Water cooled, air bearing based rotating anode x-ray illumination source

Abstract

Methods and systems for realizing a high speed, rotating anode based x-ray illumination source suitable for high throughput x-ray metrology are presented herein. A high speed rotating anode includes a water cooled rotating platen supported by radial and thrust air bearings employing cascaded differential pumping. A very high bending stiffness of the rotating assembly is achieved by spacing radial air bearings far apart and locating a rotary motor and thrust bearings between the radial air bearings. The high bending stiffness increases the mechanical stability of the rotating assembly during high speed operation, and thus decreases vibration at the location of impingement of the electron beam on the rotating anode material. In some embodiments, magnetic thrust bearings are employed and the air gap is controlled to maintain a desired gap over an operational range of up to three millimeters.