- Email: [email protected]
Investigations of scintillation characterization of Ce-activated Tl2LiGdBr6 single crystal
Accepted Manuscript Investigations of Scintillation Characterization of Ce-activated Tl2LiGdBr6 Single Crystal H.J. Kim, Gul Rooh, H. Park, Sunghwan Kim PII:
S1350-4487(15)30100-1
DOI:
10.1016/j.radmeas.2015.12.021
Reference:
RM 5502
To appear in:
Radiation Measurements
Received Date: 21 October 2015 Revised Date:
21 December 2015
Accepted Date: 22 December 2015
Please cite this article as: Kim, H.J., Rooh, G., Park, H., Kim, S., Investigations of Scintillation Characterization of Ce-activated Tl2LiGdBr6 Single Crystal, Radiation Measurements (2016), doi: 10.1016/j.radmeas.2015.12.021. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Investigations of Scintillation Characterization of Ce-activated Tl2LiGdBr6 Single Crystal H. J. Kima*, Gul Roohb, H. Parka, and Sunghwan Kimc
RI PT
a
Department of Physics, Kyungpook National University, Daegu 702-701, Korea b Department of Physics, Abdul Wali Khan University, Mardan,23200, Pakistan c Department of Radiological Science, Cheongju University, Cheongju 360-764, Korea *
SC
Corresponding author. Tel.:+82-53-950-5323; fax: +82-53-956-1739. E-mail address: [email protected] (H.J. Kim).
M AN U
Abstract
New single crystal of Ce-doped Tl2LiGdBr6 (TLGB) was investigated under x-ray and γ-ray excitation. Two zone vertical Bridgman technique was used to grow this scintillation material. Under X-ray excitation, typical Ce3+ ion emission was observed between 397 and 456 nm peaking at 422 nm. An energy resolution of 17% (FWHM) and 17,400±1700 ph/MeV light yield was obtained for 662 keV γ-rays excitation. Under γ-rays excitation from a
137
Cs source, two
TE D
decay time components of 29 ns (92%) and 197 ns (8%) were found at room temperature. Further investigation is underway for the optimization of the Ce-concentration in the host lattice. We expect improvement in the scintillation properties with a good quality crystal of this material.
EP
Key words: A1. Elpasolite , B3. Scintillation, B2. Light yield, A1. Energy resolution, A1. Crystal
1.
AC C
PACS codes: (i) 29.30. Kv, (ii) 78.70. En, (iii) 78.70. Ps, (iv) 81.10. Fq
Introduction
The rare earth ions doped materials are widely used as scintillation detectors due to their high light yield, excellent energy resolution and fast scintillation response (Yanagida et al., 2013; Glodo et al., 2010; van Loef et al., 2001; Shah et al., 2003; Mares et al., 2003; Higgins et al., 2008). Among the high performance scintillators, Ce-activated scintillators gain attention due to its allowed 4f→5d excitation followed by 5d→4f emission. In many host lattices Ce3+ ion showed a high light yield, excellent energy resolution and fast decay (Bizarri and Dorenbos, 2007; Rooh et al., 2008; Zhuravleva et al., 2011). Therefore, Ce-activated elpasolites scintillators
ACCEPTED MANUSCRIPT
are developed for radiation detectors and the reported results of different elpasolites showed excellent performance (Combes et al., 1999; Glodo et al., 2008; Rooh et al., 2012; Rooh et al., 2013; Shirwadkar et al., 2011). Bulk crystal growth is possible due to the cubic or near cubic structures of elpasolites. Until now more than thousand compounds belongs to elpasolite crystal
RI PT
family are reported, which have widened the selection range of the host for the radiation detector. It is therefore important to evaluate these compounds by doping different rare earths in their host lattice. Although most of the elpasolites shows good energy resolution and non-proportionality, but exhibit low light yield, long decay time components and moderate effective Z-number which
SC
restrict their use in the applications where high light yield and fast scintillation decay is required. This paper reports on preliminary results of our newly grown Tl2LiGdBr6: 10% Ce3+ (TLGB)
M AN U
single crystal. This crystal is grown by vertical Bridgman technique and belongs to elpasolite crystal family. Presented results include X-ray induced emission spectrum, energy resolution, light yield and decay time measurements at room temperature. The presence of Li and Gd elements in the TLBG makes this scintillator useful for the neutron detection.
