Effects of soil moisture on the detection of buried explosives by radiative neutron capture

The effect of soil moisture on the sensitivity for detecting buried landmines by neutron capture reactions has been experimentally investigated. An explosive simulant melamine sample has been placed at different depths in soil having different water contents. In dry soil it is found that the decrease of counting rate by increasing the depth follows the decrease of the average solid angles. In the case of soil with higher water content, an extra yield of prompt gamma-rays following thermal neutron capture in nitrogen is evidenced due to the extra moderation provided by the presence of additional hydrogen nuclei.