Low magnetic disturbance analysis and testing of a novel proof mass type for gravitational reference sensor system

The proof mass used for gravitational-wave or Earth-gravity-field detection is usually comprised of materials such as gold–platinum alloys, which have a high density and low magnetic susceptibility, in order to reduce the magnetic disturbance produced by the geomagnetic field and the spacecraft itself. This article highlights a novel alloy composed of gold and iridium and having a 17-mm diameter spherical proof mass. Three solid samples of 5？×？5？×？3？mm are presented for application in an inner satellite or proof mass based on an inner-formation flying system. The magnitudes of magnetic susceptibility of gold and iridium are of approximately the same order. A wide range of mixture ratios for gold and iridium are compared to those of gold and platinum with the same magnetic susceptibility. The density and magnetic susceptibility of the new alloy are evaluated. It is noted that the magnetic susceptibility can reach orders of 10？5, and the magnetic disturbance on proof mass can be reduced to less than 10？10？m/s2, which satisfies the inner-formation flying system requirement