Experimental research on detecting explosives by pulsed fast thermal neutron analysis

摘要

An explosive detection system based on the pulsed fast thermal neutron analysis (PFTNA) is developed. The 14 MeV D-T pulsed neutron generator, console, bismuth germanate (BGO) detector, main amplifier, gate circuit and 4096 multichannel analyzer (MCA) are applied in this system. The neutron collimator and shielding device are also designed to reduce the unnecessary external interference and improve the detection efficiency. Using the system, the explosive mimic (urea) is detected and identified by calculating the ratio of hydrogen atoms to oxygen atoms (H/O). The influence of detection conditions, such as detection distance and sample mass, to the experimental results is investigated. It shows that, when the high voltage of main amplifier is 755 V, the count rate is 4000 n/s, the sample is placed as close as possible to the bottom of the neutron generator, and the sample mass is more than 800 g, the sample can be distinguished well by comparing the H/O ratio. It is confirmed that the explosives can be detected by the detection system, which provides a new method for detecting explosives.