Effects of non-uniform gas distribution on residual gas noise in space-borne gravitational wave detectors

Residual gas noise limits the measurement accuracy of space-borne inertial sensors and is critical for space-borne gravitational wave detection. Unlike conventional sensors, space-borne inertial sensors exhibit complex boundaries, anisotropy, and multiple outgassing sources, leading to non-uniform gas distributions. However, this phenomenon and its effect on residual gas noise have not been discussed in previous studies. This study focuses on the analysis of non-uniform gas distribution and its effect on residual gas noise in space-borne inertial sensors. Non-uniform gas distribution was simulated and characterized with a quasi-Gaussian distribution. A model for residual gas noise in constrained spaces with non-uniform gas distribution was developed and analyzed. Results show that the gas distribution within the inertial sensor's constrained space differs from that in free space. Non-uniform gas distribution leads to extra noise, which reaches up to 2.02 × 10−16 (N/Hz1/2). This additive value accounts for about 20% of TianQin's total noise budget. The extra noise originates from prolonged gas molecule escape time and gradient-induced external friction. This study evaluated the non-uniform gas distribution, and its findings are significant for the space-borne gravitational wave detectors.