• 분석과학
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• 제16권5호
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• pp.1041-1051
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• 2003

즉발감마선 중성자방사화법 (PGAA)은 시료내 미량 및 주원소를 빠르게 비파괴적으로 분석하는 방법으로 주로 광물, 금속, 석탄, 시멘트, 석유, 코팅, 제지 등 다양한 산업체에서 실시간 분석법으로 매우 유용하다. 이 방법은 제약과 관련된 산업체 또는 연구업무에도 활용되며, 마약 또는 폭발물과 같은 위험물질의 탐지에도 이용되고 있다. 본 총설은 즉발감마선 중성자 방사화법의 현재의 기술현황과 앞으로 연구추진 경향에 대하여 서술하였다. PGAA 시스템은 중성자 선원, 증성자 핵반응으로부터 발생하는 즉발감마선을 측정하기위한 다중채널분석기와 A/D 변환기 등의 전자모듈과 고분해능 HPGe 검출기로 구성된다. 속중성자의 콤프턴 산란에 의한 높은 바탕값은 감마-감마 동시계수장치의 도입으로 개선될 수 있다. 현재 $^{252}Cf$를 사용한 즉발감마선 중성자 방사화 장치는 수용액중에 존재하는 원소들의 실시간분석을 위해 한국원자력연구소에서 개발중에 있다. 이 장치는 다양한 마약 및 폭발물 또는 화학무기의 탐지에도 응용될 수 있다.

• Nuclear Engineering and Technology
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• 제48권3호
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• pp.778-784
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• 2016

HyperGam-U was recently developed to determine uranium enrichment based on ${\gamma}$- and X-ray spectroscopy analysis. The $XK_{\alpha}$ region of the uranium spectrum contains 13 peaks for $^{235}U$ and $^{238}U$ and is used mainly for analysis. To describe the X-ray peaks, a Lorentzian broadened shape function was used, and methods were developed to reduce the number of fitting parameters for decomposing the strongly overlapping peaks using channel-energy, energy-width, and energy-efficiency calibration functions. For validation, eight certified reference material uranium samples covering uranium enrichments from 1% to 99% were measured using a high-resolution planar high-purity germanium detector and analyzed using the HyperGam-U code. When corrections for the attenuation and true coincidence summing were performed for the detection geometry in this experiment, the goodness of fit was improved by a few percent. The enrichment bias in this study did not exceed 2% compared with the certified values for all measured samples.

• 천문학회지
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• 제46권1호
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• pp.49-63
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• 2013

Nonthermal radiation from supernova remnants (SNRs) provides observational evidence and constraints on the diffusive shock acceleration (DSA) hypothesis for the origins of Galactic cosmic rays (CRs). Recently it has been recognized that a variety of plasma wave-particle interactions operate at astrophysical shocks and the detailed outcomes of DSA are governed by their complex and nonlinear interrelationships. Here we calculate the energy spectra of CR protons and electrons accelerated at Type Ia SNRs, using time-dependent, DSA simulations with phenomenological models for magnetic field amplification due to CR streaming instabilities, Alf$\acute{e}$enic drift, and free escape boundary. We show that, if scattering centers drift with the Alf$\acute{e}$en speed in the amplified magnetic fields, the CR energy spectrum is steepened and the acceleration efficiency is significantly reduced at strong CR modified SNR shocks. Even with fast Afv$\acute{e}$nic drift, DSA can still be efficient enough to develop a substantial shock precursor due to CR pressure feedback and convert about 20-30% of the SN explosion energy into CRs. Since the high energy end of the CR proton spectrum is composed of the particles that are injected in the early stages, in order to predict nonthermal emissions, especially in X-ray and ${\gamma}-ray$ bands, it is important to follow the time dependent evolution of the shock dynamics, CR injection process, magnetic field amplification, and particle escape. Thus it is crucial to understand the details of these plasma interactions associated with collisionless shocks in successful modeling of nonlinear DSA.

