• 한국방사선학회논문지
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• 제17권6호
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• pp.897-902
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• 2023

본 논문에서는 휴대용 X-ray 검출기의 방사선 고감도 검출에 대한 실현 가능 여부를 확인하기 위한 SiPM의 특성 분석을 목적으로 한다. 휴대용 X-ray 검출기는 환자의 위치에 빠르게 접근하여 실시간 이미지를 획득함으로써 의사들은 신속하게 진단을 수행할 수 있는 장점이 있지만 이러한 이동성은 선량 감지의 어려움을 동반한다. 기존 검출기에서는 SiPM을 X-ray Trigger를 판별하는 단순한 용도로 사용하고 있다. SiPM을 통한 X-ray의 고감도 검출 가능 여부를 확인하기 위해 7종의 SiPM Sensor를 비교 선정하고 특성 분석을 진행하였다. 최종 시험에 사용한 SiPM은 10 nGy 수준의 극저선량 조사 조건에서 Signal 구분이 가능하며, 관전압에 따라 Signal 상승곡선의 기울기가 변하는 것이 확인되었다. X-ray 선량에 따라 SiPM의 signal level 및 지속시간이 변화되는 특성을 이용한 고감도 측정이 가능할 것으로 보인다.

• Nuclear Engineering and Technology
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• 제52권1호
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• pp.164-169
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• 2020

Use of SiPM has been considered as an alternative to PMT, because of its compact size, low-operating voltage, non-sensitive to electromagnetic, low costs and so on. The main limitation for the use of SiPM is due to its small sensitive area compared to PMT that limits the light collection, and therefore the sensor energy resolution. In this article we studied the effect of increasing the number of SiPM by connecting them in parallel to increase the active detection area. This allowed us to compare the different energy resolution measurements. ¹³⁷Cs has been selected as reference to study the energy resolution for 662 keV gamma-rays. Another investigation was to compare the minimum detectable gamma energy under various SiPM configurations. It has been found that the use of 4 SiPM arrays can greatly improve the energy resolution up to 4% than only one SiPM array, meanwhile use of more than 2 SiPM arrays does not increase the energy resolution significantly. Thus we can conclude that for a large area of cylindrical scintillator (3 × 3 inches), the use of SiPMs are limited to a certain number or certai active area depending on the commercial SiPMs, and its cost should be less than traditional PMT for the cost-effective and compact size considerations. It is well known that the gain of SiPM varies with temperature. In this article, we also calibrated gain to guarantee the same position of photoelectric peak in response of different temperatures.

• Nuclear Engineering and Technology
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• 제54권7호
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• pp.2564-2571
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• 2022

SiPMs are generally coupled into whole columns in gamma energy spectrum measurement, but the relationship between the distribution of whole SiPM columns and the energy resolution of the measured energy spectra is rarely reported. In this work, ∅ 3 × 3 inch NaI scintillator is placed on an 8 × 8 SiPM array, and the energy resolution of the ¹³⁷Cs peak at 662 keV corresponding to the γ-ray is selected as a reference. Each SiPM is switched to explore the influence of the number of SiPM arrays, distribution position, and reflective layer on the energy resolution of SiPMs. Results show that without coupling, the energy resolution is greatly improved when the number of SiPMs ranges from 4 to 32. However, after 32 slices (the area covered by SiPMs relative to the scintillator reaches 25.9%), the improvement in energy resolution and total pulse count is not obvious. In addition, the position of SiPMs relative to the scintillator does not exert much impact on the energy resolution. Results also indicate that by adding a reflective film (ESR), the energy resolution of the tested group increases by 10.38% on average. This work can provide a reference for the design and application of miniaturized SiPM gamma spectrometers.

• 전기전자학회논문지
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• 제26권3호
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• pp.510-514
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• 2022

