Abstract
In digital neutron imaging, the neutron scintillator screen is a limiting factor of spatial resolution and neutron capture efficiency and must be improved to enhance the capabilities of digital neutron imaging systems. Commonly used neutron scintillators are based on 6LiF and gadolinium oxysulfide neutron converters. This work explores boron-based neutron scintillators because 10B has a neutron absorption cross-section four times greater than 6Li, less energetic daughter products than Gd and 6Li, and lower γ-ray sensitivity than Gd. These factors all suggest that, although borated neutron scintillators may not produce as much light as 6Li-based screens, they may offer improved neutron statistics and spatial resolution. This work conducts a parametric study to determine the effects of various boron neutron converters, scintillator and converter particle sizes, converter-to-scintillator mix ratio, substrate materials, and sensor construction on image quality. The best performing boron-based scintillator screens demonstrated an improvement in neutron detection efficiency when compared with a common 6LiF/ZnS scintillator, with a 125% increase in thermal neutron detection efficiency and 67% increase in epithermal neutron detection efficiency. The spatial resolution of high-resolution borated scintillators was measured, and the neutron tomography of a test object was successfully performed using some of the boron-based screens that exhibited the highest spatial resolution. For some applications, boron-based scintillators can be utilized to increase the performance of a digital neutron imaging system by reducing acquisition times and improving neutron statistics.
Highlights
The purpose of this study was to conduct a combinatorial study of boron‐based neutron scintillators to determine if (1) borated scintillator screens could offer improved neutron imaging scintillators to determine if (1) borated scintillator screens could offer improved neutron imaging capabilities compared to current widely-used screens and (2) which parameters produced the best capabilities compared to current widely‐used screens and (2) which parameters produced the best performing screens
Photons reflected off the substrate undergo further diffusion in the scintillator material with the increased path-length, degrading the spatial resolution
Epithermal neutron tomography can exhibiting 67% higher epithermal neutron detection efficiency for the same thickness
Summary
Neutron imaging is a nondestructive examination technique that measures neutron transmission to examine a sample’s internal structure. This technique has been used in a variety of studies, including those of nuclear fuels and materials [1,2,3,4,5,6], cultural heritage objects [7,8,9], fuel cells [10,11,12,13,14], turbine blades [15,16,17], and many others. Digital neutron imaging techniques are an essential capability. J. Imaging 2020, 6, 124; doi:10.3390/jimaging6110124 www.mdpi.com/journal/jimaging.
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