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Abstract: Vacuum Ultra violet (VUV) scintillators, have a short decay time around several ns, and therefore can be used in high counting rate applications. New Nd-doped BaY2F8 VUV scintillator crystals were successfully grown by a micro-pulling down (μ-PD) method and their optical properties and radiation response were investigated. All the BaY2F8 samples with 0.5, 1, 3, 7 and 10 mol% Nd concentration had 5d-4f luminescence peaks at 185, 237 and 270 nm. Although this scintillator has low light output around 70 photons/5.5-MeV alpha, which was determined from our pulse height measurement, we found that the decay time of this crystal reached 13 ns which is a typical value for the VUV scintillators. [Copyright &y& Elsevier]

Abstract: Pr:Gd3(Ga,Al)5O12 single crystals were grown by the micro-pulling down (μ-PD) method. All grown crystals were greenish and transparent with 3.0mm in diameter, 15–30mm in length. Neither visible inclusions nor cracks were observed. Luminescence and scintillation properties were measured. The substitution at the Al3+ sites by Ga3+ in garnet structure has been studied. In these crystals, Pr3+ 5d–4f emission is observed with 340nm wavelength. Pr1%:Gd3Ga3Al2O12 shows highest emission intensity. The light yield of Pr:Gd3Ga3Al2O12 sample with 3mmφ×1mm size was around 4500photon/MeV. Scintillation decay time was 7.9ns (0.5%), 46ns (0.7%) and 214ns (98.8%). [Copyright &y& Elsevier]

Abstract: Ce:Gd2Lu1(Ga,Al)5O12 single crystals were grown by the micro-pulling down (μ-PD) method. All grown crystals were yellow and transparent with 3.0mm in diameter, 15–30mm in length. Neither visible inclusions nor cracks were observed. Luminescence and scintillation properties were measured. The substitution at the Al3+ sites by Ga3+ and at the Lu3+ sites by Gd3+ in garnet structure has been studied. In these crystals, Ce3+ 4f–5d emission is observed with 500–530nm wavelength. The decay accelerates with increasing Ga and Ce concentration. Ce1%: Gd2Lu1Ga3Al2O12 shows the highest emission intensity. The light yield of Ce:Gd2Lu1Ga3Al2O12 sample with 3mmφ×1mm size was around 22,000photon/MeV using calibration from 55Fe direct irradiation peak to APD. Scintillation decay time was around 50ns. The theoretical density is 6.88g/cm3. [Copyright &y& Elsevier]

Abstract: Transparent Nd:Y2O3 ceramics were produced by vacuum sintering. Their fundamental optical constants including optical transmittance, reflectivity, absorption coefficient, refractive index, extinction coefficient, and dielectric constant were evaluated. Scintillation characteristics including radio-luminescence and light yield under α (241Am 5.5MeV) excitation are reported as well. [Copyright &y& Elsevier]

• (Ce 0.015 La 0.600 Y 0.385) 2 Si 2 O 7 single crystal was grown by the micro-pulling-down method. • Quenching temperature of (Ce 0.015 La 0.600 Y 0.385) 2 Si 2 O 7 was determined to be 526 K. • Light output of (Ce 0.015 La 0.600 Y 0.385) 2 Si 2 O 7 was determined to be ~12,000 photons/MeV. We have grown Ce-doped (La,Y) 2 Si 2 O 7 single crystal by micro-pulling-down method and investigated its optical and scintillation properties. We have successfully prepared the single crystal with (Ce 0.015 La 0.600 Y 0.385) 2 Si 2 O 7 composition. The observed thermal quenching process could be characterized by the quenching temperature (T 50%) of 526 K and its activation energy was determined to be 0.62 eV. Further considering the thermal quenching factors, it was found that the thermal quenching was caused by at least the thermal ionization and maybe also by classical thermal quenching. The light output and scintillation decay time were evaluated to be ~12,000 photons/MeV and ~42 ns, respectively. These results indicate that (Ce 0.015 La 0.600 Y 0.385) 2 Si 2 O 7 has a great potential for application in scintillation materials. [ABSTRACT FROM AUTHOR]

