Neutron spectroscopy can provide unique information about nano-scale structure and dynamics in condensed matter.  As sample sizes shrink and the understanding of complex correlated phenomena becomes increasingly dependent on more detailed, time-consuming, surveys of energy and momentum space, the need for higher sample flux, lower background, and faster data acquisition become increasingly important. To meet this demand in the long wavelength regime (~ 2 Å  l < 6 Å), an advanced cold neutron spectrometer, MACS (Multi Analyzer Crystal Spectrometer), is being developed for the NIST Center for Neutron Research (NCNR)

A novel doubly focusing neutron monochromator has been developed as part of MACS. The instrument utilizes a unique vertical focusing element that enables active vertical and horizontal focusing with a large, 357-crystal (1428 cm²), array. The design significantly reduces the amount of structural material in the beam path as compared to similar instruments. Optical measurements verify the excellent focal performance of the device. Mounted at the NIST cold neutron source, the instrument produces a monochromatic beam (DE = 0.2 meV) with flux f > 10⁸ n/cm²/s.