Experimental Technique
2.1.
Crystal growth
TE D
2.
Single crystal of TLGB with 10% Ce-concentration has been grown by two zone vertical
EP
Bridgman technique. Stoichiometric amounts of TlBr, LiBr, GdBr3 and CeBr3 from SigmaAldrich or Alfa-Aesar having ~99.999% purity were loaded in quartz ampoule inside argon purged glovebox. The whole charge was melted at 450 oC. After the growth process, we
AC C
observed many cracks in the whole crystal body, therefore a very small irregular piece having approximate dimensions of ϕ8 x 1~2 mm3 was obtained and polished for the scintillation characterization of TLGB. Due to the hygroscopic nature, TLGB was kept in mineral oil. TLGB belongs to the elpasolite crystal family and the calculated density was found to be 5.30 g/cm3. The effective Z-number of the grown crystal was found to be 66.
2.2.
Equipment
ACCEPTED MANUSCRIPT
The X-ray induced luminescence spectra of TLGB: 10% Ce3+ were obtained at room temperature by using X-ray tube (DRGEM. Co.) having a tungsten anode operating at 50 kV and 1 mA. The emission spectra were measured by utilizing a spectrometer (QE65000 fiber optic spectrometer) made by Ocean Optics. Pulse height spectrum was measured with a Hamamatsu R6233
RI PT
photomultiplier tube (PMT) at room temperature. TLGB: 10% Ce crystal was wrapped in several layers of 0.1-mm-thick UV reflecting Teflon tape and coupled directly to the entrance window of the PMT using index matching optical grease. After irradiation with γ-rays from 137Cs source, the analog signals generated in the crystal were shaped with a Tennelec TC 245 spectroscopy
SC
amplifier and fed into a 25-MHz flash analog-to-digital converter (FADC). A software threshold was set to trigger an event by using a self-trigger algorithm on the field programmable gate array
M AN U
(FPGA) chip on the FADC board. The FADC output was recorded into a personal computer by using a USB2 connection, and the recorded data were analyzed with a C++ data analysis program (So et al., 2008). For the decay time measurement, optically coupled crystal of TLGB: 10% Ce3+ with a PMT (Hamamatsu R6233) was excited by 662 keV γ-rays from a 137Cs source. The electrical signals generated in the PMT were fed into a 400-MHz FADC (Kim et al., 2010).
3.
TE D
From the recorded pulse shape information, the decay time of TLGB: 10% Ce3+ was measured.
Results and discussion
3.1. X-ray excited luminescence The x-ray induced emission spectrum of the TLGB: 10% Ce3+ is shown in Fig. 1 at room
EP
temperature. Such emission spectrum is attributed to 5d → 4f transition of the Ce3+ ion, which is due to the transition from the lowest 5d level to 2F5/2 and 2F7/2 levels of the 4f1 configuration
AC C
(Mori and Nakayama, 2003). The observed emission spectrum is located between 397 and 456 nm peaking at 422 nm. This emission spectrum is attractive with respect to γ-ray spectroscopy, since it matches with the quantum efficiency curve of the modern photosensors.
3.2.
Pulse height spectra
The pulse height spectrum of the TLGB: 10% Ce3+ is shown in Fig. 2. After applying a Gaussian fit to the photopeak of 662 keV γ-ray from a 137Cs source an energy resolution of 17 % (FWHM) is obtained. The grown sample of TLGB: 10% Ce3+ has many body cracks which adversely affect its energy resolution, therefore the obtained poor energy resolution is assigned to the
ACCEPTED MANUSCRIPT
sample cracks. Moreover, the obtained energy resolution of TLGB: 10% Ce3+ is far behind the required energy resolution of >3.0% (FWHM) in many applications, however, improvement in the scintillation properties is expected with optimized, crack free and good quality samples of
3.3.
