High thermal conductivity waveguide window for use in a free electron laser
Schultheiss T., Christina V., Cole M., Rathke J., Elliott T., Nguyen V., Phillips L., Preble J.
A high thermal conductivity waveguide window with a goal of propagating greater than 100 kW average power operating at 1500 Mhz has been designed, analyzed and tested. The favorable material properties of Beryllia (BeO) make this possible. The window is brazed to a soft copper frame and then the frame is brazed to a KOVAR flange, providing the vacuum seal. RF analysis combined with thermal/structural analysis shows the benefits of the material. The KOVAR flange with a CTE, coefficient of thermal expansion, that matches that of BeO enables a strong braze joint. RF testing to 35 kW has been successful. This design can be expanded to applications with lower frequencies and higher average power, i.e., larger windows.