Low Temperature Performance of a Superconducting Angular Accelerometer

Abstract

An angular accelerometer has been developed that has an amplifier noise limited resolution of better than 10-10 rad s-2 Hz-112. The device consists of a superconducting niobium proof mass suspended by a torsional spring. A superconducting circuit and SQUID amplifier are used to measure angular displacement of the proof mass, which is proportional to the acceleration at frequencies below the natural resonance frequency. To prevent low-level linear accelerations from generating detectable angular accelerations, very precise mass balancing is necessary. Using room temperature measurements and wire EDM machining, the proof mass's center of gravity can be controlled to within 0.2 mi- crons. In recent tests conducted at 4.2 K, performance better than 3x10-9 rad s-2 Hz-112 has been observed. The noise floor can be traced to seismic and thermal inputs. Manufacturing details and performance tests are discussed. INTRODUCTION