Development of a 670 GHz extended interaction klystron amplifier

Summary form only given. Extended interaction klystrons have been demonstrated at frequencies up to 218 GHz CW and 229 GHz pulsed. Modern design, fabrication, and measurement technologies show promise of extending their operation into the THz range of frequencies. Extensive use of 3D physics-based design tools, in particular, has enabled us to select promising design approaches and to understand phenomena that affect EIK scaling to sub-millimeter wavelengths. This paper describes the challenges in, some novel approaches to, and our progress on the development of a 670 GHz EIK power amplifier meeting demanding requirements for output power, gain, bandwidth, and efficiency.