In the laser plasma interaction of quantum electrodynamics (QED)-dominated regime, γ-rays are generated due to synchrotron radiation from high-energy electrons traveling in a strong background electromagnetic field. With the aid of 2D particle-in-cell code including QED physics, we investigate the preplasma effect on the γ-ray generation during the interaction between an ultraintense laser pulse and solid targets. We found that with the increasing preplasma scale length, the γ-ray emission is enhanced significantly and finally reaches a steady state. Meanwhile, the γ-ray beam becomes collimated. This shows that, in some cases, the preplasmas will be piled up acting as a plasma mirror in the underdense preplasma region, where the γ-rays are produced by the collision between the forward electrons and the reflected laser fields from the piled plasma. The piled plasma plays the same role as the usual reflection mirror made from a solid target. Thus, a single solid target with proper scale length preplasma can serve as a manufactural and robust γ-ray source.
When an ultrashort laser pulse incidents onto a plasma mirror, there exist fast electron ejections, terahertz (THz) radiation, and harmonic generation simultaneously. We investigated the correlation of these three emission phenomena at a preplasma density gradient scale length of (0.05–1)λ and sub-relativistic laser intensity (a0 = 0.4) via particle-in-cell simulation. It is shown that THz radiation is positively correlated with fast electron ejections. As the gradient scale length increases, both enhance first, reach a maximum at 0.4λ, and then degrade at a longer scale length. Harmonic generation, on the other hand, presents the strongest radiation at a sharp surface of 0.05λ and then decays continuously at a softer gradient, indicating that it has an anti-correlation with the fast electron ejections at first (<0.4λ) but turns into a positive correlation at a softer gradient. We find that the laser energy absorption mechanism plays a vital role in the correlation among these emission phenomena. At a sharp boundary of <0.4λ gradient scale length, the Brunel mechanism is dominated, and the absorption rate increases gradually with the increasing gradient scale length. However, at the softer boundary of >0.4λ, the absorption rate decreases continuously according to stochastic heating, and the dependence on laser polarization is eventually lost. The transition of laser absorption mechanisms alters the correlation among fast electrons, THz driven by ejected fast electrons via coherent transition radiation, and harmonics excited by bounded electrons.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.