Patent ID: 7505544

Claim:
A method of determining whether explosives or controlled substances are present in an object comprising confounders, comprising: transporting the object through a cavity in a shielded apparatus, said cavity comprising one or more turns which preclude a straight line trajectory through the cavity; generating neutron particles from a plurality of neutron sources by pulsing the neutron sources simultaneously, each source having an intensity of about 10 7 neutrons/second or less; irradiating the object with the neutron particles to cause the object to generate gamma rays; detecting the gamma rays with a plurality of gamma ray detectors; analyzing the gamma counts associated with the object; determining that an explosive or controlled substance is present in the object when the relative atomic percentages of elements comprising the object are substantially similar to the relative atomic percentages of elements associated with known explosives and controlled substances; determining that an explosive or controlled substance is not present in the object when the relative atomic percentages of elements comprising the object are not substantially similar to the relative atomic percentages of elements associated with known explosives and controlled substances; and pulsing the neutron sources sequentially if it is determined that an explosive or controlled substance is present in the object.