THz transition radiation of electron bunch laser-accelerated in long-scale near-critical density plasmas

TL;DR

This paper investigates THz transition radiation generated by laser-accelerated electron bunches in near-critical density plasmas, combining analytical modeling with simulations and experiments to optimize and understand the radiation's properties.

Contribution

It provides a detailed analytical framework including diffraction and decoherence effects for THz transition radiation, validated by simulations and experiments, aiding in optimization and mechanism distinction.

Findings

Analytical model agrees with experimental measurements.

Transition radiation characteristics can be optimized using the model.

The approach helps distinguish transition radiation from other THz generation mechanisms.

Abstract

Direct laser electron acceleration in near-critical density plasma produces collimated electron beams with high charge $Q$ (up to $\mu$C). This regime could be of interest for high energy THz radiation generation, as many of the mechanisms have a scaling $\propto Q^2$. In this work we focused specifically on challenges that arise during numerical investigation of transition radiation in such interaction. Detailed analytical calculations that include both diffraction and decoherence effects of characteristics of transition radiation in the THz range were conducted with the input parameters obtained from 3D PIC and hydrodynamic simulations. The calculated characteristics of THz radiation are in good agreement with the experimentally measured ones. Therefore, this approach can be used both to optimize properties of THz radiation and distinguish the transition radiation contribution if several mechanisms of THz radiation generation are considered.