Design and testing of secondary mirrors for the core CXRS diagnostic system in ITER

The core Charge Exchange Recombination Spectroscopy (core CXRS) diagnostic system for ITER is projected with 7 consecutive in-vacuum mirrors. Based on overall system stability, maintenance and lifetime considerations, ITEr grade Stainless Steel 316L(N) was chosen as first candidate for the substrate of the mirrors two to seven. A robust design with remote handling friendly bolted interface has been devised. It features uniformly distributed internal temperature control with minimal welds. The design, simulation results and plans for a prototype are discussed. s 4–7 are planned with a multilayer dielectric coating at preferably >98% reflectivity. The ability to manufacture such a coating on SS316L(N)-substrate which works reliably under ITER conditions is investigated. A 64 λ/4 layer coating of TiO2 and SiO2 was chosen for initial investigations. Adhesion tests were carried out and testing under ITER-conditions is under preparation. The paper covers the coating, sample manufacturing and status of the testing.