Optimizing ZnS/⁶LiF scintillators for wavelength-shifting-fiber neutron detectors

Abstract

In this paper we compare the performance of grooved and flat ZnS/ 6 LiF scintillators in a wavelengthshifting-fiber (WLSF) detector.Flat ZnS/ 6 LiF scintillators with the thickness L=0.2-0.8 mm were characterized using photon counting and pulse-height analysis and compared to a grooved scintillator of approximately 0.8 mm thick.While a grooved scintillator considerably increases the apparent thickness of the scintillator to neutrons for a given coating thickness, we find that the flat scintillators perform better than the grooved scintillators in terms of both light yield and neutron detection efficiency. The flat 0.8-mm-thick scintillator has the highest light output, and it is 52% higher compared with a grooved scintillator of same thickness. The lower light output of the grooved scintillator as compared to the flat scintillator is consistent with the greater scintillator-WLSF separation and the much larger average emission angle of the grooved scintillator. We also find that the average light cone width, or photon travellength as measured using time-of-flight powder diffraction of diamond and vanadium, decreases with increasing L in the range of L=0.6-0.8 mm. This result contrasts with the traditional Swank diffusion model for micro-composite scintillators, and could be explained by a decrease in photon diffusion-coefficient or an increase in micro-particle content in the flat scintillator matrix for the thicker scintillators.I.

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.…”

“…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.…”

Bright lead-free Cs3Cu2I5 perovskite scintillators for thermal neutron detection

“…For example, the 6 LiF/ZnS:Ag neutron scintillator has large area coverage and high neutron detection efficiency. [13][14][15] However, its slow response limits the count rate capability. The self-absorption and scattering of scintillation light in the 6 LiF/ZnS:Ag make the scintillator opaque and limit its light output.…”

Optical identification and quantification of single neutron detection in 6LiF/ZnS scintillators using a CMOS camera

“…On the other hand, very bright ZnS scintillators, mixed with 6 LiF in various proportions, offer a matchless light output in the green or blue spectrum (depending on whether their activator is copper or silver), but their efficiency is limited by their own opacity [7] to a value of around 20% in a flat configuration. Efficiencies of over 40% have been reached by tilting the scintillator layer in the direction of neutron propagation [6], by grooving it [8], or by arranging for light collection inside the scintillator [9]. This type of scintillator offers a remarkably efficient neutron discrimination over γ-rays when coupled to photomultiplier tubes or silicon photomultipliers.…”