Frequency Increase and Damping of Nonlinear Electron Plasma Oscillations in Cylindrical Symmetry

Abstract

Radial electron plasma oscillations excited by a laser wake field are measured by frequency domain interferometry. In the nonlinear regime we observe two important effects: (i) an increase of the oscillation frequency and (ii) the damping of the oscillation in a few plasma periods. Simulations show that this last effect is related to the presence of a steep radial density gradient near the focus edge. {copyright} {ital 1997} {ital The American Physical Society}