Study on temperature noise suppression characteristics of passive thermal control materials in gravitational wave detection

Abstract

Space-borne gravitational wave (GW) detector requires high detection sensitivity in millihertz band. Temperature noise characterized by temperature amplitude spectral density (TASD) in target frequency band (0.1 mHz–100 mHz) must be limited to μK Hz−1/2 level. However, TASD at ultra-low frequency ascends sharply, leading to temperature noise suppression failure of passive thermal control material (PTM). In this paper, we proposed ‘frequency barrier’ to denote the sharply TASD transition at ultra-low frequency and developed temperature noise transmission model to study the effect of heat flow spectral characteristics and PTM thermophysical properties on TASD and frequency barrier. The results showed that reducing PTM thermal conductivity could decrease TASD apparently at certain heat flow frequency, but minimum TASD limit exist which increases with decreasing heat flow frequency. Frequency barrier decreases with decreasing thermal conductivity and increasing specific heat capacity of PTM. High heat capacity materials accumulate more heat, while low thermal conductivity materials attenuate more temperature fluctuations, enabling effective temperature noise suppression at low heat flow frequency and broadening PTM’s temperature noise suppression range. The obtained frequency barrier correlation provides guidance for the material selection criterion of temperature noise suppression in space-borne GW detection.