Generation of bright collimated vortex γ-ray via laser driven cone-fan target.

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. [ABSTRACT FROM AUTHOR]