본 논문에서는 고감도 보급형 방사선 측정센서 모듈 개발을 제안한다. 제안하는 측정센서 모듈은 섬광체+광증배소자(SiPM) 센서 최적화 구조설계, 센서 드라이버용 증폭과 필터 및 제어회로 설계, 근거리 통신을 포함한 제어회로 설계, 센서 기구설계 및 제작, 시제품에 적용되는 GUI 개발 등으로 구성된다. 섬광체+광증배소자(SiPM) 센서 최적화 구조 설계는 센서 구조 설계를 위한 섬광체와 광증배소자(SiPM)의 특성을 확인하여 설계한다. 센서 드라이버용 증폭과 필터 및 제어회로 설계는 SiPM을 이용하여 섬광체로 방사선에 의해 발생하는 미세 섬광신호를 처리하도록 설계한다. 근거리 통신을 포함한 제어회로 설계는 근거리 무선통신 기능을 지원하기 위한 MCU 설계 및 유선 통신 지원을 통해 데이터 전송이 가능하도록 설계를 수행한다. 센서 기구설계 및 제작은 플라스틱 섬광체에서 발생한 미세 섬광 신호를 광증배소자(SiPM)에 전달하기 위해 플라스틱 섬광체 외부에 반사지(미러링)를 감싸 발생한 섬광이 반사되어 효율을 높이도록 설계한다. 시제품에 적용되는 GUI 개발은 각 화면에 따라 상단에 날짜와 시간을 표현하며, 측정단위 및 시간, 초, 알람 레벨, 통신상태, 배터리 용량 등이 표현되도록 한다. 제안된 시스템의 성능을 평가하기 위하여 공인시험기관에서 실험한 결과는 방사선량 측정 범위가 30𝜇Sv/h ~ 10mSv/h로 측정되어서, 현재 국내외에서 상용으로 판매되는 제품들 중에서 최고수준 범위와 같은 결과가 산출되었다. 또한, ±7.4%의 측정 불확도가 측정되어서 국제 표준인 ±15% 이하에서 정상동작 됨이 확인되었다

• 한국환경과학회지
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• 제26권12호
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• pp.1333-1339
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• 2017

Coal-fired power plants emit various Particulate Matter(PM) at coal storage pile and ash landfill as well as the stack, and affect the surrounding environment. Field Emission Scanning Electron Microscopy and Energy Dispersive X-ray analyzer(FE-SEM/EDX) were used to develop identification factor and the physico-chemical analysis of PM emitted from a power plant. In this study, three samples of pulverized coal, bottom ash, and fly ash were analyzed. The pulverized coal was spherical particles in shape and the chemical composition of C-O-Si-Al and C/Si and C/Al ratios were 200~300 on average. The bottom ash was spherical or non-spherical particles in shape, chemical composition was O-C-Si-Al-Fe-Ca and C/Si and C/Al ratios were $4.3{\pm}4.6$ and $8.8{\pm}10.0$. The fly ash was spherical particles in shape, chemical composition was O-Si-Ai-C-Fe-Ca and C/Si and C/Al ratios were $0.5{\pm}0.2$ and $0.8{\pm}0.5$.

• Nuclear Engineering and Technology
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• 제52권10호
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• pp.2346-2352
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• 2020

Dual-energy x-ray absorptiometry (DXA) is the noninvasive method to diagnose osteoporosis disease characterized by low bone mass and deterioration of bone tissue. Many global companies and research groups have developed the various DXA detectors using a direct photon-counting detector such as a cadmium zinc telluride (CZT) sensor. However, this approach using CZT sensor has some drawback such as the limitation of scalability by high cost and the loss of efficiency due to the requirement of a thin detector. In this study, a SiPM based DXA system was developed and its performance evaluated experimentally. The DXA detector was composed of a SiPM sensor coupled with a single LYSO scintillation crystal (3 × 3 × 2 ㎣). The prototype DXA detector was mounted on the dedicated front-end circuit consisting of a voltage-sensitive preamplifier, pulse shaping amplifier and constant fraction discriminator (CFD) circuit. The SiPM based DXA detector showed the 34% (at 59 keV) energy resolution with good BMD accuracy. The proposed SiPM based DXA detector showed the performance comparable to the conventional DXA detector based on CZT.

• Bulletin of the Korean Chemical Society
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• 제8권4호
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• pp.242-246
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• 1987

The hydrogen abstraction reactions of $SiH_4, SiH_2Cl_2 \;and\; SiHCl_3$ by ground state chlorine atoms generated photochemically from chlorine molecules have been studied at temperatures between 15 and $100^{\circ}C.$ The absolute rates for the reactions have been obtained by a competition technique using ethane as a competitor. The rate expressions ($in cm^3/mol/s$) are found to conform to an Arrhenius rate law: $k_{SiH_4} = (7.98 {\pm} 0.42) {\times} 10^{13}$ exp $[-(1250 {\pm}20)/T].$ $k_{SiH_2Cl_2} = (2.25 {\pm} 0.12) {\times} 10^{15}$ exp[-(1010 ${\pm}$ 10)/T]. $k_{SiHCl_3} = (9.04 {\pm} 0.28) {\times} 10^{14}\; exp[-(1200 {\pm} 10)/T].$ The activation energies obtained from this study represent the same trend as with the carbon analogues, while this trend was not found with respect to the bond dissociation energies among silicon compound homologues. These anomalous behaviors were interpreted in terms of electronic effects and of the structural differences between these compounds.

