an apparatus used to control a workpiece inside a vacuum chamber . the workpiece is supported on a workpiece holder in the vacuum chamber . the workpiece is isolated from the atmosphere outside of the vacuum chamber by differentially pumped vacuum seals and an integral air bearing support . the differentially pumped vacuum seals and integral air bearing support allow for multiple independent motions to be transmitted to the workpiece supported by the workpiece holder . the workpiece holder motions provided are rotation about the x axis , translation back and forth along the y direction of an x - y plane on the surface of the workpiece holder , and rotation of the workpiece in the x - y plane about its z axis . concentric seals , oval for the translation motion and circular for the rotational motion , are differentially pumped through common ports to provide successively decreasing pressure and gas flow in order to reduce the gas load into the vacuum vessel to a negligible rate .