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Gadolinium pyrosilicate (GPS, Gd2Si2O7) single crystals with different doping concentrations of Tb (0.1–2.0 mol%) are successfully fabricated using the floating-zone technique. In this work, the dependence of Tb-doping concentration on the photoluminescence (PL) and scintillation properties of Tb-doped GPS (Tb:GPS) has been investigated. The PL emission contour graph shows multiple emissions, with the strongest emissions at 378 nm for 0.1% and 0.5% Tb-doping and 544 nm for 1.0% and 2.0% Tb-doping, corresponding to Tb3+ 4f-4f transitions. The PL lifetimes of the specimens range from 4.89 to 5.22 ms. The scintillation spectra exhibit comparable wavelength and intensity trends to the PL emission. The scintillation lifetimes of the specimens range from 2.41 to 3.88 ms. The Tb:GPS specimens demonstrate a relatively excessive afterglow level, with Af20 values ranging from 1640 to 7250 ppm and Af40 values ranging from 136 to 362 ppm. Using recently developed pulse height measurement for millisecond decay scintillators, under excitation at 662 keV γ-rays, the 1.0% Tb:GPS specimen exhibits the highest scintillation light yield among all other specimens at 95,600 ph/MeV, making Tb:GPS one of the highest light yield oxide scintillators. [ABSTRACT FROM AUTHOR]

Eulytite-type Ba3RE(PO4)3 (RE = Y, La, and Lu) single crystals were synthesized by the floating zone method, and their scintillation properties were investigated. The powder X-ray diffraction measurement revealed that the single phase of Ba3RE(PO4)3 samples were successfully synthesized. The samples exhibited a luminescence peak due to self-trapped exciton at around 400 nm under vacuum ultraviolet and X-ray irradiation. The X-ray-induced scintillation decay time constants of the samples were several microseconds at room temperature. In the 241Am α-ray irradiated pulse height spectra, all the samples showed a clear full energy peak, and the absolute light yields of the Ba3Y(PO4)3, Ba3La(PO4)3, and Ba3Lu(PO4)3 single crystals were estimated to be 960, 1160, and 1220 ph/5.5 MeV-α, with a typical error of ±10%, respectively. The scintillation light yields of the Ba3RE(PO4)3 have been quantitatively clarified for the first time. [ABSTRACT FROM AUTHOR]

Mg4Ta2O9 single crystals doped with 0.01, 0.1, and 1% Er were grown using the floating zone method, and their photoluminescence and scintillation properties were studied. X-ray diffraction analysis confirmed that all samples had a hexagonal structure of Mg4Ta2O9. The samples showed that the emission peak at 1550 nm was due to 4f−4f transitions of Er3+ ions, with quantum yields of 32.9, 46.6, and 18.0% for 0.01, 0.1, and 1% doping concentrations, respectively. All samples showed scintillation with a broad emission band at 350 nm due to charge transfer from Ta5+ to O2− ions and emission peak at 1550 nm due to 4f−4f transition of Er3+ ions. The dose rate response functions showed that the detection limit for all samples was 0.06 Gy/h for scintillation detector applications. [ABSTRACT FROM AUTHOR]

The Nd-doped LaMgAl11O19 single crystals were synthesized by the floating zone method, and the photoluminescence and scintillation properties were evaluated. Under X-ray irradiation, several sharp emission peaks due to the 4f–4f transitions of Nd3+ were observed at 900, 1060, and 1340 nm in the near-infrared range, and the decay curves show the typical decay time for Nd3+. The samples show good afterglow properties comparable with practical X-ray scintillators. The 1% and 3% Nd-doped LaMgAl11O19 samples show a good linearity in the dynamic range from 6–60,000 mGy/h. [ABSTRACT FROM AUTHOR]

Undoped, 0.5, 1.0, and 2.0% Nd-doped Bi4Si3O12 (BSO) crystals were synthesized by the floating zone method. Regarding photoluminescence (PL) properties, all samples had emission peaks due to the 6p–6s transitions of Bi3+ ions. In addition, the Nd-doped samples had emission peaks due to the 4f–4f transitions of Nd3+ ions as well. The PL quantum yield of the 0.5, 1.0, and 2.0% Nd-doped samples in the near-infrared range were 67.9, 73.0, and 56.6%, respectively. Regarding X-ray-induced scintillation properties, all samples showed emission properties similar to PL. Afterglow levels at 20 ms after X-ray irradiation of the undoped, 0.5, 1.0, and 2.0% Nd-doped samples were 192.3, 205.9, 228.2, and 315.4 ppm, respectively. Dose rate response functions had good linearity from 0.006 to 60 Gy/h for the 1.0% Nd-doped BSO sample and from 0.03 to 60 Gy/h for the other samples. [ABSTRACT FROM AUTHOR]

Nd-doped CaWO4 single crystals with dopant concentrations of 0.1, 0.5, and 1% were synthesized by the floating zone method. The transmission, photoluminescence, and scintillation properties were evaluated from ultraviolet to near-infrared (NIR) ranges. An emission peak due to transitions of the host was observed at 400 nm, and several sharp peaks originating from Nd3+ 4f–4f transitions were confirmed at 900, 1060, and 1300 nm. The quantum yields of 0.1, 0.5, and 1% Nd-doped samples were 70.7, 79.5, and 61.2%, respectively, when monitored, and excited wavelengths were 750–1500 nm and 590 nm. Decay times consistent with typical Nd3+ transitions were obtained when NIR ranges were monitored. Additionally, the energy transfer between the host and Nd3+ occurred according to the decay measurement. The relationship between X-ray irradiated dose rate and intensity in the range of NIR was investigated by combining the crystals with an InGaAs-photodiode. The lowest detectable dose rate retaining the linearity of the present crystals was 0.3–0.06 Gy/h. [ABSTRACT FROM AUTHOR]

