitting force through the vacuum housing by abutment one with the other; one such bearing element being mounted movably on the container and the other movably mounted on the vacuum housing for co-operation with the corresponding bearing element of an adjacent magnet coil assembly. A component electromagnet 1 is contained in an outer vacuum housing 2 with an energizing coil (not shown) disposed in a coolant container 3 for a cryogenic medium, e.g. helium; enclosed in housing 2. A central position 4 of the periphery of container 3 carries adjacent bearing elements 5, 6 adjustably movable parallel to the sense of the magnetic forces operating between magnet 1 and adjacent individual magnets (not shown). Vacuum bellows 9, 10 carried by the walls 13, 14 of housing 2 bear on the ends of members 7, 8. Elements 11, 12 in prolongation elements 5, 6 extend from bellows ends 7, 8 and pass through bores in walls 13, 14; allowing the bellows to be compressed by elements 5, 16. The ends 17, 18 of elements 11, 12 are retained by wedge-shaped distance pieces 19, 20 mounted on a tube (not shown) extending slidably through the walls of ring-shaped spacers 21, 22 disposed in vacuum tight manner between housing 2 and that of adjacent magnets. Thus elements 11, 12 are enclosed in vacuum enclosures defined by spacers 21, 22 and bellows 9, 10. Housing 2 is held at ambient temperature and container 3 at cryogenic temperature while housing 2 is evacuated and a nitrogen cooled radiation shield 25 is interposed between it and container 3. When a magnet assembly of plural such magnet arrangements is de-energized, no force is exerted on electromagnet 1 while elements 5, 6 are retracted from abutment with elements 11, 12. Heat transmission through bellows 9, 10 into coolant container 3 is interrupted by vacuum gaps 15, 16. When the composite magnet system is energized elements 5, 6 move apart to abut base members 7, 8 of bellows 9, 10 which are compressed until elements 11, 12 engage distance pieces 19, 20 in force transmitting manner with adjacent individual magnets. The elements 5, 6 may be positionally adjusted by a drive shaft (not shown) extending vacuum tightly through housing 2 to rotate worms 26, 27 through differential gear (not shown) to engage teeth on elements 5, 6 to move them to and from walls 13, 14 so as to compress bellows 9, 10 uniformly. The bellows may be of steel sheet and elements 11, 12 of metal or glass reinforced plastic, while distance pieces 19, 20 are positioned by tubes fixed within spacers 21, 22. In a modification (Fig. 2) a coolant container 31 and outer vacuum vessel 32 are shown; a radiation shield 34 surrounding container 31 bearing carried by a spring bellows and pressure surface 35 screwed to a member 33 concentric with the bellows which engages the wall of container 31. Shield 34 is cooled by liquid nitrogen circulating in a pipe 38, and surface 35 is opposed by bearing element 39 where end 41 is engaged and fixed to piston 43 of a coaxial pressure cylinder 44; the projecting end of the piston being connected to vacuum vessel 32 over spring bellows 48 so that hydraulic fluid injected through duct 50 extrudes the piston so that element 39 compresses the surface 35 and member 33 abuts the coolant container 31. Hydraulic pressure is maintained or released by a non-return valve of duct 50, and its relief piston 43 is restored by spring bellows 48 to disengage surface 35 and element 39. Member 33 is then repositioned by spring bellows 37 to leave gap 52 between it and the coolant container in which is a magnet coil (not shown) cryogenically cooled in liquid helium. Pressure is applied to transmit mechanical force between container 31 and vessel 32 only when the magnets are energized. A further hydraulic assembly may be assembled back to back with outer surface 60. Plural such assemblies may be used to space apart individual magnets in TOKAMAK toroids or in linear superconductive magnet assemblies used in thermonuclear plasma physics whereby large mechanical forces are to be counterbalanced and resisted with minimum heat exchange.