RI PT
TLGB.
Light Yield
For the light yield measurement at room temperature, the pulse height spectra of the TLGB: 10% Ce3+ and a calibrated LYSO (calculated light yield of LYSO = 33,000 ph/MeV having almost
SC
same dimensions of TLGB: 10%Ce3+) crystals are obtained with a Hamamatsu R6233 PMT. Light yield measurement is performed without considering the quantum efficiency of the photocathode of the PMT for TLGB: 10% Ce3+ and LYSO crystals. However, the emission
M AN U
wavelengths of TLGB: 10% Ce3+ matched with LYSO, therefore LYSO is used as a reference crystal for the determination of light yield (Rooh et al., 2010). During the measurements, TLGB: 10% Ce3+ and LYSO crystals are excited with 662 keV γ-rays from a
137
Cs source by using
similar conditions of PMT high voltage, shaping time and amplifier gain. The output electrical signals generated in the PMT are amplified with a Tennelec TC 245 shaping amplifier with
TE D
different shaping time of the amplifier and digitized with a 25 MHz flash analog-to-digital converter (FADC). From the recorded pulse height spectra, the estimated light yield of the TLGB: 10% Ce3+ is found to be 17,400±1700 ph/MeV. Figure 3 shows the pulse height spectra of TLGB:
3.4.
EP
10% Ce3+ and LYSO crystals, the channel number corresponds to the light yield.
Decay times
Scintillation decay time measurement of TLGB: 10% Ce3+ is performed under γ-ray excitation
AC C
using 137Cs source at room temperature. Figure 4 shows the decay time spectrum of TLGB: 10% Ce. After applying fit to the data in Fig. 4, we obtained two exponential decay components of 29 ns and 197 ns with emission light intensities of 92% and 8%, respectively. The observed fast decay component of 29 ns suggests that direct energy transfer by the electron-hole capture is possible in this scintillator. In case of direct electron-hole capture, one would expect a decay time component of 30 ns, similar to the decay of optical excitation of the 5d state of Ce3+ ion at room temperature (Rooh et al., 2010).
ACCEPTED MANUSCRIPT
4. Conclusion Scintillation properties of the single crystal of TLGB: 10% Ce3+ is reported. This material is grown by the vertical Bridgman technique using two zone furnace. Under X-ray excitation Ce3+ ion emission is observed between 397 and 456 nm peaking at 422 nm. Preliminary results
RI PT
showed that the obtained energy resolution and light yield could be improved with the optimized and crack free samples of TLGB. The observed fast decay component is attributed to typical Ce3+ ion. Considering the fast decay component, high density and effective Z-number, this material has the ability to detect X- and γ-rays very efficiently in different applications which
SC
include positron emission tomography (PET), single photon emission computed tomography (SPECT) and computed tomography (CT). Further investigation on the crystal growth procedure
Acknowledgment
M AN U
and optimization of Ce-concentration of TLGB is underway.
These investigations have been funded by the Ministry of Science and Technology, Korea (MEST) (No.2015R1A2A1A13001843).
TE D
References
Bizarri, G., and Dorenbos, P., 2007. Charge carrier and exciton dynamics in LaBr3:Ce3+ scintillators: Experiment and model. Phys. Rev. B, 75, 184302. Combes, C. M., et al., 1999. Optical and scintillation properties of pure and Ce doped Cs2LiYCl6
EP
and Li3YCl6: Ce3+ crystals. J. Lumin., 82, 299-305. Glodo, J., et al., 2008. Scintillation properties of 1 inch Cs2LiYCl6: Ce3+ crystals. IEEE
AC C
Trans.Nucl.Sci.55, 1206-1209.
