COHERENCE VOLUMES AND NEUTRON-SCATTERING

We describe neutron scattering in a space-time frame-complementary to the van Hove picture. Based on the theory of partial coherence from li ght optics, neutron beams may be represented by correlation volumes, w hich are defined by the wavelength distribution and by optical element s like guides, slits, choppers or crystals. Size and shape of these ti ny volumes tin space and time determine the volume of coherent interac tion within the samples, which are represented by pair correlation fun ctions. The beam correlation volumes also determine the resolution or the experiment and if the signal is proportional to a Fourier transfor m of the sample correlation function. Here we give a simple approach t o this theory with various examples, (C) 1998 Elsevier Science B.V. Al l lights reserved.