PEAK ENERGY SHIFT DEPENDENT ON SOURCE POSITION IN GAMMA-RAY ENERGY MEASUREMENT BY USING A CLOSED-ENDED COAXIAL HPGE DETECTOR

The source position effect in the gamma-ray energy measurement by usin g a closed-ended coaxial HPGe detector is investigated at the energy o f 1332 keV. The shift of the gamma-ray peak energy is measured as a fu nction of source-to-detector distance for axial and radial positions o f the Co-60 source. By using Monte Carlo method, the interaction of ga mma-rays in the detector material is simulated, and then the peak shif t due to field increment effect and charge trapping effect is calculat ed. The measured shift reasonably agrees with the calculated value. Fo r the axial direction, the positive peak shift occurs, and the shift i ncreases significantly within 3 cm from the detector. At the distance of 0.5 cm, the measured shift becomes 42 eV. For the radial direction, the negative peak shift within 9 eV occurs. The dependence of peak sh ift on the source-to-detector distance for the radial direction is muc h weaker than that for the axial direction.