• Nuclear Engineering and Technology
• /
• v.53 no.6
• /
• pp.1947-1954
• /
• 2021

In the nuclear medicine imaging, quality control (QC) process using quadrant bar phantom is fundamental aspect of evaluating the spatial resolution. In addition, QC process of gamma camera is performed by daily or weekly. Recently, Monte Carlo simulation using the Geant4 application for tomographic emission (GATE) is widely applied in the pre-clinical nuclear medicine field for modeling gamma cameras with pixelated cadmium telluride (CdTe) semiconductor detector. In this study, we modeled a pixelated CdTe semiconductor detector and quadrant bar phantom (0.5, 1.0, 1.5, and 2.0 mm bar thicknesses) using the GATE tool. Similarity analysis based on correlation coefficients and peak signal-to-noise ratios was performed to compare image qualities for various source to collimator distances (0, 2, 4, 6, and 8 cm) and collimator lengths (0.2, 0.4, 0.6, 0.8, and 1.0 cm). To this end, we selected reference images based on collimator length and source to collimator distance settings. The results demonstrate that as the collimator length increases and the source to collimator distance decreases, the similarity to reference images improves. Therefore, our simulation results represent valuable information for the modeling of CdTe-based semiconductor gamma imaging systems and QC phantoms in the field of nuclear medicine.

• Nuclear Engineering and Technology
• /
• v.54 no.12
• /
• pp.4652-4659
• /
• 2022

Among the detector materials available at room temperature, thallium bromide (TlBr), which has a relatively high atomic number and density, is widely used for gamma camera imaging. This study aimed to verify the usefulness of TlBr through quantitative evaluation by modeling detectors of various compound types using Monte Carlo simulations. The Geant4 application for tomographic emission was used for simulation, and detectors based on cadmium zinc telluride and cadmium telluride materials were selected as a comparison group. A pixel-matched parallel-hole collimator with proven excellent performance was modeled, and phantoms used for quality control in nuclear medicine were used. The signal-to-noise ratio (SNR), contrast to noise ratio (CNR), sensitivity, and full width at half maximum (FWHM) were used for quantitative analysis to evaluate the image quality. The SNR, CNR, sensitivity, and FWHM for the TlBr detector material were approximately 1.05, 1.04, 1.41, and 1.02 times, respectively, higher than those of the other detector materials. The SNR, CNR and sensitivity increased with increasing detector thickness, but the spatial resolution in terms of FWHM decreased. Thus, we demonstrated the feasibility and possibility of using the TlBr detector material in comparison with commercial detector materials.

• Nuclear Engineering and Technology
• /
• v.55 no.5
• /
• pp.1718-1733
• /
• 2023

The virtual Frisch-grid method for room-temperature radiation detectors has been widely used because of its simplicity and high performance. Recently, side electrodes were separately attached to each surface of the detectors instead of covering the entire detector surface with a single electrode. The side-electrode structure enables the measurement of the three-dimensional (3D) gamma-ray interaction in the detector. The positional information of the interaction can then be utilized to precisely calibrate the response of the detector for gamma-ray spectroscopy and imaging. In this study, we developed a 3D position-sensitive 5 × 5 × 12 mm³ cadmium-zinc-telluride (CZT) detector and applied a flattening method to correct detector responses. Collimated gamma-rays incident on the surface of the detector were scanned to evaluate the positional accuracy of the detection system. Positional distributions of the radiation interactions with the detector were imaged for quantitative and qualitative evaluation. The energy spectra of various radioisotopes were measured and improved by the detector response calibration according to the calculated positional information. The energy spectra ranged from 59.5 keV (emitted by ²⁴¹Am) to 1332 keV (emitted by ⁶⁰Co). The best energy resolution was 1.06% at 662 keV when the CZT detector was voxelized to 20 × 20 × 10.

• Journal of the Korean Magnetics Society
• /
• v.26 no.2
• /
• pp.39-44
• /
• 2016

Determination of the structural, electronic, and magnetic properties of the magnetically doped bismuth-telluride alloys are drawing lots of interest in the fields of the thermoelectric application as well as the research on magnetic interaction and topological insulator. In this study, we performed the first-principles electronic structure calculations within the density functional theory for the Gd doped bismuth-tellurides in order to study its magnetic properties and magnetic phase stability. All-electron FLAPW (full-potential linearized augmented plane-wave) method is employed and the exchange correlation potentials of electrons are treated within the generalized gradient approximation. In order to describe the localized f-electrons of Gd properly, the Hubbard +U term and the spin-orbit coupling of the valence electrons are included in the second variational way. The results show that while the Gd bulk prefers a ferromagnetic phase, the total energy differences between the ferromagnetic and the antiferromagnetic phases of the Gd doped bismuth-telluride alloys are about ~1meV/Gd, indicating that the stable magnetic phase may be changed sensitively depending on the structural change such as defects or strains.

