| 摘要 |
A method for detecting the presence of a predetermined amount of oxygen and nitrogen in a luggage type container as a screening technique for determining the presence of an explosive in the container. Generating and accelerating a beam of monoenergetic protons at a neutron generating target formed of boron. Rapidly and periodically subjecting the proton beam to an energy degrading medium upstream of the neutron generating target to thereby selectively degrade the energy of the protons of the proton beam during the time the median is in place while allowing the energy of the proton beam to remain at the original energy when the degrading median is removed. Directing the energy variant proton beam at the boron target to generate an energy variant neutron beam, the neutron beam containing on resonant neutrons at a resonant energy of nitrogen or oxygen nuclei and containing off resonant neutrons outside the resonant energy of the nuclei of nitrogen and oxygen. First detecting, measuring and comparing on resonant neutrons removed by interactions with nuclei of oxygen, and off resonant neutron passing through the luggage container, and, in response to a determination of the presence of predetermined amount of oxygen in the container, then detecting, measuring and comparing on resonant neutrons removed by interactions with nuclei of nitrogen, and off resonant neutrons passing through the luggage container for determining the presence of a predetermined level of nitrogen.
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