On the imaging of land mines using e⁺−e⁻ pair production

Abstract

The problem of disposing of abandoned land mines is very serious in many countries. Anti-personnel land mines (APM's) contain as little as 50 gram or less of explosive, which is enough to take off an adult's foot, or to kill a child. Anti-tank mines (ATM's), designed to penetrate the armour on the bottom of a tank, are much larger. Current techniques of finding them are not adequate. All practical high explosives contain 20% or more of nitrogen, which has a thermal neutron cross section of 75 mbarn, producing γ's of up to 10.8 MeV. The idea of using this property to detect explosives has been tested by others, but because of backgrounds is unable to find anything less than several hundred grams of explosive. The refinement proposed here is to convert the γs, track the resulting e⁺−e⁻ pairs in MWPC's, and use the information to locate the γ source, i.e. the mine. The directional information provided should reduce the backgrounds considerably. Result of an experimental test are presented, and possibilities for the future discussed.