The use of CVD diamond as a high power, wide bandwidth, waveguide window in the free electron maser amplifier

The free electron maser is a relativistic electron beam device capable of providing very high microwave power over a wide frequency bandwidth (∼1 MW CW, 125%). To exploit the full potential of this device, it is necessary to research and develop components that have both a high average power and wide bandwidth capability. High power, together with wide bandwidth, is believed to be a unique requirement. One of the major problems in generating such high levels of microwave power from a vacuum tube, has been finding a suitable material for the RF output window. Computer modelling of a diamond window in a circular waveguide has been undertaken using HFSS, a finite element program. This model allowed the insertion loss, transmission loss and modal conversion to be examined for a number of configurations of window thickness and recess depth.