Scintillation characterizations of Tl₂LiLuCl₆: Ce³⁺ single crystal

Rooh, Gul,Kim, H.J.,Jang, Jonghun,Kim, Sunghwan Elsevier 2017 Journal of luminescence Vol.187 No.-

<P><B>Abstract</B></P> <P>We report the growth and scintillation characterization of Tl<SUB>2</SUB>LiLuCl<SUB>6</SUB> single crystals, developed from the melt using two-zone vertical Bridgman technique, while doped with 0.5, 1, 3 and 5 mol% Ce concentration. X-ray-induced emission spectra shows Ce<SUP>3+</SUP> emission ranging from 370 to 540-nm wavelength. Energy resolution, light yield and decay time of the grown samples are measured under γ-ray excitation at room temperature. Energy resolution of 5.6% FWHM with 27,000±2700ph/MeV light yield is found for 1mole% Ce-doped sample. For the same dopant concentration, three decay components are also observed. Variation of scintillation properties is observed as a function of dopant concentration in the material. It will provide excellent detection efficiency for X- and γ-rays due to its high effective Z-number and density. It is expected that such scintillator will be a potential detector for the medical imaging techniques.</P>

Tl₂GdCl₅ (Ce³⁺): A New Efficient Scintillator for X-and <tex> $\gamma$</tex>-Ray Detection

Rooh, Gul,Khan, Arshad,Kim, H. J.,Park, H.,Kim, Sunghwan Professional Technical Group on Nuclear Science 2018 IEEE transactions on nuclear science Vol.65 No.8

<P>We are in the process of developing novel thallium-based inorganic halide compounds for X- and <TEX>$\gamma $</TEX>-ray radiation detections. In this paper, novel cerium-activated single crystals of Tl<SUB>2</SUB>GdCl<SUB>5</SUB> are reported along with a pure Tl<SUB>2</SUB>GdCl<SUB>5</SUB>. The two-zone vertical Bridgman method is used to grow this scintillator from its melt. Luminescence studies are performed under ultraviolet and X-ray excitations at room temperature. All of the Ce-activated samples exhibit similar emission bands in the range of 350–430 nm, with a peak around 388 nm, attributed to the <TEX>$5d~\to ~4f$</TEX> radiative transition of the Ce<SUP>3+</SUP> ion. In the pure sample, an intense luminescence band appeared owing to the presence of the Tl<SUP>+</SUP> ion in the host lattice, along with the typical Gd<SUP>3+</SUP> emission (~310 nm). Scintillation properties, such as energy resolution, light yield, and decay time, are evaluated under the <TEX>$\gamma $</TEX>-ray excitation. The scintillation properties vary with the Ce<SUP>3+</SUP>-concentration. The best performances are obtained for the 5-mol% Ce-activated crystal, which, under a 662-keV <TEX>$\gamma $</TEX>-ray excitation, exhibited an energy resolution of 5% (full-width at half-maximum) and light yield of 53 000 ± 5300 ph/MeV. Fast scintillation decay components followed by slow components are observed for all grown samples. The measured scintillation properties of Tl<SUB>2</SUB>GdCl<SUB>5</SUB>, which has high density and effective Z-number, reveal its large potentials as a radiation detector in medical imaging techniques.</P>

TlSr₂Br₅: New intrinsic scintillator for X-ray and γ-ray detection

Rooh, Gul,Khan, Arshad,Kim, H.J.,Park, H.,Kim, Sunghwan Elsevier 2017 Optical materials Vol.73 No.-

<P><B>Abstract</B></P> <P>New thallium based intrinsically activated scintillator for X-ray and gamma ray detection is reported. Luminescence and scintillation properties are measured under X-ray and γ-ray excitation sources at room temperature. This compound is grown from the melt using two zones vertical Bridgman method. X-ray induced emission spectrum exhibits intense luminescence band at 441 nm wavelength. Scintillation light yield and energy resolution are found to be 37,600 ± 3700 ph/MeV and 4.6% (FWHM), respectively under 662 keV excitation from <SUP>137</SUP>Cs source. Two decay time constants are obtained when sample is excited by γ-ray at room temperature. Measured properties revealed that this compound is a potential scintillator and could be used as radiation detector in different applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Scintillation properties of new TlSr2Br<SUB>5</SUB> crystal are presented. </LI> <LI> Efficient γ-rays detection is possible due to its high Z<SUB>eff</SUB> number and density. </LI> <LI> Energy resolution of 4.6% (FWHM) with 37,600 ± 3700 light yield is obtained. </LI> <LI> Two decay constants are observed under γ-ray excitation at room temperature. </LI> </UL> </P>

