High-Resolution Thermal Neutron Imaging With ¹⁰Boron/CsI:Tl Scintillator Screen

Abstract

High-resolution neutron imaging is difficult, due to the low-light output of neutron scintillators, and the spread of light within common neutron-sensitive scintillators as well as the spread of intermediate particles occurring during the detection process. To address this issue, we have developed a highresolution scintillator for neutron imaging by combining enriched <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> B with the well-known CsI:Tl scintillator films. CsI:Tl has excellent properties for X-ray imaging applications, due to a high light yield of 60 000 photons/MeV, and high spatial resolution, which derives from its microcolumnar structure, which channels scintillation light to the photodetector. To enable CsI:Tl to detect neutrons, <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> B (96% enriched) was deposited by electron beam directly onto the CsI:Tl film, making a layered scintillator structure in which the alphas produced by the neutron interaction with <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> B are detected in the CsI:Tl. The <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> B layer was approximately 3 μm thick, while the thickness of the CsI:Tl film was 11 μm. These novel layered scintillators were integrated into the high-resolution neutron imaging detector [“Paul Scherer Institute (PSI) Neutron Microscope”] at the Pulse OverLap DIffractometer (POLDI) beamline at the PSI. With our <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> B/CsI:Tl scintillator, we were able to achieve a spatial resolution down to 9 μm. To demonstrate the effectiveness of the layered scintillator, we present results obtained by thermal neutron imaging as well as high-resolution neutron-computed tomography. Finally, we believe there is considerable scope for future optimization of the performance of this system.