Glodo, J., et al., 2010. Concentration Effects in Eu Doped SrI2. IEEE Trans. Nucl. Sci., 57, 31228–1232.
Higgins, W. M., et al., 2008. Crystal growth of large diameter LaBr3: Ce and CeBr3. J. Cryst. Growth., 310, 2085-2089.
Kim, H. J., et al., 2010. Neutrino-less double beta decay experiment using Ca100MoO4 scintillation crystals. IEEE Trans. Nucl. Sci., 57(3), 1475-1480.
ACCEPTED MANUSCRIPT
Mares, J. A., et al., 2003. Scintillation and spectroscopic properties of Ce3+-doped YAlO3 and Lux(RE)1- xAlO3(RE=Y3+ and Gd3+) scintillators. Nucl. Instrum. Meth. Phys. Res. A, 498, 312–327. Mori, K. and Nakayama, M., 2003. Role of the core excitons formed by 4f−4f transitions of Gd3+
RI PT
on Ce3+ scintillation in Gd2SiO5:Ce3+. Phys. Rev. B 67, 165206.
Rooh,G.,et al., 2008.The growth and scintillation properties of CsCe2Cl7 crystal. J. Cryst. Growth. 311,128-131.
Single Crystal. J. Lumin. 132, 713-716.
SC
Rooh, G., et al., 2012. Luminescence and scintillation characterization of Cs2NaGdBr6: Ce3+ Rooh, G., et al., 2013. Investigation of scintillation and luminescence properties of cerium doped
M AN U
Rb2LiGdCl6 single crystals. J. Cryst. Growth 377, 28-31.
Rooh, G., et al., 2010. Luminescence and Scintillation Characteristics of Rb2LiCeBr6 Single Crystal. IEEE Trans. Nucl. Sci. 57(6), 3836-3840.
Shah, K. S., et al., 2003. LaBr3:Ce scintillators for gamma-ray spectroscopy. IEEE Trans. Nucl. Sci., 50. 2410–2413.
Shirwadkar, U., et al., 2011. Scintillation properties of Cs2LiLaBr6 (CLLB) crystals with varying
TE D
Ce3+ concentration. Nucl. Intrum and Meth. A, 652, 268-270. So, J. H., et al., 2008. The proton energy response of a LYSO crystal. J. Korean Phys. Soc. 52(3), 925.
van Loef, E. V. D., et al., 2001. High-energy-resolution scintillator: Ce3+ activated LaBr3. Appl.
EP
Phys. Lett., 79, 1573–1575.
Yanagida, T., 2013. Study of rare-earth-doped scintillators. Opt. Mater. 35, 1987-1992.
AC C
Zhuravleva, M., et al., 2011. Crystal growth and scintillation properties of Cs3CeC16 and CsCe2Cl7. J. Cryst. Growth. 318, 809-812.
TE D
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
Figure 1. X-ray induced emission spectrum of TLGB: 10% Ce3+.
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
Figure 2. Pulse height spectrum of 662 keV γ-rays from a 137Cs source, measured with TLGB: 10%
AC C
EP
TE D
Ce3+. Pulse height spectrum is acquired for 10,000 counts under 137Cs γ-rays source excitation.
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
TE D
Figure 3. Pulse height spectra of TLGB: 10% Ce3+ and LYSO: Ce3+crystals at 662 keV γ-rays.
AC C
EP
The photopeak position is proportional to the light yield.
TE D
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
Figure 4. Scintillation decay time profile of TLGB: 10% Ce3+ crystal at room temperature under
EP
Cs γ-ray excitation.
AC C
137
ACCEPTED MANUSCRIPT
Highlights
RI PT
SC M AN U TE D EP
• • •
Scintillation properties of new Tl-based alkali halide eplasolite activated by Ce3+ are presented. This material is grown by two zone vertical Bridgman technique. It possessed high Z-number, high density, fast decay component and moderate light yield. Further improvements in the crystal quality could make this scintillator best choice for the use in medical imaging.
