Modeling and Simulation of Relativistic Multiple Electron Beam Generation With Different Energies From a Single-Cathode Potential for High-Power Microwave Sources

Abstract

The traveling wave tube (TWT) has been a reliable conventional vacuum electron device (CVED) since the 1940s. Researchers, beginning in the late 1980s, extended the TWT to the relativistic electron beam regime to generate 100- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{s}\cdot $ </tex-math></inline-formula> MW power in the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${X}$ </tex-math></inline-formula> -band. Since the mid-1990s, there has been little advancement in the field. Recently, the linear theory of a multistream TWT was published, which showed superexponential amplification properties. This article describes a novel technique for producing multiple electron beams with an energy difference of about 6%–27% with comparable currents from a single cathode at a single potential for a multistream TWT. We present a new model of two nested cathodes where two annular electron beams are generated and propagated in a smooth cylindrical pipe that emerged into a strong magnetic field. The two nested cathodes are magnetically insulated coaxial diodes (MICDs). The simulation results are obtained using the MAGIC particle-in-cell (PIC) code for the experimental vacuum diode geometry of the SINUS-6 high-current electron beam accelerator at The University of New Mexico. Results are obtained, which are then: 1) compared with earlier experimental results for a single beam; 2) study the current–voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}$ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}$ </tex-math></inline-formula> ) characteristics of two electron beams powered by a single cathode at a single potential immersed in a strong magnetic field; and 3) show 6%–27% energy differences with comparable currents between two beams. This technique is viable for pulsed power-driven, relativistic electron beams for a relativistic multistream TWT.