Back-illuminated, thin photodiode arrays with trench isolation. A carbon fiber composite material 10 of the present invention contains carbon fibers 11 and a matrix 12 joining the carbon fibers 11 with each other, and the matrix has fine pores having diameters of 3. Coolant pressurized on the \u201ccold\u201d or cooler side of the wall is bled, \u201csweated\u201d, or otherwise transpired to the \u201chot\u201d wall surface in an effort to control the hot wall surface temperature by shielding the surface with a coolant layer at the surface and by removing heat via coolant flow past the surface.