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Iparraguirre I.,University of the Basque Country | Azkargorta J.,University of the Basque Country | Kamada K.,Tohoku University | Kamada K.,CandA Corporation | And 9 more authors.
Laser Physics Letters | Year: 2016

This work explores the room temperature infrared random laser (RL) performance of Nd3+ ions in a new stoichiometric Nd3Ga5O12 crystal powder. The time-resolved measurements show that the RL pulse is able to follow the subnanosecond oscillations of the pump pulse profile. The pump threshold energy and the absolute stimulated emission energy have been measured using a method developed by the authors. The laser slope efficiency is the highest compared to other Nd3+ stoichiometric RL crystals. © 2016 Astro Ltd.


Kamada K.,Tohoku University | Kamada K.,CandA Corporation | Nikl M.,ASCR Institute of Physics Prague | Kurosawa S.,Tohoku University | And 10 more authors.
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2015

The Mg, Ca, Sr and Ba 200 ppm co-doped Ce:Lu3Al5O12 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. © 2015 Published by Elsevier B.V.


Kurosawa S.,Tohoku University | Shishido T.,Tohoku University | Sugawara T.,Tohoku University | Nomura A.,Tohoku University | And 9 more authors.
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2015

Temperature dependence of scintillation properties was investigated for (Ce0.01, Gd0.90, La0.09)2Si2O7 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. © 2014 Elsevier B.V. All rights reserved.


Kurosawa S.,Tohoku University | Kurosawa S.,NICHE | Shishido T.,Tohoku University | Suzuki A.,Tohoku University | And 6 more authors.
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2014

Scintillation properties of Ce-doped (La, Gd)2Si 2O7 (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 662 keV 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 32 keV, where light output at 662 keV 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. © 2014 Elsevier B.V.


Hishinuma K.,Tohoku University | Kamada K.,Tohoku University | Kamada K.,CandA Corporation | Kurosawa S.,Tohoku University | And 5 more authors.
Key Engineering Materials | Year: 2014

Ce and Ca co-doped LiGdF4-LiF eutectics were grown and their directionally solidified eutectic (DSE) system has been investigated. In these eutectics, apart from the expected 305 nm emission of the regular Ce3+, 310 nm emission of the Gd3+ and Ce3+ -perturbed emission around 320-380 nm was observed. Ce3+-perturbed emission at 340 nm shows the intrinsic decay time of about 27 ns. In photoluminescence mechanism the observed decay time shortening of the regular Ce3+ and Gd3+ centers point to the energy transfer in the sequence the regular Ce 3+?→ (Gd3+)n?→ the perturbed Ce 3+ sites. © (2014) Trans Tech Publications, Switzerland.


Yokota Y.,Tohoku University | Kurosawa S.,Tohoku University | Nishimoto K.,Tohoku University | Kamada K.,Tohoku University | And 3 more authors.
Journal of Crystal Growth | Year: 2014

Eu doped SrI2[Eu:SrI2] bulk single crystals with 1 in. diameter were grown using a special-shaped carbon crucible and a modified micro-pulling-down furnace and their scintillation properties were investigated. As-grown Eu:SrI2bulk crystals indicated high transparency while they included several cracks in the crystals. Grown crystals indicated a single phase of SrI2structure in the powder X-ray diffraction measurement. In the X-ray radioluminescence spectrum, there was a sharp emission peak around 435 nm which originated from 5d-4f transition of Eu2+ion. Light yields of Eu5% and 7.5%:SrI2crystals under γ-ray irradiation from 137Cs radiation source were 83,000 and 85,000 ph/MeV, respectively. Their decay times under γ-ray irradiation were approximately 2 μs. © 2014 Elsevier B.V.


