Patent ID: 7145269

Claim:
A lithographic apparatus comprising: an illumination system that provides a beam of radiation, a support structure that supports a patterning device, said patterning device capable of a desired pattern onto said beam of radiation, a substrate holder that holds a substrate, a projection system that projects the patterned beam onto said substrate; and an actuator that produces a force between a first apparatus part and a second part to displace said first and second apparatus parts relative to each, wherein said first apparatus part comprises at least a part of one of said illumination system, said support structure, said substrate holder, and said projection system and said second apparatus part comprises at least another part of one of said illumination system, said support structure, said substrate bolder, and said projection system, said actuator comprising: a first magnet system subassembly and a second magnet system subassembly that comprise a main magnet system configured to provide a first magnetic field and a subsidiary magnet system configured to provide a second magnetic field, said main and subsidiary magnet systems attached to said first apparatus part; an electrically conductive element configured to produce said force based on an interaction between an electric current carried by said electrically conductive element and said first and second magnetic fields, said electrically conductive element attached to said second apparatus part and interposed between said first and second magnet system subassemblies; and a magnetic element extending substantially between outer portions of said first and second magnet system subassemblies, said magnetic element configured to guide a portion of said second magnetic field from one of said first and second magnet system subassemblies to the other one of said first and second magnet system subassemblies, wherein a distance between said electrically conductive element and said magnetic element is sufficiently large to cause a reluctance force of said actuator to be less than 1% of a maximum force produce by said actuator.