Prospects for X-ray amplification with charge-displacement self-channeling

The authors develop an analytic theory of charge-displacement self-channeling, a mechanism that can dynamically trap a short intense pulse of light. Attention is focused on the case of most interest for X-ray amplification: the strongly saturated channel, for which all free electrons are expelled from the channel core and the channel walls are overdense. Some curious results are: (1) the intensity at the channel walls is independent of the total laser power, (2) the radius of the channel increases very slowly with laser power, asymptotically as the fourth root, and (3) the power in the channel wall is a constant. It is also found that the channel is an effective waveguide for all secondary radiation. Scaling studies show that there is a substantial advantage in using the highest-frequency driving laser available. The channel is ideal for generating coherent short-wavelength radiation, perhaps well into the X-ray range