Abstract
We present a new analytical solution for the equation of motion of relativistic electrons in the focus of a high-intensity laser pulse. We approximate the electron’s transverse dynamics in the averaged field of a long laser pulse focused to a Gaussian transverse profile. The resultant ponderomotive scattering is found to feature an upper boundary of the electrons’ scattering angles, depending on the laser parameters and the electrons’ initial state of motion. In particular, we demonstrate the angles into which the electrons are scattered by the laser scale as a simple relation of their initial energy to the laser’s amplitude. We find two regimes to be distinguished in which either the laser’s focusing or peak power are the main drivers of ponderomotive scattering. Based on this result, we demonstrate how the intensity of a laser pulse can be determined from a ring-shaped pattern in the spatial distribution of a high-energy electron beam scattered from the laser. We confirm our analysis by means of detailed relativistic test particle simulations of the electrons’ averaged ponderomotive dynamics in the full electromagnetic fields of the focused laser pulse.
Highlights
Recent technological advances in ultra-intense laser systems facilitate studies of particle dynamics in electromagnetic fields of unprecedented strength [1, 2, 3, 4, 5, 6, 7, 8, 9]
We demonstrate how the intensity of a laser pulse can be determined from a ring-shaped pattern in the spatial distribution of a high-energy electron beam scattered from the laser
We confirm our analysis by means of detailed relativistic test particle simulations of the electrons’ averaged ponderomotive dynamics in the full electromagnetic fields of the focused laser pulse
Summary
Recent technological advances in ultra-intense laser systems facilitate studies of particle dynamics in electromagnetic fields of unprecedented strength [1, 2, 3, 4, 5, 6, 7, 8, 9]. We demonstrate that due to ponderomotive effects the electron bunch’s transverse distribution after scattering will exhibit a cylindrical symmetry with a transverse size determined by the maximal scattering angle This maximal scattering angle, on the other hand, is directly linked to the ratio of the laser’s peak field strength to the electron bunch’s peak energy, as was found in studies of plane wave laser fields [56, 51, 57, 58]. Provided that the latter is well characterized, as is typically feasible for accelerator bunches, the laser intensity can be directly read off.
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