• The Journal of the Korea Contents Association
• /
• v.9 no.10
• /
• pp.451-463
• /
• 2009

The purpose of this research is to develop thin film materials and fabrication process for efficient $TiO_2$/CdTe solar cells. In this work photocatalyst titanium dioxide was prepared by sol-gel procedure according to reaction condition, the mole ratio of $H_2O$/TTIP, pH of solution and aging condition of powder. The prepared titanium dioxide was thermally treated from 300 to $750^{\circ}C$. Maximum intensity of anatase phase of titanium dioxide was achieved by calcination at $600^{\circ}C$ for 2 hr. And it was mixture of anatase and rutile phase when temperature of calcination was $750^{\circ}C$. It has been known that the properties of synthesized titanium dioxide according to aging time and calcination temperature was converted to anatase phase crystal on increasing of aging time. Also the current density has been increased with aging time and temperature, the efficiency has been increased with because of reason on above results. The formation of chemical bonding on oxygen and cadmium telluride under oxygen circumstances had been observed, and oxygen of thin film surface on cadmium telluride had been decreased with the treatment of chromate and hydrazine. As results had been shown that the energy conversion efficiency of cadmium telluride use by rapidly treatmented heat at the condition of $550^{\circ}C$ under air circumstance got 12.0%, 6.0% values according to $0.07cm^2$, $1.0cm^2$ surface area, respectively.

• Journal of the Korean Chemical Society
• /
• v.53 no.5
• /
• pp.530-535
• /
• 2009

Dicyclohexyl telluride was obtained in a high yield by the reaction of cyclohexyl bromide with NaTeH(prepared in situ) in an aqueous ethanolic solution. A series of new organotelluronium salts of the general formula ${(cyclo-C_6H_11)}_2Te(R)X$ (where R = $CH_3$, X = I (1); R = $C_2H_5$, X = Br(2); R = $C_2H_5$, X = I (3); R = C_3H_5$, X = Br (4)) were prepared by the reaction of ${(cyclo-C_6H_11)}_2Te$ with the corresponding alkyl halide. Reaction of 1 with NaBPh4 gave compound 5 ( i.e. R = CH3, X = BPh4 ‒) in 78% yield. Reaction of ${(cyclo-C_6H_11)}_2Te$ with benzyl bromide and 4-bromophenacyl bromide gave unexpectedly dibenzylcyclohexyltelluronium bromide (6) and bis(4-bromophenacyl)cyclohexyltelluronium bromide (7), respectively. Reaction of 6 with NaBPh4 gave the corresponding tetraphenylborate derivative (8) in high yield. $^1H$ NMR studies revealed that in $CDCl_3$solution compound 1 eliminated alkyl halide. Conductivity, IR, $^1H\;and\;^{13}C$ NMR and thermal data for the new compounds are presented and discussed.

• Journal of the Korean Ceramic Society
• /
• v.27 no.4
• /
• pp.481-486
• /
• 1990

Microstructure of polycrystalline Lead Telluride was controlled by the change of sintering conditions. Three properties which determine the thermoelectric figure of merit of the material were measured in the temperature range of 300-650K in order to investigate the effect of each sintering condition on the thermoelectric efficiency. Based on the observed experimental results, defect structure is concluded to be more important than microstructure though both can be controlled by processing variables.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2008.02a
• /
• pp.134-134
• /
• 2008

• Solar Energy
• /
• v.8 no.2
• /
• pp.73-76
• /
• 1988

Thick films based on the mature crystalline silicon technology are expected to exhibit eversmaller cost reduction. The thin-film-based technology is, however, expected to exhibit a much sharper drop in cost as it develops. In this report, technology and recent R & D of thin film solar cell, such as amorphous silicon, cadnium telluride, copper indium diselenide and gallium arsenide, are described. Perspectives of world photovoltaic market and solar cell price are also described.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2012.05a
• /
• pp.734-736
• /
• 2012

Cadmium telluride (CdTe) films have been prepared on Corning 7059 glass, molybdenum (Mo), and polyimide (PI) substrates by r.f. magnetron sputtering technique. The influence of the sputter pressure on the structural and optical properties of these films was evaluated. In addition, a comparison of the properties of the films deposited on fferent substrates was performed.