Series of 1.0% Terbium (Tb)-doped rare-earth pyrosilicate single crystals including Lu2Si2O7 (LPS), Y2Si2O7 (YPS), Gd2Si2O7 (GPS), and La2Si2O7 (LaPS) have been prepared by the floating-zone method. After the phase confirmation by powder X-ray diffraction, the properties are measured on both photoluminescence and scintillation aspects, including the photoluminescence emission contour graph and decay times, X-ray induced scintillation spectra and decay times, afterglow profiles, and the recently developed pulse height spectra for scintillators with millisecond decay time. The results indicate the multiple emissions from Tb3+ 4f-4f transition with the dominant emission at 540 nm (5D4 → 7F5) on both ultraviolet and X-ray excitation with the decay time around 2.6–5.6 and 1.3–3.2 ms, respectively. Under the γ-ray irradiation from 137Cs, the Tb-doped LPS, YPS, GPS, and LaPS have presented scintillation light yields of 20,700, 29,600, 95,600, and 47,700 ph/MeV with ±10%, respectively, which considerably very high among the oxide scintillators. [ABSTRACT FROM AUTHOR]

Sm-doped SrCl2 crystals were prepared, and the scintillation properties such as emission spectra, decay profiles, and pulse height were investigated. Under X-ray irradiation, a broad band can be observed at 680 nm, which indicates that the major origin is due to 5d-4f transitions of Sm2+. The decay curve is approximated by one exponential function with a decay time of 10 μs, and the decay time constant is typical for Sm2+. From the pulse height of 137Cs γ-rays, 0.1% Sm:SrCl2 shows a light yield of 33,000 photons/MeV. [ABSTRACT FROM AUTHOR]

Five samples of lanthanum pyrosilicate (La2Si2O7) single crystals with 0.5–10.0% Praseodymium (Pr)-doping concentrations were synthesized by the floating-zone method. Photoluminescence and scintillation properties of these crystals were investigated in this study for the first time. The multiple emissions from electron transitions of Pr3+ were observed on both a photoluminescence emission map and scintillation spectra, including the desired emission band of Pr3+ 5d–4f transition at 250–310 nm. The major photoluminescence and scintillation decay times were approximately 19 and 26 ns, respectively. When compared with commercial scintillators such as Tl-doped cesium iodide (CsI), the Pr-doped La2Si2O7 samples presented a respectively low afterglow level of 32 ppm after 20 ms of X-ray irradiation. Under 662 keV γ-ray irradiation from 137Cs, the 3.0% Pr-doped La2Si2O7 sample presented a scintillation light yield of 3200 ph/MeV, which was the best value among the tested samples. [ABSTRACT FROM AUTHOR]

ZnO translucent ceramics were synthesized by spark plasma sintering. To improve photoluminescence (PL) and scintillation properties caused by mainly oxygen vacancies in addition to some kinds of other defects, the synthesized samples were annealed at the temperature range from 600 to 800 °C in steps of 50 °C in the air. All the ZnO samples showed PL and scintillation at around 500 nm with the decay time constants of several microseconds order. After the annealing, the absorption due to oxygen vacancies was decreased, and PL quantum yields (QYs) and scintillation light yields (LYs) were improved in comparison with the as-prepared sample. Among all the samples, the ZnO translucent ceramic annealed at 750 °C showed the highest PL QY (25.1%) and LYs (44,200 ph/5.5 MeV-α and 30,500 ph/MeV). [ABSTRACT FROM AUTHOR]

Fluorescent Ag-doped ZnS nanoparticles have been prepared and used as scintillators for detecting ionizing radiation. Results demonstrate a linear relationship between emitted luminescence and the fluence of alpha particles. These results suggest that Ag-doped ZnS nanoparticles alone could be used as solid scintillators for specific environmental and medical applications. This study deals with the investigation of some physical characteristics of hydrothermal synthesized Ag-doped ZnS nanoparticles (NPs) using different techniques. XRD analysis clear that the prepared materials have a cubic phase. Direct energy gap has been investigated using Diffuse Reflectance Spectroscopy (DRS) and well-known Kubelka–Munk function (F(R)). The energy gap is equal to 3.47 eV. Also, for PL decay, the time constant observed for decay at 480 nm is 130.6 ns for fast component and 2611.4 ns for slow component. For studding the performance of the scintillation materials, a charged particle irradiation system was designed and constructed to examine the response of a commercial and native ZnS scintillator for alpha particles. Also, Pulse height spectrum of alpha particles and gamma rays has been investigated. Enhancing the PL emission of doped ZnS is one of the paper's achievements. [ABSTRACT FROM AUTHOR]

We evaluated the photoluminescence (PL), scintillation, and dosimetric properties of Ce–doped Mg2SiO4 single crystals. As the PL and optically-stimulated luminescence (OSL) properties, the Ce–doped Mg2SiO4 showed the emission from 5d to 4f transitions of Ce3+. In the scintillation and thermally-stimulated luminescence (TSL) properties, two emission peaks due to Ce3+ and defect centers were observed. The Ce–doped Mg2SiO4 showed OSL by stimulating at 600 nm and TSL by heating at 50, 160, 195, and 370 °C. In OSL, linearly proportional responses were confirmed from 10 mGy for the 0.5 and 1% Ce–doped samples to 100 mGy for the 0.1% Ce–doped sample. In TSL, the undoped and Ce–doped samples had the linearity response from 100 to 0.01 mGy, respectively. [ABSTRACT FROM AUTHOR]

