A magnet system for use in magnetic resonance imaging. The system includes a vacuum vessel having a first wall assembly defining a bore for receiving the subject of the imaging and a pair of spaced metallic end plates welded to the ends of the first wall assembly. The system further includes a cryogenic containment vessel supported within the vacuum vessel and a coil disposed within the containment vessel for providing the magnetic field. The first wall assembly includes a weldable metallic cylindrical shell positioned intermediate the end plates and having a thickness insufficient without reinforcement to provide structural integrity during operation of the vacuum vessel. This first wall assembly further includes a reinforcement layer of a non-metallic material disposed about the metallic shell so that signals provided by gradient coils disposed inside the bore can more quickly penetrate the first wall assembly than if the metallic shell had sufficient thickness, without reinforcement to provide the necessary structural integrity.