Material and engineering issues of CVD diamond windows for high power millimeter waves

The outstanding property profile of CVD diamond with respect to millimeter wave absorption and thermo-mechanical loads is adequate for transmitting megawatt power at millimeter wavelengths through barrier windows. Accordingly the spectrum of CVD window applications diversifies beyond their use as single frequency gyrotron output windows. The engineering issues related to windows used in step-tunable arrangements and at the upper ECH&CD port of the ITER torus are presented together with a discussion of the main factors governing the dielectric loss underlying the window design.