Experimental Study of Solitons on Intense Electron Beams

Abstract

Solitons are localized persistent waves that behave like particles, preserving their properties (shape, velocity, etc.) over long distances and through collisions with other solitons. They have practical applications and are of interest to many disciplines such as condensed matter physics, plasma physics, beam physics, optics, biology and medicine. Whereas solitons in electron beams have been predicted on theoretical grounds decades ago, they have been observed experimentally only recently by Thangaraj at the University of Maryland Electron Ring (UMER). In this thesis, I report on the first systematic characterization of solitons in electron beams and confirm the soliton's particle-like behavior. The transient longitudinal space charge force on the beam bunch can launch large-amplitude waves, for example from imperfections in matching the focusing force to the beam bunch. By introducing a pulsed laser beam on a thermionic cathode, an electron beam with a narrow density perturbation is generated. The perturbation then evolves into longitudinal space charge waves that propagate along the beam. For large-amplitude initial perturbations, a soliton wave train is observed. The experimental results are reproduced by simulations with the WARP particle-incell (PIC) code.