Magnetic bearing, a rotary stage, and a reflective electron beam lithography apparatus

A magnetic bearing with an axis of rotation, wherein the magnetic bearing comprises:

• a cylindrical rotor comprising a ferromagnetic material, wherein the cylindrical rotor has an axis of symmetry, wherein the cylindrical rotor has an inner radius, wherein the cylindrical rotor has a top side that lies in a plane orthogonal to the axis of symmetry,
• a static hub, wherein the static hub has an overhang which protrudes from the static hub and is located adjacent to the top side,
• a lift magnetic actuator apparatus for controlling the distance between the top side and the overhang, a radial magnetic actuator apparatus for controlling the distance between the inner radius and the axis of rotation;
• wherein the lift magnetic actuator apparatus comprises at least one permanent magnet capable of supporting the cylindrical rotor against the gravitational force and wherein the radial magnetic actuator apparatus and/or the lift magnetic actuator apparatus comprises at least one hybrid magnet, wherein the a hybrid magnet comprises:
• a ferromagnetic core, wherein the ferromagnetic core has two slots cut in is the ferromagnetic core such that its cross section is E-shaped, wherein there is a middle section between the two slots, wherein the middle section has an outer surface whose normal points away from the ferromagnetic core,
• a coil of wire adapted for generating a magnetic field when a current is passed through the wire, wherein the coil is located within the two slots and around the middle section, and
• a permanent magnet placed on the outer surface, wherein the magnetization is aligned with the normal of the outer surface.