Abstract: A magnetic roller has a plurality of outwardly opening spacer receiving channels therearound, the roller being composed of a ferromagnetic steel; a plurality of non-magnetic spacers, each such spacer's interior surface forming a magnet receiving channel, each such spacer being composed of a non-magnetic material; a multiplicity of permanent magnets; a multiplicity of pole pieces, each such pole piece being composed of ferromagnetic steel; each non-magnetic spacer being fixedly mounted within a spacer receiving channel; the permanent magnets and pole pieces being fixedly mounted within the magnet receiving channels of the non-magnetic spacers, so that the pole pieces are alternately interspaced between the permanent magnets; and so that the permanent magnets are alternately oriented.