산화물을 첨가한 HgI2 엑스선 검출기의 특성 평가

신정욱(Jungwook Shin),김진선(Jinseon Kim),조규석(Gyuseok Jo),오경민(Kyungmin Oh),김교태(Kyotae kim),강상식(Sangsik Kang),남상희(Sanghee Nam) 한국방사선학회 2014 한국방사선학회 학술대회 논문집 Vol.2014 No.춘계

To improve the performance of HgI2 composite x-ray detector, we studied its structure that reduced charge trap and estimated electrical properties as incident x-ray energy. The composite detector exhibits lower performance in x-ray sensitivity, dark current, and reproducibility than single-crystal detector or poly-crystal detector, because dielectric constant of polymeric glue and grain size of semiconductor particles affected charge transport properties. Therefore, in order to improve the charge transport properties, metal oxide such as SiO2 or TiO2 were added to HgI2 composite x-ray detector and its characteristics were investigated. The effect of metal oxide in HgI2 composite was analysed by comparing the properties of metal oxide mixed HgI2 composite x-ray detector with those of simple HgI2 composite x-ray detector. The samples were divided into three kinds of films, HgI2/TiO2 composite x-ray detector, HgI2/SiO2 composite x-ray detector, and simple HgI2 composite x-ray detector. All samples were fabricated by sedimentation method, one kind of particle-in-binder (PIB) methods. And the each thickness of them was around 200um. To investigate electrical properties of the samples, dark current of samples was measured as a function of applied bias. As a result, when 1 V/um of the electric field was applied, 4.78 nA/cm2, 16.58 nA/cm2, and 7.10 nA/cm2 were measured for HgI2/SiO2 composite x-ray detector, HgI2/TiO2 composite x-ray detector, and simple HgI2 composite x-ray detector. And then x-ray sensitivity of samples was measured in RQA-5 condition (70kVp, 100mA, 0.03s, 21mmAl phantom). The result respectively showed 23.15 nC/mR/cm2, 19.25 nC/mR/cm2, and 24.25 nC/mR/cm2 of x-ray sensitivity for the each samples. Furthermore, reproducibility, aging effect, and signal lag of samples were measured. Consequentially, the all measured results like dark current, x-ray sensitivity, reproducibility, and signal lag showed the best properties in HgI2/SiO2 composite x-ray detector among three kinds of samples

산화물을 첨가한 HgI₂ 엑스선 검출기의 특성 평가

신정욱(Jungwook Shin),김진선(Jinseon Kim),조규석(Gyuseok Jo),오경민(Kyungmin Oh),김교태(Kyotae kim),강상식(Sangsik Kang),남상희(Sanghee Nam) 한국방사선학회 2014 한국방사선학회 학술대회 논문집 Vol.8 No.1

To improve the performance of HgI2 composite x-ray detector, we studied its structure that reduced charge trap and estimated electrical properties as incident x-ray energy. The composite detector exhibits lower performance in x-ray sensitivity, dark current, and reproducibility than single-crystal detector or poly-crystal detector, because dielectric constant of polymeric glue and grain size of semiconductor particles affected charge transport properties. Therefore, in order to improve the charge transport properties, metal oxide such as SiO2 or TiO2 were added to HgI2 composite x-ray detector and its characteristics were investigated. The effect of metal oxide in HgI2 composite was analysed by comparing the properties of metal oxide mixed HgI2 composite x-ray detector with those of simple HgI2 composite x-ray detector. The samples were divided into three kinds of films, HgI2/TiO2 composite x-ray detector, HgI2/SiO2 composite x-ray detector, and simple HgI2 composite x-ray detector. All samples were fabricated by sedimentation method, one kind of particle-in-binder (PIB) methods. And the each thickness of them was around 200um. To investigate electrical properties of the samples, dark current of samples was measured as a function of applied bias. As a result, when 1 V/um of the electric field was applied, 4.78 nA/cm2, 16.58 nA/cm2, and 7.10 nA/cm2 were measured for HgI2/SiO2 composite x-ray detector, HgI2/TiO2 composite x-ray detector, and simple HgI2 composite x-ray detector. And then x-ray sensitivity of samples was measured in RQA-5 condition (70kVp, 100mA, 0.03s, 21mmAl phantom). The result respectively showed 23.15 nC/mR/cm2, 19.25 nC/mR/cm2, and 24.25 nC/mR/cm2 of x-ray sensitivity for the each samples. Furthermore, reproducibility, aging effect, and signal lag of samples were measured. Consequentially, the all measured results like dark current, x-ray sensitivity, reproducibility, and signal lag showed the best properties in HgI2/SiO2 composite x-ray detector among three kinds of samples

방사선 검출 효율을 증가시키기 위한 반도체 검출기 제작 및 평가

박정은(Jeongeun Park),홍주연(Juyeon Hong),김교태(Kyotae Kim),허예지(Yeji Heo),조규석(Gyuseok Jo),박성광(Sungkwang Park),남상희(Sanghee Nam) 한국방사선학회 2014 한국방사선학회 학술대회 논문집 Vol.2014 No.춘계

