Lithographic apparatus and device manufacturing method

An electromagnetic actuator comprising:

• a coil assembly comprising at least one coil;
• a magnet assembly comprising a first and second magnet unit, each magnet unit comprising a magnetic yoke and a plurality of permanent magnets mounted to the magnetic yoke, the first and second magnet unit forming a magnetic circuit for receiving the coil assembly and, upon energizing of said coil, generating a force in a first direction;
• and
• a holder for holding the magnet units, wherein the magnet units are rigidly mounted to the holder;
• wherein a weight ratio of the magnet assembly over the coil assembly is smaller than a weight ratio of another magnet assembly over another coil assembly for which a ratio of force over electrical power is maximized, and
• wherein the at least one coil comprises a first coil and a second coil, the coil assembly further comprising an inner cooling plate and two separate first and second outer plates, the inner cooling plate being arranged between the first and second coils to cool the first and second coils, the first and second coils and the inner cooling plate being stacked between the first and second outer cooling plates so that the first coil is arranged between the first outer cooling plate and the inner cooling plate and the second coil is arranged between the second outer cooling plate and the inner cooling plate.