Time-Domain Multimode Analysis of a Terahertz Gyro-TWT Amplifier

High-order mode employed as the operating mode of a terahertz (THz) gyrotron traveling-wave tube (gyro-TWT) amplifier shows strong dispersion, which deteriorates the device performance in amplifying picosecond THz pulses. Theoretical investigation of a THz gyro-TWT amplifier with a lossy cylindrical circuit is carried out to study the problems, such as lossy structure design, parameters selection, frequency-domain performance, and time-domain dynamics. The robust high growth rate low-kz amplification and the broadband high-kz amplification are two preferred operation conditions. The revealed characteristics are also useful for developing THz gyro-TWTs with other kinds of over-moded circuits.