Boron-Based Neutron Scintillator Screens for Neutron Imaging

Novel flexible and conformable composite neutron scintillator based on fully enriched lithium tetraborate

Thermal neutron detection is a key subject for nuclear physics research and also in a wide variety of applications from homeland security to nuclear medicine. In this work, it is proposed a novel flexible and conformable composite thermal neutron scintillator based on a fully enriched Lithium Tetraborate preparation ([Formula: see text]Li[Formula: see text]B[Formula: see text]O[Formula: see text]) combined with a phosphorescent inorganic scintillator powder (ZnS:Ag), and is then distributed into a polydimethylsiloxane matrix. The proposed scintillator shows a good neutron detection efficiency (max. [Formula: see text] 57% with respect to the commercial EJ-420), an average light output of [Formula: see text] 9000 ph/neutron-capture, a remarkable insensitivity to [Formula: see text]-rays (Gamma Rejection Ratio <10[Formula: see text]), and an extraordinary flexibility, so as to reach extremely small curvature radii, down to 1.5 mm, with no signs of cracking or tearing. Its characteristics make it suitable to be employed in scenarios where non-standard geometries are needed, for example, to optimize the detector performance and/or maximize the detection efficiency. Finally, the response of a hybrid detector made of a plastic scintillator, wrapped with the proposed scintillator, coupled to a silicon photomultiplier array is described, and the excellent discrimination between [Formula: see text]-rays, fast and thermal neutrons resulting from data processing is demonstrated.

Performance of borated scintillator screens for high-resolution neutron imaging

The most commonly used screens for neutron imaging consist of 6LiF + ZnS. This type of screen yields the highest light output per detected neutron. For high resolution, gadolinium oxysulfide (GOS, Gadox) screens are employed, which have a much higher detection efficiency, but a light output so much lower than LiF + ZnS that measurements are often limited by photon statistics. Historically, screens using boron as a neutron-sensitive material have not been very successful. However, a new preparation method was introduced recently that produces light output higher than Gadox with detection efficiency greater than LiF + ZnS. Measurements of these new borated screens were performed at the NeXT facility at ILL, Grenoble, in comparison to a high resolution Gadox screen.

Extraordinary intense blue Tl+ lone-pair photoluminescence from thallium(I) chloride hydroborate Tl3Cl[B12H12]

Microcrystalline powder of previously unknown thallium(I) chloride hydroborate Tl₃Cl[B₁₂H₁₂] was obtained through the reaction of thallium(I) oxocarbonate Tl₂[CO₃] with an aqueous solution of (H₃O)₂[B₁₂H₁₂] in the presence of chloride anions. Tl₃Cl[B₁₂H₁₂] crystallises in a primitive, orthorhombic lattice with the space group Pnma (a = 835.189(7) pm, b = 970.132(8) pm and c = 1597.912(12) pm for Z = 4) showing a distorted hexagonal anti-perovskite type arrangement of the ions. The structure features two thallium sites with mixed coordination spheres consisting of borate related hydrogen atoms and chloride anions with coordination numbers of eleven and thirteen. Tl₃Cl[B₁₂H₁₂] shows strong excitation bands at 240 and 260 nm attributed to the ¹S₀ → ³P₂ and ¹S₀ → ³P₁ interconfigurational transitions of the Tl⁺ 6s² cations, respectively. The emission spectrum at 300 K upon VUV excitation exhibits a broad band at 440 nm with a quantum efficiency of 41%. In addition, temperature-dependent emission spectra, colour points, reflectance, decay time, thermal quenching curve and radioluminescence spectra for Tl₃Cl[B₁₂H₁₂] were determined.