Lithographic apparatus and a device manufacturing method

A lithographic apparatus comprising:

• a support constructed to support a patterning device, the patterning device being capable of imparting a radiation beam with a pattern in its cross-section to form a patterned radiation beam;
• a projection system configured to project the patterned radiation beam onto a target portion of a substrate;
• a first vacuum environment that contains said projection system;
• a second vacuum environment that contains said patterning device support;
• and
• a separator that separates the first vacuum environment and the second vacuum environment, the separator comprising an aperture for passing said projection beam from the first vacuum environment towards the patterning device and/or vice-versa,
• a plurality of blades for controlling the dimensions of said projection beam, said blades extending at least partially between said patterning device and the aperture of the separator,
• wherein said patterning device and said blades are arranged for substantially sealing the first vacuum environment from the second vacuum environment at the aperture of the separator.