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Functional possibilities of Pr:LuAG single crystal covered with plastic scintillators are demonstrated. Shift of luminescence wavelength of the hybrid scintillators towards the region of higher spectral sensitivity of photodetectors and radiation responses of the hybrid scintillators were investigated. The Pr:LuAG sample coated with bis-MSBPVD showed the better light output and energy resolution than the Pr:LuAG itself. Light output was increased up to 55% and energy resolution was also improved to 6.5%@662 keV using APD (Hamamatsu S8664-8220). In the case of MPPC (Hamamatsu S10362_33_050 3600 pixel-type), light output was increased up to 35% and energy resolution was also improved to 9.8%@662 keV. Decay curve of the Pr:LuAG sample coupled with the WLS was also measured and successfully modeled. [ABSTRACT FROM PUBLISHER]

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]

\ Pr\!\!\!\!:\!\!\!\!\! (\ Gd,\ Y)3({\ {Ga}},{\ {Al}})5 {\ {O}}12 single crystals were grown by the \mu-PD method with RF heating system. \ Pr^3+ 5d-4f emission within 300-350 nm, \ Pr^3+ 4f-4f emission within 480-650 nm and \ Gd^3+ 4f-4f emission at 310 nm are observed in \ Pr\!\!\!\!:\!\!\!\! (\ Gd,\ Y)3({\ {Ga}},{\ {Al}})5 {\ {O}}12 crystals. In order to determine light yield, the energy spectra were measured under 662 keV \gamma-ray excitation (^137\ Cs source), detected by a PMT H6521 (Hamamatsu). The light output of \ Pr1\%\!:\!\ Gd1 {\ {Y}}2{\ {Ga}}3{\ {Al}}2 {\ {O}}12 sample was of about one fifth of that of the Cz grown Pr:LuAG standard sample, i.e., around 4,000 photon/MeV. Two component scintillation decay shows the decay times (intensity) of 5.7 ns(5%), 38.7 ns (31%) and 187 ns (63%) using the PMT and digital oscilloscope TDS5032B detection. [ABSTRACT FROM PUBLISHER]

Radioluminescence properties of Nd doped KCaF3 single crystals were studied. X-ray excited luminescence spectra were measured in the vacuum ultraviolet (VUV) region by using a custom-made device filled with nitrogen atmosphere. As a result, VUV luminescence was observed at 190 nm. Radioluminescence intensity due to the core-valence luminescence (CVL) of KCaF3 decreased with increasing of Nd^3+ concentration. [ABSTRACT FROM PUBLISHER]

Pr\!\!\!\!\!:\!\!\!\!(Lu,Y)3({\ {Ga}},{\ {Al}})5O12 single crystals were grown by the micro-pulling down (\mu-PD) method. Luminescence and scintillation properties were measured. The substitution phenomenon in the Lu^3+ sites with Y^3+ and \ Al^3+ sites with \ Ga^3+ in garnet structure has been studied. Pr^3+ 5d-4f emission within 300–400 nm accompanied by weak Pr^3+ 4f-4f emission in 480–650 nm were observed in Ga 0–60 at.% substituted samples. Only Pr^3+ 4f-4f emission was observed in Ga 80 at.% substituted sample. The light yield of Pr1\%\!\!:\!\!Lu2Y1{\ {Ga}}2{\ {Al}}2O12 sample was almost the same as that of Cz grown Pr:LuAG standard. Two-component scintillation decay of 17.9 ns (93%) and 68.0 ns (7%) were obtained using the PMT and digital oscilloscope TDS5032B. Slower decay components were reduced by Ga and Y substitution in LuAG structure. [ABSTRACT FROM PUBLISHER]

Among the direct wide band-gap semiconductors, ZnO is an attractive scintillator for alpha particle monitoring. However, the undoped ZnO has a dominant slow luminescence around 500–600 nm due to lattice defects. In this study, the Mg-substituted ZnO ((Zn,Mg)O) single crystalline films with high crystallinity are investigated. Mg doping is found to improve the lattice order and suppress slow luminescent component around 500–600 nm. (Zn,Mg)O single crystalline films were grown by the Liquid Phase Epitaxy (LPE) method. Alpha-ray excited radioluminescence spectra of (Zn,Mg)O film show only one emission peak around 400 nm and decay time of a few nanoseconds. This emission is assigned to free exciton. Light yield of LPE grown (Zn,Mg)O film is evaluated of about 90% of BGO. [ABSTRACT FROM PUBLISHER]

