Application of the Two-Particle Correlation Function Approach to the Description of a Single-Pass Free Electron Laser Operated in SASE Mode

Abstract

We describe the theory of a superluminescent single-pass free electron laser based on the Bogolyubov chain of equations for multiparticle distribution functions. Special choice of the variables eliminates the retardation of interaction. A small parameter (inverse number of particles per signal growth length in the accompanying reference system) for the chain truncation is found. Expansion over this parameter makes it possible to neglect three-particle correlation functions and solve only the equations containing a single-particle distribution function and two-particle correlation functions. The calculation results are in good agreement with the conclusions based on the previously developed quasilinear theory.