In a solenoid magnet assembly, and a method for manufacture thereof, the magnet assembly includes a number of concentrically aligned coils, each including a winding impregnated with a resin. Each coil is mechanically restrained so as to hold the coils in fixed relative positions relative to each other when forming the magnet assembly. The mechanical restraint can be formed by annular support sections bonded to the respective coils, lugs bonded to the respective coils, or by lugs that are at least partially embedded in a crust formed on a radially outer surface of the respective windings.