AC C
•
S1350-4487(15)30100-1
DOI:
10.1016/j.radmeas.2015.12.021
Reference:
RM 5502
To appear in:
Radiation Measurements
Received Date: 21 October 2015 Revised Date:
21 December 2015
Accepted Date: 22 December 2015
Please cite this article as: Kim, H.J., Rooh, G., Park, H., Kim, S., Investigations of Scintillation Characterization of Ce-activated Tl2LiGdBr6 Single Crystal, Radiation Measurements (2016), doi: 10.1016/j.radmeas.2015.12.021. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Investigations of Scintillation Characterization of Ce-activated Tl2LiGdBr6 Single Crystal H. J. Kima*, Gul Roohb, H. Parka, and Sunghwan Kimc
RI PT
a
Department of Physics, Kyungpook National University, Daegu 702-701, Korea b Department of Physics, Abdul Wali Khan University, Mardan,23200, Pakistan c Department of Radiological Science, Cheongju University, Cheongju 360-764, Korea *
SC
Corresponding author. Tel.:+82-53-950-5323; fax: +82-53-956-1739. E-mail address: [email protected] (H.J. Kim).
M AN U
Abstract
New single crystal of Ce-doped Tl2LiGdBr6 (TLGB) was investigated under x-ray and γ-ray excitation. Two zone vertical Bridgman technique was used to grow this scintillation material. Under X-ray excitation, typical Ce3+ ion emission was observed between 397 and 456 nm peaking at 422 nm. An energy resolution of 17% (FWHM) and 17,400±1700 ph/MeV light yield was obtained for 662 keV γ-rays excitation. Under γ-rays excitation from a
137
Cs source, two
TE D
decay time components of 29 ns (92%) and 197 ns (8%) were found at room temperature. Further investigation is underway for the optimization of the Ce-concentration in the host lattice. We expect improvement in the scintillation properties with a good quality crystal of this material.
EP
Key words: A1. Elpasolite , B3. Scintillation, B2. Light yield, A1. Energy resolution, A1. Crystal
1.
AC C
PACS codes: (i) 29.30. Kv, (ii) 78.70. En, (iii) 78.70. Ps, (iv) 81.10. Fq
Introduction
The rare earth ions doped materials are widely used as scintillation detectors due to their high light yield, excellent energy resolution and fast scintillation response (Yanagida et al., 2013; Glodo et al., 2010; van Loef et al., 2001; Shah et al., 2003; Mares et al., 2003; Higgins et al., 2008). Among the high performance scintillators, Ce-activated scintillators gain attention due to its allowed 4f→5d excitation followed by 5d→4f emission. In many host lattices Ce3+ ion showed a high light yield, excellent energy resolution and fast decay (Bizarri and Dorenbos, 2007; Rooh et al., 2008; Zhuravleva et al., 2011). Therefore, Ce-activated elpasolites scintillators
ACCEPTED MANUSCRIPT
are developed for radiation detectors and the reported results of different elpasolites showed excellent performance (Combes et al., 1999; Glodo et al., 2008; Rooh et al., 2012; Rooh et al., 2013; Shirwadkar et al., 2011). Bulk crystal growth is possible due to the cubic or near cubic structures of elpasolites. Until now more than thousand compounds belongs to elpasolite crystal
RI PT
family are reported, which have widened the selection range of the host for the radiation detector. It is therefore important to evaluate these compounds by doping different rare earths in their host lattice. Although most of the elpasolites shows good energy resolution and non-proportionality, but exhibit low light yield, long decay time components and moderate effective Z-number which
SC
restrict their use in the applications where high light yield and fast scintillation decay is required. This paper reports on preliminary results of our newly grown Tl2LiGdBr6: 10% Ce3+ (TLGB)
M AN U
single crystal. This crystal is grown by vertical Bridgman technique and belongs to elpasolite crystal family. Presented results include X-ray induced emission spectrum, energy resolution, light yield and decay time measurements at room temperature. The presence of Li and Gd elements in the TLBG makes this scintillator useful for the neutron detection.
