Ripple and Lotus Phenomenon: Radiation Pattern Evolution of Nonlinear Thomson Scattering Under Cooperative and Competitive Effects of Applied Magnetic and Laser Field

This paper focuses on the scenario where relativistic electron nonlinear Thomson forward scattering is driven by circularly polarized laser pulses, using both theoretical analysis and numerical simulations. For the first time, we investigate how the magnetic flux density and beam waist radius jointly influence the spatiotemporal properties of radiation. For the superimposed field under different parameters, the forces exerted by the laser field and the applied magnetic field on electrons will show cooperative or competitive relationships at different moments of action. And the transformation of this relationship promotes the evolution of the electron radiation pattern in the superimposed field, which greatly changes the spatiotemporal properties of Thomson scattering. Based on this, completely new spatial distributions of radiation-ripple and lotus phenomena were discovered. In addition, the combination of parameters with the best radiation properties was selected through Big Data, and the quasi-periodicity of the azimuth angle <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${{\phi }_{\bm{p}}}$</tex-math></inline-formula> was discovered for the first time. These results will contribute to the understanding of the radiation mechanism of Thomson scattering in superimposed field and will be instructive for laboratory modulation of ultra-high-performance <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\bm{X}}/{\bm{\gamma }}$</tex-math></inline-formula>-rays.