Measurement of molten salt spectral radiation characteristics at high temperature using transmittance device without optical window

As a key heat storage medium, the spectral radiation and thermal characteristics of molten salts are crucial. Considering the effect of measurement accuracy by multiple reflections and refractions between samples and the optical window in the traditional measurement, and the corrosion of the sample to the materials of optical windows, a new method and device for measuring radiation properties of high-temperature liquid based on the transmission method and double thickness method is proposed in this study. This device removes windows, keeps high-temperature membrane then allows light source transmits directly to obtain the transmittance and optical constants. In present work, Solar Salt and Hetic were heated up to 673 K and the spectral radiation was measured by this new device, the refractive index n of Hitec in 500–1050 nm wavelength is about 1.42 and the absorption index κ is 2 × 10⁻⁷–5 × 10⁻⁷, For Solar salt, the n in measurement band is around 1.45, and the κ is 1.5 × 10⁻⁷–3 × 10⁻⁷.