Analysis of the Hourglass–Spindle-Shaped Trajectory Generated by the Collision of Circularly Polarized Laser Pulses with Electrons

This study investigates the hourglass–spindle-shaped trajectory of electron motion based on a model of electron and circularly polarized chirped laser pulse coaxial collision. The velocity, acceleration, and radiation distribution of the electron in this state of motion are systematically analyzed. The formation process of the hourglass–spindle-shaped trajectory is examined in detail. Four distinct stages of the electron–laser pulse collision process are proposed, with an in-depth analysis of the interaction dynamics and underlying mechanisms in each stage. The critical conditions for the formation of the hourglass–spindle-shaped trajectory are identified, along with the conditions for the emergence of two other possible trajectories resulting from the collision: the spiral-shaped and spindle-shaped trajectories. Additionally, a general model for analyzing electron–laser pulse collisions is proposed.