In this paper, we develop a new approach to the SASE FEL theory. It is based on the well-known system of Klimontovich-Maxwell equations. The special choice of the independent variable makes it possible to eliminate both electromagnetic field and retardation. That allows us to write down the BBGKY hierarchy for the s-particle distribution functions. Due to the smallness of the higher-order correlations we consider only two equations from the beginning of this hierarchy. © 2003 Elsevier B.V. All rights reserved.
Shevchenko, O. A., & Vinokurov, N. A. (2003). Correlation function equation for the SASE FEL. In Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment (Vol. 507, pp. 84–88). https://doi.org/10.1016/S0168-9002(03)00843-X