Design and development of EC H&CD antenna mirrors for ITER

The steering mirrors of the ITER EC H&CD antenna (250 mm × 350 mm × 30 mm) are designed to reflect 20 MW millimeter (mm)-wave beams and to control their injection angle into plasma. The mirror would be exposed to high-energy neutrons and heat flux from plasma and also heated by incident wave beams. The result of thermo-mechanical analysis indicates that the mirror design with copper alloys (dispersion strengthened copper or copper chrome zirconium) plate with stainless steel (SS316) cooling tubes inside is considered to be acceptable. Since the mirror is rotated to change the injection angle of mm-wave beams, a flexible tube to supply cooling water into the steering mirror is necessary. A mock-up of the mirror for a 90° miter bend was fabricated and the mm-wave transmission with power/pulse length of 420 kW/4.7 s was carried out. Temperature increase agrees with the expected value. Ohmic loss is estimated to be 0.21% of the incident power, which agrees with the calculation based on the electrical resistivity of DSCu at 1.8 × 10−8 Ω m. The result also indicates 1 MW, CW transmission capability of the miter bend.