Status of the Shielding Coils Fabrication for the Iseult/INUMAC Whole Body 11.75 T MRI Magnet

A neuroscience research center with very high field MRI equipment has been opened in November 2006 in the Neurospin site at CEA Saclay. One of the imaging systems will require a whole body 11.75-T MRI magnet with a 900 mm warm bore. Operating at a homogeneous field level of 11.75 T, the cryostat has external dimensions of 4.8 m in diameter and 5.0 m in length. With the large aperture and high field strength, this magnet represents a significant challenge when compared to the largest MRI systems built to date. The coil is made of a niobium-titanium conductor cooled by a He II bath at 1.8 K, permanently connected to a cryoplant. The main coil is constructed from a stack of 170 double pancakes and the magnet is actively shielded by two large coils connected in series to fulfil the stray field specifications. The two shielding coils, each of about 4 m in diameter, are presently being manufactured by Alstom STTG Magnets. This paper describes the design of these coils and presents the latest progress of their fabrication. Details are given of the results of the winding and impregnation of the two coils.