A rotary stage in a vacuum using an air bearing

•We designed a rotary stage using a porous air bearing in a vacuum.•The design parameters for the seals and vacuum pumps were optimized.•A theoretical leakage analysis was verified experimentally.•The cause of the increase in pressure during air bearing movement was determined.•The rotary air-bearing stage moved with a fine-step resolution of 0.162 μrad.

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.