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.