Experimental Technique
2.1.
Crystal growth
TE D
2.
Single crystal of TLGB with 10% Ce-concentration has been grown by two zone vertical
EP
Bridgman technique. Stoichiometric amounts of TlBr, LiBr, GdBr3 and CeBr3 from SigmaAldrich or Alfa-Aesar having ~99.999% purity were loaded in quartz ampoule inside argon purged glovebox. The whole charge was melted at 450 oC. After the growth process, we
AC C
observed many cracks in the whole crystal body, therefore a very small irregular piece having approximate dimensions of ϕ8 x 1~2 mm3 was obtained and polished for the scintillation characterization of TLGB. Due to the hygroscopic nature, TLGB was kept in mineral oil. TLGB belongs to the elpasolite crystal family and the calculated density was found to be 5.30 g/cm3. The effective Z-number of the grown crystal was found to be 66.
2.2.
Equipment
ACCEPTED MANUSCRIPT
The X-ray induced luminescence spectra of TLGB: 10% Ce3+ were obtained at room temperature by using X-ray tube (DRGEM. Co.) having a tungsten anode operating at 50 kV and 1 mA. The emission spectra were measured by utilizing a spectrometer (QE65000 fiber optic spectrometer) made by Ocean Optics. Pulse height spectrum was measured with a Hamamatsu R6233
RI PT
photomultiplier tube (PMT) at room temperature. TLGB: 10% Ce crystal was wrapped in several layers of 0.1-mm-thick UV reflecting Teflon tape and coupled directly to the entrance window of the PMT using index matching optical grease. After irradiation with γ-rays from 137Cs source, the analog signals generated in the crystal were shaped with a Tennelec TC 245 spectroscopy
SC
amplifier and fed into a 25-MHz flash analog-to-digital converter (FADC). A software threshold was set to trigger an event by using a self-trigger algorithm on the field programmable gate array
M AN U
(FPGA) chip on the FADC board. The FADC output was recorded into a personal computer by using a USB2 connection, and the recorded data were analyzed with a C++ data analysis program (So et al., 2008). For the decay time measurement, optically coupled crystal of TLGB: 10% Ce3+ with a PMT (Hamamatsu R6233) was excited by 662 keV γ-rays from a 137Cs source. The electrical signals generated in the PMT were fed into a 400-MHz FADC (Kim et al., 2010).
3.
TE D
From the recorded pulse shape information, the decay time of TLGB: 10% Ce3+ was measured.
Results and discussion
3.1. X-ray excited luminescence The x-ray induced emission spectrum of the TLGB: 10% Ce3+ is shown in Fig. 1 at room
EP
temperature. Such emission spectrum is attributed to 5d → 4f transition of the Ce3+ ion, which is due to the transition from the lowest 5d level to 2F5/2 and 2F7/2 levels of the 4f1 configuration
AC C
(Mori and Nakayama, 2003). The observed emission spectrum is located between 397 and 456 nm peaking at 422 nm. This emission spectrum is attractive with respect to γ-ray spectroscopy, since it matches with the quantum efficiency curve of the modern photosensors.
3.2.
Pulse height spectra
The pulse height spectrum of the TLGB: 10% Ce3+ is shown in Fig. 2. After applying a Gaussian fit to the photopeak of 662 keV γ-ray from a 137Cs source an energy resolution of 17 % (FWHM) is obtained. The grown sample of TLGB: 10% Ce3+ has many body cracks which adversely affect its energy resolution, therefore the obtained poor energy resolution is assigned to the
ACCEPTED MANUSCRIPT
sample cracks. Moreover, the obtained energy resolution of TLGB: 10% Ce3+ is far behind the required energy resolution of >3.0% (FWHM) in many applications, however, improvement in the scintillation properties is expected with optimized, crack free and good quality samples of
3.3.
