“Zero-power” positioning actuator for cryogenic environments by combining magnetostrictive bimetal and HTS

This research presents a novel “zero-power” actuator for cryogenic conditions by combining a magnetostrictive bimetal with a bulk high temperature superconductor (HTS) sample. This actuator is based on two phenomena; “pinning effect”, and “magnetostrictive bimetal”. The relationship between displacement of actuator and applied current was measured when the thickness of the HTS samples was 1, 2, and 3 mm. It was found that because of pinning effect part of the magnetic flux (energy), generated by the coil can be trapped (stored) in the HTS samples. Consequently, the actuator can be held in the desired position when its power is switched off. “Holding range” of actuator is directly proportional to the thickness of the HTS samples. The holding range of 4.5 micron-meter for 1mm thickness of the HTS increases to 12 micron-meter for 3mm thickness. The controllability of the actuator over its holding range was also demonstrated.