Growth and scintillation characterization of Ce³⁺-doped Rb₂LiGdBr₆ single crystals

Rooh, G.,Kim, H.J.,Kim, S.,Khan, S. North-Holland 2016 Nuclear Instruments & Methods in Physics Research. Vol.832 No.-

Growth and scintillation characterizations of the newly developed cerium doped Rb<SUB>2</SUB>LiGdBr<SUB>6</SUB> (RLGB) single crystals were investigated. RLGB, which belongs to bromo-elpasolite crystal family, was grown by the vertical Bridgman technique with nominally 1%, 5%, and 10% Ce<SUP>3+</SUP>-concentration (mole%). X-ray excited luminescence spectra show typical Ce<SUP>3+</SUP> bands between 350 to 460nm wavelength regions. A good energy resolution of 5.5% (FWHM) and light yield of 25,500+/-2600ph/MeV for 662keV γ-rays were observed at 5% Ce<SUP>3+</SUP>-concentration. Under γ-ray excitation, RLGB:Ce<SUP>3+</SUP> crystals display multi-exponential decays with Ce<SUP>3+</SUP> like decay components at 23ns and 29ns for 1% and 5% Ce-concentrations, respectively. From the results, it is expected that this scintillator could be used as a thermal neutron detector because of Li and Gd ions in the host lattice. Also, like other inorganic halide scintillators, it is very hygroscopic.

Crystal growth and scintillation characterizations of Tl₂LiYCl₆: Ce³⁺

Rooh, Gul,Kim, H.J.,Park, H.,Kim, Sunghwan Elsevier 2017 Journal of crystal growth Vol.459 No.-

<P><B>Abstract</B></P> <P>Single crystals of Tl<SUB>2</SUB>LiYCl<SUB>6</SUB> with different mole% of Ce-concentration (0.5 and 5mol%) were presented. This material belongs to Chloro-elpasolite crystal family and was grown by two zone vertical Bridgman technique. X-ray diffraction pattern of the Tl<SUB>2</SUB>LiYCl<SUB>6</SUB> single crystal was measured. X-ray diffraction analysis confirmed tetragonal crystal structure. The melting point of the sample was measured by DSC. Typical Ce<SUP>3+</SUP> ion emission spectra were observed when samples were excited by an X-ray source at room temperature. The observed emission spectra were located between 350nm and 530nm wavelength range and peaking around 430nm. Pulse height spectra of the samples under 662keV γ-rays excitation shows improvement in energy resolution with the increase of Ce-concentration in the host lattice. The energy resolutions were obtained to be 10.6% and 7.2% (FWHM) for 0.5% and 5% Ce<SUP>3+</SUP> concentration, respectively. Under γ-ray excitation, a maximum light yield of 23,800±2400ph/MeV was observed for 5% Ce-concentration. Studied samples of Tl<SUB>2</SUB>LiYCl<SUB>6</SUB>: Ce<SUP>3+</SUP> showed three exponential decay time components under γ-ray excitation. From the measured scintillation properties, we consider this material is a promising scintillator for radiation detection.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Scintillation characterization of Tl<SUB>2</SUB>LiYCl<SUB>6</SUB>: Ce<SUP>3+</SUP> were presented. </LI> <LI> Tl<SUB>2</SUB>LiYCl<SUB>6</SUB>: Ce<SUP>3+</SUP> were grown by two zone vertical Bridgman technique. </LI> <LI> It has high Z<SUB>eff</SUB> and could be a potential candidate for medical imaging technique. </LI> <LI> Energy resolution of 7.2% and light yield of 23,800±2400ph/MeV were obtained. </LI> <LI> Three decay time components were observed under γ-ray excitation. </LI> </UL> </P>