RI PT
TLGB.
Light Yield
For the light yield measurement at room temperature, the pulse height spectra of the TLGB: 10% Ce3+ and a calibrated LYSO (calculated light yield of LYSO = 33,000 ph/MeV having almost
SC
same dimensions of TLGB: 10%Ce3+) crystals are obtained with a Hamamatsu R6233 PMT. Light yield measurement is performed without considering the quantum efficiency of the photocathode of the PMT for TLGB: 10% Ce3+ and LYSO crystals. However, the emission
M AN U
wavelengths of TLGB: 10% Ce3+ matched with LYSO, therefore LYSO is used as a reference crystal for the determination of light yield (Rooh et al., 2010). During the measurements, TLGB: 10% Ce3+ and LYSO crystals are excited with 662 keV γ-rays from a
137
Cs source by using
similar conditions of PMT high voltage, shaping time and amplifier gain. The output electrical signals generated in the PMT are amplified with a Tennelec TC 245 shaping amplifier with
TE D
different shaping time of the amplifier and digitized with a 25 MHz flash analog-to-digital converter (FADC). From the recorded pulse height spectra, the estimated light yield of the TLGB: 10% Ce3+ is found to be 17,400±1700 ph/MeV. Figure 3 shows the pulse height spectra of TLGB:
3.4.
EP
10% Ce3+ and LYSO crystals, the channel number corresponds to the light yield.
Decay times
Scintillation decay time measurement of TLGB: 10% Ce3+ is performed under γ-ray excitation
AC C
using 137Cs source at room temperature. Figure 4 shows the decay time spectrum of TLGB: 10% Ce. After applying fit to the data in Fig. 4, we obtained two exponential decay components of 29 ns and 197 ns with emission light intensities of 92% and 8%, respectively. The observed fast decay component of 29 ns suggests that direct energy transfer by the electron-hole capture is possible in this scintillator. In case of direct electron-hole capture, one would expect a decay time component of 30 ns, similar to the decay of optical excitation of the 5d state of Ce3+ ion at room temperature (Rooh et al., 2010).
ACCEPTED MANUSCRIPT
4. Conclusion Scintillation properties of the single crystal of TLGB: 10% Ce3+ is reported. This material is grown by the vertical Bridgman technique using two zone furnace. Under X-ray excitation Ce3+ ion emission is observed between 397 and 456 nm peaking at 422 nm. Preliminary results
RI PT
showed that the obtained energy resolution and light yield could be improved with the optimized and crack free samples of TLGB. The observed fast decay component is attributed to typical Ce3+ ion. Considering the fast decay component, high density and effective Z-number, this material has the ability to detect X- and γ-rays very efficiently in different applications which
SC
include positron emission tomography (PET), single photon emission computed tomography (SPECT) and computed tomography (CT). Further investigation on the crystal growth procedure
Acknowledgment
M AN U
and optimization of Ce-concentration of TLGB is underway.
These investigations have been funded by the Ministry of Science and Technology, Korea (MEST) (No.2015R1A2A1A13001843).
TE D
References
Bizarri, G., and Dorenbos, P., 2007. Charge carrier and exciton dynamics in LaBr3:Ce3+ scintillators: Experiment and model. Phys. Rev. B, 75, 184302. Combes, C. M., et al., 1999. Optical and scintillation properties of pure and Ce doped Cs2LiYCl6
EP
and Li3YCl6: Ce3+ crystals. J. Lumin., 82, 299-305. Glodo, J., et al., 2008. Scintillation properties of 1 inch Cs2LiYCl6: Ce3+ crystals. IEEE
AC C
Trans.Nucl.Sci.55, 1206-1209.
Glodo, J., et al., 2010. Concentration Effects in Eu Doped SrI2. IEEE Trans. Nucl. Sci., 57, 31228–1232.