방사선 종류, 에너지 등 목적에 맞는 방사선 검출을 위해 기체 충전형 검출기, 열형광 검출기, 섬광검출기, 반도체 검출 기, 열량계 등이 이용되고 있으며, 그 중 직접 변환 방식 반도체 검출기는 신호 검출 과정에서 X선 손실량이 적고 디지털화가 가능한 장점이 있다. 본 연구에서는 직접 변환방식 반도체 검출기의 장점을 이용하고, X선 신호 수집량을 더욱 증가시켜 X선 발생 장치의 QA에 적용하고자 반도체 물질에 산화물을 혼합하여 검출기를 제작하고 신호 검출 특성을 평가하였다. 검출기 제작에는, 반도체 물질 HgI2를 산화물과 혼합하여 ITO Glass 위에 면적 3cm², 두께 210μm로 PIB법을 이용해 증착하였고, 건조시킨 검출기의 상부 전극은 진공 증착하여 형성하였다. X선 조사는100mA, 0.03s, 40~140kV로 변형하여 조사하였고, 검출기에 수집된 신호는 Oscilloscope의 파형으로 획득하였다. 제작한 검출기의 신호 특성을 기존 의 HgI2 검출기의 신호 특성과 비교하였다. 실험 결과, 기존의 HgI2 검출기에 비해 제작한 검출기의 검출 효율이 더 높은 것으로 나타났으며, 이러한 결과로써, X선 발생 장치의 QA 시 더욱 정확한 선량 측정이 가능할 것으로 사료된다. To detect the radiation, many kinds of the detectors are used such as Gas Filled Detector, Thermoluminescence detector and Scintillation counter, Semiconductor detector, Calorimeter. Especially, direct conversion semiconductor detector has the advantages such as low losses of X-ray in the process of signal detection, digitization. In this study, using PIB method, we fabricated the direct conversion semiconductor detector based HgI2 mixed with TiO2 for application to radation QA decive with increased detection efficiency. Using the fabricated the detector, we measured the X-ray signal for the quality assurance in the exposure condition of 40~140kVp, 3mAs. And evaluated electrical properties of the fabricated detector. we compared the experimental data of existing HgI2 detector with the fabricated detector. As a result of the experiment, fabricated detector shows 10% higher sensitivity and SNR than that of the existing data, Based on the results, it is considered that the fabricated detector can be precisely measured as QA of radiation device.

방사선 검출 효율을 증가시키기 위한 반도체 검출기 제작 및 평가

박정은(Jeongeun Park),홍주연(Juyeon Hong),김교태(Kyotae Kim),허예지(Yeji Heo),조규석(Gyuseok Jo),박성광(Sungkwang Park),남상희(Sanghee Nam) 한국방사선학회 2014 한국방사선학회 학술대회 논문집 Vol.8 No.1

방사선 종류, 에너지 등 목적에 맞는 방사선 검출을 위해 기체 충전형 검출기, 열형광 검출기, 섬광검출기, 반도체 검출기, 열량계 등이 이용되고 있으며, 그 중 직접 변환 방식 반도체 검출기는 신호 검출 과정에서 X선 손실량이 적고 디지털화가 가능한 장점이 있다. 본 연구에서는 직접 변환방식 반도체 검출기의 장점을 이용하고, X선 신호 수집량을 더욱 증가시켜 X선 발생 장치의 QA에 적용하고자 반도체 물질에 산화물을 혼합하여 검출기를 제작하고 신호 검출 특성을 평가하였다. 검출기 제작에는, 반도체 물질 HgI2를 산화물과 혼합하여 ITO Glass 위에 면적 3cm², 두께 210μm로 PIB법을 이용해 증착하였고, 건조시킨 검출기의 상부 전극은 진공 증착하여 형성하였다. X선 조사는100mA, 0.03s, 40~140kV로 변형하여 조사하였고, 검출기에 수집된 신호는 Oscilloscope의 파형으로 획득하였다. 제작한 검출기의 신호 특성을 기존의 HgI2 검출기의 신호 특성과 비교하였다. 실험 결과, 기존의 HgI2 검출기에 비해 제작한 검출기의 검출 효율이 더 높은 것으로 나타났으며, 이러한 결과로써, X선 발생 장치의 QA 시 더욱 정확한 선량 측정이 가능할 것으로 사료된다. To detect the radiation, many kinds of the detectors are used such as Gas Filled Detector, Thermoluminescence detector and Scintillation counter, Semiconductor detector, Calorimeter. Especially, direct conversion semiconductor detector has the advantages such as low losses of X-ray in the process of signal detection, digitization. In this study, using PIB method, we fabricated the direct conversion semiconductor detector based HgI2 mixed with TiO2 for application to radation QA decive with increased detection efficiency. Using the fabricated the detector, we measured the X-ray signal for the quality assurance in the exposure condition of 40~140kVp, 3mAs. And evaluated electrical properties of the fabricated detector. we compared the experimental data of existing HgI2 detector with the fabricated detector. As a result of the experiment, fabricated detector shows 10% higher sensitivity and SNR than that of the existing data, Based on the results, it is considered that the fabricated detector can be precisely measured as QA of radiation device.