High-resolution Neutron Diffraction using Larmor Precession for Angular and Wavelength Labelling

Abstract

A new high-resolution diffraction method is introduced without the confinement of using a highly collimated beam, necessary in conventional high-resolution diffraction. Larmor precession of a polarised neutron beam is used to label each neutron of the incident and scattered neutron beam with its wavelength and scattering angle. Giving the Larmor precession device front and back faces inclined over an angle adjusted to the scattering angle used, the wavelength–transmission angle relation of the Larmor precession matches precisely with the wavelength–scattering angle relation of the scattering vector. In this way the Larmor precession phases of different momentum transfers and thus the scattering vectors, can be measured with extremely high resolution. It should be possible to measure lattice constants with relative accuracy of better than 10⁻⁵, while using a low resolution beam, which means an effective intensity gain of orders of magnitude. Applications of this method are discussed.