Low voltage power booster TWT

Summary form only given. This paper describes a miniature, low voltage, vacuum power booster TWT design approach for wide-band (18-40 GHz.) and narrow-band (40-45 GHz.) millimeter wave power modules (MMPMs), with volumes ranging from 50-75 in³ (819-1229 cm³.). The MMPM is compact, being less than six inches in length, and employs a number of common sub-assemblies. At an operating voltage of less than 8 kV and a maximum current of 120 mA, an output power goal of greater than 40 W has been established for both the wide-band and narrow-band variants. Beam confinement is provided using an optimized Sm-Co PPM stack. Circuit losses at millimeter wavelengths are minimized using a wire-wrapped, T-shaped BeO rod support structure. Output power is transmitted through a thin alumina ceramic output window ( <.064 cm.). High overall device efficiency is achieved through the use a 2 stage depressed collector. A Ka-band prototype has been built which produced an 18 W minimum and 80 W maximum (CW power) throughout the 24-40 GHz. band. With a prime power consumption of under 300 W, the device has an overall efficiency greater than 30%. Critical design and production issues as well as efforts to extend performance to the entire 18-40 GHz band are discussed.