A new red-emitting halide scintillator Rb2HfI6 was developed using the vertical Bridgman furnace and quartz ampoule. Under X-ray irradiation, Rb2HfI6 had a broad emission band of around 725 nm. The light output and energy resolution were determined to be ~40000 photons/MeV and ~7.4% (full-width at half-maximum at 662 keV), respectively. Since red photons are transmitted with smaller losses than blue or yellow photons inside an optical fiber, a long-fiber-reading radiation detection system using the high light-output red scintillator can be established for severe or hazardous environments. We fabricated the Rb2HfI6 scintillation crystal and performed the gamma-ray detection test under high-dose irradiation condition from a 60Co source with an activity of ~100 TBq. The dynamic range of the Rb2HfI6 gamma-ray detection with a 20-m optical fiber was evaluated and compared with the previously developed Cs2HfI6 crystal and the conventional deep-red Cr: α-Al2O3 (ruby) scintillator. The gamma-ray doses from ~0.4 to ~1 kSv/h were successfully measured using Rb2HfI6 through the 20-m fiber. [ABSTRACT FROM AUTHOR]

Cesium hafnium iodide (CHI) was reported as a novel red-emitting scintillator in our previous article, while optimization of the crystal quality and evaluation of the scintillation performance were insufficient. In this study, a large and transparent CHI single crystalline specimen was obtained using slow crystal growth speed. Coupled with a Si avalanche photo-diode, the full width at half maximum energy resolution was evaluated to be 4.2 ± 0.2% at 662 keV which was the best value among conventional red-emitting scintillators. The scintillation light output, non-proportional response of light output and scintillation decay were also evaluated with a photomultiplier tube. • Cs 2 HfI 6 scintillator was grown by the vertical Bridgman-Stockberger method. • Transparent single crystal was obtained at a slower growth speed than previous report. • Pulse height spectra and scintillation decay were measured. • The FWHM energy resolution was estimated to be 4.2 ± 0.2% at 662 keV. [ABSTRACT FROM AUTHOR]

In order to obtain new scintillators with high light output and high effective atomic number ( Z eff ), we performed anion-substitution for Cs 2 HfCl 6 (CHC) scintillator, and then, we succeeded in growing Cs 2 HfI 6 (CHI) single crystalline scintillator. It had Z eff of 58, which is the same as that of CHC, and had high light output of ∼70,000 photons/MeV with 700 nm emission. However, its scintillation decay time of ∼2.5 µs was slow for practical use as gamma-ray monitor. In this study, we performed Ce 3+ /Eu 2+ doping to Hf 4+ site to improve decay time of CHI, introducing the fast 5d-4f luminescence. Ce:CHI and Eu:CHI single crystals were finally obtained by the vertical Bridgman-Stockbarger method. The luminescence spectra of the Ce:CHI and Eu:CHI were very similar to that of the non-doped CHI, which would mean that no 5d-4f luminescence of Ce 3+ /Eu 2+ was observed. The measured light output and decay time of Ce:CHI were ∼48,000 photon/MeV and 2.3 ± 0.1 µs, respectively. As for Eu:CHI, light output and decay time were ∼69,000 photon/MeV and 2.8 ± 0.1 µs, respectively. [ABSTRACT FROM AUTHOR]

Ce-doped (Gd, La) 2 Si 2 O 7 scintillation crystals are expected to be used as gamma-ray detectors for high temperature measurement. To realize scintillators for high temperature environment, we investigated (Ce 0.01 Gd 0.59−x La 0.40 Y x ) 2 Si 2 O 7 (x = 0.00, 0.05, 0.10, 0.15) single crystals grown by the micro-pulling-down method. The results showed that a 5% Y-admixed Ce-doped (Gd, La) 2 Si 2 O 7 scintillator can yield higher light output when compared with Y-free Ce-doped (Gd, La) 2 Si 2 O 7 scintillator. The light outputs at 25°C and 175°C were determined to be ∼43,000 and ∼40,000 photons/MeV, respectively. Moreover, 1 inch size 5% Y-admixed Ce-doped (Gd, La) 2 Si 2 O 7 scintillator was grown by the Czochralski technique, and its light output at 175°C kept the value of around 95% of the value at 25°C. [ABSTRACT FROM AUTHOR]

