Macroscopic Classical and Quantum Models of Inverse Compton Scattering

Abstract

Inverse Compton sources --- in which a relativistic electron beam scatters a laser pulse to produce tunable, collimated, high-energy radiation --- have emerged as promising compact radiation sources, with applications in nuclear photonics, medical imaging, and nanoscale metrology. As laser intensities increase and electron energies grow, the interaction enters the radiation reaction regime, where the energy radiated by the electron becomes a significant fraction of its kinetic energy. Predicting the scattered electron energy spectrum from first principles has remained an unsolved problem. Existing models are either classical equations of motion requiring large-scale multiparticle simulation, or quantum models relying on approximations of uncertain validity with the same simulation burden. None directly produce a spectral prediction. This dissertation presents a novel framework that resolves this deficiency. The laser pulse is represented as a coherent quantum state of the electromagnetic field and the electron beam as a statistical quantum state encoding its momentum distribution --- the natural realization of particle-field scattering within quantum electrodynamics. For a Gaussian laser pulse, a closed-form analytic expression for the scattered spectrum is derived requiring no simulation, no approximation of the laser field profile, and no large particle ensembles. The classical limit recovers Landau-Lifshitz dynamics exactly, establishing the coherent-state model as the quantum electrodynamic realization of classical radiation reaction theory. The framework is validated against existing experimental data, and fundamental structural limitations of all current modeling approaches are identified and analyzed.