Operation of ultrasonic motor in ultrahigh vacuum condition

Aiming development of ultrahigh vacuum (UHV) compatible and fully nonmagnetic actuator, the authors are researching operation of a mode rotation type ultrasonic motor in UHV. Previously, a prototype that can generates rotation at a speed of 150rpm maintaining the gas pressure of the chamber at 3×10^-6Pa was reported. In this paper, previously used plastic coating on its rotor surface is replaced with well finished zirconia ceramic to reduce gas emission from the surface. As a result, the gas pressure of the chamber during motor operation is reduced to UHV grade of 3×10^-7Pa. In addition, effects of modifying stator-rotor interface shape, rotation speed and loaded torque are investigated.