• Journal of Radiation Protection and Research
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• 제24권1호
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• pp.39-43
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• 1999

최근 개발된 감도가 좋은 LiF:Mg,Cu,Na,Si TL물결을 Teflon과 혼합한 후, 않은 디스크 형태로 압축 성형한 얇은 LiF:Mg,Cu,Na,Si Teflon 검출기를 제작하고 베타선 검출기로서의 TL 반응특성을 연구하였다. 한국원자력연구소의 $^{147}Pm,\;^{204}Tl$ 및 $^{90}Sr/^{90}Y$ 베타선원을 이용하여 두께 $2mg/cm^2$인 Kapton 박막을 덮은 상태로 베타선을 조사하였다. 제작한 않은 LiF:Mg,Cu,Na,Si 검출기들의 $^{137}Cs$에 대한 batch 균질성은 4.7%, 베타선에 대한 선량의존성은 0.1 mGy에서 100 Gy까지 선형성을 나타내고, 에너지의존성은 $^{147}Pm,\;^{204}Tl$ 및 $^{90}Sr/^{90}Y$ 베타선에 대해 각각 0.46, 1.09 및 1.06 이었다. 그리고 베타선에 대한 방향의존성은 $0.93{\pm}0.03\;(^{147}Pm),\;0.94{\pm}0.04\;(^{204}Tl)$ 및 $0.92{\pm}0.05\;(^{90}Sr/^{90}Y)$으로, 이들 얇은 LiF:Mg,Cu,Na,Si 검출기들에 대한 TL 반응특성의 결과는 국제표준기구(ISO)의 베타선량계 기준을 잘 만족하였다.

• 한국진공학회지
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• 제7권1호
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• pp.5-10
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• 1998

CAICISS장치를 이용하여 깨끗한 Si(001) 표면에서 재배열하는 dimer의 원자구조를 분석하였다. Si(001) 표면에서 dimer원자가 확실히 buckled되어 있음을 확인하였고, asymmetry(2$\times$1)구조와 c(4$\times$2)구조가 공존하고 있음을 밝혔다. dimer원자의 결합거리는 2.3$\pm$0.1$\AA$이고, buckling각은 18$\pm$$1^{\circ}$였다.

• Journal of Magnetics
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• 제22권1호
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• pp.146-149
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• 2017

In this study, we compared the standardized value of each signal intensity, the apparent diffusion coefficient (ADC) that digitizes the diffusion of water molecules, and the signal to noise ratio (SNR) using b value 0 400, 1400 ($s/mm^2$). From March 2013 to December 2013, patients with suspicion of simple compound fracture and metastatic spine cancer were included in the MR readout. We used a 1.5 Tesla Achieva MRI system and a Syn-Spine Coil. Sequence is a DWI SE-EPI sagittal (diffusion weighted imaging spin echo-echo planar imaging sagittal) image with b-factor ($s/mm^2$) 0, 400, 1400 were used. Data analysis showed ROI (Region of Interest) in diseased area with high SI (signal intensity) in diffusion-weighted image b value 0 ($s/mm^2$) Using the MRIcro program, each SI was calculated with images of b-value 0, 400, and 1400 ($s/mm^2$), ADC map was obtained using Metlab Software with each image of b-value, The ADC is obtained by applying the ROI to the same position. The standardized values ($SI_{400}/SI_0$, $SI_{400}/SI_0$) of simple compression fractures were $0.47{\pm}0.04$ and $0.23{\pm}0.03$ and the standardized values ($SI_{400}/SI_0$, $SI_{400}/SI_0$) of the metastatic spine were $0.57{\pm}0.07$ and $0.32{\pm}0.08$ And the standardized values of the two diseases were statistically significant (p < 0.05). The ADC ($mm^2/s$) for b value 400 ($s/mm^2$) and 1400 ($s/mm^2$) of the simple compression fracture disease site were $1.70{\pm}0.16$ and $0.93{\pm}0.28$ and $1.24{\pm}0.21$ and $0.80{\pm}0.15$ for the metastatic spine. The ADC ($mm^2/s$) for b value 400($s/mm^2$) was statistically significant (p < 0.05) but the ADC ($mm^2/s$) for b value 1400 (p > 0.05). In conclusion, multi - b value recognition of signal changes in diffusion - weighted imaging is very important for the diagnosis of various spinal diseases.