High-power THz radiation generation during oblique-collision of two electron beams into a plasma

The Langmuir waves excited by two counter-propagating electron beams via two-stream instability, collide to each other at an oblique angle, which forms a high level density modulation in the interaction region, where the both beam electrons are trapped. As a result, spatially-localized Langmuir wave-packets with large amplitude of longitudinal electric field are formed, which give rise to the bursts of electromagnetic radiation. Our two-dimensional particle-in-cell simulations for oblique-collision of low-density electron beams with different transverse profiles, show that a strong THz emission is obtained at second-harmonic of plasma frequency with a narrow spectral-width in vacuum, which is enhanced significantly compared to the head-on-collision^1-2. The THz power-conversion efficiency is reached around ~ 0.0725, for the continuous injection of electron beams into the plasma, which makes it suitable for applications requiring high-power narrow-band THz radiation sources.