Self-Mode-Locking Operation Regimes in a TWT With Low-Level Delayed Feedback

We study the time-domain system of equations of a traveling wave tube (TWT) with delayed feedback. Under conditions of low-depth feedback, we find the self-mode-locking operation regimes characterized by the generation of correlated sequences of ultrashort pulses. The existence of these regimes is verified within 3-D simulations of an experimentally implemented
${W}$
-band TWT using the particle-in-cell method. With increasing beam current, the regimes of generation of pulse sequences with duration of about 380, 180, 130, and 80 ps, duty factor of about 25%, and peak efficiency of about 14% are obtained.