Enhanced position resolution for ZnS:Ag/ ^6 LiF wavelength shifting fibre thermal neutron detectors

The high neutron intensity, improvements in neutron delivery and increasingly more complex experiments at neutron scattering facilities, i.e. J-PARC, SNS, ISIS, CSNS and ESS, which is presently under construction, drive the development of neutron scattering instruments and their associated detectors. High position resolution is one of the most demanding detector requirements and is particularly relevant of neutron reflectometry applications. Scintillator detectors using ZnS:Ag/ ^6 LiF coupled to wavelength shifting fibre (WLSF) are currently employed in several neutron scattering facilities, including J-PARC, SNS, ISIS and CSNS. For WLSF-based scintillation detectors, the position reconstruction is routinely achieved by determining the combination of fibres that absorb scintillation light. The use of position reconstruction algorithms, analysing light spread in the system, leads to an increase in the position resolution. The optimisation of a centre of gravity interpolation method for linear position-sensitive detectors has been developed, and a factor 2 improvement in position sensitivity has been achieved. The investigation of the light spread over the fibres and the detector performance in correlation with the reconstructed position resolution are discussed.