VARIATIONALLY IMPROVED FERMI BEAM SOLUTIONS

The time-independent, transmission problem for a purely scattering, ho mogeneous slab of finite thickness is considered. This problem corresp onds to a planar beam of radiation impinging perpendicularly upon one surface of a source-free slab. The scattering process is assumed suffi ciently peaked in the forward direction so that the Fokker-Planck diff erential scattering operator can be used. Further, the slab is assumed sufficiently thin so that radiation backscattering is negligibly smal l. Generally, this problem is approximated by the classic Fermi soluti on. By using the recently reported solution for an obliquely incident pencil beam, we show that the Fermi solution (or any other approximate solution) can be improved via a variational formalism. Copyright (C) 1996 Elsevier Science Ltd