On the relationship between the gain of Stimulated Raman Backscatter of a short-pulse laser in a plasma and the Pierce parameter for XFELs

Abstract

It is shown that the convective gain of Stimulated Raman Backscatter (SRBS) within a single laser wavelength in the strongly coupled regime is equivalent to the Pierce parameter commonly used to describe high gain x-ray Free Electron Lasers (XFELs). The comparison utilizes the fact that the gain is a Lorentz invariant so the Pierce parameter is written in terms of the FEL parameters in the electron beam's rest frame. It is thus inferred that there is a direct correspondence of the physics between SRBS in the strong-coupled regime and high gain XFELs in the Compton regime.