Neutron spin echo and three-axis spectrometers

Abstract

The application of the neutron spin echo (NSE) technique to three-axis spectroscopy is discussed. After a brief introduction which recalls the precession-field geometry required in this case, detailed calculations of performance are presented for two typical cases. Effects of detuning the precession fields from their focused conditions are included explicitly in these calculations which should then be a guide to the design and use of such a spectrometer. It is shown that the three-axis NSE technique can be used to measure both phonon line widths and the wave vector distributions of (quasi)-elastic scattering. In the latter case, resolution similar to that available with the best X-ray spectrometers can be achieved. Finally, design calculations for precision magnets suitable for use with three-axis spectrometers are presented.