| 摘要 |
ACTIVELY SHIELDED MR MAGNET WITHOUT CRYOGENS An actively shielded refrigerated superconductive magnet is provided. The magnet includes a generally cylindrical vacuum vessel having an axially extending bore. A plurality of superconductive main coils are positioned in the vacuum vessel concentrically surrounding and spaced away from the bore. A pair of superconductive shield coils having a larger diameter than the superconductive main coils are situated in the vacuum vessel, concentric with the superconductive main coils. The superconductive shield coils are situated at either end of the superconductive main coils. The superconductive shield coils and the superconductive main coils are electrically connected to one another so that the superconductive shield coils and the superconductive main coils are capable of carrying current in opposite circumferential directions. Thermal shield means enclose the superconductive main and shield coils, with the thermal shield spaced away from the vacuum vessel and superconductive main and shield coils. Two stage cryocooler means is provided for cooling the superconductive main and shield coils, and the thermal shield.
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