Assessment of Laser Transmission Mirror Materials for ITER Edge Thomson Scattering Diagnostics

An assessment of in-vessel metallic mirror materials for the transmission of the laser beam used in the ITER edge Thomson scattering diagnostics is reported. The transient temperature increase due to the laser pulse irra-diation on the laser transmission mirror is calculated by a one-dimensional heat conduction equation. Candidate mirror materials are discussed based on a comparison between the numerical calculation and current data relevant to the laser-induced damage threshold (LIDT). Gold, silver, and copper are considered promising because of its high reflectivity. The LIDT is evaluated considering multi-pulse effects and used to determine the necessary size for the laser transmission mirror for the ITER edge Thomson scattering diagnostics