Peak amplitude dependence of radiation properties of nonlinear Thomson scattering under an applied magnetic field

Xiaotian Gong¹FeiYang Gu^2*Youwei Tian^1*

• ¹College of Science, Nanjing University of Posts and Telecommunications, Nanjing, China
• ²Bell Honors School, Nanjing University of Posts and Telecommunications, Nanjing, China

This paper presents a systematic investigation of peak amplitude effects on nonlinear Thomson scattering characteristics under combined magnetic field irradiation and tightly focused circularly polarized Hermite-Gaussian laser pulses. Through theoretical modeling and numerical simulations, we establish a comprehensive framework analyzing three critical aspects: electron dynamics, spatial radiation patterns, and spectral power distribution. Our results demonstrate a non-monotonic relationship between laser peak amplitude (a₀) and radiation performance metrics. Specifically, an optimal regime emerges at a₀=10, achieving a balance between exceptional collimation (angular divergence <2.5°) and maximum radiation intensity (∼10⁷ a.u.), which represents a 3-order-ofmagnitude enhancement compared to lower amplitude regimes (𝑎 0 <3).Notably, we report the discovery of a magnetic field-induced inverted cyclonic radiation pattern when a₀ exceeds 3, revealing a previously unrecognized coupling mechanism between relativistic electron trajectories and external magnetic confinement. Furthermore, we develop a novel visualization methodology that synergistically correlates real-time electron trajectories with instantaneous radiation power maps, enabling unprecedented resolution of radiation dynamics during different motion phases. These findings not only advance fundamental understanding of magnetooptically controlled Thomson scattering, but also provide practical guidelines for optimizing compact X-ray sources in applications requiring tunable high-energy photon beams.