Study on Crystal Growth and Scintillation Characteristics of Cs<tex> $_{2}$</tex> LiCeCl<tex> $_{6}$</tex>

Rooh, Gul,Kim, H J,Sunghwan Kim IEEE 2010 IEEE transactions on nuclear science Vol.57 No.3

<P>In this work, we present the crystal growth and scintillation properties of our newly developed scintillation crystal, Cs-2 LiCeCl6, for a gamma-ray spectroscopy. This scintillation crystal is grown by using the vertical Bridgman method. The crystal of this material belongs to the elpasolite family characterized by a cubic structure and potentially can be easily grown in large volumes. Under the X-ray excitation, cerium emission band is observed to peak at 385 nm and 405 nm. An energy resolution (full width at half maximum over the peak position) of 5.5 % was observed for the 662 keV full absorption peak. We measured an absolute light yield of 22 000 photons/MeV of absorbed gamma-ray energy. The crystal shows three main scintillation decay time components of 101 ns (42%), 557 ns (35%) and 2.9 mu s (23%). This material is highly hygroscopic and special attention was paid during data taking and handling processes. We believe that the Cs-2 LiCeCl6 crystal can be a promising material for medical imaging and radiation detection. Moreover due to the presence of Li ions, this scintillation crystal can also be a possible candidate for thermal neutron detection.</P>

Study of the Scintillation Properties and of the Proton-Induced Radiation Damage in the K2CeCl5 Single Crystal

Gul Rooh,Heedong Kang,박환배,Jinho Moon,이상훈,김성환,Kyeryung Kim,김홍주 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.5

In this paper, we report on the scintillation properties of the K2CeCl5 single crystal before and after proton irradiation. The crystal of this scintillator was grown by using the Czochralski pulling technique and it was cut with dimension of 6×4×3 mm3. The scintillation properties, such as the absolute light yield, the proportionality of the response and the energy resolution, as functions of the γ-ray energy were calculated prior to the proton beam exposure. The light output deviates from a linear response by 10 % in the energy range between 31-keV and 1275-keV. Irradiation of the K2CeCl5 single crystal was carried out at the Korea Institute of Radiological and Medical Science. In order to measure the induced radiation damage in the K2CeCl5 crystal, we subjected the sample to the 45-MeV proton beam of the MC-50 cyclotron and the scintillation properties were measured prior to and after the irradiation. The emission spectra before and after the irradiation showed the same emission band between wavelengths of 350 nm and 400 nm with a peak center at 375 nm. After exposure to the proton beam, the K2CeCl5 single crystal showed a lower light yield and a deteriorated energy resolution. In addition, we compared the decay time of the crystal before and after the proton irradiation.

Cerium-Doped <tex> ${\rm Cs}_{2}{\rm NaGdCl}_{6}$</tex> Scintillator for X-Ray and <tex> $\gamma$</tex> -Ray Detection

Gul Rooh,Kim, H. J.,Park, H.,Sunghwan Kim,Hua Jiang IEEE 2014 IEEE transactions on nuclear science Vol.61 No.1

<P>New single crystals of Ce-doped Cs<SUB>2</SUB>NaGdCl<SUB>6</SUB> are investigated under x-ray and γ-ray excitation. These scintillation crystals are grown by two zone vertical Bridgman technique and belong to elpasolite crystal family. Energy resolution, scintillation light yield, non-proportionality, energy resolution as a function of γ-rays energies and scintillation decay time measurements are presented. Ce<SUP>3+</SUP>-related x-ray excited emission is observed between 360 and 450 nm wavelength region at room temperature. At higher Ce-concentration both self-trapped exciton (STE) and Gd<SUP>3+</SUP> emissions are disappeared and enhance Ce<SUP>3+</SUP> emission. Under 662 keV γ-rays excitation, Cs<SUB>2</SUB>NaGdCl<SUB>6</SUB> shows an energy resolution of 5.2%, (FWHM) at 1% Ce-concentration. Best energy resolution of 4.8% (FWHM) is obtained for 10% Ce-concentration. No significant improvement is observed in the energy resolution of Cs<SUB>2</SUB>NaGdCl<SUB>6</SUB> with the increase of Ce-concentration. The highest light yield of about 21,000 ph/MeV is obtained for 10% Ce-doped crystal. At room temperature three decay time components are found under γ-ray excitation for all Ce-doped samples. This material is highly hygroscopic.</P>