• Journal of Radiation Protection and Research
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• 제22권1호
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• pp.15-21
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• 1997

인체 T-림프구에서 감마선과 대표적 화학 독성물질인 pentachlorophenol(PCP)의 돌연변이 효과를 hypoxanthine phosphoribosyl transferase(hprt) 유전자의 돌연변이 빈도로써 측정하였다. 감마선은 $^{137}$Cs원을 사용하여 세포의 초기배양 시기에 0-3.0 Gy를 조사하였고, PCP는 세포의 초기배양시 최종농도 0-100 ppm으로 24시간 투여하였다. 돌연변이세포는 6-thioguanine을 처리 하에 세포가 성장하는 능력으로 분류하였다. 방사선에 의한 돌연변이빈도는 1.0 Gy, 2.0 Gy와 3.0 Gy 선량에서 대조군보다 약40%, 400%와 750% 증가하였고 0.2 Gy와 0.5 Gy의 선량에서는 유의성 있는 변화가 없었다. PCP를 15 ppm, 25 ppm 그리고 50 ppm을 처리하였을 때 대조군보다 각각 30%, 90% 및 520%정도 증가하였다.

• 한국정보통신학회논문지
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• 제21권1호
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• pp.223-228
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• 2017

본 연구에서는 광대역 펄스감마선 탐지센서 최적화 설계를 수행하고 설계결과를 기반으로 탐지센서를 제작하여 전기적 특성을 분석하였다. 탐지센서의 최적화 설계를 위해 펄스감마선의 시간에 따른 에너지 프로파일로 부터 입력 변수를 도출하고 탐지감도 제어회로를 통하여 출력전류 범위를 결정하였다. 도출된 변수를 바탕으로 N-type Epi Wafer 및 TCAD(Technology Computer Aided Design)로 설계하고 제작하였다. 제작된 탐지센서의 전기적 특성 분석 결과 -3.3V 전압에서 12pA의 누설전류와 -5V의 전압에서 완전 공핍화 되는 특성을 가짐을 확인하였다. 제작된 센서의 포항가속기연구소 TEST LINAC 시험결과 감마선 설정 선율의 펄스방사선에 대해 고감도의 광전류를 생성시킴을 확인하였다.

• Biomedical Engineering Letters
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• 제8권4호
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• pp.383-392
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• 2018

For prompt gamma ray imaging for biomedical applications and environmental radiation monitoring, we propose herein a multiple-scattering Compton camera (MSCC). MSCC consists of three or more semiconductor layers with good energy resolution, and has potential for simultaneous detection and differentiation of multiple radio-isotopes based on the measured energies, as well as three-dimensional (3D) imaging of the radio-isotope distribution. In this study, we developed an analytic simulator and a 3D image generator for a MSCC, including the physical models of the radiation source emission and detection processes that can be utilized for geometry and performance prediction prior to the construction of a real system. The analytic simulator for a MSCC records coincidence detections of successive interactions in multiple detector layers. In the successive interaction processes, the emission direction of the incident gamma ray, the scattering angle, and the changed traveling path after the Compton scattering interaction in each detector, were determined by a conical surface uniform random number generator (RNG), and by a Klein-Nishina RNG. The 3D image generator has two functions: the recovery of the initial source energy spectrum and the 3D spatial distribution of the source. We evaluated the analytic simulator and image generator with two different energetic point radiation sources (Cs-137 and Co-60) and with an MSCC comprising three detector layers. The recovered initial energies of the incident radiations were well differentiated from the generated MSCC events. Correspondingly, we could obtain a multi-tracer image that combined the two differentiated images. The developed analytic simulator in this study emulated the randomness of the detection process of a multiple-scattering Compton camera, including the inherent degradation factors of the detectors, such as the limited spatial and energy resolutions. The Doppler-broadening effect owing to the momentum distribution of electrons in Compton scattering was not considered in the detection process because most interested isotopes for biomedical and environmental applications have high energies that are less sensitive to Doppler broadening. The analytic simulator and image generator for MSCC can be utilized to determine the optimal geometrical parameters, such as the distances between detectors and detector size, thus affecting the imaging performance of the Compton camera prior to the development of a real system.

