Magnetic pole-piece support

A pole piece support comprising a frame having a spaced array of non-magnetic support structures, wherein disposed between at least a pair of adjacent non-magnetic support structures is a magnetic pole piece supported along at least a portion of its body by the adjacent non-magnetic support structures, wherein at least one support structure comprises a stiffening bar extending through an aperture defined in the body of the support structure, wherein the stiffening bar is pre-tensioned, wherein the support structures are connected at each end to an end support and are supported intermediate their ends by an intermediate support structure that is formed as a ring structure.