Study on Scintillation Characteristics of BGSO Single Crystals

Hua Jiang,Rooh, Gul,Kim, H. J.,Lee, J. M.,Lee, Y. J.,Sunghwan Kim IEEE 2014 IEEE transactions on nuclear science Vol.61 No.1

<P>This paper presents a report on the growth and scintillation characterization of Bi-4 (Ge1-xSix)(3)O-12 (BGSO) single crystals with x = 0.1, 0.2, 0.3, 0.5, 0.7, 0.8, and 0.9. The scintillator is grown by using the Czochralski pulling method. By employing a suitable rotation and pulling rates, high quality BGSO single crystals have been grown. Photoluminescence and X-rays induced emission spectra show a broad emission band in the wavelength range from 350 to 700 nm. Light yield and decay time under gamma-ray excitation are studied for various values of x in BGSO. Light yield decreases with the increasing value of x. For all the grown samples, the decay time spectrum contained three components at room temperature. This report also includes the measurement of the temperature dependence of the scintillation light yield of BGSO crystal with x = 0.1. A change in the light yield is observed between 100 and 300 K. The light yield of BGSO at 100 K is observed eight times higher than that at 300 K.</P>

Physical, structural and luminescence investigation of Eu³⁺-doped lithium-gadolinium bismuth-borate glasses for LEDs

Zaman, F.,Rooh, G.,Srisittipokakun, N.,Wongdeeying, C.,Kim, H.J.,Kaewkhao, J. Elsevier 2018 SOLID STATE SCIENCES Vol.80 No.-

<P><B>Abstract</B></P> <P>The aim of the current report is to fabricate Eu<SUP>3+</SUP>-doped glasses with the chemical composition of 50Li<SUB>2</SUB>O-15Gd<SUB>2</SUB>O<SUB>3</SUB>-5Bi<SUB>2</SUB>O<SUB>3</SUB>-(30-x)B<SUB>2</SUB>O<SUB>3</SUB>-xEu<SUB>2</SUB>O<SUB>3</SUB> (where x = 0.5, 1.0, 1.5, 2.0 and 2.5 mol%), with the help of conventional melt quenching technique. The fabricated glasses have been studied with help of physical, structural and luminescence properties for application of LEDs. The structural properties were investigated by XRD and FTIR spectra. Physical properties have been measured. Direct and indirect optical energy band gap (E<SUB>g</SUB>) have been calculated and found to be increasing with Eu<SUB>2</SUB>O<SUB>3</SUB> concentration. Luminescence spectra have been observed from photo and radioluminescence spectra and found in good agreement with each other, however the concentration quenching was not determined for the samples. The high-covalence and asymmetric nature was confirmed from Photoluminescence emission and RL emission transition as well as from the higher values of luminescence intensity ratio. The JO parameters have been found for the better performance of lasing materials. The lifetime's data have been found to be decreasing from 1.64 to 1.50 ms, which is the confirmation of energy transfer in Eu<SUP>3+</SUP> ions through cross relaxations. From the calculated properties it has been suggested that the present glass samples might be good for red-light emitting devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Li<SUB>2</SUB>O-Gd<SUB>2</SUB>O<SUB>3</SUB>-Bi<SUB>2</SUB>O<SUB>3</SUB>-B<SUB>2</SUB>O<SUB>3</SUB> glasses doped with Eu<SUP>3+</SUP> prepared. </LI> <LI> E<SUB>g</SUB> found to be increasing with Eu<SUB>2</SUB>O<SUB>3</SUB> concentration. </LI> <LI> Red emission observed from photo and radioluminescence. </LI> <LI> Asymmetric nature was confirmed PL. </LI> <LI> JO analysis was applied and found good for lasing materials. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>