Ce1%, 2% and 3% doped Gd3(Ga,Al)5 O12 (GAGG) single crystals were grown by the Cz method. Luminescence and scintillation properties were measured. Light yield change along the growth direction and effects of Ce concentration on scintillation properties in Ce:GAGG were studied. Ce^3+ 5d-4f emission within 520–530 nm was observed in the Ce:GAGG crystals. The Ce1%:GAGG sample with 3\times 3\times 1~mm size showed the highest light yield of 46000 photon/MeV. The energy resolution was 7.8%@662 keV. With increasing solidification fraction, the LY were decreased. It is proposed that the increase of Ga concentration along the growth direction is the main cause of the decrease of LY. The scintillation decay times were accelerated with increasing Ce concentration in the Ce:GAGG crystals. The scintillation decay times were 92.0 ns, 79.1 ns and 68.3 ns in the Ce1, 2 and 3% GAGG, respectively. [ABSTRACT FROM PUBLISHER]

We manufactured transparent optical ceramic of Pr 0.2–1% doped Lu3Al5 O12 (Pr:LuAG) by the sintering method. We compare its optical and scintillation properties with the single crystal counterpart grown by the conventional Czochralski method. So far the scintillation ceramic of Pr:LuAG appeared inferior to its single crystal analog especially in terms of light yield. However, in the present case our ceramic Pr 0.25%-doped sample exhibited by 20% higher light yield compared to single crystal under \gamma-ray excitation. Furthermore, in the ceramic sample the slower scintillation decay components were suppressed and the defect related host emission as well. The optimized technology of optical ceramics thus appears very competitive to single crystals and opens great practical prospectives for the former materials in the field of fast scintillators. [ABSTRACT FROM PUBLISHER]

The crystals of 0.1, 0.5, 1, and 3% Ho doped Lu3Al5O12 (Ho:LuAG) grown by the micro-pulling-down method were examined for their scintillation properties. At wavelengths longer than 300 nm, Ho:LuAG crystals demonstrated around 60% transparency with many absorption peaks attributed to Ho^3+ 4f^10-4f^10 transitions. When excited by ^241Am \alpha-ray to obtain radio luminescence spectra, broad host emission and four sharp Ho^3+4f^10-4f^10 emission peaks were detected in the visible region. Light yields and decay time profiles of the samples irradiated by ^137Cs\gamma-ray were measured using photomultiplier tubes R7600 (Hamamatsu). Ho 0.5%:LuAG showed the highest light yield of 3100 \pm 310 photons/MeV among the present samples. The decay time profiles were well reproduced by two components exponential approximation consisting of 0.5–1 \mus and 3–6 \mus. [ABSTRACT FROM PUBLISHER]

Fluoride single crystals have a wide band gap. Thus, we were interested in studying the scintillation properties of fluoride single crystals. We investigated the scintillation properties of fluoride crystals grown by the micro-pulling-down and annealing methods. The time required to grow crystals using these methods is lesser than that using conventional methods such as the Czochralski and Bridgman methods. Both ZnF2 and PbF2 exhibited small light outputs of less than 1,000 photons/MeV, while BaF2 and CeF3 exhibited light outputs of \sim6,000 and \sim2,000 photons/MeV, respectively. In addition, BaF2 is a well-known fast scintillator, but it also has a slow component. We tested a BaF2 crystal with a Ce/La co-dopant and observed the suppression of the slow component. [ABSTRACT FROM PUBLISHER]

In this study, we investigated the relation between crystallinity and scintillation properties of Pr:LuAG crystals grown by Czochralski (Cz) method. The crystallinity was determined as the dislocation density using the X-ray rocking curve technique. The scintillation pulse-height spectra were collected under 662 keV ^137Cs~\gamma\mathchar"702D ray excitation to evaluate the light yield and energy resolution. It was confirmed that both the light yield and energy resolution correlates with the crystalinity; however, the other factors also have an influence. [ABSTRACT FROM PUBLISHER]

