Journal of the Korean Society of Radiology (한국방사선학회논문지)

The Korean Society of Radiology (한국방사선학회)
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An Analysis into the Dose Rate of Photoneutron Occurring in a Linear Accelerator

선형가속기에서 발생하는 광중성자 선량률 분석

  • Jang, Howon (Department of LED Convergence Engineering, Pukyong National University) ;
  • Jin, SeongJin (Department of Radiation Oncology, Inje University Haeundae Paik Hospital) ;
  • Je, Jaeyong (Department of Radiological Technology, Dong-Eui Institute of Technology)
  • 장호원 (부경대학교 LED융합공학과) ;
  • 진성진 (인제대학교 해운대백병원 방사선종양학과) ;
  • 제재용 (동의과학대학교 방사선과)
  • Received : 2017.11.22
  • Accepted : 2017.12.31
  • Published : 2017.12.31
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Abstract

This research aims at measuring the changes in the dose rate of photoneutron occurring in the process of the investigation into the 10 MV photon beam with a linear accelerator. In addition, the life time of the photoneutron after the end of irradiation was to be analyzed. The photoneutron were measured with a $BF_3$ proportional counter, and the measurement results of the dose rate of the photoneutron were analyzed in 3 parts at intervals of 2 seconds. The measurement results showed that the photoneutron were generated fastest when there was no metal plate inside the radiation field and when there was a lead plate, and that, as for the time that shows the final dose rate at the level of background, the life time was about 1 minute and 40 seconds regardless of the kinds of materials. Therefore, the dose rate according to the time until the photoneutron run out was proved to be different depending on the sorts of the materials and the threshold energy. However, final life time showed similar results regardless of the kinds of the materials, it can be concluded that the kinds of materials don't get involved in the life time of photoneutron.

본 연구는 선형가속기를 이용하여 10 MV 광자선을 조사하는 과정에서 발생하는 광중성자의 선량률 변화를 측정하고자 하였다. 또한 방사선 조사가 종료된 후 광중성자의 수명을 분석하고자 하였다. 광중성자측정은 $BF_3$ 비례계수관을 사용하였으며, 광중성자의 선량률 측정결과를 2초 간격으로 3부분으로 나누어 분석 하였다. 측정결과 조사야 내에 금속판이 없는 경우와 납판이 존재할 때 광중성자의 발생이 가장 빠르게 나타났으며, 최종적으로 백그라운드 수준의 선량률을 나타내는 시간은 물질의 종류와 무관하게 약 1분 40초 정도의 수명시간을 나타내었다. 따라서 광중성자가 수명을 다할 때까지의 시간에 따른 선량률은 물질의 종류와 임계에너지에 따라 다르게 나타내었다. 그러나 최종 수명시간은 물질의 종류에 관계없이 비슷한 결과를 나타내었으므로 물질의 종류가 광중성자의 수명시간에는 크게 관여하지 않는다고 판단되어진다.

Keywords

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