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We use numerical simulations to demonstrate that a source of bright collimated vortex γ-ray with large orbital angular momentum and small divergence can be achieved by irradiating an intense circularly polarized laser on a cone-fan target. In the all-optical setup, electron beam of energy with hundreds of MeV and also vortex laser pulse are formed. A considerable fraction of angular momentum of laser is converted to electron beam and furthermore to final vortex γ-ray, which are roughly 27.8% and 3%, respectively. The conversion efficiency of energy from laser to them is around 41% and 3.8%. Moreover, comparative simulations for different inner sizes of the cone reveal that there exists an optimal size making the highest angular momentum of γ-ray photons. For simulations with different laser modes, the circularly polarized laser is more appropriate rather than the Laguerre–Gaussian one to generate vortex γ-ray.

The nonlinear Thomson scattering of an electron motion in a combining field constituted by an elliptically polarized laser and a background magnetic field is investigated. The dependence of electron trajectories, fundamental frequency, maximum radiation power in the spatial distribution, and the corresponding spatial angle on ellipticity are obtained. In addition, we find that the angular distributions of scattering spectra with respect to the azimuthal angle exhibit symmetry regardless of the order of harmonics, laser intensity, magnetic resonance parameter, and initial axial momentum. Meanwhile, the polar angle distribution of the spectra increasingly approaches the laser propagation direction with the laser intensity, magnetic resonance parameter, and initial axial momentum. The maximum radiated power increases, and the corresponding polar angle decreases. The optimal angle for the maximum radiated power per unit of solid, the corresponding photon number, and the photon brightness can be obtained, which implies that high-quality extreme ultraviolet (XUV) and/or x rays can be generated by the studied scheme when suitable parameters are chosen.

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