Performance improvements of wavelength-shifting-fiber neutron detectors using high-resolution positioning algorithms

Abstract

Three high-resolution positioning methods based on the FluoroBancroft linear-algebraic method [S. B. Andersson, Opt. Express 16, 18714 (2008)] are proposed for wavelength-shifting fiber (WLSF) neutron detectors. Using a Gaussian or exponential-decay light-response function, the non-linear relation of photon-number profiles vs. x-pixels was linearized and neutron positions were determined. After taking the super-Poissonian photon noise into account, the proposed algorithms give an average of 0.03-0.08 pixel position error much smaller than that (0.29 pixel) from a traditional maximum photon algorithm (MPA). The new algorithms result in better detector uniformity, less position misassignment (ghosting), better spatial resolution, and an equivalent or better instrument resolution in powder diffraction than the MPA. These improvements will facilitate broader applications of WLSF detectors at time-of-flight neutron powder diffraction beamlines, including single-crystal diffraction and texture analysis.

Detector needs for STS instruments

“…These emit more light than GS20, but are not transparent to their own light and have a large afterglow. Research into improved scintillators has shown that better scintillators are possible [Richards 2021, Sykora 2018, Wang 2015, Wang 2016)], and could potentially raise the count rate capability of WLS detectors.…”

“…In scintillators, this is more challenging since the scintillator materials tend to have a sufficient density to stop Compton/photo electrons. Typically, a sub-mm scintillator thickness is needed to [Wang 2016] allow an efficient threshold rejection of gamma-rays. Some scintillators allow pulse shape discrimination [Wang, Riedel 2016].…”

“…More unknown are the efforts needed to achieve the necessary sensitive area, increase position resolution to 1 mm and decrease gamma-sensitivity. Other scintillator options may be considered [Richards 2021, Sykora 2018, Wang 2015, Wang 2016] in the event of issues with pixelization of 1 mm, and if the required gamma insensitivity cannot be reached with GS20.…”

Nanoparticle ZnS:Ag/6LiF—a new high count rate neutron scintillator with pulse shape discrimination

“…Most scintillation detectors at scattering facilities employ either cerium doped lithium glass scintillators (e.g. GS20) or ZnS:Ag/ 6 LiF, which both possess notable limitations [23][24][25][26][27][28][29][30].…”

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

“…With this type of position reconstruction, the accuracy of position determination is, at best, the same as the fibre pitch. In the past few years, several algorithms have been developed at SNS [38,39] and at J-PARC [23,34,40]. In one case the position resolution reached down to ≈ 100 µm resolution for a neutron imaging application using specifically made 100-µm-diameter fibres and a fibre optic taper which serves as an image magnifier [41], hence increasing the spatial resolution.…”