Scintillators emit visible luminescence when irradiated with X-rays. Given the unlimited tissue penetration of X-rays, the employment of scintillators could enable remote optogenetic control of neural functions at any depth of the brain. Here we show that a yellow-emitting inorganic scintillator, Ce-doped Gd3(Al,Ga)5O12 (Ce:GAGG), can effectively activate red-shifted excitatory and inhibitory opsins, ChRmine and GtACR1, respectively. Using injectable Ce:GAGG microparticles, we successfully activated and inhibited midbrain dopamine neurons in freely moving mice by X-ray irradiation, producing bidirectional modulation of place preference behavior. Ce:GAGG microparticles are non-cytotoxic and biocompatible, allowing for chronic implantation. Pulsed X-ray irradiation at a clinical dose level is sufficient to elicit behavioral changes without reducing the number of radiosensitive cells in the brain and bone marrow. Thus, scintillator-mediated optogenetics enables minimally invasive, wireless control of cellular functions at any tissue depth in living animals, expanding X-ray applications to functional studies of biology and medicine. Scintillators emit visible luminescence when irradiated with X-rays and may enable remote optogenetic control of neurons deep in the brain. The authors inject an inorganic scintillator to activate and inhibit midbrain dopamine neurons in freely moving mice by X-ray irradiation to modulate place preference behavior. [ABSTRACT FROM AUTHOR]

Photoluminescence and scintillation properties of undoped and Eu-doped 20CsCl–20BaCl2–60ZnCl2 (CBZ) glasses were investigated. The Eu-doped CBZ glasses indicated photoluminescence and scintillation with two emission peaks around 420 and 610 nm due to the 5d–4f transition of Eu2+ and the 4f–4f transition of Eu3+, respectively. The undoped CBZ glass showed emission peaking around 500 nm under excitation at 130 nm, and the possible emission origin would be self-trapped excitons (STEs). From measurements at low temperatures, the 0.3% Eu-doped CBZ glass shows an emission peak around 420 and 450–700 nm, and they would be considered to be the 5d–4f transition of Eu2+ and STEs, respectively. [ABSTRACT FROM AUTHOR]

(C6H5C2H4NH3)2Pb1−xZnxBr4 (x = 0.05, 0.1, and 0.25) single crystals were fabricated as a two-dimensional quantum-confined scintillator by the poor-solvent diffusion method. In the photoluminescence (PL) emission map, two emission peaks due to the excitons in the inorganic layer were observed at around 410 and 440 nm. The PL quantum yields of x = 0.05, 0.1, and 0.25 samples were 21.7, 25.3, and 21.0% with typical errors of ± 2%, respectively. By measuring scintillation spectra under X-ray irradiation, the emission peak due to free excitons can be observed at around 440 nm. According to the pulse-height spectra under 137Cs γ-ray (662 keV) irradiation, the light yields of x = 0.05, 0.1, and 0.25 samples were about 15,100, 17,800, and 14,100 ph/MeV with experimental error of ± 10%, respectively. [ABSTRACT FROM AUTHOR]

The local structure around the dopant atom in Nd(8 mol%):LaF3 single‐crystal scintillator is analyzed by X‐ray fluorescence holography experiments in combination with a sparse modeling algorithm. The average local environment of Nd is reconstructed up to large distances of about 12 Å and confirms a substitution of La atoms with Nd with only small crystal lattice distortions. The experimental findings are substantiated by comparison with reference data from La holograms and with computationally generated holograms based on a model structure of the dopant site. [ABSTRACT FROM AUTHOR]

Ce-doped RE3Al5O12 (Ce:REAG, RE=Tb, Dy, Ho, Er, Tm and Yb) single crystals were synthesized by the optical Floating Zone method. The transmittance is approximately 80% in all the samples, and absorptions by rare-earth ions were observed. Under X-ray irradiation, Ce:TbAG, Ce:DyAG, Ce:HoAG and Ce:TmAG exhibit scintillation signals with a broad emission band around 500–700 nm, which is attributable to the 5d–4f transitions of Ce3+. Several emission peaks due to F+ centers and 4f–4f transitions of trivalent rare-earth ions are also observed in some samples. In afterglow properties, Ce:Tb3Al5O12 and Ce:Yb3Al5O12 showed better afterglow levels than the other samples. [ABSTRACT FROM AUTHOR]

Ce-doped CaHfO3 crystals were synthesized by the floating zone method, and the photoluminescence and scintillation properties were evaluated. The crystals exhibit photoluminescence peaking at 440 nm, and the decay time constants are typical value due to the 5d-4f transition of Ce3+. The X-ray-induced scintillation decay time curves indicate short decay time constant around 15-35 ns. From the pulse height spectra under 57Co (122 keV) gamma-ray irradiation, the scintillation light yields are estimated; and, the 0.3% Ce-doped sample shows the highest light yield of approximately 8100 ph/MeV among the samples. The light yield is comparable with that of Bi4Ge3O12 and MHfO3 (M = Ba, Sr or Ca) which is a scintillator with high density. [ABSTRACT FROM AUTHOR]

Abstract We have investigated scintillation and thermoluminescence properties of the 20SrO-20BaO-40Nb 2 O 5 -20P 2 O 5 (SBNP) glass and glass-ceramics containing Sr 0.5 Ba 0.5 Nb 2 O 6 crystallites. The SBNP glasses were prepared by a conventional melt-quenching method. The obtained glasses were annealed at various temperatures and holding times for nucleation and growth of nanocrystallites. X-ray diffraction patterns revealed that samples were either glass or glass-ceramic containing Sr 0.5 Ba 0.5 Nb 2 O 6 nanocrystallites, and heat treatments at higher temperatures and longer holding times have promoted the crystallization. Furthermore, radioluminescence and TL intensities were higher for the glass-ceramics than glass; thus, efficient luminescence can be yielded in glass-ceramics. [ABSTRACT FROM AUTHOR]

We have developed CsBr transparent ceramics doped with various concentrations of Tl (0.01, 0.1, 0.2, 0.3 and 0.5 mol%) by spark plasma sintering and then investigated for scintillator applications. Regarding the scintillation properties, all the samples showed emission peaking around 360 nm due to 3P1 → 1S0 transitions of Tl+ ion. In addition, all the samples showed emission due to off-center self-trap exciton, which appeared around 490 nm. Among the present samples, the 0.2% Tl-doped sample showed the highest light yield (22,000 photons/MeV) under 137Cs exposure. Moreover, the scintillation response demonstrated a good linearity with gamma-ray energies of 109Cd, 57Co, 133Ba, 22Na and 137Cs sources. [ABSTRACT FROM AUTHOR]