1 in. diameter Mg 0.05, 0.1, 0.2, 0.5 mol% and Zr 0.015% co-doped Ce1%:GGAG crystals were grown by Cz method. Relationship between Mg concentration and absorption, luminescence, light output, decay time, timing resolution was investigated. Mg 0.2 mol% co-doped sample showed the fastest timing resolution of 165 ps among the Mg-co-doped samples. [ABSTRACT FROM AUTHOR]

Ce-doped Lu 2 Si 2 O 7 scintillator contains radioactive isotope 176 Lu which causes an unwanted intrinsic background signal. The development of scintillators with reduced Lu concentration were required in some applications. In this study, we developed the Gd admixed lutetium pyrosilicate, where the average ion radius at the rare earth site was similar to the Tm 3+ ion radius, for which the RE 2 Si 2 O 7 (RE=Tm, Yb, Lu) crystal structure is stable from room temperature to melting point. We have grown (Ce x Lu 1−x−y Gd y ) 2 Si 2 O 7 (x=0.01, y=0.00, 0.05, 0.10) single crystals. Their crystal systems were monoclinic with a space group C 2/ m . The absorption spectra revealed the energy transitions in Ce and Gd ions might be occurred. The light output was degraded and decay time was accelerated comparing the Gd 5% admixed sample with the Gd 10% one. [ABSTRACT FROM AUTHOR]

Ce-doped (Gd, La) 2 Si 2 O 7 scintillators have fast decay time and keep high light output even at high temperature (∼150°C). To improve the scintillation properties such as light output and decay time, Ce-doped (Gd, La) 2 Si 2 O 7 scintillators codoped with the divalent ions (e.g. Mg 2+ , Ca 2+ ) have been studied. In this study, we focused on the other divalent ions (Sr 2+ and Ba 2+ ), and investigated their effect on the scintillation properties and temperature dependence of light output. The absorption due to Ce 4+ was not observed for Sr or Ba codoping. The light outputs were degraded by Sr 2+ or Ba 2+ codoping, while the decay times at room temperature were not changed for the samples codoped with divalent ions. On the other hand, the temperature dependence of light output for Ba-codoped sample was improved, and the light output value at 175°C was 36,000 photons/MeV, which was 93% of that at 25°C. [ABSTRACT FROM AUTHOR]

(Ce 0.01 Gd 0.59 La 0.40 ) 2 Si 2 O 7 single crystal (La40% sample) was grown by the micro-pulling-down method to study its scintillation properties and their temperature dependence. In addition, we investigated the relation between these properties and La concentration comparing the crystal with (Ce 0.01 Gd 0.90 La 0.09 ) 2 Si 2 O 7 (La9% sample). As results, the light output of the La40% sample at 25°C was similar to that of the La9% sample. On the other hand, the decay time of the La40% sample was slower than that of the La9% sample at 25°C. The light output of La40% sample had a small decrease rate at high temperature when compared with that of La9% sample. [ABSTRACT FROM AUTHOR]

The In-doped LiCaAlF 6 [In:LiCAF] single crystals were grown by the micro-pulling-down (μ-PD) method, and the phases, chemical compositions, transmittance and radioluminescence spectra were investigated. All the grown crystals showed high transparency and single phase of LiCAF without visible cracks and inclusions except for the end part of In2%:LiCAF crystal which included the impurity phase. In the radioluminescence spectra of the In:LiCAF crystals under X-ray irradiation, the emission peak around 750 nm was revealed. [ABSTRACT FROM AUTHOR]

Mg co-doping effects on scintillation properties of Ce:Lu 1 Gd 2 (Ga,Al) 5 O 12 (LGGAG) were investigated. Mg 200 ppm co-doped Ce:LGGAG single crystals were prepared by micro pulling down method. Absorption and luminescence spectra were measured together with several other scintillation characteristics, namely the scintillation decay and light yield to reveal the effect of Mg co-doping. Ce 4+ charge transfer absorption was observed below 300 nm in Mg,Ce:LGGAG which is in good agreement with previous reports. The scintillation decay times were accelerated by Mg co-doping. [ABSTRACT FROM AUTHOR]

