[Show abstract][Hide abstract] ABSTRACT: Cerium doped scintillators are characterized by an excellent energy resolution, a very high light yield and fast timing properties. In this work, we grew a CeBr3 (p = 5.18 g/cm3) single crystal by the Bridgman method using a two-zone transparent vertical furnace. The CeBr3 is crystallized in the hexagonal structure of the UCl3 type. We investigated the thermoluminescence (TL) of the CeBr3 such as glow curve, dose response, fading etc. TL is a convenient technique to understand the charge trapping and detrapping mechanisms that result from the interaction of the radiation with the existing defects in material, which may interfere with the scintillator response. We determined the kinetic parameters of the TL traps of the CeBr3 scintillator such as activation energy, frequency factor, and kinetic order by using peak shape method, variable heating rate method, and initialize method.
Journal of Nuclear Science and Technology 08/2014; 45(sup5):575-578. DOI:10.1080/00223131.2008.10875920 · 1.45 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We manufactured and characterized a silicon micro-strip detector to be used in a beam tracker. A silicon detector features a DC-coupled silicon strip sensor with VA1_Prime2 analog readout chips.The silicon strip sensors have been fabricated on 5-in. wafers at Electronics and Telecommunications Research Institute (Daejeon, Korea). The silicon strip sensor is single-sided and has 32 channels with a 1 mm pitch, and its active area is 3.2 by 3.2 cm2 with 380 μm thickness. The readout electronics consists of VA hybrid, VA Interface, and FlashADC & Control boards. Analog signals from the silicon strip sensor were being processed by the analog readout chips on the VA hybrid board. Analog signals were then changed into digital signals by a 12 bit 25 MHz FlashADC. The digital signals were read out by the Linux-operating PC through the FlashADC-USB2 interface. The DAQ system and analysis programs were written in the framework of ROOT package.The beam test with the silicon detector had been performed at CERN beam facility. We used a 150 GeV electron beam out of the SPS(Super Proton Synchrotron) H2 beam line. We present beam test setup and measurement result of signal-to-noise ratio of each strip channel.
Journal of Nuclear Science and Technology 08/2014; 45(sup5):556-559. DOI:10.1080/00223131.2008.10875915 · 1.45 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A portable data acquisition (DAQ) system with embedded microcontroller was developed for radiation detection and environment monitoring purpose. The developed DAQ system consists of an ATMEGA128 of high performance, low-power 8-bit AVR microcontroller made by ATMEL and a AD7746 24-bit capacitance to digital converter. A software based Universal Serial Bus (USB) and a RS-232 serial port is used for the communication between the developed system with a main computer. The developed DAQ system has 8-channels analog to digital converter (ADC) with 10-bit resolution. The ADC has singled ended mode, differential mode using inside amplifier and it has maximum signals sampling rate 50-Kbit per second. It has discriminator capability with an analog comparator and signal counter capability with a 16-bit timer/counter. It can also measure precious capacitance, temperature and voltage with the functionality of the AD7746. The developed embedded DAQ system was tested with scintillation crystal irradiated with in radioactive sources. This embedded DAQ system is simple but portable and useful for radiation and environment monitoring.
Journal of Nuclear Science and Technology 08/2014; 45(sup5):852-585. DOI:10.1080/00223131.2008.10875922 · 1.45 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A silicon sensor is very attractive material for medical imaging due to its intrinsic high resolution and fast readout. Silicon sensors of various types were fabricated on a 380 μm-thick n-type, float zone, 5 in. wafer which has high resistivity, orientation, and is double-sided polished. We manufactured not only DC- and AC-coupled strip sensors but also pixel sensors and RC chips. The RC chips were fabricated for the purpose of using signal readout of the DC-coupled strip sensors. Electrical characteristics of the fabricated silicon sensors, leakage current and capacitance as a function of reverse bias voltage, were measured. Coupling capacitors and biasing resistors in the AC-coupled strip sensors were made by separating implantation from metallization strips with a thin oxide layer and made of polysilicons, respectively. The capacitance and resistance of each channel in the AC-coupled sensor were measured and compared with target values. The signal-to-noise ratio of the fabricated large pixel sensor was also measured by using a 90Sr radioactive source.
