| Popis: |
We are trying to establish a landmine detection system by combining the D-D fusion neutron source. The principle idea of the presently developing system is based on the detection of capture gamma-rays from explosive. We are focusing on the detection of 2.22 MeV and 10.83 MeV capture gamma-rays from hydrogen and nitrogen, respectively, since all explosive contain these elements. To detect 10.83 MeV capture gamma-rays, the main detector is employed a BGO scintillator, which is surrounded by annular shaped NaI(T1) scintillator with a hole of 1' in diameter to facilitate the use of anti-coincidence technique to suppress backgrounds and coincidence technique to detect 511 keV escape gamma-rays. To use anti-coincidence technique and coincidence technique, the dual MCA circuit is employed. To examine the performance of this anti-coincidence technique, a preliminary experiment was carried out by using a 60Co gamma-ray source, and it was found that background level of gamma-rays is suppressed. And to examine the performance of this coincidence technique, melamine was irradiated by 252Cf neutron source, and the counts of 10.83 MeV region was increased by 27% than previous system of NIM modules by using only anticoincidence technique. On the basis of these experimental results, a series of experiments by combining with the D-D neutron source was conducted. It was found that the capture gamma-rays of 10.83 MeV from nitrogen could be detected clearly. |
