• Nuclear Engineering and Technology
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• 제42권4호
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• pp.426-433
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• 2010

The characteristic X-rays emitted from materials after gamma ray exposure was simulated and measured. A CdTe semiconductor detector and a $^{57}Co$ radiation source were used for energy spectroscopy. The types of materials could be identified by comparing the measured energy spectrum with the theoretical X-ray transition energy of the material. The sample composition was represented by the $K_{\alpha1}$-line (Siegbahn notations), which has the highest intensity among the characteristic X-rays of each atom. The difference between the theoretic prediction and the experimental result of K-line measurement was < 0.61% even if the characteristic X-rays from several materials were measured simultaneously. 2D images of the mixed materials were acquired with very high selectivity.

• 천문학회보
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• 제40권1호
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• pp.53.3-54
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• 2015

We are developing large arrays of X-ray microcalorimeters for applications in X-ray astronomy. X-ray microcalorimeters can detect the energy of X-rays with extremely high resolution. High-resolution Imaging spectroscopy enabled by these arrays will allow us to study the hot and energetic nature of the Universe through the detection of X-rays from astronomical objects such as neutron stars or black holes. I will introduce the state-of-the-art X-ray microcalorimeters being developed at NASA/GSFC and the future X-ray observatory missions based on microcalorimeters.

• 한국방사선학회논문지
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• 제7권1호
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• pp.51-55
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• 2013

엑스선의 에너지가 높으면 엑스선이 피사체(object)를 통과하여 영상의 대조도를 떨어뜨리고 엑스선의 에너지가 낮으면 영상의 대조도는 증가시키지만 엑스선이 피사체에 흡수되어 환자의 피폭선량을 증가시킨다. 그러므로 적정한 엑스선 에너지는 영상의 질과 피폭선량에 영향을 미치는 매우 중요한 요소이다. 본 논문에서는 새로운 양극물질을 사용하는 유방촬영 장치의 도입에 따라 방사선 선질이 다양해진 유방촬영장치의 영상품질관리와 환자선량관리을 위하여 유방촬영장치의 타겟 물질에 따른 에너지스펙트럼을 시뮬레이션하고 팬텀 영상의 화질을 비교하였다.

• Design & Manufacturing
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• 제16권2호
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• pp.33-38
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• 2022

Currently, Korea is an aging society, and it is expected to enter a super-aging society in about 4 years. Accordingly, many X-ray technologies are being developed. In X-rays, 99% of X-rays are converted into heat energy and 1% into light energy (X-rays). 99% of the thermal energy raises the temperature of the anode and its surroundings, and the cooling system is an important factor as overheating can affect the deterioration of X-ray quality and shortened lifespan. There is a method of forced air cooling using natural convection. Therefore, in this study, when X-rays were taken 5 times, Flow analysis was performed on heat removal according to temperature rise and cooling time for the heat generated at the anode of the X-ray tube (input power 60kW, 75kW, 90kW). Based on one-shot, the most rapid temperature rise section increased by more than 57% to 0.03 seconds, A constant temperature rises from 0.03 seconds to 0.1 seconds, It is judged that the temperature rises by about 8.2% or more at one time. After one-shot cooling, the cooling drops sharply from about 60% to 0.03 seconds, It is judged that the temperature has cooled by more than 86% compared to the temperature before shooting. One-shot is cooled by more than 86% with cooling time after 0.1 seconds, As the input power of the anode increases, the cooling temperature gradually increases. Since the tungsten of the anode target inside the X-ray tube may be damaged by thermal shock caused by a rapid temperature rise, an improvement method for removing thermal energy is required when using a high-input power supply.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1999년도 전력전자학술대회 논문집
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• pp.234-238
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• 1999

In order to radiate X-ray, the low ripple stabilized high voltage DC over the range of 40KV to 150KV is directly inflicted to X-ray tube. The energy characteristics of the radiated X-ray depend on the pulsating waveforms of the DC voltage supplied X-ray tube. In general, the low ripple voltage waveforms with fast rising times are required to increase with the dosage per unit time lest the exposure time should be longer in orde that the motion artifacts of an object may be eliminated in actual. The conventional types of X-ray generators were bulky in physical size and heavy in weight, and the control accuracies of the output voltages were not always satisfactory. The high frequency switching inverter and converter technology on power conversion and control systems have been greatly closed up introducing new power semiconductor devices. To decreasing the volume and the weight of high voltage transformer, and to stabilize ripple, a high frequency PWM inverter is connected between DC source and high voltage transformer. This paper describes the output characteristics according to stabilize ripple of X-ray tube voltage and compared the reproducibility, direcibility and doesage.

