Evaluation of magnetic torque noise of the test mass for space-borne gravitational wave detection

Abstract

Abstract Space-based gravitational wave detection imposes extremely stringent requirements on the acceleration noise of test mass (TM), with magnetic effect being one of the significant noise sources. Prior assessments of magnetic effects have only considered the translational acceleration of the center of mass. This work systematically evaluates the disturbing forces and torques produced by magnetic effects on all six degrees of freedom, with particular emphasis on the magnetic torque noise and the resulting force noise coupled into the sensitive axis. Based on the derivation of magnetic potential energy, a finite element calculation method for estimating magnetic torque noise is established, which incorporates the spatial distributions of both the residual magnetic moment and the magnetic susceptibility. The resulting residual acceleration noise along the optical sensitive axis is then calculated, taking into account the crosstalk effects of the center-of-mass to centroid offset, electrostatic coupling, and TM-laser interferometer coupling. This noise lies on the order of 10 -17 ms -2 Hz -1/2 @0.1 mHz. The results indicate that the main contribution to magnetic torque noise comes from the coupling between the residual magnetic moment and the spacecraft's magnetic field, while the contribution from magnetic inhomogeneity accounts for 16%.