The emission and sublimation of graphites coated with pyrolytic carbon (PyC) has been measured under irradiation with pulse laser beams to examine the effects of pulse heat load on the role of the coating. Under a heat load density of 640 MW/m2 and a pulse length of 1 ms, gas emission, sublimation and vacuum degradation are enhanced by the PyC coating. This is mainly due to very low thermal conductivity of the PyC film in the surface normal direction resulting in an enhanced temperature rise during the heat load. On the other hand, the gas emission, sublimation and vacuum degradation of the coated specimens were small relative to the non-coated specimens when compared on the basis of the measured peak surface temperature. Thus the surface coating with PyC may be effective in reducing the gas emission when the carbon temperature increases gradually but can be harmful to vacuum and surface stability in the case of pulse high heat load.
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