• Journal of Radiation Protection and Research
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• 제41권2호
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• pp.81-86
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• 2016

Background: For positron emission tomography (PET) application, cadmium zinc telluride (CZT) has been investigated by several institutes to replace detectors from a conventional system using photomultipliers or Silicon-photomultipliers (SiPMs). The spatial and energy resolution in using CZT can be superior to current scintillator-based state-of-the-art PET detectors. CZT has been under development for several years at the Korea Atomic Energy Research Institute (KAERI) to provide a high performance gamma ray detection, which needs a single crystallinity, a good uniformity, a high stopping power, and a wide band gap. Materials and Methods: Before applying our own grown CZT detectors in the prototype PET system, we investigated preliminary research with a developed discrete type data acquisition (DAQ) system for coincident events at 128 anode pixels and two common cathodes of two CZT detectors from Redlen. Each detector has a $19.4{\times}19.4{\times}6mm^3$ volume size with a 2.2 mm anode pixel pitch. Discrete amplifiers consist of a preamplifier with a gain of $8mV{\cdot}fC^{-1}$ and noise of 55 equivalent noise charge (ENC), a $CR-RC^4$ shaping amplifier with a $5{\mu}s$ peak time, and an analog-to-digital converter (ADC) driver. The DAQ system has 65 mega-sample per second flash ADC, a self and external trigger, and a USB 3.0 interface. Results and Discussion: Characteristics such as the current-to-voltage curve, energy resolution, and electron mobility life-time products for CZT detectors are investigated. In addition, preliminary results of gamma ray imaging using 511 keV of a $^{22}Na$ gamma ray source were obtained. Conclusion: In this study, the DAQ system with a CZT radiation sensor was successfully developed and a PET image was acquired by two sets of the developed DAQ system.

• Journal of Radiation Protection and Research
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• 제39권1호
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• pp.14-20
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• 2014

원전 내 방사선작업종사자 피폭량의 대부분은 계획예방정비기간 중 냉각재계통에 존재하는 $^{58}Co$, $^{60}Co$등과 같은 CRUD에 의하여 일어난다. 따라서 원전 내 방사선작업종사자의 피폭 최적관리를 위해서는 냉각재계통의 선원항을 사전에 파악할 필요가 있다. 이 연구는 원전 내 선원항을 알아보기 위해 국내 최초로 계획예방정비 기간 중 증기발생기 부근에서 CZT 반도체 검출기를 이용한 배관 직접 측정법을 사용하였다. 또한 신규원전과 노후원전에서 선원항의 차이를 알아보기 위해 두 원전에서 측정한 결과를 비교 하였고 노후원전에 대하여는 정지화학처리에 따른 선원항의 변화를 측정하였다. 노후원전에서 정지화학처리에 따른 선원항 변화는 발견되지 않았으며, 신규원전 및 노후원전의 주요 선원항은 $^{58}Co$와 $^{60}Co$ 였고, $^{59}Fe$는 신규원전에서만 $^{137}Cs$와 $^{95}Zr$는 노후원전에서만 보였다. $^{58}Co/^{60}Co$의 비율은 노후원전보다 신규원전에서 크게 나타났으며 운전연한이 증가 할수록 반감기가 긴 $^{60}Co$의 비방사능이 커지기 때문이다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1997년도 춘계학술대회 논문집
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• pp.338-341
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• 1997

According to reports, it is impossible to make Ohmic Contact with high resistivity p type CdTe or CdZnTe semiconductor theoretically. But it is in need of making Ohmic Contact to fabricate semiconductor radiation detector By electroless deposition method using gold chloride solution, we made Ohmic Contact of Au and p-Cd$_{80}$Zn$_{20}$Te which grown by High Presure Bridgman Method in Aurora Technologies Corporation. We investigated the interface with Rutherford Backscattering Spectrometry and Auger electron spectroscopy. And we evaluated the degree of Ohmic Contact for the Au/CdZnTe interface by the I/V characteristic curve. As a result, we concluded that it showed excellent Ohmic Contact property by tunneling mechanism through the interface.e.

• Nuclear Engineering and Technology
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• 제43권6호
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• pp.567-572
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• 2011

A sensitivity analysis of the methods used to evaluate the transport properties of a CdZnTe detector was performed using two different radiations (${\alpha}$ particle and gamma-ray) emitted from an $^{241}Am$ source. The mobility-lifetime products of the electron-hole pair in a planar CZT detector ($5{\times}5{\times}2\;mm^3$) were determined by fitting the peak position as a function of biased voltage data to the Hecht equation. To verify the accuracy of these products derived from ${\alpha}$ particles and low-energy gamma-rays, an energy spectrum considering the transport property of the CZT detector was simulated through a combination of the deposited energy and the charge collection efficiency at a specific position. It was found that the shaping time of the amplifier module significantly affects the determination of the (${\mu}{\tau}$) products; the ${\alpha}$ particle method was stabilized with an increase in the shaping time and was less sensitive to this change compared to when the gamma-ray method was used. In the case of the simulated energy spectrum with transport properties evaluated by the ${\alpha}$ particle method, the peak position and tail were slightly different from the measured result, whereas the energy spectrum derived from the low-energy gamma-ray was in good agreement with the experimental results. From these results, it was confirmed that low-energy gamma-rays are more useful when seeking to obtain the transport properties of carriers than ${\alpha}$ particles because the methods that use gamma-rays are less influenced by the surface condition of the CZT detector. Furthermore, the analysis system employed in this study, which was configured by a combination of Monte Carlo simulation and the Hecht model, is expected to be highly applicable to the study of the characteristics of CZT detectors.