Cr-doped (Gd x Y 1− x ) 3 Ga 5 O 12 crystals ( x =0.00, 0.25, 0.50, 0.75 and 1.00) were grown by the micro-pulling-down method and examined for their possible application as red and infrared scintillating detectors in medical field. Although Cr:(Gd 0.75 Y 0.25 ) 3 Ga 5 O 12 and Cr:Gd 3 Ga 5 O 12 had similar X-ray diffraction patterns, other samples showed some change in lattice constant. All the crystals had broad emission bands in the red and infrared region when excited by either 450 nm photons or X rays. These bands were associated with 4 T 2 →A 2 transitions. Moreover, redshift of the emission-peak wavelengths ( 4 T 2 → 4 A 2 ) and absorption peaks ( 4 A 2 → 4 T 1 and 4 T 2 ) was observed with increase of Gd content ( x ) in Cr-doped (Gd x Y 1 −x ) 3 Ga 5 O 12 due to the change of the crystal fields. The crystals had scintillation emissions in the wavelength region suitable for the real time dose monitoring in radiation therapy. [ABSTRACT FROM AUTHOR]

We grew Lu-substituted CeBr 3 [(Ce 1− x Lu x )Br 3 ] crystals by a modified micro-pulling-down method to increase the effective atomic number and to investigate effects of the Lu substitution on the crystal growth, phase generation, chemical composition, and optical and scintillation properties. The (Ce 1− x Lu x )Br 3 crystals with x =0 and 0.01 had high transparency while the milky parts were generated in the crystals with x =0.05 and 0.20. By the analysis of chemical composition, the estimated Z eff increased to 47.9. On the other hand, the light yields were systematically decreased and decay times were increased with increasing Lu concentration. [ABSTRACT FROM AUTHOR]

The Li + co-doped Ce:Lu 3 Al 5 O 12 single crystals were prepared by micro pulling down method. Absorption and luminescence spectra were measured together with several other scintillation characteristics, namely the scintillation decay and light yield to reveal the effect of the co-doping. The smooth Ce 4+ CT absorption below 350 nm is clearly enhanced with increasing concentration of Li. The scintillation decays were accelerated and light yields were increased by Li co-doping. [ABSTRACT FROM AUTHOR]

(Ce x Yb 1−x ) 2 Si 2 O 7 (x = 0.00, 0.01) single crystals were grown by the micro-pulling-down method to test the possibility of its application as infra-red scintillator for medical imaging. Powder X-ray diffraction analysis indicated that the crystals were single-phase materials. The radioluminescence spectra of the crystals demonstrated presence of two near infra-red emission peaks (at 1010 and 1030 nm). The emission peaks at 420 and 580 nm ascribed to defects were also observed in the crystals. The human body has maximum transmission in wavelength range from 650 to 1200 nm. Therefore, Yb 2 Si 2 O 7 is expected to be used as efficient infra-red scintillator for medical applications. [ABSTRACT FROM AUTHOR]

We grew Na and K co-doped Eu:SrI 2 [Na,Eu:SrI 2 and K,Eu:SrI 2 ] crystals by a modified micro-pulling-down method to reveal the co-doping effects on the crystal growth and scintillation properties. The non-codoped, Na0.5%, Na1.0%, K0.5% and K1.0%,Eu:SrI 2 crystals indicated high transparency while the milky parts were generated in the Na5.0% and K5.0%,Eu:SrI 2 crystals. The light yields of Na,Eu:SrI 2 and K,Eu:SrI 2 crystals under γ-ray irradiation were decreased by the Na and K co-doping. On the other hand, there was a small change within 940–1020 ns in the decay times by the Na and K co-doping. In the light yield proportionality under γ-ray irradiation, the non-proportionality in the low energy region was improved by Na and K co-doping. [ABSTRACT FROM AUTHOR]

