A spectroscopic method to measure directional spectral emissivity for homogeneous and heterogeneous semi-transparent materials, giving access to a large spectral 10–12 000 cm−1 range and to temperatures lying between 600 and 3000 K is reported. Sample heating is supplied by a carbon dioxide laser and the blackbody flux reference is obtained with a lanthanum chromite furnace. Experimental results obtained with this setup on several dielectric oxides such as silica, alumina, and magnesia are in good agreement with the results obtained by an indirect method based on the Kirchhoff’s laws. A brief overview of the setup abilities and a detailed discussion of the emissivity spectra are also proposed.

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The thermal behaviour of Hall effect thrusters was investigated by means of calibrated infrared thermal imaging performed in the 8-9 µm spectral domain. Study on the variation of the steady state temperature of Hall thruster elements like discharge chamber (channel) walls and anodes along with discharge voltage and propellant (xenon) mass flow rate confirms that energy loss mechanisms, which are responsible for the heating of the thrusters, are a direct consequence of interactions between charged particles and surfaces. In order to obtain new insights into plasma surface interactions inside a thruster, the channel wall temperature was monitored over a broad range of electrical power stretching from 400 W to 5.5 kW for three types of thrusters with different designs, dimensions and operation domains, namely SPT100-ML, PPS ® 1350-G and PPSX000-ML. Note that over the range of thruster operating conditions the facility backpressure varies from 10 −5 to 6 × 10 −5 mbar. In addition, the effect of discharge chamber wall material on temperature field was also investigated using dielectric BN-SiO 2 and AlN walls as well as conducting graphite walls. For a given thruster geometry and material, a simple relationship between the mean wall temperature and the input electrical power can be established, in contradiction to the complex dynamics of such a magnetized plasma medium. Besides, thruster thermal history and degree of wear do not have a strong impact on power losses inside the channel.

Current technologies of concentrated solar power plants (CSP) are under extensive industrial development hut still suffer from lack of adapted thermal energy storage (TES) materials and systems. In the case of e.xtended storage (some hours), thousands of tonnes of materials are concerned leading to high investment cost, high energy and GHG contents and major conflicts of use. In this paper, recycled industrial ceramics made by vitrification of asbestos containing wastes (ACW) are studied as candidates to be used as sensible TES material. The material presents no hazard, no environmental impact, good thermophysicalproperties (/.= 1.4 W m~' K~': Cp = 1025 J kg'' K'': p= 3100 kg m~^) and at very low investment cost. Thanks to the vitrification process of the wastes, the obtained ceramics is very stable up to 1200 °C and can be directly manufactured with the desired shape. The vitrified ACW can be used as TES material for all kinds of the CSP processes (from medium up to high concentration levels) with properties in the same tange than other available materials but with lower cost and without conflict of use. The proposed approach leads also to sustainable TES allowing a pay back of the energy needed for the initial waste treatment. Eurthermore, this new use of the matter can enhance the waste treatment industry instead of landfill disposal.

A new approach to modeling using semi-quantum dielectric function models is proposed for the retrieval of the optical functions from infrared spectra. The powerful points of the method are shown throughout the analysis of two semitransparent materials, MgO and KBr. All the results are discussed in light of those obtained with classical techniques. This type of model is able to retrieve, for example, the extinction index in a range that covers at least six orders of magnitude and gives access to highly valuable information about high-order phonon processes.

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The aim of this paper is to propose simple and reliable methods to measure temperatures exceeding 1500 • C by pyrometry on dielectric heteropolar compounds. By adopting a spectroscopic approach based on a knowledge of the material (chemical composition, texture, size), it is suggested first to work at the Christiansen wavelength that is nearly independent of temperature, the texture, and the shape. Second, recent developments concerning plate blackbodies that are operable up to 1600 K are presented. Such compact systems are suitable to be installed in industrial heating devices in order to easily calibrate the pyrometer. KEY WORDS: blackbody; black metal; Christiansen wavelength; heteropolar dielectric material.

is performed using a new type of radio‐frequency resonator.