X-ray laser based on channel radiation

A relativistic electron beam propagating through planar or axial channels in a crystal can populate bound transverse energy eigenstates. Spontaneous dipole transitions between these discrete eigenstates lead to narrow-width, highly polarized X-rays that are strongly forward peaked in intensity. To obtain an observable gain from induced emission, the electron beam current density must be 10/sup 7/-10/sup 8/ A/cm/sup 2/ for one-pass amplification. The authors discuss several ways to reduce this current density requirement. The net result of the analysis is that observable gain should be possible for an electron beam current density of 10/sup 4/-10/sup 5/ A/cm/sup 2/. To achieve such a current density, consider a field emission electron gun similar to that used for scanning electron microscopy. The authors have also studied several methods of accelerating the beam and increasing the current without increasing the transverse energy of the beam by using a pulsed source.<>