Strontium aluminoborate glasses with different concentrations of Ce (0, 0.01, 0.05, 0.1 and 0.5 mol%) were synthesized by the conventional melt-quenching technique. After the synthesis, photoluminescence (PL), scintillation and dosimetric properties of the samples were evaluated systematically. In the photoluminescence and scintillation spectra, a sharp peak around 370 nm due to the 5d-4f transitions of Ce was observed. The 0.05% Ce-doped sample showed the highest intensity in PL and scintillation among the samples investigated. The 0.01–0.1% Ce-doped samples also showed thermally-stimulated luminescence (TSL) with a glow peak of around 90 °C after X-ray irradiation. The TSL response of 0.01–0.05% Ce-doped samples increased monotonically with X-ray dose over a dose range of 10 − 1 –10 4 mGy. [ABSTRACT FROM AUTHOR]

In this study, we have synthesized Sr(PO) glasses non-doped and doped with Ce (0.01, 0.05, 0.1, 1.0 and 3.0 mol%) prepared by the conventional melt-quenching method and investigated the optical properties [transmittance spectra, photoluminescence (PL) spectra, PL excitation spectra and PL decay times], scintillation properties with X-rays (scintillation spectra, scintillation decay times) and thermally-stimulated luminescence (TSL) properties (glow curves and dose response functions). The PL spectrum of the Ce-doped samples consist of an intense emission band due to the 5d-4f transitions of Ce ion peaking at 350 nm. The decay time of the corresponding emission was 32-37 ns depending on the Ce concentration. The samples also showed scintillation with X-ray having a spectrum of an intense emission band peaking at 350 nm due to the Ce ions, and decay time was 34-217 ns. The TSL glow peaks were observed at 190 and 450 °C for the Ce-doped glasses, and the dynamic range was confirmed at least over a three orders of magnitude 10-10 mGy. [ABSTRACT FROM AUTHOR]

BaSiO:Eu single crystals with different Eu concentration of 0.5, 1.0 and 2.0 % were grown by the floating zone method. In the photoluminescence and scintillation spectra, a broad emission band appears around 560 nm due to 5d-4f transitions of Eu, and the decay time constants are around 300 ns which is a typical time constant of Eu. From the pulse height spectrum, relative light yield under Cs γ-ray irradiation of the 1.0 % Eu-doped sample is ~8100 ph/MeV, and the optimum Eu concentration in this material are around 1.0 %. [ABSTRACT FROM AUTHOR]

Abstract: Dopant free eutectic scintillators 6LiF–SrF2 and 6LiF–CaF2 were developed by the vertical Bridgeman method for the purpose of thermal neutron detection. The molar ratio of LiF and Ca/SrF2 was 4:1 on its eutectic composition. The α-ray induced radioluminescence spectra of the scintillators showed intense emission peak at 300nm due to the emission from the self-trapped exciton in Ca/SrF2 layers. When the samples were irradiated with 252Cf neutrons, 6LiF–SrF2 and 6LiF–CaF2 exhibited the light yields of 4700 and 9400ph/n, respectively. Scintillation decay times of 6LiF–SrF2 and 6LiF–CaF2 were accepted for scintillation detectors, 90 and 250ns, respectively. [Copyright &y& Elsevier]

Abstract: Luminescence and scintillation properties of Tm3+ 0.1–15% doped CaF2 crystals were systematically investigated. The crystals were grown by a simple solidification method which allowed us to obtain single crystals conveniently. In X-ray induced radio luminescence spectra, the luminosity of the self-trapped-exciton (STE) emission of CaF2 at 270nm decreased with increasing of Tm3+ concentration. The Tm3+ 5d-4f transition based emission lines appeared at 175nm (4f115d high spin state (HS)→ 3H6) and at 165nm (low spin state (LS) to 3H6). Pulse height spectra were measured under α-ray irradiation by using vacuum ultra-violet (VUV) sensitive photomultiplier tube (PMT) R8778 and Tm3+ 0.1% doped specimen exhibited the highest light yield. [Copyright &y& Elsevier]

Abstract: Capability of thermal neutron detection was examined for LiCaAlF6 (LiCAF) scintillators doped with 3d-transition metal ions. Their radioluminescence spectra were measured with an 241-Am source to simulate 6Li(n, α)3H reaction. The sufficiently intense radioluminescence was observed for the Mn, Co and Cu dopants, while only a weak one was observed for Ti, V, Fe and Ni. A Mn doped LiCAF crystal, which showed the highest radioluminescence intensity, was coupled with a Si avalanche photodiode for the examination of its neutron response. It was confirmed that the average current of the photodiode clearly increased under excitation with 13.5 meV neutron flux. [Copyright &y& Elsevier]

LiCaAlF6 scintillators are one of the attractive scintillators for neutron detection. To reduce the effect on gamma-rays, the Ce doped LiCaAlF6 scintillators can discriminate the neutron and gamma-ray events based on the pulse shape discrimination technique. To apply the scintillators for the oil logging, the high temperature characteristics must be investigated. In this paper, the temperature dependence of the neutron-gamma discrimination based on pulse shape discrimination technique in the Ce:LiCaAlF6 scintillator is investigated as one of the high temperature characteristics. The property of pulse shape discrimination in the Ce:LiCaAlF6 has small temperature dependence ranging from 25^\circC to 150^\circC. We concluded that the Ce:LiCaAlF6 scintillators can discriminate neutron and gamma-ray events under high temperature condition up to 150^\circC. [ABSTRACT FROM PUBLISHER]