The ns 2 -type metal elements (Pb and Sn) doped LiCaAlF 6 single crystals were grown by a micro-pulling-down (μ-PD) method. Pb doped LiCaAlF 6 [Pb:LiCAF] crystals showed high transparency and single phase of the LiCAF structure. However, we could not obtain Sn:LiCAF crystals due to the evaporation of SnF 2 during the crystal growth. There was an absorption peak around 193 nm in the transmittance spectrum of Pb:LiCAF crystal. In the radioluminescence spectrum of the Pb:LiCAF crystal under X-ray irradiation, two emission peaks around 200 and 830 nm were observed. [ABSTRACT FROM AUTHOR]

1300 or 1400 °C pre–sintered Al/Ce/Mg:SrHfO 3 and Al/Ce:SrHfO 3 ceramics were prepared by the Spark Plasma Sintering (SPS) in order to search for a new scintillation material with a high–effective atomic number(Z eff ) and good light output. The SrHfO 3 has a high Z eff of 60, and high gamma–ray detection efficiency is expected. Meanwhile it has a high melting point of over 2500 °C, and single crystal is hard to be grown. On the other hand, high melting materials can be prepared as ceramics, and the SPS method is a simple process to fabricate the ceramics within a few hours. Thus, we prepared the samples using the SPS method, and their optical and scintillation properties were investigated. We found that Al/Ce/Mg:SrHfO 3 and Al/Ce:SrHfO 3 ceramics had an emission wavelength at around 400 nm originating from 5d–4f transition of Ce 3+ . Moreover, Al/Ce/Mg:SrHfO 3 pre-sintered at a temperature of 1400 °C had a light output of approximately 5,000 ph/MeV. In this paper, the light output of Mg-co-doped samples was improved compared with the Mg-free ones. The light output also depends on the pre-sintering temperature. [ABSTRACT FROM AUTHOR]

(Gd 0.75 ,Ce 0.015 ,La 0.235 ) 2 Si 2 O 7 (Ce:La-GPS) single crystals co-doped with 0, 100, 200, 500 and 1000 ppm Zr were grown by the Czochralski process, and their scintillation properties were investigated. We investigated the co-doping effect of a stable tetravalent ion in Ce:La-GPS for the first time. The scintillation decay times in the faster component were shortened with increasing the Zr concentration. While the non-co-doped sample showed ∼63 ns day time, the Zr 100, 200, 500 and 1000 ppm co-doped samples showed ∼61, ∼59, ∼57, ∼54 ns, respectively. Additionally, light output, photon nonproportional response (PNR) and other optical properties were investigated. [ABSTRACT FROM AUTHOR]

Pr doped (Lu,Gd) 3 (Ga,Al) 5 O 12 single crystals were grown by the micro-pulling down (μ-PD) method. The crystals were greenish and transparent with 3.0 mm in diameter, 10–30 mm in length. Neither visible inclusions nor cracks were observed. Luminescence and scintillation properties were measured. The substitution at the Al 3+ sites by Ga 3+ in garnet structure has been studied. The Pr 3+ 5d–4f emission is observed within 300–380 nm wavelength superposed with 312 nm emission line of Gd 3+ . Pr0.2%:Lu 2.5 Gd 1 Ga 3 Al 2 O 12 shows highest emission intensity. The light yield of Pr0.2%:Lu 2.5 Gd 0.5 Ga 2 Al 3 O 12 sample with diameter 3 mm×1 mm size was around 8000 ph/MeV. Two-exponential approximations of scintillation decay showed 39.6 ns (30.6%) and 151 ns (69.4%) decay times. [ABSTRACT FROM AUTHOR]

Eu doped CaF 2 /Li 3 AlF 6 eutectics were grown by μ-PD method. The directionally solidified eutectic with well-aligned 600 nm diameter Eu:CaF 2 scintillator fibers surrounded with Li 3 AlF 6 was prepared. The grown eutectics showed an emission peak at 422 nm ascribed to Eu 2+ 4f–5d transition from Eu:CaF 2 scintillation fiber. Li concentration in the Eu:CaF 2 –Li 3 AlF 6 eutectic is around 0.038 mol/cm 3 ,which is two times higher than that of LiCaAlF 6 single crystal (0.016 mol/cm 3 ). The light yield of Eu:CaF 2 –Li 3 AlF 6 eutectic was around 7000 ph/neutron. The decay time was about 550 ns (89%) and 1450 ns (11%). [ABSTRACT FROM AUTHOR]

