We investigated scintillation properties of organic–inorganic layered perovskite-type compounds under gamma-ray and X-ray irradiation. A crystal of the hybrid compounds with phenethyl amine (17 × 23 × 4 mm) was successfully fabricated by the poor-solvent diffusion method. The bulk sample showed superior scintillation properties with notably high light yield (14,000 photons per MeV) under gamma-rays and very fast decay time (11 ns). The light yield was about 1.4 time higher than that of common inorganic material (GSO:Ce) confirmed under 137Cs and 57Co gamma-rays. In fact, the scintillation light yield was the highest among the organic–inorganic hybrid scintillators. Moreover, it is suggested that the light yield of the crystal was proportional with the gamma-ray energy across 122–662 keV. In addition, the scintillation from the crystal had a lifetime of 11 ns which was much faster than that of GSO:Ce (48 ns) under X-ray irradiation. These results suggest that organic–inorganic layered perovskite-type compounds are promising scintillator for gamma-ray detection.

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The measurement of spatially resolved high doses in microbeam radiation therapy has always been a challenging task, where a combination of high dose response and high spatial resolution (microns) is required for synchrotron radiation peaked around 50 keV. The x-ray induced Sm3+ → Sm2+ valence conversion in Sm3+ doped fluorophosphates glasses has been tested for use in x-ray dosimetry for microbeam radiation therapy. The conversion efficiency depends almost linearly on the dose of irradiation up to ∼5 Gy and saturates at doses exceeding ∼80 Gy. The conversion shows strong correlation with x-ray induced absorbance of the glass which is related to the formation of phosphorus-oxygen hole centers. When irradiated through a microslit collimator, a good spatial resolution and high “peak-to-valley” contrast have been observed by means of confocal photoluminescence microscopy.

There is a special need to develop a dosimetry technique with a large-dynamic range and high-spatial resolution to characterize the microstructured X-ray beams used in microbeam radiation therapy (MRT) for cancer. We report the synthesis and characterization of oxyfluoride glass-ceramic (SiO 2 -Al 2 O 3 -CaF 2 -CaO-SmF 3 ) plates, which contain trivalent-samarium-doped calcium fluoride (CaF 2 :Sm 3+ ) nanocrystals, for use as a dosimetric detector material, particularly for MRT applications. Our approach utilizes the extent of Sm 3+ ?Sm 2+ valence reduction caused by X-ray irradiation as a probe of the X-ray dose delivered; and confocal fluorescent microscopy is used to read out the distribution of valence reduction through the photoluminescence (PL) signal. Our study showed that the Sm 3+ ?Sm 2+ valence reduction takes place in CaF 2 nanocrystals, but not in the glass matrix. The Sm 2+ shows PL emission predominantly due to the fast 4f 5 5d 1 ? 7 F 0 transition, which allows us to read out the detector plate at a high scanning speed. Further, our experiments showed that the detection dose range reaches several thousands of grays, and X-ray dose distribution is detected at a micrometer scale. In addition, the Sm 2+ signal can be erased either by heating the irradiated sample at a suitable high temperature or by exposing it to UV light; and the erased glass-ceramic plate is reusable. The new Sm-doped oxyfluoride glass-ceramic with CaF 2 nanocrystals reported in this work shows potential for practical use in highdose and high-resolution dosimetry for MRT. J. McKittrick-contributing editorManuscript No. 34020.

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Eu-doped SrAl2O4 (Eu:SrAl2O4) crystals are prepared by a floating zone (FZ) method. In photoluminescence (PL), an intense broad emission peak around 510 nm due to 5d-4f transition of Eu 2+ appear under excitation at 250-450 nm. The PL decay time constants are about 800 ns due to the 5d-4f transitions of Eu 2+. In the nondoped sample, emission peaks around 480 and 560 nm are observed upon excitation at 316 nm. The X-ray induced scintillation spectra also show an intense broad emission peak around 510 nm, and the decay time constants are approximately 500 ns. In the pulse height spectra of the 2.5% Eu:SrAl2O4 crystal, the absolute light yield is ~46000 ph/MeV. In thermally stimulated luminescence (TSL) after X-ray irradiation, strong TSL glow peaks are observed at 120 and 400 o C. In optically stimulated luminescence (OSL) after X-ray irradiation, emission peaks are observed around 510 nm while exposing the samples to the stimulation light at 800 nm.

Fluorophosphate and fluoroaluminate glasses doped with trivalent samarium were evaluated as sensors of x-ray radiation for microbeam radiation therapy at the Canadian Light Source using the conversion of trivalent Sm3+ to the divalent form Sm2+. Both types of glasses show similar conversion rates and may be used as a linear sensor up to ∼150 Gy and as a nonlinear sensor up to ∼2400 Gy, where saturation is reached. Experiments with a multi-slit collimator show high spatial resolution of the conversion pattern; the pattern was acquired by a confocal fluorescence microscopy technique. The effects of previous x-ray exposure may be erased by annealing at temperatures exceeding the glass transition temperature Tg while annealing at TA < Tg enhances the Sm conversion. This enhancement is explained by a thermally stimulated relaxation of host glass ionic matrix surrounding x-ray induced Sm2+ ions. In addition, some of the Sm3+-doped glasses were codoped with Eu2+-ions but the results show that there is no marked improvement in the conversion efficiency by the introduction of Eu2+.

We report the distinct scintillation properties of the well-known Ga2O3 semiconductor material. Under UV excitation, the photoluminescence (PL) emission peak appeared near a wavelength of 380 nm with a quantum yield of 6%, and fast decays of 8 and 793 ns were observed. In contrast, the X-ray-induced scintillation spectrum showed an intense emission band near a wavelength of 380 nm, whose decay curve was reproduced using two exponential decay components with time constants of 8 and 977 ns. The pulse height spectrum of 137Cs γ-rays measured using Ga2O3 showed a clear photoabsorption peak with a light yield of 15000 ± 1500 photons/MeV.