Zebing Zhou

Patch potentials on conductive surfaces introduce significant electrostatic disturbances in high-precision experiments, including space-based gravitational wave detection. In this work, we systematically investigate the effects of various surface treatment processes—including organic cleaning, acid cleaning, ion sputtering, thermal annealing, gold coating, and atmospheric exposure—on the surface potential distribution of the AuPt alloys that were developed for fabricating the test masses used in space-based gravitational wave detection. Kelvin probe force microscopy characterization reveals that while conventional organic cleaning and thermal annealing offer limited improvements, acid cleaning significantly suppresses potential fluctuations, reducing the root-mean-square (RMS) values by over a factor of two. Notably, ion sputtering proves to be the most effective technique, consistently yielding highly homogeneous surfaces and producing an approximately fourfold reduction in the RMS values. Auger electron spectroscopy confirms that this enhancement stems from the thorough removal of carbon-, sulfur-, and oxygen-containing surface contaminants. Furthermore, the treated surfaces exhibit robust environmental stability, retaining their homogeneity even after one month of exposure to ambient conditions in a clean environment. These findings provide essential guidance for optimizing surface-treatment strategies in applications such as high-precision inertial sensors.

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%.

Electrostatic stiffness is a key parameter governing space inertial sensor, and its precise characterization via applied actuation voltages is critical for determining the residual acceleration of the test mass along the sensitive axis. In this paper, we investigate the dependence of this stiffness on the maximum actuation range within a dedicated model. A closed-loop calibration experiment utilizing a custom-designed two-stage torsion pendulum equipped with capacitive sensors and an AC feedback control system was performed. For electrostatic stiffness near 10 ⁻⁴ N m ⁻¹ , measurements agree with theoretical predictions within a 1.6% deviation. The stiffness exhibits direct proportionality to both the maximum actuation force and torque. These results validate the constant stiffness model and provide guidelines for optimizing in-orbit electrostatic control parameters.

The high-precision inertial sensor is a key technology for space-based gravitational wave detection missions. AC high-voltage electrostatic actuators with an output capability of hundreds of volts are required to capture and control the test mass after its initial release by the locking mechanism, and this is critical for achieving scientific mode. This paper proposes high-voltage electrostatic actuators with a step-up transformer, which could eliminate the need for a high-voltage power supply. The transformer is specially designed to provide an amplification of around 15 and a frequency range of over 50–1000 Hz. Testing has confirmed that the actuator can deliver a high-voltage output of approximately 150 V. Its amplification coefficient exhibits a response relationship with changes in input voltage and frequency, and the resulting minor nonlinearity does not affect capture control after closed-loop compensation. This work provides an alternative scheme for high-voltage electrostatic actuators.

Test masses for gravitational wave detectors require ultralow magnetic susceptibility (χ<10-6 cm3/mol). Binary AuPt alloys are promising, but trace Cu is inevitably introduced during fabrication. Using fully relativistic first-principles within the Korringa-Kohn-Rostoker coherent-potential approximation (KKR-CPA) calculations combined with virtual crystal approximation, we quantitatively link composition, electronic structure, and magnetic response of AuPtCu ternary alloys. Our results show that for Au content between 78-81% and Cu up to 5%, the alloy retains χ<10-6 cm3/mol, meeting the ultralow magnetic susceptibility requirement on test masses. The calculated three-dimensional magnetic phase diagram reveals strongly nonlinear susceptibility variation with composition, deviating up to 40% from linear mixing. For the first time, we identify a zero-susceptibility contour for Au concentrations from 70% to 81%, offering a wide and tunable window for experimental synthesis. This work not only clarifies the microscopic origin of ultralow susceptibility in ternary alloys, through reduced Pt d-band density of states and weakened Stoner enhancement, but also provides a quantitative map for designing ultralow-susceptibility alloys for gravitational wave detectors and MRI-compatible devices.