A neutron Fourier chopper for single crystal reflectivity measurements: some general design considerations

Neutron single-crystal analysis of complex protein structures requires the collection of intensity data on a large number of reflections. The use of time-of-flight analysis (in particular Fourier time-of-flight analysis employing phase detection) of diffraction data, offers a significant increase in the efficiency of the use of reactor neutrons. Such a method would facilitate the use of neutron diffraction in protein structure work. In this paper, we investigate the use of the Fourier chopper in single-crystal work. We examine the effect of various system parameters (frequency stability, flight path fluctuations, collimation, sample mosaic spread, inaccuracy in phase detection, and statistical counting errors) and determine general specifications for such an apparatus. None of these specifications appears to be beyond present day technology.