Bright γ-ray source with large orbital angular momentum from the laser near-critical-plasma interaction

Abstract

We propose a laser-plasma based new method to generate bright $\gamma$-rays carrying large orbital angular momentum, by interacting a circularly polarized Laguerre--Gaussian laser pulse with a near-critical hydrogen plasma confined in an over-dense solid tube. In the first stage of the interaction, it is found via fully relativistic three-dimensional particle-in-cell simulations that high-energy helical electron beams with large orbital angular momentum are generated. In the second stage, this electron beam interacts with the laser pulse reflected from the plasma disc behind the solid tube, and helical $\gamma$ beams are generated with the same topological structure having the electron beams. The results show that the electrons receive angular momentum from the drive laser, which can be further transferred to the $\gamma$ photons during the interaction. The $\gamma$ beam orbital angular momentum is strongly dependent on the laser topological charge $l$ and laser intensity $a_0$, which scales as $L_{\gamma} \propto a^{4}_{0}$. A short (duration of 5 fs) isolated helical $\gamma$ beam with an angular momentum of $-3.3\times10^{-14}$ kg m$^2$/s is generated by using the Laguerre--Gaussian laser pulse with $l=2$. The peak brightness of the helical $\gamma$ beam reaches $1.22\times10^{24}$ photons s$^{-1}$mm$^{-2}$mrad$^{-2}$ per 0.1$\%$BW (at 10 MeV), and the laser-to-$\gamma$-ray angular momentum conversion rate is approximately $2.1\%$.

Local wavelength evolution and Landau damping of electrostatic plasma wave driven by an ultra-relativistic electron beam in dense inhomogeneous plasma

“…Recently, experiments on energy transfer and dissipation in the interaction of intense laser or electron beams with plasma have been carried out [16][17][18][19][20][21][22]. Transport of highenergy electrons in plasmas is also relevant to many applications of intense lasers and particle accelerators, such as tabletop particle and radiation sources [23][24][25][26][27][28][29][30][31], as well as for diagnostics of materials under extreme conditions [32].…”