Development of a tuneable channel cut crystal

We have developed the first tuneable channel cut crystal for ultra small an gle neutron scattering and neutron optical experiments. The Darwin range of a perfect crystal can be reduced down to a fraction of its natural width. This "Darwin reduction" was realised without any change of the beam geometr y which yields an intensity gain relative to conventional asymmetric Bragg diffraction. With such tuneable channel cut crystal peaks nearly delta -pea ks can experimentally be realised. (C) 2001 Elsevier Science B.V. All right s reserved.