Determining mode excitations of vacuum electronics devices via three-dimensional simulations using the SOS code

Examined the feasibility of determining via simulation the mode excitation behavior of vacuum electronic devices. The SOS code was used to compute the resonance modes (frequency-domain information) of sample devices and separately to compute the transient behavior of the same devices. Then a new code, DOT, to compute appropriate dot products of the time-domain and frequency-domain results and the transient behavior of individual modes in the device. Modes in a coupled-cavity traveling-wave tube (CCTWT) section excited with coaxial E-probes (cable stubs) and with an electron beam were analyzed in separate simulations. The authors examined whether the transient waves were forward or backward waves for each case. Finally, they computed the hot-test mode frequencies of the CCTWT section