Abstract: In order to develop novel vacuum ultra violet (VUV) emitting scintillators, we grew Nd 0.5%, Tm 0.5%, and Er 0.5% doped LuF3 scintillators by the μ-pulling down method, because LuF3 has a very wide band gap and Nd3+, Tm3+, and Er3+ luminescence centers show fast and intense 5d–4f emission in VUV region. Transmittance and X-ray induced radioluminescence were studied in these three samples using our original spectrometer made by Bunkou-Keiki company. In the VUV region, transmittance of 20–60% was achieved for all the samples. The emission peaks appeared at approximately 180, 165, and 164nm for Nd3+, Tm3+, and Er3+ doped LuF3, respectively. Using PMT R8778 (Hamamatsu), we measured their light yields under 241Am α-ray excitation. Compared with Nd:LaF3 scintillator, which has 33 photoelectrons/5.5MeV α, Nd:LuF3 and Tm:LuF3 showed 900±90 and 170±20ph/5.5MeV-α, respectively. Only for the Nd doped one, we can detect 137Cs 662keV γ-ray photoabsorption peak and the light yield of 1200±120ph/MeV was measured. We also investigated their decay time profiles by picosecond pulse X-ray equipped streak camera, and the main decay component of Nd:LuF3 turned out to be 7.63ns. [Copyright &y& Elsevier]

Abstract: Ce 1%, Eu 1%, and Eu 2%-doped LiSrAlF6 (LiSAF) single crystals were grown by the micro-pulling-down method for thermal neutron applications. The crystals were transparent, 2.0 mm in diameter and 20–40 mm in length. Neither visible inclusions nor cracks were observed. Their transmittance spectra were measured. The strong absorption lines were observed at 200, 240, and 300 nm for Ce:LiSAF due to Ce3+ 4f–5d transition. In Eu:LiSAF, 200 (4f–5d) and 300 (4f–4f) nm absorption lines were detected. The samples demonstrated strong emission peaks at 300 nm (Ce:LiSAF) and 370 nm (Eu:LiSAFs) when they were irradiated with 241Am α-rays simulating the α-particles from the 6Li(n, α) reaction. Thermal neutron responses were examined under 252Cf irradiation. The absolute light yield of Ce, Eu 1%, and Eu 2% crystals were 3400, 18000, and 30000 ph/n, respectively. Main components of the scintillation decay time of Ce, Eu 1%, and Eu 2%-doped LiSAFs were 63, 1293, and 1205 ns. [Copyright &y& Elsevier]

Abstract: Thermal neutron imaging with Ce-doped LiCaAlF6 crystals has been performed. The prototype of the neutron imager using a Ce-doped LiCaAlF6 scintillating crystal and a position sensitive photomultiplier tube (PSPMT) which had 64 multi-channel anode was developed. The Ce-doped LiCaAlF6 single crystal was grown by the Czochralski method. A plate with dimensions of a diameter of 50×2mm2 was cut from the grown crystal, polished, and optically coupled to PSPMT by silicone grease. The 252Cf source (<1MBq) was sealed with 43mm of polyethylene for neutron thermalization. Alphabet-shaped Cd pieces with a thickness of 2mm were used as a mask for the thermal neutrons. After corrections for the pedestals and gain of each pixel, we successfully obtained two-dimensional neutron images using Ce-doped LiCaAlF6. [Copyright &y& Elsevier]

Abstract: Eu2+ 0.1, 0.5, 1, and 2mol% doped LiCaAlF6 single crystalline scintillators were grown by the micro-pulling down (μ-PD) method. Eu2+ 2mol% doped LiCaAlF6 was also prepared using the Czochralski method. In the transmittance spectra, 4f–5d absorption lines appeared around 200–220 and 290–350nm. An intense emission at 375nm due to Eu2+ 5d–4f transition was observed under 241Am α-ray excitation. When 252Cf excited pulse height spectra were measured, Eu 2% doped one showed the highest light yield of 29,000ph/n with 1.15μs decay time. Using the 2inchφ Czochralski grown one coupled with the position sensitive photomultiplier tube covered by Cd mask with various size (1, 2, 3, and 5mm) pin holes, thermal neutron imaging was examined. As a result, the spatial resolution turned out to be better than 1mm. [Copyright &y& Elsevier]

Abstract: Sixty millimeter diameter single crystal of Nd3+ doped LiLuF4 was successfully grown by the Czochralski technique. No remarkable absorption due to unfavorable impurities was observed from optical absorption measurements in the vacuum ultra-violet spectral region. The high crystallinity and homogeneous luminescence characteristics were found from X-ray rocking curve and cathode-ray luminescence respectively. X-ray excited luminescence spectrum was measured and the significant 4f25d–4f3 luminescence at 182nm was observed in the grown crystal. The pulse height spectrum was taken upon γ-ray irradiation. As a result, the grown crystals demonstrated sufficient response to the γ-ray showing the light yield of 420±30photons/MeV. The decay curve under α-ray irradiation was also investigated and described by two component decay kinetics which consists of the decay constants of 34 and 450ns. [Copyright &y& Elsevier]

Abstract: We developed a modified micro-pulling-down (μ-PD) method for the crystal growth of halide materials with highly hygroscopic nature. A removable chamber system of the modified μ-PD method that can enter a globe box filled with Ar gas enabled to handle starting materials, set up a crucible and hot zone, grow a single crystal from the melt and take out a grown crystal without exposing to outside atmosphere. By the modified μ-PD method, CeCl3 and Ce 1% doped LaBr3 single crystals, which were famous as scintillator with high light yield and energy resolution were grown. Grown CeCl3 and Ce:LaBr3 single crystals indicated high transparency and they have no visible cracks and inclusions. In photoluminescence measurements, emission peak around 365nm was observed for CeCl3 single crystal and Ce:LaBr3 single crystal indicated two emission peaks around 360 and 380nm, which originated from 5d–4f transition of Ce3+ ion. [Copyright &y& Elsevier]

