# 환경준위 알파입자측정을 위한 다중선 비례계수기 개발(I)

• Oh, Pil Jae (Korea Research Institute of Standards and Science) ;
• Park, Tae Soon (Korea Research Institute of Standards and Science) ;
• Lee, Min Kie (Korea Research Institute of Standards and Science) ;
• Kim, Kyung Hwa (Korea Research Institute of Standards and Science)
• 오필제 (한국표준과학연구원 화학방사선연구부) ;
• 박태순 (한국표준과학연구원 화학방사선연구부) ;
• 이민기 (한국표준과학연구원 화학방사선연구부) ;
• 김경화 (한국표준과학연구원 화학방사선연구부)
The muiltiwire proportional counter for the measurement of low-level and environmental $\alpha$ particles emitting nuclides was developed. External dimension of the devloped multiwire proportional counter is $350{\times}290{\times}30mm$ and the sensitivity area is $250{\times}200mm$. The wall material of the detector was selected the stainless steel to prevent the deformation by external impact and to obtain minimum background. The anode and cathode wires were used the stainless steel material of diameter $50{\mu}m$. The spacing of each wires are 10.0mm, 5.0mm and the numbers of total wire are 21, 42 lines, respectively. The multiwire proportional counter was designed that the measurement source is placed within the detector to prevent the wall absorption effect and the efficiency variation by various source heights. The characteristics of the developed detector have been investigated to obtain the plateau, operating voltage, background, counting efficiency, position sensitivity and energy resolution etc. For the $^{241}Am$ nuclide, the calculated LLD(Lower Limit of Detection) is 5.0mBq/L which is lower than 40mBq/L of recommended LLD value by ISO(International Organization for Standardization).