Calibration of a thin metal foil for infrared imaging video bolometer to estimate the spatial variation of thermal diffusivity using a photo-thermal technique.
Calibration of a thin metal foil for infrared imaging video bolometer to estimate the spatial variation of thermal diffusivity using a photo-thermal technique.
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校准用于红外成像视频测辐射热计的薄金属箔，以使用光热技术估计热扩散率的空间变化。
DOI：
10.1063/1.4873713
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
Takashi Watanabe
中科院分区：
文献类型：
--
作者：
S. Pandya;B. Peterson;R. Sano;K. Mukai;E. Drapiko;A. Alekseyev;T. Akiyama;Muneji Itomi;Takashi Watanabe
红外成像视频测辐射热计（IRVB）是研究大型螺旋装置中高温等离子体三维辐射结构的重要诊断仪器，采用薄金属箔作为IRVB的宽带辐射吸收体。箔的二维（2D）热扩散方程需要数值求解，以估计通过针孔几何形状落在箔上的辐射。除了温度的时空变化之外，金属箔的热、物理和光学性质也是代码的输入，用于可靠地估计来自照射箔的等离子体的排气功率。箔非常薄且尺寸相当大，这些性质的不均匀性需要通过适当的校准程序来确定。用于增加表面发射率的石墨喷涂也有助于热性能的变化。本文讨论了热像技术在测定薄金属箔-石墨复合材料有效面内热扩散率空间变化中的应用。本文还讨论了这种技术的优点，根据目前正在实践的其他校准技术的局限性和缺点。该技术最初应用于已知厚度和热性能的材料进行验证，最后应用于具有两种不同厚度的金和铂的薄箔。据观察，石墨层的热扩散率的估计的效果变得更明显，为更薄的箔和测量值是约2.5-3倍低于文献值。还观察到，由于涂层导致的热扩散率的百分比降低对于高热扩散率材料（例如金）来说较低。这一事实也可以解释，尽管部分，铂箔的灵敏度高于黄金。
A thin metal foil is used as a broad band radiation absorber for the InfraRed imaging Video Bolometer (IRVB), which is a vital diagnostic for studying three-dimensional radiation structures from high temperature plasmas in the Large Helical Device. The two-dimensional (2D) heat diffusion equation of the foil needs to be solved numerically to estimate the radiation falling on the foil through a pinhole geometry. The thermal, physical, and optical properties of the metal foil are among the inputs to the code besides the spatiotemporal variation of temperature, for reliable estimation of the exhaust power from the plasma illuminating the foil. The foil being very thin and of considerable size, non-uniformities in these properties need to be determined by suitable calibration procedures. The graphite spray used for increasing the surface emissivity also contributes to a change in the thermal properties. This paper discusses the application of the thermographic technique for determining the spatial variation of the effective in-plane thermal diffusivity of the thin metal foil and graphite composite. The paper also discusses the advantages of this technique in the light of limitations and drawbacks presented by other calibration techniques being practiced currently. The technique is initially applied to a material of known thickness and thermal properties for validation and finally to thin foils of gold and platinum both with two different thicknesses. It is observed that the effect of the graphite layer on the estimation of the thermal diffusivity becomes more pronounced for thinner foils and the measured values are approximately 2.5-3 times lower than the literature values. It is also observed that the percentage reduction in thermal diffusivity due to the coating is lower for high thermal diffusivity materials such as gold. This fact may also explain, albeit partially, the higher sensitivity of the platinum foil as compared to gold.