Abstract: Nd3+ doped CaF2 single crystal scintillator has been investigated. We tried to grow 1%, 5%, 10%, 20%, 30% and 40% Nd3+ doped CaF2 single crystals by the simple melt-solidifying method. Powder X-ray diffraction (XRD) patterns were measured to identify the phase of all the samples. The XRD patterns of all the samples were similar to CaF2. Those samples are compared in terms of their X-ray-excited radioluminescence spectra, transmittance, α-ray-excited decay time and light yield. When the X-ray is used for excitation, luminescence is observed in the VUV region. Transmittance of the crystals is more than 70% at wavelengths longer than about 180nm. In the decay kinetics, the fast components of the samples are distributed in less than 25ns time range and the slow components of sample are distributed in more than 90ns. These decay times became shorter with increasing Nd3+ concentration. They are related to the Nd3+ 5d-4f VUV emission. The light yields of samples are distributed in 5–2500 photon/5.5MeV α-ray and decrease with increasing Nd3+ concentration. [ABSTRACT FROM AUTHOR]

Abstract: Nd concentration dependence on the scintillation properties of Nd x Ba1− x F2+ x (x =0.001–0.5) crystals were investigated. From X-ray induced emission spectra, the intensity from an intrinsic luminescence of BaF2 including core-valence luminescence and self-trapped-exciton (STE) emission were decreased with an increase of Nd concentration. Decay times under 241Am α-ray excitation were evaluated by the Photomultiplier Tube (PMT) Hamamatsu R8778 that was sensitive across the vacuum ultra-violet (VUV) and visible wavelength range. The average decay times indicated that Nd doped BaF2 with lower Nd concentration has obviously slower decay times than that of samples with higher Nd concentration because the decay time of STE emission was slower than that of the core–valence luminescence in BaF2 and the emission of 5d–4f transition on Nd3+. The light yield of fast Nd3+ 5d–4f luminescence was quite lower than STE emission of BaF2. [ABSTRACT FROM AUTHOR]

Abstract: Two-inch diameter Nd3+ doped LaF3 single crystals were successfully grown by the Czochralski technique. No remarkable absorption due to unfavorable impurities or color centers was observed from optical absorption measurements in the vacuum ultra-violet spectral region. The high crystallinity and homogeneous Nd3+ distribution were found from X-ray rocking curve and chemical composition analysis, respectively. X-ray excited luminescence spectrum was measured and the significant 4f25d–4f3 luminescence at 173nm was observed in the grown crystal. The pulse height spectrum and scintillation decay curves were taken upon γ-ray irradiation. As a result, the grown crystals demonstrated sufficient response to the γ-ray, the light yield of 140±30photons/MeV, and fast scintillation decay of 7.6ns. [Copyright &y& Elsevier]

In order to develop novel scintillating materials, we grew 0.5 mol%, 1 mol%, and 3 mol% Nd-doped LuLiF4 scintillators by the micro-pulling down method, because LuLiF4 has a very wide band gap and Nd3+ shows fast and intense 5d-4f emission as a luminescence center. The transmittance and emission peaks were examined in these three samples by using our original spectrometer made by Bunkou-Keiki Company. At wavelengths longer than 180 nm, approximately 60-80% transmittance with three absorption peaks around 140, 160 and 175 nm and emission peak at approximately 180 nm were observed for all the crystals. Light yields and decay time constants of the samples irradiated by 241Am αray were measured using photomultiplier tubes R8778 (Hamamatsu). The light yield of the 1 mol% doped LuLiF4 was 700 photons/ 5.5MeV α that is much greater than that of Nd:LaF3 scintillator (100 photons/5.5MeV α). As for decay time profiles, the main component of Nd:LuLiF4 was 12 ns in the case of α-ray irradiation. 137Cs 662 keV γ-ray photoabsorption peak was detected in 1 mol% doped LuLiF4 only, and the light yield was 300 ph/MeV. [ABSTRACT FROM AUTHOR]

Doubly doped LaF3:Er, Nd scintillation crystals were grown by modified micropulling-down method. The Er codoping was chosen to enhance the energy transfer from the host lattice to the Nd3+ luminescence center via the 5d-levels of Er3+, which can be enabled by the overlap of Er3+ 5d-4f emission spectrum with the Nd3+ 4f-5d absorption. However, no relevant energy transfer was found by photo- and radioluminescence spectra measurements. The reasons of no significant positive effect of Er codoping are discussed. [ABSTRACT FROM AUTHOR]

Transparent K3LuF6 single crystals doped with rare earth ions were successfully grown by the micro-pulling down method (µ-PD). X-ray diffraction measurements showed that the as-grown crystals possess monoclinic structure with P21 /n space group. The radio- and photoluminescence spectra of the grown crystals were measured in the vacuum ultraviolet (VUV) and ultraviolet (UV) region. The intrinsic luminescence of K3LuF6 was observed at 163 and 200 nm. Nd-doped crystals displayed, in contrast, emission at 183 nm, due to the Nd3+ 5d-4f transition, and their radioluminescence intensity increases with increasing Nd concentration. Tm:K3LuF6 showed high emission intensity at 190 nm in the radio- and photoluminescence spectra (λexc = 155 nm). Moreover, the emission intensity of 0.5%Tm:K3LuF6 was higher than that of 5%Tm:K3LuF6. Concerning Er:K3LuF6, the emission at 165 nm was detected for the 0.5%Er:K3LuF6. [ABSTRACT FROM AUTHOR]

Because there is an overlap of the 5d-4f emission transition of Tm3+ and absorption transition of Nd3+, an energy transfer between Nd3+ and Tm3+ in LaF3 was supposed to enhance the efficiency of the previously studied Nd:LaF3 scintillation material. In this study, 0.1% and 1%Tm, Nd, and Tm, Nd codoped LaF3 single crystals scintillators were developed using micro-pulling down method (µ-PD), and their optical properties in the vacuum ultraviolet (VUV) region were evaluated. Tm3+ codopant did not show positive contribution to VUV emission, but energy transfer between Nd3+ and Tm3+ cannot be excluded, although the photoluminescence spectra point just to a competition for energy between the two ions. Gamma-ray response was also measured using the pulse-height distribution measurement. [ABSTRACT FROM AUTHOR]