• Journal of Astronomy and Space Sciences
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• 제30권3호
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• pp.133-140
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• 2013

Most of high energy cosmic rays (CRs) are thought to be produced by diffusive shock acceleration (DSA) at supernova remnants (SNRs) within the Galaxy. Fortunately, nonthermal emissions from CR protons and electrons can provide direct observational evidence for such a model and place strong constraints on the complex nonlinear plasma processes in DSA theory. In this study we calculate the energy spectra of CR protons and electrons in Type Ia SNRs, using time-dependent DSA simulations that incorporate phenomenological models for some wave-particle interactions. We demonstrate that the time-dependent evolution of the self-amplified magnetic fields, Alfv$\acute{e}$nic drift, and escape of the highest energy particles affect the energy spectra of accelerated protons and electrons, and so resulting nonthermal radiation spectrum. Especially, the spectral cutoffs in X-ray and ${\gamma}$-ray emission spectra are regulated by the evolution of the highest energy particles, which are injected at the early phase of SNRs. Thus detailed understandings of nonlinear wave-particle interactions and time-dependent DSA simulations of SNRs are crucial in testing the SNR hypothesis for the origin of Galactic cosmic rays.

• 한국안전학회지
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• 제18권2호
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• pp.50-55
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• 2003

Radiation degradation of crosslinked polyethylene(XLPE) was investigated using thermogravimetric analysis(TGA), The results of TGA were compared with FT-IR, melting temperature, oxidation induction time, and elongation at break on the XLPE exposed by $\gamma$-ray. 5% decomposition temperature of $\gamma$-ray irradiated XLPE showed similar tendencies with the case of elongation at break. Both properties agreed below 1000 KGy, however, did not show any remarkable characteristics above 1000 kGy, these properties can be useful to evaluate the radiation degradation of XLPE for only low irradiated region. Above 1000 kGy, the thermal decomposition activation energy showed decreased, on the contrary, increasing below 1000 kGy. Compared with FT-IR spectrum of irradiated XLPE, it was confirmed that the oxidation reaction was still occurring below 1000 kGy. Radiation degradation of XLPE was dependent upon the irradiation doses, TGA can be a useful tool to evaluate the degradation.

• Nuclear Engineering and Technology
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• 제54권2호
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• pp.462-468
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• 2022

The selection and effective utilization of peak-fitting software for conventional gamma-ray spectrum analysis is significant for accurate determination of the mass fraction of elements, particularly in complex peak regions. Majority of the peak-fitting programs can derive similar peak characteristics for singlet peaks, but very few programs can deconvolute multi-peaks in a complex region. The deconvolution of multi-peaks requires special peak-fitting functions, such as left and right-skew distributions. In the this study, 843.76 keV (²⁷Mg) peak area from the complex region (840 keV-850 keV) determined and compared using four different peak-fitting programs, namely, GammaVision, Genie2000, HyperLab, and HyperGam. The 843.76 keV peak interfered with 841.63 keV (^152mEu) and 846.81 keV (⁵⁶Mn). The total Mg concentration was determined through k₀-instrumental neutron activation analysis by applying the isotopic interference correction factor ²⁷Al(n,p)²⁷Mg through the simultaneous determination of Al concentration. HyperLab and HyperGam peak-fitting programs reported consistent peak areas, and resultant concentrations agreed with the certified values of matrix-certified reference materials.

• Journal of Astronomy and Space Sciences
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• 제30권3호
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• pp.141-143
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• 2013

We propose jitter radiation and jitter self-Compton process in this work. We apply our model to the study of GRB prompt emission and GeV-emission. Our results can explain the multi-wavelength spectrum of GRB 100728A very well.