Kurosawa S.,Tohoku University | Kurosawa S.,NICHE | Shoji Y.,Tohoku University | Yokota Y.,NICHE | And 6 more authors.
Journal of Crystal Growth | Year: 2014

Ce:Gd3(AlxGa1-x)5O12 (x=2.5/5 and 3/5, Ce:GAGG-2.5 and Ce:GAGG-3) crystals were grown by the Czochralski process in order to reduce cost of the starting materials as compared with conventional Ce:Gd3Al2Ga3O 12 (Ce:GAGG-2) crystal which have high light output. Although perovskite phase was detected in Ce:GAGG-3, Ce:GAGG-2.5 had single-phase garnet structure. Solidification fraction for the Ce:GAGG-2.5 growth was 0.52. Optical properties including transmittance, emission, and excitation spectra of 30 samples cut from the Ce:GAGG-2.5 bulk ingot did not depend on their original position along the growth axis. These samples had light outputs of approximately 58,000±3000 photons/MeV. However, scintillation decay times varied from 140 to 200 ns and depended on the position clearly. © 2013 Elsevier B.V.


Sibczynski P.,National Center for Nuclear Research | Iwanowska-Hanke J.,National Center for Nuclear Research | Moszynski M.,National Center for Nuclear Research | Swiderski L.,National Center for Nuclear Research | And 7 more authors.
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2015

We have studied the scintillation properties of cerium doped gadolinium aluminum gallium garnet (GAGG:Ce) scintillators with various Al-to-Ga ratio. Having many advantages, like high density (6.63 g/cm3), high light output, fair energy resolution and quite fast decay time, the scintillators are an excellent solution for gamma rays detection. In this paper performance of the GAGG:1%Ce crystals with different Al-to-Ga ratios is presented. The study covered measurements of emission spectra, light output, energy resolution and non-proportionality for each crystal. It was observed that the light output of the recently obtainable crystals varies from 40,000 to 55,000 ph/MeV. Maximum emission wavelength of about 520 nm promotes silicon based photodetectors for use with these scintillators. The best energy resolution of 3.7% at 662 keV, measured with Hamamatsu S8664-1010 APD, was obtained for the sample with the minimum gallium content. This result is close to these obtained with the group of scintillators retaining very good energy resolution, like LaCl3 and CeBr3. © 2014 Elsevier B.V. All rights reserved.


Yokota Y.,Tohoku University | Kurosawa S.,Tohoku University | Ohasi Y.,Tohoku University | Kamada K.,Tohoku University | And 3 more authors.
Journal of Crystal Growth | Year: 2016

A shape-controlled Ce doped Y3Al5O12 (Ce:YAG) single crystal has been grown by a micro-pulling-down method using an Ir crucible with a square die. The as-grown Ce:YAG single crystal has square-shape and flat surfaces with high transparency. The shape-controlled Ce:YAG single crystal showed more than 70% transmittance from 530nm to 900nm without any cutting and polishing. An emission peak around 540nm was observed in the radioluminescence spectrum under X-ray irradiation. In addition, the light yield and energy resolution under γ-ray irradiation of the as-grown crystal without any cutting and polishing were approximately 23,000pH/MeV and 16%, respectively. © 2016 Elsevier B.V.


Yokota Y.,Tohoku University | Kudo T.,Tohoku University | Ohashi Y.,Tohoku University | Medvedev A.,Tohoku University | And 5 more authors.
Materials | Year: 2015

Ca3Nb(Ga1-xAlx)3Si2O14 (CNGAS) single crystals with various Al concentrations were grown by a micro-pulling-down (μ-PD) method and their crystal structures, chemical compositions, crystallinities were investigated. CNGAS crystals with x = 0.2, 0.4 and 0.6 indicated a single phase of langasite-type structure without any secondary phases. In contrast, the crystals with x = 0.8 and 1 included some secondary phases in addition to the langasite-type phase. Lattice parameters, a- and c-axes lengths, of the langasite-type phase systematically decreased with an increase of Al concentration. The results of chemical composition analysis revealed that the actual Al concentrations in as-grown crystals were almost consistent with the nominal compositions. In addition, there was no large segregation of each cation along the growth direction. © 2015 by the authors.

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