The soil moisture and its relevance to the landmine detection by neutron backscattering technique

The detection of landmines by using available technologies is a time consuming, expensive and extremely dangerous job, so that there is a need for a technological breakthrough in this field. Atomic and nuclear physics based sensors might offer new possibilities in de-mining. Among the available nuclear techniques, the neutron backscattering technique (NBT), based on the detection of the produced thermal neutrons, is thought to be the most promising for field applications. We discuss here two limitations of NBT, being related to the soil moisture. First, the critical value of the soil moisture, reached when the density of the hydrogen atoms in the landmine is equal to that in the background soil, defines a condition for which the detection is not possible. Critical values are small for some of the landmine types, thus suggesting the application of the method to and countries, where the soil moisture is lower than 10%. Furthermore, small-scale variations of the soil moisture content, experimentally determined for different soil types, are found to be capable of generating false positive readings. To avoid this problem, the integration of the NBT with a second sensor, as the metal detector, is proposed.