High temperature refractory member with radiation emissive overcoat

This patent describes a heat radiator for radiating heat generated by high temperature plasma in a plasma accelerator/decelerator having an interior portion in contact with the plasma and an exterior portion not in contact with the plasma. It comprises: a first layer made of a refractory material having a first spectral emissivity coefficient, the refractory material being disposed in the interior of the plasma accelerator/decelerator so as to contact the plasma and be heated by the plasma and wherein the refractory material is capable of withstanding temperatures of 1000 degrees C. or higher without melting; and a second radiative layer forming a portion of the exterior of the plasma accelerator/decelerator and mechanically and thermally coupled to the first layer to radiate heat from the first layer away from the interior of the plasma accelerator/decelerator, the second layer being made of a radiation emissive material including zirconium diboride