The invention provides devices and methods for depositing uniform coatings using cylindrical magnetron sputtering. The devices and methods of the invention are useful in depositing coatings on non-cylindrical workpiece surfaces. An assembly of electromagnets located within the bore of a hollow cylindrical emitter is used to form a magnetic field exterior to and near the exterior surface of the emitter. The magnet assembly configuration is selected to provide a magnetic field configuration compatible with the workpiece surface contour. The electromagnet assembly may be a plurality of magnet units, each unit having at least one electromagnet. The magnetic field strength from each magnet unit is separately and electrically adjustable. Each electromagnet in the assembly has a coil of electrically conducting material surrounding a specially shaped core of magnetic material.