Generation of bright collimated vortex $\gamma$-ray via laser driven cone-fan target

TL;DR

This paper demonstrates through simulations that irradiating a cone-fan target with a high-intensity circularly polarized laser produces a bright, collimated vortex gamma-ray beam with high angular momentum, efficiency, and quality.

Contribution

The study introduces a novel laser-target setup for generating high-brilliance vortex gamma-rays with significant angular momentum and optimized parameters for maximum efficiency.

Findings

High peak brilliance of gamma-ray beam (~5×10^{22} photons/s/mm^2/mrad^2/0.1% BW at 10 MeV.

Conversion efficiencies of laser energy to gamma-ray (~3.8%) and electrons (~41%).

Optimal cone radius enhances gamma-ray angular momentum to about 2.8×10^6 ħ.

Abstract

We use numerical simulations to demonstrate that a source of bright collimated vortex $\gamma$-ray with large orbital angular momentum can be achieved by irradiating a circularly polarized laser with an intensity about $10^{22}\rm{W/{cm^2}}$ on a cone-fan target. In the studied setup, electron beam of energy of hundreds of MeV and vortex laser pulse are formed. And furthermore a high quality vortex $\gamma$-ray is yielded with small divergence of $5^{\circ}$ and high peak brilliance $\sim5\times10^{22}$ photons ${\rm\cdot s^{-1} \cdot mm^{-2} \cdot mrad^{-2}}$ $0.1\%\mathrm{BW}$ at $10\mathrm{MeV}$. A considerable fraction of angular momentum of laser is converted to electron beam and vortex $\gamma$-ray, which are roughly $27.8\%$ and $3\%$, respectively. And the conversion efficiency of energy from laser to electron beam and vortex $\gamma$-ray are around $41\%$ and $3.8\%$. Moreover, comparative simulations for different right radius of cone reveal that there exists an optimal size that makes the highest angular momentum of $\gamma$-ray photons to be around $2.8\times10^6\hbar$. The comparative simulations for different laser modes exhibit that it is more appropriate to choose the circularly polarized laser to generate vortex $\gamma$-ray than the Laguerre-Gaussian one.