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

A neuroscience research center with a very high field magnetic resonance imaging (MRI) equipment was opened in November 2006 in the Neurospin site at CEA Saclay. One of the imaging systems requires 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 real challenge when compared to the largest MRI systems ever built. The coil is made from a copper-stabilized niobium-titanium conductor cooled by a superfluid helium bath at 1.8 K and permanently connected to a cryo-plant. 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 fulfill the stray field specifications. The two shielding coils, each of about 4 m in diameter, are presently being manufactured by Alstom Power Systems STTG Magnets, Belfort. This paper describes the design of these coils and presents the latest progress of their fabrication. Details are given of the winding technique, impregnation method, and the first results of electrical and geometrical tests.