In spaceborne gravitational-wave detectors, the stringent requirements on the magnetic cleanliness of the test masses (TMs) make the development of ground-based characterization techniques of their magnetic properties important. An electrostatically controlled torsion pendulum has been built to measure the magnetic properties of TianQin-like solid TMs. The remanent magnetization $m_r$ and the magnetic susceptibility $\chi$ of TMs can be measured at the level of 1 nA ${\mathrm{m}}^2$ and $8\times {10}^{-7}$, respectively. The precisions of measurements are mainly limited by the mechanical sensitivity of silicon fiber. The experimental results from a solid tungsten TM as an example show that the apparatus provides a feasible way to investigate the bulk effect of a full-size TM for the TianQin mission with enough resolution.

• Received 27 July 2020
• Revised 23 November 2020
• Accepted 7 December 2020

DOI:https://doi.org/10.1103/PhysRevApplied.15.014008