First Observation of Dispersive Shock Waves in an Electron Beam

TL;DR

This paper reports the first experimental observation of dispersive shock waves in an intense electron beam, demonstrating their formation, properties, and agreement with theoretical models, thus extending dispersive hydrodynamics to charged particle beams.

Contribution

It provides the first experimental evidence of dispersive shock waves in an electron beam, confirming theoretical predictions and establishing a new platform for studying nonlinear wave physics.

Findings

DSWs observed in electron beams with soliton-like leading peaks

Wave-train width increases linearly with time, matching KdV predictions

Peaks show decreasing amplitude and velocity, consistent with dispersive shock ordering

Abstract

Dispersive shock waves (DSWs) are expanding nonlinear wave trains that arise when dispersion regularizes a steepening front, a phenomenon observed in fluids, plasmas, optics, and superfluids. Here we report the first experimental observation of DSWs in an intense electron beam, using the University of Maryland Electron Ring (UMER). A localized induction-cell perturbation produced a negative density pulse that evolved into a leading soliton-like peak followed by an expanding train of oscillations. The leading peak satisfied soliton scaling laws for width^2 vs inverse amplitude and velocity vs amplitude, while the total wave-train width increased linearly with time, consistent with Korteweg--de Vries (KdV) predictions. Successive peaks showed decreasing amplitude and velocity toward the trailing edge, in agreement with dispersive shock ordering. These results demonstrate that intense charged particle beams provide a new laboratory platform for studying dispersive hydrodynamics, extending nonlinear wave physics into the high-intensity beam regime.