(Lu0.1Y0.9)AlO3\!\!:\!\!Nd0.1\% crystal was grown by the \mu -PD method and pure YAP single crystal was prepared as a reference sample. Then, two annealing procedures were performed for each sample at 1350^\circC and 1500^\circC for 20 hours in oxygen atmosphere to improve the crystallinity and scintillation properties. The XRD results for all the samples were consistent with JCPDS data (#33-0041) and possessed a space group of orthorhombic Pbnm while no impurity peaks were observed. The FWHM values of X-ray rocking curve measurements of the as-grown crystals and the crystals annealed at 1500^\circC were 70 and 200 arcsec, respectively. It can be due to the onset of decomposition. In the transmittance measurements, intense absorption peaks were observed approximately at 240 and 290 nm and they were consistent with the bands for color centers: the two-electron F center and one-electron F^+ center, respectively. These absorptions were enhanced by Lu substitution. The radio-luminescence spectra show several emission peaks due to Nd^3+ 4f-4f transitions and the most intense of which were assigned to ^2 F(2)5/2-^{4} F5/2, ^2 F(2)5/2-^{4}G7/2 and ^2 F(2)5/2 -^{4}G9/2 transitions at 395, 540 and 550 nm, respectively. The light yield after annealing annealing was as high as 5025 \pm 500~(Nphe/\rm MeV) when using Si-APD (S8664). The scintillation decay time constants were evaluated to be 3.44–3.80 \mus for each sample. Afterglow upon X-ray excitation of the as-grown and annealed samples coupled with PIN Si-photodiode was found to be approximately 1200 and 1000 ppm after 100 ms. [ABSTRACT FROM PUBLISHER]

Ce:(Lu,Y)3(Ga,Al)5 O12 single crystals were grown by the \mu-PD method with RF heating system. In these crystals, Ce^3+ 4f-5d emission is observed within 500-530 nm wavelength. Emission peak shifts to shorter wavelength and the decay accelerates with increasing Ga concentration. In the case of Ce:Lu2 Y1(Ga,Al)5 O12 series,the Ce0.2% Lu2 Y1Ga3Al2 O12 crystal showed the highest emission intensity. In order to determine light yield, the energy spectra were measured under 662 keV ã-ray excitation (^137 Cs source) and detection by an APD S8664-55(Hamamatsu). The light yield was calibrated from Fe^55 direct irradiation peak to APD. The light yield of Ce0.2%: Lu2 Y1 Ga3 Al2 O12 sample was of about 30,000 photon/MeV. Dominant scintillation decay time was of about 50 ns. [ABSTRACT FROM PUBLISHER]

Nd and Tm-doped Lu-admixed \BaY2 \F 8 crystals were grown by micro-pulling-down method. Lu was added to modify the host matrix to suppress the unwanted energy transfer from exciton levels to the \Tm^3+ 4f-levels. It was found that low Tm and Nd codoping does not bring much improvement of the scintillation performance and that 1%Nd-doped \BaY 0.8\Lu1.2 \F 8 single crystal reached nearly the same scintillation efficiency as the \LaF 3\:Nd8\% one, which is known as a suitable candidate for a VUV scintillator. It is clear there is a considerable room for an optimization of this material by changing the Lu/Y ratio and increasing the content of Nd. On the other hand, very high Tm concentrations (around 20%) suppress the excitonic emission (and also the 4f-4f emission) while increasing the 5d-4f one significantly. [ABSTRACT FROM PUBLISHER]

Undoped and Cu^+-doped lithium aluminate LiAlO2 singe crystals have been grown using micro-pulling down (\mu-PD) technique. After cutting and polishing, optical properties and scintillation characteristics of the crystals were examined. From the transmittance measurements, Cu^+-doped crystal showed absorption band around 270 nm, which is corresponding to the transition between Cu^+3d^10 and 3d^94s states. Ultra violet emission peak appeared around 360 nm under 270 nm excitation. The emission decay time was calculated to be about 17.3 \mus. ^241Am 5.5 MeV alpha-ray excited radioluminescence spectra exhibited intense luminescence band at 360 nm due to the Cu^+3d^94s\mathchar"702D 3d^10 transitions. By the pulse height spectra ^252Cf neutron source excitation, the scintillation light output of Cu^+-doped LiAlO2 was found to be about 8700 ph/n. [ABSTRACT FROM PUBLISHER]