• 한국의학물리학회지:의학물리
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• 제4권2호
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• pp.37-47
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• 1993

Jones 모델 및 HKB모델을 이용하여 Laplace transform방법으로 6MV X-ray의 대략적인 에너지 스펙트럼을 분석하였다. Jones모델은 투과계수 0.1이하에서는 Laplace transform방법이 적용될 수 없는 심한 제약을 받는다는 것을 알 수 있었다. HKB모델에 의한 에너지 스펙트럼은 대체로 실제의 에너지 스펙트럼과 일치하는 형태를 나타내지만 6MeV에너지 이상의 영역에서 길게 꼬리를 이루는 단점이 있었다.

• 한국세라믹학회지
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• 제53권5호
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• pp.568-573
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• 2016

We explore the crystalline structure and phase transition of lithium thiophosphate ($Li_7P_3S_{11}$) solid electrolyte using electron microscopy and X-ray diffraction. The glass-like $Li_7P_3S_{11}$ powder is prepared by the high-energy mechanical milling process. According to the energy dispersive X-ray spectroscopy (EDS) and selected area diffraction (SAD) analysis, the glass powder shows chemical homogeneity without noticeable contrast variation at any specific spot in the specimen and amorphous SAD ring patterns. Upon heating up to $260^{\circ}C$ the glass $Li_7P_3S_{11}$ powder becomes crystallized, clearly representing crystal plane diffraction contrast in the high-resolution transmission electron microscopy image. We further confirm that each diffraction spot precisely corresponds to the diffraction from a particular $Li_7P_3S_{11}$ crystallographic structure, which is also in good agreement with the previous X-ray diffraction results. We expect that the microscopic analysis with EDS and SAD patterns would permit a new approach to study in the atomic scale of other lithium ion conducting sulfides.

• Journal of Astronomy and Space Sciences
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• 제5권2호
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• pp.143-158
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• 1988

Since the successful observation by Uhuru, the first astronomical satellite, X-ray astronomy has become one of the rapidly developing fields in astronomy. The scientific results provide us the unique opportunity to understand the high energy nature of X-ray sources. We now know that our galaxy contains many different types of X-ray sources such as the compact X-ray sources, galactic bulge sources in addition to the Sun, the brightest X-ray sources in the sky. In this study we review the general properties of galactic X-ray sources, the characteristics of periodic compact X-ray sources, and bursters as well as the models.

• 천문학회보
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• 제43권2호
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• pp.43.1-43.1
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• 2018

Young pulsar wind nebulae, powered by energetic central pulsars, are often observed as bright extended sources in the X-ray band. They are believed to accelerate electrons and positrons to very high energy and can possibly explain the positron excess observed by Fermi and AMS. The electron distribution in these PWNe can be best studied by X-ray satellites because emission in the X-ray band is produced by direct synchrotron radiation of the electrons and positrons. We present NuSTAR studies of PWNe and discuss the implication. Future studies to help further our understanding of particle acceleration will be briefly discussed.

• 대한방사선치료학회지
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• 제20권1호
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• pp.31-36
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• 2008

목 적: X선이 조사된 물질의 색변화를 통하여 방사선 측정 및 선량분포확인을 위한 물질로서의 가능성에 대하여 평가하고자 한다. 대상 및 방법: 순수한 KCl과 KCl에 희토류 물질인 Eu를 0.5 mol% 첨가하여 초크랄스키 방법으로 각각의 단결정을 성장시키고 선형가속기를 이용하여 X선조사선량에 따른 KCl결정의 색 변화를 관찰하였다. 결 과: 고 에너지 X선조사에 의해 KCl:Eu 단결정은 가시광의 푸른색 형광과 함께 자주색을 나타내었고 순수한 KCl 단결정은 눈으로 확인할 수 있을 정도의 형광은 관찰되지 않았지만 보라색으로 착색되었다. 결 론: KCl 단결정의 색 변화는 X선으로 인하여 안정된 색 중심이 생기고 이러한 색변화는 X선 측정물질과 펜톰으로 유용하게 사용되어질 것이다.