Adjustable resolution Bragg reflection systems

In this paper is described the realization of an idea due to J. W. M. Dumond who, almost 50 years ago, suggested that Bragg diffraction peaks might be made narrower by multiple reflection [Dumond (1937). Phys. Rev. 52, 872-883]. The optical elements which result belong to a family of harmonic free monochromators, X-ray and neutron polarizers whose properties make feasible many new Bragg diffraction optical systems.