Spatial Collapse of Beam-Driven Plasma Waves

Electron-plasma waves driven unstable by an electron beam are observed to be backscattered by stationary density perturbations to form standing waves. Above a certain threshold these standing waves develop into sharply localized ($\ensuremath{\sim}10{\ensuremath{\lambda}}_{\mathrm{D}}$) intense fields, $\frac{{{E}_{max}}^{2}}{4\ensuremath{\pi}{n}_{0}\ensuremath{\kappa}{T}_{e}}\ensuremath{\approx}1$. Significant fractions of beam electrons are scattered in velocity space by these stationary spikes of high-frequency field.