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이희석,고인수 한국물리학회 2006 새물리 Vol.53 No.2
The research facilities for nuclear physics, the Pohang High Energy Radiation Facility (PHERF) and the Pohang Neutron Facility (PNF), were constructed by using, respectively, a 2.5-GeV electron linac at the Pohang Light Source and an 80-MeV test electron linac at the Pohang Accelerator Laboratory. Neutrons of one tenth per incident electron an a thick target like Ta are generated through photonuclear reactions caused by an electromagnetic shower. Valuable research related to nuclear physics has been conducted since 1998 by using these pulsed neutron sources with continuous energy spectra. Differential production yields of neutrons, protons, and deuterms are measured in the energy range from a few MeV to 400 MeV. Total cross sections for several elements have been measured by using neutrons below 1 keV. These experimental results are used as basic data for benchmarking well-known Monte Carlo codes and nuclear data evaluation codes. Application studies using high-energy radiation have also been carried out in various fields. 포항가속기연구소는 포항방사광가속기의 2.5 GeV 전자선형가속기와 80 MeV 시험용 전자선형가속기를 각각 이용하여 펄스형 중성자 실험시설, PHERF와 PNF를 구축하였으며 핵물리학 연구 등에 활용하고 있다. Ta 표적 등에 입사하는 전자에 의해 유발된 광전자사태 과정 중의광핵반응으로부터 입사전자 1개당 0.1개의 중성자를 생성한다. 연속스펙트럼을 가지는 두 펄스형 중성자 선원을 이용하여 1998년 이후핵물리학과 관련된 다양한 연구를 수행하고 있다. 2.5 GeV 전자의 충돌에의해 생성되는 수 MeV에서 400 MeV에 이르는 광중성자 및 양성자, 중양자의 미분 생성률을 측정하였고, 1 keV 이하의 중성자를 이용하여주요 원소에 대한 전단면적 측정을 수행하고 있다. 이러한 실험결과는다양한 Monte Carlo 코드와 핵자료코드의 벤치마킹용 자료로서 인용되고있다. 또한 고에너지 방사선장을 이용한 응용연구도 수행하고 있다.
저밀도 음영을 나타내는 종격동 종양의 전산화단층촬영 소견
이희석 대한영상의학회 1991 대한영상의학회지 Vol.27 No.5
A variety of mediastinal masses contain areas with CT attenuation values lower than that of chest wall musculature and higher than that of subcutaneous fat. In some cases, the low attenuation is not absolute but is relative to the enhancing wall of the lesion or to the surrounding structure on contrast CT images. In these cases, precise determination of the attenuation values discloses a density equivalent to that of soft tissue. The authors retrospectively analysed the CT findings of 28 cases of pathologically proven mediastinal masses containing low-attenuation areas. Thymic lesions, germ cell tumors and intrathoracic goiters were mostly in the superior portion of the anterior mediastinum, but neurogenic tumors and forgut cysts were the largest masses. However, there was no specific relation in size of the other masses. Foregut cyst showed the lowest attenuation density and thymic lisions and intrathoracic goiters showed relatively higher attenuation than other lesions. Through analysing the size, location, shape, density and enhancement effect in pre-and post-contrast studies, CT is helpful in differentiating Low-Attenuation Mediastinal Masses.