1. Radiation Instrumentation Research Division, Korea Atomic Energy Research Institute, Daejeon 305-353, Republic of Korea
2. School of Electronics Engineering, College of IT Engineering, Kyungpook National University, Daegu 702-701, Republic of Korea
3. Department of Mechanical Equipment Development, Radiation Technology eXcellence (RTX), Daejeon 305-500, Republic of Korea
4. Department of Electronics Engineering, Sejong University, Seoul 143-747, Republic of Korea