M.S. Thesis Defense: Yichao Mo
Monday, August 20, 2012
2:00 p.m. Room 1207, Energy Research Facility
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ANNOUNCEMENT: M.S. Thesis Defense
Name: Yichao Mo
Prof. Rami A. Kishek, Chair
Prof. Patrick G. O'Shea
Prof. Victor L. Granatstein
Date/Time: Monday, August 20, 2012 at 2pm
Location: Large Conference Room 1207, Energy Research Facility
Title: Experimental Study of Solitons on Intense Electron Beams
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 plasma physics, beam physics, optics, biology and medicine. Whereas solitons in electron beams have been predicted on theoretical grounds decades ago, this thesis reports on the first experimental observation of them, at the University of Maryland Electron Ring (UMER).
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. Both theoretical and experimental proof of solitons are shown. We also explore the soliton dependence on beam current, perturbation strength and width. The experimental results are reproduced by simulations with the WARP particle-in-cell (PIC) code.