Abstract:

Neutrons are considered to be a confirmatory tool for the detection of explosives and landmines when used in combination with other conventional methods such as metal detector or x-ray based technique etc. However in order to design a neutron based device for such purpose, it is required that a detailed simulation study be carried out to choose and optimize the neutron source and detector combination. Such a simulation study not only helps in choosing the best suited method for a particular application but also helps in correct use of chosen method.

The aim of this paper is to carry out simulation studies for both landmine and explosive detection. Though each problem requires a specific solution and systems suited for a particular application may not be of use for different applications, there may still be situations where though the method of detection may differ but devices and components may remain common. We have carried out simulation studies for explosive detection in large cargo using tagged neutron system. The potentials and limitations of the tagged neutron technique in different configurations of cargo are brought out. Similarly preliminary simulation using a D-D neutron generator has been carried out for a simulated mine consisting of 100 g of TNT buried at various distances inside soil and it has been compared with the simulation result for a californium based system.

We have computed the backscattered neutrons along with nitrogen capture gamma from the different kind of objects hidden under the soil. The effect of depth at which landmine is buried inside ground and moisture content of ground is investigated using Monte Carlo simulations.

Calculations have also been done for a variety of innocuous objects like polythene block, and wooden objects embedded in the soil in order to estimate the true signal for explosives. It is observed that backscattered neutrons alone would not give unambiguous results. To make the detection less unambiguous, we have also estimated the number of capture gamma from nitrogen in explosives. More systematic simulations are being carried out to test the utility of different types of neutron sources for reliable landmine detection. The paper will present detailed result of such calculations.