Date of Award

Summer 8-2026

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Physics

Program/Concentration

Physics

Committee Director

Balša Terzic

Committee Member

Geoffrey Krafft

Committee Member

Alexandre Deur

Committee Member

Lawrence Weinstein

Committee Member

Sookyung Joo

Abstract

Inverse Compton sources — in which a relativistic electron beam scatters a laser pulse to produce tunable, collimated, high-energy radiation—have emerged as among the most promising compact radiation sources, with applications ranging from nuclear photonics to medical and nanoscale imaging and metrology. The most viable current tabletop configuration couples laser-wakefield acceleration with inverse Compton scattering, producing GeV-scale electron beams over millimeter distances. 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 — the primary observable of these experiments — from first principles has remained an unsolved problem. Existing models are either classical equations of motion in which spectra are aggregated via large-scale multiparticle simulation, or quantum models that rely on approximations of uncertain validity and face the same simulation burden. None directly produce a spectral prediction. This dissertation presents a novel framework that resolves this deficiency. Building on a unified variational treatment of classical and quantum electrodynamics, 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. This is the natural realization of scattering a laser pulse by an electron beam within quantum electrodynamics, as opposed to the traditional particle-particle scattering perspective presented in quantum field theories. Moreover, it yields the scattered spectrum as a primary analytic output. For a Gaussian laser pulse, a closed-form expression for the scattered spectrum is derived that requires no simulation, no approximation of the laser field profile, and no large particle ensembles. The classical limit of the framework recovers Landau-Lifshitz dynamics — the appropriate self-consistent description of classical radiation reaction — exactly, establishing the coherent-state model as its quantum electrodynamic counterpart. The framework is validated against existing experimental data, and the fundamental structural limitations of all current modeling approaches are identified and analyzed.

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DOI

10.25777/d5ke-qb95

ISBN

9798193214434

ORCID

0009-0001-1069-630X

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