Simplified active shield superconducting magnet assembly for magnetic resonance imaging

Abstract

An improved actively shielded superconducting magnet in which the main and bucking coils are directly wound onto respective coil support structures made of glass fiber-reinforced epoxy. The main and bucking coil cartridges are held in a fixed concentric relationship via a pair of flanges located at opposite ends of a helium vessel. During manufacture of the main and bucking coil cartridges, the outer diameters of the respective coil support structures are machined with high precision. Also, the diameters of two concentric grooves are precisely machined on the inner surface of each helium vessel end flange to match the outer diameters of the main and bucking coil support structures, so that at room temperature the main and bucking coil cartridges can slide smoothly into these grooves. The helium vessel is made of aluminum alloy and has a coefficient of thermal expansion which is greater than that of the fiber-reinforced epoxy coil support structures. When the helium vessel is filled with liquid helium, the helium vessel end flanges hold the main and bucking coil cartridges tightly with predetermined amount of interference due to differential contraction of the aluminum alloy and the fiber-reinforced epoxy materials. This provides mechanical support to the main and bucking coil cartridges and ensures their concentricity. The relative axial positions of the main and bucking coil cartridges are fixed using the same working principle.

Dependencies are inferred from the claim text.