The single-moderator neutron spectrometer is the result of developments in multisphere neutron spectrometer design. Multisphere is a multimoderator-based neutron spectrometer technique to measure the neutron spectrum with the most comprehensive energy range from electron-volt to gigaelectron-volt. Developing a multisphere into a single moderator aims to obtain a more practical device with regard to mobility and measurement techniques. We also review the layered-moderator design, a multisphere development with a single detector.

This paper ends with a review of the development of single-moderator designs with multidetectors, with regard to the various forms of moderators, types of detectors used, and validation results of each model. The development of the single-moderator neutron spectrometer in the geometric aspect of the moderator produces two dominant moderator shapes: spherical and cylindrical. The spherical shape is applied to measure the multidirectional neutron beam, while the cylindrical shape is used for the monodirectional beam. Validation results of 2.5% to 3.2% on single-sphere designs and 2% to 8% on single-cylindrical designs indicate that the developed single-moderate neutron spectrometer designs can replace multisphere-type spectrometers.