Carbon-based materials thermal development testing and selection process for first wall and divertor applications

Carbon-based materials are being investigated for use as plasma facing surfaces in the burning plasma experiment (BPX) fusion device. Specifically, carbon-carbon (C-C) composites have been proposed in designs for both inboard limiter and divertor surfaces. This paper describes a development program to test and evaluate candidate composites and to select the composite type most suitable for the BPX requirements. Tests were formulated to examine the effects of composite architectures (fiber type, fiber placement and volume fraction, and matrix fraction) and composite processing on composite conductivity. Specimens of 1D, 2D, and 3D C-C composite architectures were tested in the High Temperature Materials Laboratory at Oak Ridge National Laboratory using an automated laser flash system to determine the thermal diffusivity of these candidate materials. Costs were considered as part of the selection process. Results indicate that a relatively inexpensive, low conductivity, multidimensional fiber composite will meet design requirements for the inboard limiter design. The high heat flux in the divertor region necessitates further material development to achieve a material that will meet this region's performance requirements.