We have grown shape-controlled langasite-type crystals by the micro-pulling-down (μ-PD) method. Columnar shaped La3Ta0.5Ga5.5O14 (LTG), Ca3NbGa3Si2O14 (CNGS), Ca3TaGa3Si2O14 (CTGS), Sr3NbGa3Si2O14 (SNGS), and Sr3Ta- Ga3Si2O14 (STGS) crystals were grown using a Pt-Rh crucible with a 3-mm-diameter columnar die at the bottom. All grown crystals showed high transparency except for the peripheral area and diameter of approximately 3 mm. The chemical phases at the central parts of the grown crystals were identified as a single phase of langasite-type structure and their lattice parameters were almost the same as those of crystals grown by the Czochralski (Cz) method; however, some impurity phases were observed in the peripheral area. In X-ray rocking curve measurements, the grown crystals indicated equivalent crystallinity to the crystal grown by the Cz method. The piezoelectric constant d11 of the CNGS crystal was 3.98 pC/N; this value is well correlated with those of previous reports. [ABSTRACT FROM AUTHOR]

We grew column-shaped Sr3NbGa3Si2O14 (SNGS) and Sr3TaGa3Si2O14 (STGS) langasite-type piezoelectric single crystals by the micro-pulling-down (μ-PD) method. 3-mm-diameter SNGS and STGS crystals were grown using a Pt-Rh crucible with a 3-mm-diameter columnar die. According to X-ray rocking curve measurements, the grown crystals had crystallinity equivalent to that of crystals grown by the Czochralski (Cz) method. The crystals were single-phase materials with langasite-type crystal structure. The lattice parameters of the grown crystals were almost consistent with those of crystals grown by the Cz method. [ABSTRACT FROM AUTHOR]

Pr3+ doped LuYAP crystal was grown by the Czochralski method with 1 inch diameter and 10 cm length. In order to compare scintillation characteristics, Pr3+ doped YAP crystal was also grown by the micro-pulling-down method. Absorption spectra of them were measured and Pr3+ 4f → 45f5d and 4f2d → 4f absorption lines were observed at 230, 470, and 600 nm, respectively. In photoluminescence measurements, here excited by Xe lamp pulse of wavelength around 223, 250 and 280 nm emission lines due to Pr3+ 45fd → 4f transition were detected. When coupled with PMT R7600 and irradiated by gamma-rays, gamma-ray induced light yields were estimated as 1900 ph/MeV for Pr:LuYAP and 5600 ph/MeV for Pr:YAP. In both crystals, light yield non-proportionality and energy resolution were investigated by individual lines in the gamma-ray energy range from 59.5 keV to 1408 keV. The gamma-ray excited decay time constants turned out to be 9.8 ns for Pr:LuYAP and 9.0 ns for Pr:YAP. [ABSTRACT FROM AUTHOR]

In order to detect the breast cancer at the early stage with high efficiency, we intend to develop positron emission mammography (PEM), using Pr:LuAG single crystal as a scintillator of this scanner. PEM has the same mechanism of PET, where two 511 keV annihilation gamma-rays are detected by two gamma cameras at opposite side, and reconstruction of the data shows the position of the cancer with malignancy grades. After cutting and polishing processes for each crystal to a physical dimensions of 2.1 x 2.1 x 15 mm³, Pr:LuAG array covered with BaSO4 reflector was used as a sensor head. The one camera unit consisted of 20 x 64 pixels optically coupled with three H8500-03 multi anode PMTs. Our PEM required four cameras at each side. Finally, eight cameras were installed in both sides of the prototype instrument and the spatial resolution was evaluated using the 18F in the breast phantom. [ABSTRACT FROM AUTHOR]

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]

Using the liquid phase epitaxy (LPE) method we prepared the high crystalline quality In3+ doped ZnO thin film scintillators with different Indium concentration of 26, 53, and 141 ppm. We evaluated their optical properties and radiation response, because there are few reports of radiation response of In-doped ZnO scintillator. In order to imitate the scintillator application, we measured the alpha-ray excited luminescence spectra. The emission bands peaking around 375 and 500 nm were observed, and with an increment of In3+, the intensity of both bands decreases. In the measurement of light yield, we optically coupled the sample with PMT R7600 by a silicone grease, and excitation was provided by 241Am 5.5 MeV α-rays. The samples showed of about 10% of the light yield of BGO scintillator which was used as a reference. Under the same excitation the scintillation decay was measured in all the samples as well. [ABSTRACT FROM AUTHOR]