Measurement of the Bidirectional Reflectance Distribution Function of Tungsten Surface Sputtered in Argon Plasma

For ITER spectroscopic measurements, it is important to understand the optical reflection characteristics of divertor surface for an accurate measurement because stray light in may be large. We set up a goniophotometer that measures and investigated bidirectional reflectance distribution function tungsten samples sputtered argon plasma. The specimens at temperatures lower than recrystallization temperature exhibited smooth surfaces strong specular reflections their characteristics. Recrystallized crystals likely grew approximately equal temperature, resulting weak reflection.