Masanori Koshimizu

Scintillation property of rare earth-free SnO-doped oxide glass

The authors have demonstrated scintillation of rare earth (RE)-free Sn-doped oxide glass by excitation of ionizing radiation. It is notable that light emission is attained for RE-free transparent glass due to s2-sp transition of Sn2+ centre and the emission correlates with the excitation band at 20 eV. We have also demonstrated that excitation band of emission centre can be tuned by the chemical composition of the host glass. The present result is valuable not only for design of RE-free inorganic amorphous oxide scintillator but also for revealing the band structure of oxide glass by irradiation of ionizing radiation.

Subnanosecond time-resolved x-ray measurements using an organic-inorganic perovskite scintillator

We have developed a fast x-ray detector using an organic-inorganic perovskite scintillator of phenethylamine lead bromide (PhE-PbBr4). The scintillator had a dominant light emission with a fast decay time of 9.9 ns. An x-ray detector equipped with a 0.9-mm-thick PhE-PbBr4 crystal was used to detect nuclear resonant scattering in N61i (the first excited level: 67.41 keV; lifetime: 7.6 ns) by using synchrotron radiation. With this detector, we could successfully record the decaying gamma rays emitted from N61i with a time resolution of 0.7 ns (full width at half maximum) and a relatively high detection efficiency of 24%.

Timing property of undoped BaCl2 single crystal scintillator

Scintillation characteristics of undoped BaCl2, a novel fast scintillation material, were investigated. Scintillation photons with wavelength ranging from 250–600 nm were observed with two luminescence bands at 300 and 400 nm. The scintillation time profiles consisted of two lifetime components. The shorter component had a lifetime of 1.6 ns, while the longer one had a lifetime of several tens of nanoseconds. The origin of the fast component has been attributed to self-trapped excitons, whereas the slow component is considered to be an extrinsic luminescence. The photoelectron yield of the fast component of BaCl2 coupled to a bialkali photocathode was comparable to that of BaF2. This shows that BaCl2 is a promising scintillation material that can be used for measurements at a high counting rate or with an excellent timing property.

Comparative study of scintillation properties of Cs2HfCl6 and Cs2ZrCl6

The photoluminescence and scintillation properties of Cs2HfCl6 and Cs2ZrCl6 crystals were investigated. Two emission bands in the photoluminescence spectra were observed at 375 and 435 nm for the Cs2HfCl6 crystal and at 440 and 479 nm for the Cs2ZrCl6 crystal. Similar spectra were observed for radioluminescence. The decay time constants were found to be about 2.2 and 8.4 µs for Cs2HfCl6 and 1.5 and 7.5 µs for Cs2ZrCl6. The scintillation light yields were estimated to be 27,500 and 25,100 photons/MeV for Cs2HfCl6 and Cs2ZrCl6, respectively.

X-ray detection capability of a BaCl2 single crystal scintillator

The x-ray detection capability of a scintillation detector equipped with a BaCl2 single crystal was evaluated. The scintillation decay kinetics can be expressed by a sum of two exponential decay components. The fast and slow components have lifetimes of 1.5 and 85 ns, respectively. The total light output is 5% that of YAP:Ce. A subnanosecond timing resolution was obtained. The detection efficiency of a 67.41 keV x-ray is 87% for a detector equipped with a BaCl2 crystal 6-mm thick. Thus, excellent timing resolution and high detection efficiency can be simultaneously achieved. Additionally, luminescence decay characteristics under vacuum ultraviolet excitation have been investigated. Radiative decay of self-trapped excitons is thought to be responsible for the fast scintillation component.

Organic-Inorganic Hybrid Scintillator for Neutron Detection Fabricated by Sol-Gel Method

Novel scintillating materials for neutron detection were fabricated by using the sol–gel method. The scintillating materials comprised borosilicate glass and poly(ethylene glycol) (PEG). The scintillation characteristics were examined under He irradiation, and it was found that the scintillation intensity increased with the concentration of PEG. It also increased linearly with the concentration of fluor 2-(4-tert-butylphenyl)-5-(4-biphenylyl)-1,3,4-oxadiazole (B-PBD). Furthermore, the scintillation intensity of the best sample was comparable to that of the commercially available plastic scintillator BC-454. It was shown that a fluor with larger solubility in the starting solution would further improve the scintillation property.

Optical and scintillation properties of Nd-doped SrAl2O4 crystals

Abstract Nd-doped SrAl2O4 (Nd:SrAl2O4) crystals were prepared by a floating zone (FZ) method with different dopant concentrations. The photoluminescence (PL) measurements under visible light excitations confirmed strong near infrared (NIR) emissions around 890 nm, which is due to the 4f-4f transitions of Nd3+, and the decay time constants were 300–400 μs. Furthermore, VUV excitations revealed two broad emissions around 250–450 and 500–700 nm, which were attributed to self-trapped excitons (STEs) perturbed by Nd3+. Moreover, the X-ray induced scintillation spectra showed some small peaks at around 380 nm in addition to NIR emissions at 1064 nm similarly seen in PL. The former scintillation decay time constants were 30–40 μs. In the undoped sample, these emissions mentioned above were not present but a weak broad emission around 450 nm appeared. In thermally stimulated luminescence (TSL) after X-ray irradiation, strong TSL glow peaks were observed in the Nd-doped samples at around 100 and 250 °C.

Thallium magnesium chloride: A high light yield, large effective atomic number, intrinsically activated crystalline scintillator for X-ray and gamma-ray detection

We report the luminescence and the scintillation properties of a newly developed thallium magnesium chloride (TlMgCl3) crystal. The crystal sample can be easily fabricated from the melt using the Bridgman method. The photoluminescence band appeared near the wavelength of 405 nm under excitation at 230 nm. An X-ray-induced scintillation spectrum showed an intense emission band near the wavelength of 405 nm. The decay time constant was estimated to be approximately 60 ns (~25%) and 350 ns (~75%) using a bi-exponential fitting. The scintillation light yield reached 46,000 photons/MeV with an energy resolution of 5% at 662 keV.

High-energy X-ray detection by hafnium-doped organic-inorganic hybrid scintillators prepared by sol-gel method

With the aim of enhancing the efficiency with which plastic scintillators detect high-energy X-rays, hafnium-doped organic-inorganic hybrid scintillators were fabricated via a sol-gel method. Transmission electron microscopy of sampled material reveals the presence of HfxSi1−xO2 nanoparticles, dispersed in a polymer matrix that constitutes the active material of the X-ray detector. With HfxSi1−xO2 nanoparticles incorporated in the polymer matrix, the absorption edge and the luminescence wavelength is shifted, which we attribute to Mie scattering. The detection efficiency for 67.4-keV X-rays in a 0.6-mm-thick piece of this material is two times better than the same thickness of a commercial plastic scintillator-NE142.

Poly[bis(phenethyl­ammonium) [di­bromido­plumbate(II)]-di-μ-bromido]]

Crystals of the title compound, {(C6H5C2H4NH3)2[PbBr4]}n, were grown at room temperature from a solution in N,N-dimethylformamide (DMF) using nitromethane as the poor solvent. This perovskite-type organic–inorganic hybrid compound consists of well ordered sheets of corner-sharing disordered PbBr6 octahedra separated by bilayers of phenethylammonium cations. The octahedra are rotated and tilted due to N—H⋯Br hydrogen bonds with the ammonium groups, generating a superstructure in the unit cell similar to that of the tetrachloridoplumbate (C6H5C2H4NH3)2[PbCl4].