Abstract
Microwave sources transform the kinetic energy of an electron beam into microwaves through the interaction of electrons with a periodic slow wave structure (SWS). A metamaterial (MTM) waveguide is proposed for use in a microwave oscillator instead of a conventional periodic SWS that has been used for a long time to generate high power microwave radiation. MTMs have interesting properties such as the negative refractive index, low group velocity, and below cutoff propagation, among others. In this work, we study the interaction of a multibeam cathode with a set of MTM structures inside a cylindrical waveguide. We developed a structure comprising a number of MTM metallic plates that have periodicity in the axial direction and are repeated in the azimuthal coordinate. Using eigenmode simulations, we obtained negative dispersion around the operating frequency where the group velocity is negative and extremely small. The fully electromagnetic, relativistic particle-in-cell codes MAGIC and CST Particle Studio and the fully electromagnetic software tool CST Microwave Studio were used to obtain the results in this study.
Highlights
Metamaterials (MTMs) exhibit exotic electromagnetic properties such as negative permittivity and negative permeability which are not found in nature
Microwave sources transform the kinetic energy of an electron beam into microwaves through the interaction of electrons with a periodic slow wave structure (SWS)
Both BWOs and TWTs operate based on Cherenkov radiation, which generates coherent output power from an electron beam passing through a slow wave structure (SWS) with phase velocity less than the speed of light
Summary
Metamaterials (MTMs) exhibit exotic electromagnetic properties such as negative permittivity and negative permeability which are not found in nature. A MTM-based microwave-generating BWO using a complementary split ring resonator (CSRR) SWS to provide negative permittivity in combination with a TM mode to interact with a high-power electron beam was designed. The eigenmode solver enforces a phase advance Du across the structure period in the axial direction of propagation It repeats the simulation for different phase advances to find the dispersion diagram for the MTM-loaded waveguide. In addition to the MTM SWS dispersion diagram, the beam line of x 1⁄4 kz0 is plotted in Fig. 3 to describe the interaction point, where x is the angular frequency, 0 is the electron beam average axial velocity, and kz 1⁄4 pDu (p 1⁄4 16 mm periodicity) is the wavenumber. The electric field that the electron beam experiences when passing through the SWS (emitter diameter is 1 mm) is a left-handed TM-like mode
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