Design and Performance of a Prototype Polarization Modulator Rotational System for Use in Space Using a Superconducting Magnetic Bearing

We present the design and the mechanical and thermal performances of a prototype rotational mechanism using a superconducting magnetic bearing (SMB) for a space compatible polarization modulator. The rotational mechanism consists of an SMB with an optical encoder and a three-grip mechanism that holds a levitating rotor until a high-temperature superconducting array (YBCO) cools down below its critical temperature. After the successful operation of a grip mechanism, the rotor magnet levitates at 10-16 K, and we conduct spin-down measurements. We estimate the heat dissipation from the rotor rotation and an optical encoder. From the mechanical and thermal performances of the prototype rotation mechanism, we did not find the potential no-go results from this SMB technology for use in a future space mission. The development of this rotational mechanism is targeting for use of a polarization modulator for a space mission to probe the comic inflation by measuring the cosmic microwave background polarization.