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The European fusion reactor research facility, called International Thermonuclear Experimental Reactor (ITER), is one of the most challenging projects that involves design and testing of hundreds of separately designed reactor elements and peripheric modules. One of the core elements involved in plasma heating are gyrotrons. They are used as a microwave source in electron–cyclotron resonance heating systems (ECRH) for variable injection of RF power into the plasma ring. In this work, the development and application of an alumina-titania 60/40 mixed oxide ceramic absorber coating on a copper cylinder is described. The cylinder is part of a dummy load used in gyrotron testing and its purpose is to absorb microwave radiation generated by gyrotrons during testing phase. The coating is applied by means of atmospheric plasma spraying (APS). The absorber coating is deposited on the inner diameter of a one-meter cylindrical tube. To ensure homogeneous radiation absorption when the incoming microwave beam is repeatedly scattered along the inner tube surface, the coating shows a varying thickness as a function of the tube length. By this it is ensured that the thermal power is distributed homogeneously on the entire inner tube surface. This paper describes a modeling approach of the coating thickness distribution, the manufacturing concept for the internal plasma spray coating and the coating characterization with regard to coating microstructure and microwave absorption characteristics.

In this article, we describe a system suitable for the evaluation of residual stress in ceramic coating under industrial conditions. Laser ablation is used for material removal, and digital holography measures the displacements produced by the residual stress release around the processed area. The residual stresses at different depths below the surface of the coating are calculated by finite element method from the displacements, the shapes of the machined surface, and the material parameters. Experimental results are presented. Index Terms-Ceramic coating, digital holography residual stress. I. INTRODUCTION C ERAMIC coatings are commonly used to improve the wear or heat resistance of technical components or to provide electrically nonconductive surfaces [1]. The spraying techniques usually used for coating [2] induce unwanted residual

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