Measuring remanent magnetic moment of test masses by a compound pendulum in a magnetic shielding room

In space-borne gravitational wave detection, the remanent magnetic moment of test masses is one of the primary contributors to residual acceleration noise. During the ground test phase, precisely measuring the remanent magnetic moment of the test masses under an ultra-weak magnetic field is crucial for assessing its suitability for the space mission. In this work, we developed a compound pendulum apparatus within the magnetic shielding room, utilizing the pendulum’s periodic motion to convert the remanent magnetic moment into a modulated magnetic field. The measurement resolution of remanent magnetic moment reaches a level of 0.2 nAm².