Thermal induced noise on test mass with copper alloy electrode housing for spaceborne gravitational wave detection

The temperature gradient effect (TGE) is an important disturbance source in the inertial sensor, the core payload of space gravitational wave detectors. The inertial sensor electrode, made of copper alloy with high thermal conductivity, is expected to achieve lower temperature gradient, but its outgassing characteristics need to be verified experimentally. In this work, we have developed a torsion pendulum and measured the TGE of the copper alloy electrode. The measurement results show that the upper limit of the outgassing effect of this copper alloy gravitational reference sensor is about $18.0\mathrm{pN}/K$, and the total TGE is less than $30.2\mathrm{pN}/K$ at 293 K, which can be ignored in the application of gravitational wave detection. Our work reveals key physical properties associated with TGE and provides a viable alternative for specialized equipment applications in spaceborne gravitational wave detection missions and beyond.