Journal of Nuclear Science and Technology 08/2014; 45(sup5):560-563. DOI:10.1080/00223131.2008.10875916 · 1.45 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: New scintillation crystal of a Ba0.20Sr0.80Cl2 grown by the Czochralski technique is reported. The grown crystal was cut into a size of 10×10×10 mm3. The lattice parameter of the grown crystal is a = b = c = 7.041 Å and the crystal structure is cubic. The luminescence and scintillation properties of the Ba0.20Sr0.80Cl2 crystal were studied. The luminescent characteristics were measured with ultraviolet (UV) light and X-ray source to study the emission spectra of the crystal. Scintillation properties of the crystal such as pulse height spectra, energy resolution, α/β ratio, light output, proportionality curve, and fluorescence decay time were measured with the various radioactive γ-ray sources and α-source at room temperature. The light output of the crystal was compared with that of the CsI(Tl) crystal and the absolute light output was measured with avalanche photodiode (APD). While the light output of the crystal was less than that of the CsI(Tl), the energy resolution was approximately 6.9% for 137Cs 662 keV γ-ray with PMT which is similar to that of the CsI(Tl) crystal for 137Cs γ-rays.
Journal of Nuclear Science and Technology 08/2014; 45(sup5):568-571. DOI:10.1080/00223131.2008.10875918 · 1.45 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Since capacitively coupled readout has an advantage of shielding the readout electronics from sensor leakage current, we fabricated an AC-coupled single-sided silicon strip sensor on 5-in. 380 μm-thick wafer and its active area is 3.2 × 3.2 cm2. It has 64 implanted and readout strips with a strip pitch of 500 μm. Two silicon strip sensors were mounted perpendicularly one another to get two-dimensional position information with a 5 mm space gap. Two low noise analog ASICs, VA1 chips, were used for signal readout of the strip sensor. The single-sided silicon strip detector (SSSD) consists of the two AC-coupled single-sided strip sensors and readout electronics. The SSSD was housed in an Al light-tight box. A CsI(Tl) scintillation crystal and a 2-in. photomultiplier tube were used to trigger signal events. The data acquisition systems were based on a 64 MHz FADC and control softwares for the PC-Linux platform. Experiments were performed at room temperature and silicon sensors were fully depleted. The SNRs were measured to be 29.1 ± 2.2 and 26.4 ± 0.3, respectively, for a 45 MeV proton beam and a 90Sr radioactive source. Imaging tests were performed using a Pb phantom with a 90Sr radioactive source and a 45 MeV proton beam, respectively. From the two-dimensional hit distribution, the phantom images were obtained and the position resolution was estimated to be about 240 μm.
Journal of Nuclear Science and Technology 08/2014; 45(sup5):344-347. DOI:10.1080/00223131.2008.10875859 · 1.45 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Avalanche photodiode (APD) is a kind of photodiode that internally amplifies the photocurrent by an avalanche effect. The quantum efficiency of the APD is about 80% which is five times higher than that of typical photomultiplier tube (PMT). A 16 mm diameter of beveled-edge large area avalanche photodiode (LAAPD) made by Advanced Photonics was used for the CsI(Tl) scintillator characterization. A CsI(Tl) crystal was attached to LAAPD and energy spectra were measured with various γ-ray sources. Measurements of energy spectra of the CsI(Tl) crystal to optimize the energy resolutions were performed with different shaping time constants by shaping amplifier and with different gains by high voltage variation. The absolute light yield and energy resolution of CsI(Tl) crystals were measured with the LAAPD for 662 keV γ-rays from a 137Cs source. The LAAPD was calibrated with X-ray of 55Fe source for the calibration of the number of e-h pairs per channel. The absolute light yield of newly developed SrCl2 scintillation crystal is determined by this method. This study shows that it is possible to use the LAAPD for the characterization of newly developed scintillation crystal and for the photo-sensor of scintillation detector.
