DESIGN, ANALYSIS AND TESTING OF A HIGH THERMAL CONDUCTIVITY WAVEGUIDE WINDOW FOR USE IN A FREE ELECTRON LASER *

Design, Analysis, and testing of a waveguide window with a goal of propagatin g greater than 100 kW average power operating at 1500 Mhz has been performed. This is made possible by the favorable material properties of Beryllia (BeO). Brazing the window to a soft copper frame and then brazing the frame to a KOVAR flange provides the vacuum seal. RF analysis combined with thermal/structural analysi s 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, and higher powers will be tested in the near future. The basics of this design can be expanded to applications with lower frequencies and higher average power.