High-Frequency Magnetic Response Measurement of Test Mass With a Fluxgate Magnetometer for Gravitational Wave Detection

For spaceborne gravitational wave detectors, such as LISA and TianQin, the disturbance caused by the coupling of test masses and the external magnetic fields is one of the main sources of the residual acceleration noise. Although the detection frequency band is from 0.1 mHz to 1 Hz, magnetic fields with frequencies higher than 1 Hz can still contribute to the noise through down conversion effect. Therefore, it is necessary to measure the ac magnetic susceptibility or magnetic response of the test mass (TM) at higher frequency for the evaluation of the magnetic noise. In this work, we propose a magnetic field response measurement method by directly probing the induced magnetic field of the TM placed in a spatially uniform magnetic field. The frequency can be measured up to 1500 Hz, satisfying the requirement of spaceborne gravitational wave detection.