Ion-channel laser

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 ω∼2${\gamma }^2$ ${\mathrm{\omega }}_{\mathrm{\beta }}$. Growth is enhanced by optical guiding in the ion channel, which acts as a dielectric waveguide, with fiber parameter V∼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.