Development of a thermal neutron sensor for Humanitarian Demining

Increasing the Personnel Safety of a Landmine Detection System using Proper Shielding Materials

It has been proven that landmine detection systems based on prompt gamma neutron activation analysis method can be used effectively in detecting low metal content mines. Unfortunately, neutron and gamma radiations of these systems are inevitable. Therefore, the personnel safety of these devices is one of the major limitations in using these systems. In this work, a system composed of a moderated americium-beryllium neutron source was considered. We have investigated different thicknesses of proper neutron shielding materials such as polyethylene and boric acid around the system to shield neutrons and increase the safety conditions for the operators. The effect of using different thicknesses of a cylindrical lead shield (around the source) for shielding the gamma radiation of the source was also studied. Several experiments were done to measure neutron and gamma dose equivalent rate at different distances from the source. Most of the results were compared with the results obtained by Monte Carlo N-particle transport 4C code. Finally, we found a system that is safe for the operators who work at about a 1 m distance from the landmine detection system.

The detection of landmines by neutron backscattering: Exploring the limits of the technique

Neutron backscattering (NB) sensors have been proposed for Humanitarian De-mining applications. Recently, a prototype hand-held system integrating a NB sensor in a metal detector has been developed within the EU-funded DIAMINE Project. The results obtained in terms of performance of the NB systems and limitations in its use are presented in this work. It is found that the performance of NB sensors is strongly limited by the presence of the soil moisture and by its small-scale variations. The use of the neutron hit distribution to reduce false alarms is explored.

Detection of landmines by using 14MeV neutron tagged beams

A large-area scanning system using 14 MeV tagged neutrons has been built. The associated (4)He particles emitted in the D+T reaction are detected in an array of Parallel Plate Avalanche Counters that defines a scanning plane having about 10 x 100 cm(2) area. Coincident gamma-rays are detected by 10 BaF(2) scintillators. The capability of the system to determine the presence and the position of samples and to perform an on-line background subtraction is demonstrated. Test with landmines are also reported. This technique allows a significant improvement of the signal-to-noise ratio searching for hidden threat materials. The use with portable sealed-tube generators is foreseen.