THE 30 M SMALL-ANGLE NEUTRON-SCATTERING INSTRUMENTS AT THE NATIONAL-INSTITUTE-OF-STANDARDS-AND-TECHNOLOGY

Two high-resolution, general-purpose, small-angle neutron scattering i nstruments have been constructed at the National Institute of Standard s and Technology's Center for Neutron Research. The instruments are 30 m long and utilize mechanical velocity selectors, pinhole collimation and high-data-rate two-dimensional position-sensitive neutron detecto rs. The incident wavelength, wavelength resolution and effective lengt h of the instruments are independently variable, under computer contro l, and provide considerable flexibility in optimizing beam intensity a nd resolution. The measurement range of the instruments extends from 0 .0015 to 0.6 Angstrom(-1) in scattering wavevector, corresponding to s tructure in materials from 10 Angstrom to nearly 4000 Angstrom. The de sign and characteristics of the instruments, and their modes of operat ion, are described, and data are presented which demonstrate their per formance.