Abstract: Nd3+ 1%, 5% and 10% doped BaF2 single crystals were grown by the micro-pulling down method. Photoluminescence properties, including excitation and emission spectra and luminescence decay were measured under synchrotron radiation excitation at the Superlumi station in HASYLAB at DESY (Hamburg, Germany). The Nd3+ related 5d-4f emission lines peaking around 180 nm, 230 nm, and 260 nm, identified as the 5d–4Ij, 5d–4Fj, and 5d–2Gj transitions, were observed under 140–168 nm excitation. In photoluminescence decay under the 160 nm excitation, the dominant component decay time is about 12, 2.5 and 1.2 ns for Nd3+ 1%, 5% and 10% concentration, respectively. The decay time shortening is explained by the concentration quenching effect. Transmittance of Nd1% sample is about 80% for wavelengths above 185 nm. Finally, gamma-ray responses, non-proportionality and energy resolution of Nd1% sample were compared with the undoped BaF2 scintillator. The light yield of the Nd1%:BaF2 is about 93% of that of undoped BaF2. ©2009 Elsevier Ltd. All rights reserved. [Copyright &y& Elsevier]

Ce2% : 6LiCaAlF6 (6LiCAF) single crystal (nominal composition) with 2 mm in diameter and 50 mm in length was grown by the micro-pulling-down method. Emission from the perturbed Ce3+ centers was observed in an α-ray excited radioluminescence. The neutron response was compared with Li-glass (GS20, Saint-Gobain) using 252Cf. The scintillation decay time of Ce2% 6LiCAF is 38 nsec, which is twice as short as that of GS20. Using Hamamatsu photomultiplier H7416 the photoelectron yield about a half of that of GS20 has been measured for the Ce : 6LiCAF single crystal. Considering the light yield of GS20 (6000 phot/neutron) and the spectral correction due to the different emission peak position in both materials, the light yield of Ce : 6LiCAF single crystal is estimated about 4200 phot/neutron. [ABSTRACT FROM AUTHOR]

Sm-doped CaCl 2 , SrCl 2 , and BaCl 2 bulk crystals were synthesized using the conventional vertical Bridgman method, and the photoluminescence, radioluminescence, and detector properties were evaluated. The Sm-doped CaCl 2 , SrCl 2 , and BaCl 2 samples show a broad emission band at 750, 690, and 650 nm, respectively, which is attributable to the 5d-4f transitions of Sm2+. The pulse height spectra under 137Cs γ-rays (662 keV) show that the Sm-doped CaCl 2 and SrCl 2 exhibit 9300 and 33000 photons/MeV, respectively. These samples can be used for γ-ray measurements in the red to NIR region. • Sm-doped CaCl 2 , SrCl 2 , and BaCl 2 crystals were synthesized using the conventional vertical Bridgman method. • The photoluminescence, radioluminescence, and detector properties were evaluated. • The samples show a broad emission band at 600–800 nm due to Sm2+. • Sm-doped CaCl 2 , SrCl 2 , and BaCl 2 exhibit light yield of 9300, 33000, and 16000 photons/MeV, respectively. [ABSTRACT FROM AUTHOR]

LaMgAl 11 O 19 :Er single crystals were examined as candidates for scintillators emitting near-infrared luminescence, and their radioluminescence and scintillation detector characteristics were assessed. Upon exposure to X-ray, distinct emission peaks appear at ∼550 and ∼1540 nm and are attributable to Er3+ ions. The decay curves also exhibited characteristic decay times associated with Er3+ ions. Particularly, the 3% Er-doped sample showed a discernible linearity in the dynamic range of dose rate from 1 to 50,000 mGy/h, indicating the potential utility in applications requiring precise and reliable radiation measurements. • Er-doped LaMgAl 11 O 19 crystals were synthesized by the floating zone method. • The samples show a broad emission band at 380 nm due to host and sharp peaks at 550 and 1540 nm due to Er3+. • The 3% Er-doped sample showed a good linearity in the dynamic range of dose rate from 1 to 50,000 mGy/h. [ABSTRACT FROM AUTHOR]

Borate glasses are considered to be host materials for thermoluminescent phosphors owing to their high thermally-stimulated luminescence (TSL) sensitivity and low effective atomic number. Herein, we fabricated the Dy-doped B 2 O 3 –Al 2 O 3 –SrO glasses to develop the phosphors for radiation dosimetry, and investigated their photoluminescence (PL), scintillation and TSL properties, systematically. The Dy-doped samples showed clear emission peaks at 480 and 570 nm due to 4f-4f transitions of Dy3+ in PL, and the 0.5 % Dy-doped sample exhibited the highest quantum efficiency of 0.24 under excitation wavelength of 350 nm among the sample tested. The decay time constants of the Dy-doped samples were 0.25–0.84 ms, which were typical values for the 4f-4f transition of Dy3+. In scintillation, the Dy-doped samples showed emissions with sharp peaks at 480 and 570 nm with the decay time constants of 0.51–0.86 ms due the 4f-4f transitions of Dy3+. The scintillation intensity of the 0.5 % Dy-doped sample was the highest among the samples investigated. Furthermore, the Dy-doped samples exhibited TSL with a main glow peak at approximately 90 °C after X-ray irradiation of 10,000 mGy, and the dynamic range of the 0.1–1.0 % Dy-doped samples was found to be 0.1–10,000 mGy. [ABSTRACT FROM AUTHOR]