• 대한방사선기술학회지:방사선기술과학
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• 제25권2호
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• pp.71-75
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• 2002

검출능력이 우수하고 가격이 저렴하며 소형으로 제작할 수 있는 반도체검출기 중에서도 광전소지인 포토다이오드를 이용하였는데 이 소자는 특정표면이 입사광에 대하여 반응을 나타내는 소자인데 광 강도가 증가함에 따라 저항이 감소하는 특성을 이용하여 방사선 검출기를 제작하였다. 제작된 측정기는 접속식 측정기에 의해 검사치를 측정하여 기준치를 정하고 기존의 비접속형 측정기를 이용하여 제작된 비접속형 측정기와 정확성을 비교 검토하였다. 비교 결과 3가지 측정기의 모든 측정치가 기준치 범위에 속하였으며 정밀도를 분석하기 위하여 백분율 평균오차의 평균치를 구하였는데 기준측정기의 백분율평균오차의 평균치가 -0.02이고 비교측정기가 -0.22, 제작한 측정기가 0.17이었다.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2005년도 추계학술발표회
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• pp.735-736
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• 2005

• Nuclear Engineering and Technology
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• 제55권10호
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• pp.3844-3853
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• 2023

Although radiation and chemotherapy methods for cancer therapy have advanced significantly, surgical resection is still recommended for most cancers. Therefore, intraoperative imaging studies have emerged as a surgical tool for identifying tumor margins. Intraoperative imaging has been examined using conventional imaging devices, such as optical near-infrared probes, gamma probes, and ultrasound devices. However, each modality has its limitations, such as depth penetration and spatial resolution. To overcome these limitations, hybrid imaging modalities and tracer studies are being developed. In a previous study, a multi-modal laparoscope with silicon photo-multiplier (SiPM)-based gamma detection acquired a 1 s interval gamma image. However, improvements in the near-infrared fluorophore (NIRF) signal intensity and gamma image central defects are needed to further evaluate the usefulness of multi-modal systems. In this study, an attempt was made to change the NIRF image acquisition method and the SiPM-based gamma detector to improve the source detection ability and reduce the image acquisition time. The performance of the multi-modal system using a complementary metal oxide semiconductor and modified SiPM gamma detector was evaluated in a phantom test. In future studies, a multi-modal system will be further optimized for pilot preclinical studies.

• 한국의학물리학회지:의학물리
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• 제26권4호
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• pp.280-285
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• 2015

방사선 치료분야 중 근접치료는 방사성 동위원소를 체내에 직접 삽입하여 병변 세포를 사멸시키는 치료법으로써, 주로 고선량률 치료가 시행되고 있다. 현재 치료계획과 실제 선량 방출범위의 일치성 여부는 Film/Screen 시스템을 통해 확인하고, 확인된 선량분포에 따라 방사선 치료를 시행하고 있다. 선량 분포 확인 시 F/S 시스템을 이용할 경우, Film 현상조건에 따른 신호 왜곡과 반음영에 의한 저분해능으로 인하여 치료계획과의 선량 분포 일치성을 정량적으로 파악하기 힘든 단점이 있다. 본 연구에서는 방사선 근접치료 시 치료계획과 동일한 선량 분포 여부를 확인하는 디지털 검출시스템의 기초 연구를 진행하고자, PIB법을 이용한 $HgI_2$ 반도체 검출센서를 제작하였다. 또한 이를 근접치료선원을 이용해 평가함으로써, QA 시스템으로 이용 가능성을 검증하고자 하였다. 근접치료 범위의 확인을 위하여 SDD의 변화에 대한 신호 수집량을 평가한 결과, 치료 범위 이상의 거리에서는 산란선으로 추정되는 낮은 신호만이 측정되었으므로 치료 계획시와 동일한 치료 범위를 정량적으로 확인할 수 있었다. 또한 동일한 ${\gamma}$-선 조사 조건에 대한 재현성 평가 결과, 변동계수 1.5% 이내인 것을 확인하였다. 이와 같은 결과를 바탕으로, 본 연구에서 제작한 센서는 방사선 근접치료 QA 시스템으로 적용 가능할 것이라 사료된다.

• 반도체디스플레이기술학회지
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• 제16권2호
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• pp.15-18
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• 2017

In this study, we have studied the characteristics of the organic photodiode varying due to the blending conditions of the quantum dots (QDs). The active layer of the photodiode was formed with poly (3-hexylthiophene) and phenyl-C61-butyric acid methyl ester, and CdSe QDs with and without ZnS shell were blended in the active layer. The photodiode with CdSe/ZnS QDs showed the highest power conversion efficiency (PCE) and short-circuit current (Jsc). The performance change of the organic photodiode by X-ray irradiation was also measured. Regardless of X-ray irradiation conditions, the photodiode with CdSe/ZnS QDs showed better stability than other cases.

• 방사선산업학회지
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• 제10권1호
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• pp.37-41
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• 2016

The recent prevalence of PET examinations in Korea has led to an increase in the number of cyclotrons. The medical isotope $^{18}F$ produced in most cyclotron facilities currently operating in Korea is emitted into the environment during the production of [$^{18}F$]FDG, a cancerdiagnosis reagent. The amount of [$^{18}F$]FDG synthesized determines the radioactive concentration of $^{18}F$ in the exhaust. At some facilities, this amount temporarily exceeds the emission limit. In this study, we evaluated the $^{18}F$ radioactivity concentration in the exhaust from the cyclotron facility at Chosun University. The $^{18}F$ radioactivity concentration was measured using an air sampler and a HPGe semiconductor detector. The measurements showed that the radioactive concentration of $^{18}F$ in the exhaust at the cyclotron facility at Chosun University was the highest during [$^{18}F$]FDG synthesis but remained under the legal limit of $2,000Bq\;m^{-3}$.