$L$ -Band Relativistic Traveling Wave Oscillator Based on a Circular Corrugated Waveguide

A coupling impedance (Z
₀
≈ 9 Ω) between a relativistic electron beam and a fundamental harmonic of a TM01 wave slowed down to the speed of light in a circular corrugated waveguide is calculated. The geometry of a relativistic (≈420 keV) traveling wave oscillator (TWO) with an operating frequency of 1.25 GHz is optimized using this calculations by the fully electromagnetic particle-in-cell (PIC) code KARAT. The transient time obtained in PIC simulations is 26 ns. A microwave power of 340 MW is also obtained in PIC simulations at an electron beam current of 3.0 kA in strong (≈0.3 T) and weak (≈0.08 T) guiding magnetic fields, which corresponds to the oscillator efficiency ≈27%.