We have tested high-temperature responses of prototype neutron detectors equipping Ce-doped lithium silicate glass (GS20), LiCaAlF 6 :Ce, LiCaAlF 6 :Eu, LiCaAlF 6 :Ce, Na, and LiCaAlF 6 :Eu, Na. These detectors were prepared by coupling of the scintillators to a photomultiplier tube (PMT) for high-temperature environments (R1288, Hamamatsu). In the pulse height spectra under thermal neutron irradiation in the temperature range from 25 °C to 150 °C, peak heights of all the samples decreased with increasing temperatures. The decreasing rates for the peak heights of LiCaAlF 6 scintillators were lower than that of GS20. The LiCaAl F 6 scintillators can be used in the temperature range from 25 °C to 150 °C. [ABSTRACT FROM AUTHOR]

Abstract Eu-doped Ba x Sr 1- x Al 2 O 4 (x = 0, 0.1, 0.3 and 0.5) single crystals were synthesized by the floating zone method and then characterized for scintillation applications. All the crystal samples exhibit photoluminescence and scintillation with a broad emission around 510 nm. The decay time constants of the latter emission are typical for the 5d-4f transitions of Eu2+. From the pulse height spectra measured under 137Cs gamma-ray, the estimated light yields of Eu:SrAl 2 O 4 , Eu:Ba 0.1 Sr 0.9 Al 2 O 4 Eu:Ba 0.3 Sr 0.7 Al 2 O 4 , and Eu:Ba 0.5 Sr 0.5 Al 2 O 4 crystal samples are 42,000, 30,000, 22,000 and 20,000 photons/MeV, respectively. The observed light yields are notably high, and the fact indicates that Eu:Ba 0.5 Sr 0.5 Al 2 O 4 crystals are good candidates of scintillator materials for gamma-ray measurements. Graphical abstract Image 1 Highlights • Eu-doped (Ba,Sr)Al 2 O 4 single crystals were synthesized by the floating zone method. • The samples exhibit PL and scintillation with a broad emission around 510 nm. • From pulse height spectra, the light yields of Eu:SrAl 2 O 4 and Eu:Ba 0.5 Sr 0.5 Al 2 O 4 crystals are 42,000 and 20,000 photons/MeV. [ABSTRACT FROM AUTHOR]

Abstract We examined the optical and luminescence properties of BaO-TiO 2 -SiO 2 (BTS) glasses and BTS glass-ceramics (GCs). The 40BaO-20TiO 2 -40SiO 2 (BTS40) GC obtained by heat treatment at glass transition temperature (T g) + 50 °C exhibited bulk crystallization, whereas surface crystallization was obtained for the 33.3BaO-16.7TiO 2 -50SiO 2 (BTS50) and 30BaO-15TiO 2 -55SiO 2 (BTS55) GCs by the same heat treatment. The photoluminescence (PL) excitation spectra changed depending on the chemical composition. After crystallization, the peaks of the PL and the scintillation spectra were blue-shifted, indicating the local coordination change of the Ti species. A large enhancement of X-ray induced scintillation was observed in the BTS40 system, though the precursor BTS40 glass exhibited lower scintillation intensity despite its higher effective atomic number (Z eff). Since the volume fraction of Ba 2 TiSi 2 O 8 crystallites in the BTS40 GC is higher than the other GCs, the enhancement in scintillation intensity reflects an increase in number density of emission centers in Ba 2 TiSi 2 O 8 crystallites after crystallization. Highlights • BaO-TiO 2 -SiO 2 glasses were prepared by a melt-quenching method. • Heat-treatment of glasses was performed at the T g + 50 °C to obtain the glass-ceramics. • Volume fraction of Ba 2 TiSi 2 O 8 decreased with increasing SiO 2 fraction. • Intensity of emission, especially X-ray scintillation, was affected by the Ba 2 TiSi 2 O 8 volume fraction in the glass-ceramics. [ABSTRACT FROM AUTHOR]

In this work, we have investigated optical and scintillation properties of 0.35–0.65% Ce:(Gd 0.32 Y 0.68 ) 3 Al 5 O 12 (Ce:GYAG) transparent ceramics prepared by the vacuum sintering method. Obtained samples showed high transmittance in the spectral region longer than 500 nm, and two strong absorption bands were clearly observed below 380 nm and between 400 and 500 nm due to the 4f-5d transitions of Ce 3+ . Under UV and X-rays, we have also observed emission due to the 5d-4f transitions of Ce 3+ which appeared around 500–700 nm. The emission decay profile of PL consisted of a single exponential decay component with the decay time of 62.7–64.1 ns while the scintillation decay profile was approximated by a second-order exponential decay function with the decay times of 87.3–100 ns and 1.14–1.32 μs. In addition, it has been revealed that 0.65% Ce:GYAG transparent ceramic showed a notable light yield of 18,000 ph/MeV and low afterglow (13 ppm). [ABSTRACT FROM AUTHOR]

We systematically investigated photoluminescence (PL), scintillation and dosimeter properties of rare-earth (RE) doped NaPO 3 -Al(PO 3 ) 3 (NAP) glasses. The NAP glasses doped with a series of RE ions (La-Yb, except Pm) with a consistent concentration (0.3 wt%) were prepared by the conventional melt-quenching method. The PL and scintillation decay time profiles showed fast (ns) and slow (μs or ms) components: the fast components from 15 to 100 ns were due to the host or 5d-4f transition emission, and the slow components from 15 μs to 5 ms were due to the 4f-4f transitions of RE. The thermally stimulated luminescence (TSL) was evaluated as a dosimeter property, and glow peaks appeared around 400 °C in all the samples. The TSL dose response function was examined in the dose range from 10 mGy to 10 Gy. Among the samples tested, Nd and Tb doped glasses showed higher signal by at least one order of magnitude than those of non-doped and other RE-doped samples. Over the dose range tested, the TSL signals are linearly related with the incident X-ray dose, showing a potential for practical applications. [ABSTRACT FROM AUTHOR]