RESEARCH ON MICROWAVE WINDOW MULTIPACTOR AND ITS INHIBITION

Abstract

Abstract : The problem of multipactor at microwave windows is discussed and the results of theoretical and experimental studies on multipactor at a single dielectric surface are presented, with information on the power levels at which such discharges may be expected to occur. Methods of eliminating multipactor at windows are described and include surface coatings, applied by evaporating titanium in vacuum or sputtering titanium monoxide in argon or mercury, and grooves cut in te window surface perpendicular to the electric field. Factors affecting the nature of the surface coatings during application and in subsequent tube processing are described. A wide variety of coatings has been evaluated at S-band on alumina, beryllia, and quartz windows at power levels up to 100 Mw peak equivalent transmitted power and average dissipation equivalent to over 300kw of average power. The maximum peak power supported by multipactor resistant windows was limited by arcing at the metal-dielectric seal. Various methods of increasing the threshold power for arcing have been tried. The most successful arrangement employed a window ceramic of 'H' shaped cross section in which the metal-dielectric seal was located in a region of weak electric intensity. (Author)