Ion-channel laser

Abstract

A relativistic electron beam propagating through a plasma in the ion-focused regime exhibits an electromagnetic instability with peak growth rate near a resonant frequency \ensuremath{\omega}\ensuremath{\sim}2${\ensuremath{\gamma}}^{2}$${\mathrm{\ensuremath{\omega}}}_{\mathrm{\ensuremath{\beta}}}$. Growth is enhanced by optical guiding in the ion channel, which acts as a dielectric waveguide, with fiber parameter V\ensuremath{\sim}1(I/${\mathit{I}}_{\mathit{A}}$${)}^{1/2}$. A 1D theory for a laser making use of this instability is formulated, scaling laws are derived, and numerical examples are given. Possible experimental evidence is noted.