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The first neutron Fourier diffractometer at the pulsed neutron source, the High Resolution Fourier Diffractometer (HRFD), is described. The HRFD combines both high neutron flux at the sample position, -107n/cm2/s, provided by the IBR-2 high flux pulsed reactor, and high resolution, very close to 0.001, over a wide range of d-spacings. The paper deals with the basic principles of HRFD, its design, and performance. Examples of structural experiments are also given.

At the IBR-2 pulsed reactor (FLNP, JINR, Dubna), a specialized time-of-flight instrument, the Fourier-Stress-Diffractometer (FSD), is under construction. This instrument is intended for the measurement of internal stresses in bulk samples by using high-resolution neutron diffraction. One of the main components of the diffractometer is a new-type of detector with combined electronic-geometric focusing, uniting a large solid angle and a small geometric contribution to the instrumental resolution. The first two modules of the detector, based on ZnS(Ag)/ 6 LiF scintillation screen with wavelength shifting fiber readout have been developed and tested. In this paper, the design of the detector and associated electronics are described. The method of time focusing surface approximation using the screen flexibility is proposed. Characteristics of tested modules in comparison with a detector of previous generation are presented and advantages of the new detector design for high-resolution diffractometry are discussed.