Journal of Nuclear Science and Technology 08/2014; 45(sup5):586-589. DOI:10.1080/00223131.2008.10875923 · 1.45 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this paper, crystal growth and scintillation properties of Rb<sub>2</sub>CeBr<sub>5</sub> crystal are presented. The crystal was grown with the Bridgman method using a two zone transparent furnace. The investigation of scintillation properties of the crystal were performed under the excitation by X-ray and gamma;-ray at room temperature. The emission spectrum of the Rb<sub>2</sub>CeBr<sub>5</sub> was observed in the range of 360 ~ 440 nm, peaking at 390.5 nm, which is due to the 5d rarr 4f transitions of the Ce<sup>3+</sup>. The decay time of the Ce<sup>3+</sup> emission was composed two components. The fast component was 56.1 ns (98.8%), and the slow component was 329.9 ns (1.2%). The energy resolution of the crystal was obtained to be 6.9% for the <sup>137</sup>Cs 662 keV gamma-ray. The absolute light yield of the Rb<sub>2</sub>CeBr<sub>5</sub> crystal is about 34,000 phs/MeV, and the non-proportionality of the crystal was also measured.
[Show abstract][Hide abstract] ABSTRACT: We present results of design and simulation of the n-substrate reverse type avalanche photodiode (APD), which internally amplifies the photocurrent by an avalanche process, with the diffusion and the epitaxial methods. We aim to develop the APD which is coupled with scintillating materials for X-ray and delta-ray detections. The purpose of this simulation is to investigate optimal design parameters including guarding of the reverse type APD to meet device performance requirement as one of detector components. These optimized conditions obtained from simulation study can be applied in fabrication of the reverse type APD. In this simulation, both process and device simulations of APDs have been done by using a 2D simulation package, Athena and Atlas, from Silvaco International. The n-substrate reverse type APD based on the optimized design parameters will be fabricated and tested in near future.
[Show abstract][Hide abstract] ABSTRACT: We present the luminescent and scintillation characteristics of CsI:CO<sub>3</sub> single crystals. The CsI:CO<sub>3</sub> single crystals were grown by using Czochralski method for different concentrations of CO<sub>3</sub> from 0.007 to 0.1 mole%. The crystals were cut into a size of 10 mm times 10 mm times 5 mm. The luminescent characteristics were measured with X-rays to study the emission spectra of the CsI:CO<sub>3</sub> crystals. The scintillation properties of the CsI:CO<sub>3</sub> crystals such as fluorescence decay time, energy resolution, pulse height spectra, proportionality, and relative light output were studied by using various gamma-ray sources with a photomultiplier tube (PMT) at room temperature. The absolute light outputs of the crystals were also measured with an avalanche photo-diode (APD).
[Show abstract][Hide abstract] ABSTRACT: In this paper, we report on the improved scintillation properties of Cs2NaCeCl6 crystal. The Cs2NaCeCl6 crystal was grown by the Czochralski technique in the dimensions of ⊘10×4 mm3. X-ray excited luminescence measurements of the Cs2NaCeCl6 crystal showed a doublet emission spectrum in the wavelength range from 370 to 440 nm, peaking at 380 and 410 nm. An energy resolution (FWHM of peak position) for the 662-keV full energy peak of 8.3% was observed at room temperature. The scintillation properties were studied by using different gamma ray sources. We measured an absolute light yield of 20,000 photons/MeV of absorbed γ-ray energy. The crystal shows three main scintillation decay time components of 91 ns (36%), 601 ns (33%) and 3.2 μs (31%). The results show a good proportionality for light output versus γ-ray energy. The light output deviates from the linear response of 8% between the measured range of energy.
[Show abstract][Hide abstract] ABSTRACT: We report on a new scintillation crystal, CsCe2Cl7, for γ-ray spectroscopy. The crystal was grown using the Czocralski pulling method. X-ray excited luminescence measurements of the CsCe2Cl7 showed a broad emission band in the wavelength range from 370 to 470 nm with a peak centre at 410 nm. An energy resolution (FWHM of peak position) for the 662 keV full energy peak of 5.5% was observed at room temperature. The results showed a good proportionality for light output versus γ-ray energy. The light output deviation from the linear response is about 10% between the energy range of 31 and 1333 keV. We measured a light yield of 28,000 photons/MeV of absorbed γ-ray energy. The scintillation decay curve of CsCe2Cl7 can be described by a single exponential decay function with a decay time of 50 ns. Overall, these measurements clearly indicate that CsCe2Cl7 can exhibit attracting scintillation properties, and we believe that the CsCe2Cl7 crystal is a promising material for medical imaging and radiation detection.
