Simulations of electromagnetic emissions produced in a thin plasma by a continuously injected electron beam

TL;DR

This study uses 2D particle-in-cell simulations to investigate electromagnetic emissions from a thin plasma with a continuously injected relativistic electron beam, revealing efficient harmonic generation without intermediate plasma eigenmodes.

Contribution

First to consider realistic continuous beam injection in thin plasma simulations, analyzing emission mechanisms and harmonic generation in laboratory-relevant conditions.

Findings

Efficient fundamental and second harmonic emissions are generated.

Emission does not require intermediate plasma eigenmodes, resembling antenna radiation.

Thin plasma emission characteristics differ from infinite plasma cases.

Abstract

In this paper, electromagnetic emissions produced in a thin beam-plasma system are studied using two-dimensional particle-in-cell simulations. For the first time, the problem of emission generation in such a system is considered in the realistic formulation allowing for the continuous injection of a relativistic electron beam through the plasma boundary. Specific attention is given to the thin plasma case in which the transverse plasma size is comparable to the typical wavelength of beam-driven oscillations. Such a case is often implemented in laboratory beam-plasma experiments and has a number of peculiarities. Emission from a thin plasma does not require intermediate generation of electromagnetic plasma eigenmodes, as in the infinite case, and is more similar to the regular antenna radiation. In this work, we determine how efficiently the fundamental and second harmonic emissions can be generated in previously modulated and initially homogeneous plasmas.