An ultrasonic motor for cryogenic temperature using bolt-clamped Langevin-type transducer

In this study, a small ultrasonic motor driven under cryogenic temperature conditions has been fabricated and evaluated. Since transducer performance generally decreases at cryogenic temperatures, we designed and fabricated a bolt-clamped Langevin-type transducer for operation at cryogenic temperature. We simulated the influence of thermal stress on the transducer. The results from simulation were used to design the transducer, and it was then used to fabricate an ultrasonic motor for cryogenic temperature. The maximum diameter and the height of the motor are 30 mm and 38.7 mm. To enable the motor to be driven at cryogenic temperature, we evaluated the relationship between the contact pre-load and the lowest rotatable temperature. The motor's driving performance was evaluated at both room temperature and cryogenic temperatures. In a 4.5 K helium gas ambient, the rotation speed and starting torque were 133 rpm and 0.03 mu N m when the applied voltage was 50 Vp-p.