[Show abstract][Hide abstract] ABSTRACT: Crystal growth, luminescence, and scintillation properties of a CeBr<sub>3</sub> crystal are presented. The crystal was grown with Bridgman method using two-zone transparent furnace and cut to Oslash10 times 10 mm<sup>3</sup>. The investigation of luminescence and scintillation properties of the CeBr<sub>3</sub> was performed under the excitation by ultraviolet and gamma-rays at room temperature. The emission spectrum of the CeBr<sub>3</sub> was observed in the range of near ultraviolet to violet, which is due to the 5d rarr 4f transition of Ce<sup>3+</sup>. The decay time of the Ce<sup>3+</sup> emission was measured to be approximately 20 ns. The energy resolution of the CeBr<sub>3</sub> single crystal was obtained to be 4.9% for the <sup>137</sup>Cs 662 keV gamma-rays. The relative signal of the CeBr<sub>3</sub> crystal by the <sup>137</sup>Cs gamma-rays is about three times higher than that of a CsI:Tl crystal when a bi-alkali PMT was used. The nonproportionality in the gamma-ray energy of the crystal was also measured. The study showed that the CeBr<sub>3</sub> crystal is the promising candidate for the PET application. The CeBr<sub>3</sub> crystal with high light output and fast decay time affords its use for the particle detection in a high counting rate environment such as nuclear and high-energy physics.
[Show abstract][Hide abstract] ABSTRACT: In this paper, we present scintillation properties of the new developed single crystals of Ba<sub>x</sub>Sr<sub>1-x</sub>Cl<sub>2</sub> for different concentration of x. We manufactured Ba<sub>0.12</sub>Sr<sub>0.88</sub>Cl<sub>2</sub>, Ba<sub>0.20</sub>Sr<sub>0.80</sub>Cl<sub>2</sub>, Ba<sub>0.22</sub>Sr<sub>0.78</sub>Cl<sub>2</sub> crystals, and CsI(Tl) crystal as reference by using the Czochralski method. The crystals were cut into a size of 5 times 10 times 10 mm<sup>3</sup>. The X-ray diffraction technique was used to verify the structure of crystals. The emission spectra were measured with X-ray excitation at room temperature. Scintillation properties of the crystals such as pulse height spectra, energy resolution, alpha/beta ratio, relative light output, proportionality, and fluorescence decay time were measured with the various radioactive gamma sources at room temperature. The light output of these crystals were compared with that of the CsI(Tl) crystal. The differences in relative light outputs, energy resolutions, and decay times among these crystals were studied in detail.
[Show abstract][Hide abstract] ABSTRACT: We grew a Gd-doped lead chloride single crystal by the Bridgman method and investigated scintillation properties of the crystals at low temperature. We measured the relative light yield, energy resolution, fluorescence decay time, and proportionality of the crystals for the gamma-ray at low temperature. The energy resolution is measured to be 25.6% for the<sup>137</sup>Cs 662 keV gamma-ray, and the fluorescence decay time of the crystal is composed of two components with decay times of 1.35 and 6.20 mus at 173 K.
[Show abstract][Hide abstract] ABSTRACT: The aim of this study is to develop scintillation crystals for the study of neutrinoless beta<sup>+</sup>/EC decay process. The <sup>84</sup>Sr isotope is one of the potential candidates for the neutrinoless beta<sup>+</sup>/EC decay process. None of the scintillation crystals containing a strontium element up till now were used for the study of neutrinoless beta<sup>+</sup>/EC decay process. In general our crystal growth program include studies of starting material preparation, growth procedures and characterization of grown crystals. We grew a SrCl<sub>2</sub> single crystal by using the Czochralski method. The cylindrical shape of the SrCl<sub>2</sub> crystal was cut into the dimensions of Oslash2 times 1.5 cm<sup>3</sup>. The scintillation properties were studied by using various gamma ray sources and an alpha source. The scintillation properties such as energy resolution, light output, linearity and decay time were presented. In particular, the alpha/beta light ratio and possibility of a pulse shape discrimination between alpha and gamma quanta using a <sup>210</sup>Po alpha source were studied.