Eu doped BaCl 2 /LiF eutectics were grown by the micro-pulling down method and their directionally solidified eutectic (DSE) system has been investigated. The grown eutectic showed main phases of cubic LiF and orthorhombic BaCl 2 . In these eutectics, the 399 nm emission of Eu 2+ 4f5d was obtained. It shows the intrinsic decay time of about 410 ns. The light yield of the 1-mm-thick eutectic showed 7000 ph/5.5 MeV alpha-ray. [ABSTRACT FROM AUTHOR]

In order to obtain new scintillator with higher effective atomic number, a pyrosilicate crystal with a composition (Ce 0.01 , Gd 0.54 , La 0.25 , Lu 0.20 ) 2 Si 2 O 7 (Ce:LaLu-GPS) was grown by the floating zone method. Emission wavelengths of this material were at 370 and 390 nm. Gamma-ray-excited pulse height and scintillation decay measurement showed that Ce:LaLu-GPS had a light output of 34,000±2000 photons/MeV, an FWHM energy resolution of 6.9±0.2%, and the decay time components of 59±1 ns (13%) and 570±20 ns (87%). [ABSTRACT FROM AUTHOR]

The Mg, Ca, Sr and Ba 200 ppm co-doped Ce:Lu 3 Al 5 O 12 single crystals were prepared by micro pulling down method. Absorption and luminescence spectra were measured together with several other scintillation characteristics, namely the scintillation decay and light yield to reveal the effect of the co-doping. The scintillation decays were accelerated by both Mg and Ca co-dopants. The Mg co-doped samples showed the fastest decay and the highest light yield among the co-doped samples. [ABSTRACT FROM AUTHOR]

The Mg and Ca co-doped Ce:Gd 3 Al 2 Ga 3 O 12 single crystals were prepared by micro pulling down method with a wide concentration range 0–1000 ppm of the codopants. Absorption and luminescence spectra were measured together with several other scintillation characteristics, namely the scintillation decay and light yield to reveal the effect of Mg and Ca co-doping. The scintillation decays were accelerated by both Mg and Ca codopants. Comparing to Ca co-doping, the Mg co-doped samples showed much faster decay and comparatively smaller light output decrease with increasing Mg dopant concentration. [ABSTRACT FROM AUTHOR]

(Eu 0.01 , Gd 0.90 , La 0.09 ) 2 Si 2 O 7 (Eu:La–GPS) and (Tb 0.01 , Gd 0.9 0 , La 0.09 ) 2 Si 2 O 7 (Tb:La–GPS) crystals were grown by the floating zone method, and their optical and scintillation properties were investigated. Gd 3+ -to-Tb 3+ or –Eu 3+ energy transfer processes were found, and photo-luminescence and radio-luminescence emission spectra showed 5 D 0 – 7 F i ( i = 1–4) Eu 3+ transitions in Eu:La–GPS, and 5 D 3 – 7 F i ( i = 3–6) and 5 D 4 – 7 F i ( i = 3–6) transitions in Tb:La–GPS. Using these scintillators, alpha-ray imaging was possible with a CMOS camera. These materials can be used for X-ray detection as well. [ABSTRACT FROM AUTHOR]

Nd 1 mol% doped (Lu, Gd) 3 (Ga, Al) 5 O 12 (LGGAG) single crystals were grown by the micro-pulling down (μ-PD) method. Luminescence and scintillation properties such as absorption, excitation and emission spectra, light yield and decay time were evaluated. Nd1%:Lu 3 Al 5 O 12 showed the highest light output of around 8200 photons/MeV among the grown crystals. Scintillation decay time of Nd:Y 3 Al 5 O 12 was 1.32 μs (36%) 2.02 μs (64%). Nd:Lu 3 Ga 3 Al 2 O 12 was relatively high dense scintillator of 7.38 g/cm 3 with good light yield of 6800 photons/MeV and scintillation decay time of 0.20 μs (5%) 2.60 μs (95%). [ABSTRACT FROM AUTHOR]

