Anti-reflection treatments for JET millimeter wave diagnostic windows

This paper discusses low-power windows for millimeter-wave diagnostics on the JET torus. When tritium is used as a fusion fuel in JET repairs will be difficult on the radioactive machine and additional precautions must be taken to avoid vacuum leaks. Double, interpumped vacuum windows will be necessary. Window design is further restricted by the requirement that the bond between the window itself and its supporting ferrule must withstand repeated cycling to a working temperature of about 250 C. The most satisfactory arrangement for low power millimeter waves uses z-cut crystal quartz windows, gold diffusion bonded to stainless steel ferrules, as manufactured by the Special Techniques Group of AEA Technology. Where possible wedged windows are avoided for ease of alignment