Higgins, W. M., et al., 2008. Crystal growth of large diameter LaBr3: Ce and CeBr3. J. Cryst. Growth., 310, 2085-2089.
Kim, H. J., et al., 2010. Neutrino-less double beta decay experiment using Ca100MoO4 scintillation crystals. IEEE Trans. Nucl. Sci., 57(3), 1475-1480.
ACCEPTED MANUSCRIPT
Mares, J. A., et al., 2003. Scintillation and spectroscopic properties of Ce3+-doped YAlO3 and Lux(RE)1- xAlO3(RE=Y3+ and Gd3+) scintillators. Nucl. Instrum. Meth. Phys. Res. A, 498, 312–327. Mori, K. and Nakayama, M., 2003. Role of the core excitons formed by 4f−4f transitions of Gd3+
RI PT
on Ce3+ scintillation in Gd2SiO5:Ce3+. Phys. Rev. B 67, 165206.
Rooh,G.,et al., 2008.The growth and scintillation properties of CsCe2Cl7 crystal. J. Cryst. Growth. 311,128-131.
Single Crystal. J. Lumin. 132, 713-716.
SC
Rooh, G., et al., 2012. Luminescence and scintillation characterization of Cs2NaGdBr6: Ce3+ Rooh, G., et al., 2013. Investigation of scintillation and luminescence properties of cerium doped
M AN U
Rb2LiGdCl6 single crystals. J. Cryst. Growth 377, 28-31.
Rooh, G., et al., 2010. Luminescence and Scintillation Characteristics of Rb2LiCeBr6 Single Crystal. IEEE Trans. Nucl. Sci. 57(6), 3836-3840.
Shah, K. S., et al., 2003. LaBr3:Ce scintillators for gamma-ray spectroscopy. IEEE Trans. Nucl. Sci., 50. 2410–2413.
Shirwadkar, U., et al., 2011. Scintillation properties of Cs2LiLaBr6 (CLLB) crystals with varying
TE D
Ce3+ concentration. Nucl. Intrum and Meth. A, 652, 268-270. So, J. H., et al., 2008. The proton energy response of a LYSO crystal. J. Korean Phys. Soc. 52(3), 925.
van Loef, E. V. D., et al., 2001. High-energy-resolution scintillator: Ce3+ activated LaBr3. Appl.
EP
Phys. Lett., 79, 1573–1575.
Yanagida, T., 2013. Study of rare-earth-doped scintillators. Opt. Mater. 35, 1987-1992.
AC C
Zhuravleva, M., et al., 2011. Crystal growth and scintillation properties of Cs3CeC16 and CsCe2Cl7. J. Cryst. Growth. 318, 809-812.
TE D
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
Figure 1. X-ray induced emission spectrum of TLGB: 10% Ce3+.
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
Figure 2. Pulse height spectrum of 662 keV γ-rays from a 137Cs source, measured with TLGB: 10%
AC C
EP
TE D
Ce3+. Pulse height spectrum is acquired for 10,000 counts under 137Cs γ-rays source excitation.
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
TE D
Figure 3. Pulse height spectra of TLGB: 10% Ce3+ and LYSO: Ce3+crystals at 662 keV γ-rays.
AC C
EP
The photopeak position is proportional to the light yield.
TE D
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
Figure 4. Scintillation decay time profile of TLGB: 10% Ce3+ crystal at room temperature under
EP
Cs γ-ray excitation.
AC C
137
ACCEPTED MANUSCRIPT
Highlights
RI PT
SC M AN U TE D EP
• • •
Scintillation properties of new Tl-based alkali halide eplasolite activated by Ce3+ are presented. This material is grown by two zone vertical Bridgman technique. It possessed high Z-number, high density, fast decay component and moderate light yield. Further improvements in the crystal quality could make this scintillator best choice for the use in medical imaging.
AC C
•