Ce doped SrHfO 3 /SrAl 12 O 19 eutectics were grown by the micro pulling down (μ-PD) method and their directionally solidified eutectic system has been investigated. Investigations of obtained eutectic structure, luminescence and scintillation performances were also performed. Eutectics were grown at the speed of 0.60–0.90 mm/min. In the eutectics, Ce 3+ 4f–5d emission was observed at 410 nm. The eutectics showed light yield of around 300 photon/5.5 meV alpha-ray by 241 Am excitation. Scintillation decay time was 26.4 ns (45%) with slower decay component of 263 ns (55%). [ABSTRACT FROM AUTHOR]

Temperature dependence of scintillation properties was investigated for (Ce 0.01 , Gd 0.90 , La 0.09 ) 2 Si 2 O 7 grown by floating zone method. The light output over 35,000 photons/MeV was found constant in the temperature range from 0 °C to 150 °C. In addition, FWHM energy resolution of Ce:La-GPS (roughly 7–8%) at 662 keV remained constant up to 100 °C. Thus, this crystal can be applied to oil well logging or other radiation detection application at high temperature conditions. [ABSTRACT FROM AUTHOR]

Cr-doped (Gd X Y 1 − X ) 3 Al 5 O 12 ( X = 0, 0.25, 0.50) crystals prepared by the micro-pulling down method were investigated to develop a infra-red scintillator for implantable patient dosimeter in radiation therapy. In order to evaluate their optical and scintillation performance, the following properties were measured: (i) transmittance between ultra-violet and near-infra red region, (ii) photoluminescence spectra under Xe-lamp excitation, and (iii) X-ray excited radio-luminescence spectra. Cr:Y 3 Al 5 O 12 and Cr:(Gd 0.25 Y 0.75 ) 3 Al 5 O 12 crystals showed increased transmittance of 80%, while Cr:(Gd 0.50 Y 0.50 ) 3 Al 5 O 12 had a lower transmittance of 40% due to its polycrystalline structure. In addition, all the Cr:(Gd X Y 1− X ) 3 Al 5 O 12 crystals showed sharp scintillation luminescence peaks ascribed to Cr 3+ d–d transitions. Therefore, these results suggested that Cr:Y 3 Al 5 O 12 and Cr:(Gd 0.25 Y 0.75 ) 3 Al 5 O 12 crystals can be candidate materials for the dosimeter use. [ABSTRACT FROM AUTHOR]

Eu:SrI2 and La, Gd or Lu co-doped Eu:SrI2 single crystals were grown by a modified micro-pulling-down method and the effects of rare-earth (RE) co-doping on the crystal growth and scintillation properties were investigated. RE-free Eu7.5 mol%:SrI2 and La, Gd or Lu 1 mol% co-doped Eu7.5 mol:SrI2 single crystals with high transparency were obtained. The powder X-ray diffraction measurements revealed that all the grown crystals had a single phase of SrI2 structure. In the X-ray radioluminescence spectra, emission peaks around 435 nm were observed for the Eu:SrI2 and La co-doped Eu:SrI2 specimens. The light yield of the La co-doped Eu7.5%:SrI2 specimens were lower than that of the RE-free Eu7.5%:SrI2 specimen due to the generation of some defects by La co-doping. [ABSTRACT FROM AUTHOR]

Highlights: [•] Yb-doped Gd3Al2Ga3O12 (Yb:GAGG) crystal was grown by a micro-pulling down method. [•] Crystal structure and average chemical composition of Yb:GAGG was examined. [•] Yb:GAGG crystal was highly transparent in infra-red region from 650 to 1200nm. [•] Yb:GAGG showed infra-red scintillation peaks at 1030nm under X-ray excitation. [ABSTRACT FROM AUTHOR]

Abstract: We have investigated the optical properties of 1mol% Nd-doped SrBr2 crystal grown by the Bridgman technique for an X-ray scintillator application. We succeeded in obtaining a transparent crystal, whose X-ray diffraction was measured under dry condition because of its hygroscopic nature. Roughly, we estimated that 90% of this crystal dissolved within 300min. under 25°C and 65–70% humidity. Under excitation by 270 and 400nm photons several emission peaks originating from 4F3/2 or 4G i1→4I i2 (i1=5/2 and 7/2 and i2=13/2, 11/2, and 9/2) transitions of Nd3+ were observed. 1mol% Nd:SrBr2 had a maximum quantum yield of approximately 45%. Additional emission peaks were observed under X-ray excitation. [Copyright &y& Elsevier]

