Efficiency of the detection of explosive using the spectral dynamics analysis of reflected signal

We investigate the efficiency of spectral dynamics analysis (SDA) method for the detection of both explosives hidden under various substances and explosives in their mixture. The detection occurs using the THz signal reflected from the substance. The main difficulty concludes in multi-reflection of THz wave from the substance, in which the explosive is packed. Our investigation shows that because of their structure these substances can be opaque for THz radiation at certain frequencies. Nevertheless, this question requires additional investigation. The action of the THz pulse, inclined at various angles to the sample surface, on substance is analyzed. It should be stressed that at inclined falling of THz wave, one can get more information about explosive in comparison with the case of normal falling of THz wave. As a result, the growth of the detection probability takes place. New features demonstrate the mixture of explosives. Under certain conditions on concentrations of substances in the mixture, the compound substance displays own properties not as mechanical combination of properties of initial substances during the time interval of action the main THz pulse. For the detection and identification in this case, one needs to use the long time interval signal from the substance. Other requirement consists in inclined falling of THz pulse to detect and identify the explosive.