A rotary stage in a vacuum using an air bearing

Abstract

We present a design for a precision rotary air-bearing stage that can be used as a positioning system in vacuum applications, and evaluate its performance. The rotary stage used a vacuum-compatible air bearing, direct-drive motor, and high-resolution encoder to move precisely in a vacuum. The air bearing used a differential exhaust scheme with optimally designed parameters to minimize the air leakage into the vacuum chamber. The vacuum level was estimated from a theoretical leakage analysis and verified experimentally. The results show that a vacuum of 4 × 10−4 Pa was achieved during operation of the air-bearing stage, with an increase in the pressure of 0.5% at a velocity of 300 rpm, and a rotational resolution of 0.162 μrad and rotational accuracy of 0.23 μm in the radial direction.