Abstract: Nd and Yb doped CaYAlO4 crystals have been grown by the micro-pulling down method. The segregation coefficient along the growth direction and the radial dopant distribution were measured by using electron probe micro-analysis (EPMA). The X-ray induced luminescence spectra in the spectral range from 300 to 1500nm were measured: Nd and Yb doped CaYAlO4 showed intense peaks at 990 and 1045nm, respectively. These crystals would be promising materials for near infrared emission scintillators. [Copyright &y& Elsevier]

Scintillation properties of Ce-doped (La, Gd)2Si2O7 (Ce:La-GPS) crystal were measured with Si avalanche photodiode (APD, Hamamatsu S8664-55). Since Ce:La-GPS is a novel scintillator, its scintillation properties have been evaluated using the APD for the first time. This crystal grown by floating zone method had a good light output of 41,000±1000 photons/MeV and FWHM energy resolution at 662keV was 4.4±0.1% at 23.0±0.2°C. The photon non-proportional response (PNR) of Ce:La-GPS was approximately 65% at 32keV, where light output at 662keV was normalized to 100%. Moreover, the temperature dependence of the light outputs was determined to be approximately 0.15%/°C from −10 to 30°C. [ABSTRACT FROM AUTHOR]

Highlights: [•] Scintillation properties of GAGG:Ce & LuAG:Ce are compared. [•] LY dependence on sample height and shaping time are studied. [•] Intrinsic LY of 56,500ph/MeV and loss coefficient of 0.175cm−1 are obtained for GAGG:Ce. [•] Intrinsic LY of 29,000ph/MeV and loss coefficient of 0.380cm−1 are obtained for LuAG:Ce. [•] PL decays at room and low temperatures are studied for GAGG:Ce. [Copyright &y& Elsevier]

Abstract: High scintillation efficiency of Eu-doped LiSrAlF6 (LiSAF) and LiCaAlF6 (LiCAF) codoped with alkali metal ions has been reported in our recent studies. Thus in this paper, we demonstrated the scintillation properties of 1% Ce-doped LiSAF crystals with 1% alkali metal ions co-doping to increase the light yield and understand the scintillation mechanism. The crystals showed intense emission band corresponding to the 5d-4f transition of Ce3+, and their light yields under thermal neutron excitation were higher than that of the Ce only doped crystal. Especially, the light yield of Ce–Na co-doped crystal exceeded about two times that of Ce only doped one. [Copyright &y& Elsevier]

Highlights: [•] Ce:Gd3(Ga,Al)5O12 single crystals grown by floating zone method under atmosphere with different O2 content. [•] Ga evaporation from melt suppressed in oxygen-rich atmosphere. [•] Highest light yield obtained for 100% oxygen atmosphere. [•] Intense slow decay component observed for oxygen-free atmosphere. [ABSTRACT FROM AUTHOR]

Abstract: Sc2O3, Y2O3 and Lu2O3 transparent ceramics were prepared by the spark plasma sintering (SPS) method. After polishing, the samples were semitransparent. Their optical transmittance was 10–40% at 500 nm which corresponded with their semi-transparency. In the X-ray induced emission spectra, a broad emission peak appeared around 335 nm in each sample. For this wavelength, scintillation decay time for Y2O3 and Sc2O3 were 22 and 48 ns, respectively. The light yield of Sc2O3, Y2O3 and Lu2O3 was 16,200, 2600, and 200 ph/5.5 MeV-alpha, respectively, which followed from the alpha-ray induced pulse height spectra. The gamma-ray induced light yield of Sc2O3 was 11,500 ph/MeV, which is 1.4 times larger than that of conventional single crystal BGO (Bi4Ge3O12) scintillator. Light yield non-proportionality and energy resolution of Sc2O3 were examined for the first time. [Copyright &y& Elsevier]