The calibration of neutron time-of-flight diffractometers for amorphous materials

A method of calibrating the scattering vector (Q) scale for a neutron time-of-flight diffractometer is outlined. An expression for the neutron wavelength and scattering vector corresponding to a given time channel is developed using a power series approximation in neutron wavelength, lambda, for the mean emission time of the neutrons from the source. Standard wavelength and scattering vectors are discussed. The method is applied to the calibration of the total scattering spectrometer (TSS) at the Harwell linac and is shown to be accurate to better than one tenth of the resolution width of any given counter for a range of scattering vectors spanning two orders of magnitude. (orig.)