Patent ID: 6928131

Claim:
A method for detecting an explosive in an object under investigation, comprising the following steps: (a) initially exposing the object under investigation to X-rays for purposes of detecting whether the object contains a nitrogen-containing explosive having an average density range of 1.25 to 2.00 g/cm 3 ; (b) recording the X-rays that have passed through the object under investigation; (c) finding areas of the object under investigation with a density of organic materials exceeding a pre-established value, on a basis of a value of X-ray attenuation; (d) identifying articles contained in the aforementioned found areas of the object under investigation with said density of organic materials higher than the pre-established value, on a basis of an analysis of said recorded X-rays; (e) selecting among said areas of the object under investigation an area containing an unidentified article; (f) in case all the articles are identified as not containing a nitrogen-containing explosive having an average density range of 1.25 to 2.00 g/cm 3 the process of detecting is stopped; (g) in case any article is unidentified the method of detecting further comprising: (h) determining the dimensions and position of said unidentified article in the object under investigation, on a basis of an analysis of said recorded X-rays; (i) evaluating a mass of a nitrogen-containing explosive being detected based on an average density range of 1.25 to 2.00 g/cm 3 which corresponds to said dimensions of the unidentified article; (k) exposing to thermal neutrons the selected area of the object under investigation containing the unidentified article; (l) recording, using at least two gamma-ray detectors, gamma-ray quanta with the energy of 10.8 MeV and pairs of simultaneously emitted cascade gamma-ray quanta emitted by said area of the object under investigation exposed to thermal neutrons; (m) counting pairs of said cascade gamma-ray quanta recorded simultaneously; (n) determining the overall intensity of gamma rays emitted by the object under investigation; (o) determining a threshold value for said overall intensity of gamma rays emitted by the object under investigation, on a basis of said evaluated mass of the explosive being detected which corresponds to the dimensions of the unidentified article; (p) making a decision about presence of a nitrogen-containing explosive having an average density range of 1.25 to 2.00 g/cm 3 in the object under investigation in the event that said overall intensity of gamma rays emitted by the object under investigation exceeds the said threshold value.