An improved apparatus for measuring the spectral directional emissivity in the wavelength range between 1 µm and 20 µm at temperatures up to 2400 K is presented in this paper. As a heating unit an inductor is used to warm up the specimen, as well as the blackbody reference to the specified temperatures. The heating unit is placed in a double-walled vacuum vessel. A defined temperature, as well as a homogenous temperature distribution of the whole surrounding is ensured by a heat transfer fluid flowing through the gap of the double-walled vessel. Additionally, the surrounding is coated with a high-emitting paint and serves as blackbody-like surrounding to ensure defined boundary conditions. For measuring the spectral directional emissivity at different emission angles, a movable mirror is installed in front of the specimen, which can be adjusted by a rotatable arrangement guiding the emitted radiation into the attached FTIR-spectrometer. The setup of the emissivity measurement apparatus (EMMA) and the measurement procedure are introduced, and the derived measurement results are presented. For evaluating the apparatus, measurements were performed on different materials. The determined emissivities agree well with values published in literature within the derived relative uncertainties below 4% for most wavelengths.

中文翻译：

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一种改进的高温发射率测量装置的开发和评估

本文介绍了一种改进的仪器，用于在高达 2400 K 的温度下测量 1 µm 至 20 µm 波长范围内的光谱定向发射率。作为加热单元，电感器用于加热样品，以及指定温度的黑体参考。加热装置放置在双壁真空容器中。流过双壁容器间隙的传热流体确保了确定的温度以及整个环境的均匀温度分布。此外，周围涂有高发光涂料，并用作类似黑体的周围，以确保定义的边界条件。为了测量不同发射角度的光谱定向发射率，在样品前面安装了一个可移动的反射镜，可通过将发射的辐射引导到连接的 FTIR 光谱仪中的可旋转装置进行调整。介绍了发射率测量仪 (EMMA) 的设置和测量程序，并给出了导出的测量结果。为了评估设备，对不同材料进行了测量。确定的发射率与文献中公布的值非常吻合，大多数波长的衍生相对不确定度低于 4%。