Analysis of the ultralow background gamma-ray measurement system

There are always sources of background affecting the ultralow background gamma-ray measurement system which will detect and analyze gamma-rays emitted from environmental and swipe samples. The techniques mentioned below were applied on this system to reduce these background sources; (1) materials of known radiopurity to surround the diode, (2) an active external anticosmic shield to reduce the background continuum due to interactions of cosmic particles with the detector and passive lead shielding, and (3) nitrogen gas flowed into the sample counting chamber to minimize the introduction of ubiquitous radon decay nuclei. The test results showed that 10-2 order reduction of system background at the low energy region (0∼2.5 MeV) is achieved by application of these background reduction techniques. This system will be applied to analyze the environmental and swipe samples in order to monitor the nuclear activities. (author). 17 refs., 11 tabs., 26 figs