Structural support member allowing alignment adjustment between coil formers in a magnet system

An MRI magnet assembly comprises main magnet coils 112 - 122 wound on a main coil former 128 and shield coils 124, 126 wound on shield coil former 130. A structural support member 138 is affixed to the main coil former 128 and to the shield coil former 130 to provide structural support and enable longitudinal alignment adjustment between the main coil former 128 and the shield coil former 130. The structural member 138 holds the shield coils in place, without the shield coils being fixed to the cryogenic vessel 132. A locking mechanism 140 may be engaged to fix the relative positions of the main and shield coils about an isocentre 142 after adjusting their alignment. The main coil former is fixed to the cryogenic vessel by mountings 137. The structural member has a mechanical stiffness sufficient to suppress any instability caused by forces generated between the main and shield coils.