Abstract
Inverse Thomson scattering is a well-known radiation process that produces high-energy photons both in nature and in the laboratory. Nonlinear inverse Thomson scattering occurring inside an intense light field is a process which generates higher harmonic photons. In this paper, we theoretically show that the higher harmonic gamma-ray produced by nonlinear inverse Thomson scattering of circularly polarized light is a gamma-ray vortex, which means that it possesses a helical wave front and carries orbital angular momentum. Our work explains a recent experimental result regarding nonlinear inverse Thomson scattering that clearly shows an annular intensity distribution as a remarkable feature of a vortex beam. Our work implies that gamma-ray vortices should be produced in various situations in astrophysics in which high-energy electrons and intense circularly polarized light fields coexist. Nonlinear inverse Thomson scattering is a promising radiation process for realizing a gamma-ray vortex source based on currently available laser and accelerator technologies, which would be an indispensable tool for exploring gamma-ray vortex science.
Highlights
An optical vortex is an electromagnetic wave with a phase that varies azimuthally along the direction of propagation1, 2
If gamma-ray vortices in the energy region of 1 < E < 30 MeV are generated, one may study the specific interaction between gamma-ray vortices and atomic nuclei via nuclear resonance fluorescence and photonuclear reactions whose reactions depends on the total angular momentum of an incoming gamma-ray. It has been proposed on theoretical grounds that gamma-ray vortices may be generated using inverse Thomson scattering between a high energy electron and an optical vortex laser16–18
We propose for the first time an alternative method to generate a gamma-ray vortex using nonlinear inverse Thomson scattering (NITS) of a high energy electron and an extremely intense circularly polarized laser
Summary
An optical vortex is an electromagnetic wave with a phase that varies azimuthally along the direction of propagation . If gamma-ray vortices in the energy region of 1 < E < 30 MeV are generated, one may study the specific interaction between gamma-ray vortices and atomic nuclei via nuclear resonance fluorescence and photonuclear reactions whose reactions depends on the total angular momentum of an incoming gamma-ray It has been proposed on theoretical grounds that gamma-ray vortices may be generated using inverse Thomson scattering between a high energy electron and an optical vortex laser. We propose for the first time an alternative method to generate a gamma-ray vortex using nonlinear inverse Thomson scattering (NITS) of a high energy electron and an extremely intense circularly polarized laser. A recent measurement of the annular profile of second harmonic X-rays of NITS using a circularly polarized laser strongly supports our theoretical prediction
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