Determination of HCNO concentrations by fast neutron scattering analysis

A single-shot nanosecond neutron pulsed technique for the detection of fissile materials

“…After this collision the elastically scattered neutron will change its energy E n (and speed v) depending on the mass of the nucleus-scatterer, the angle of scattering, and the kinematics of the elastic scattering of neutrons in dependence of these parameters can easily be calculated, as represented in figure 2 [1].…”

“…For light elements of the first part of the periodic table of elements the energy change in a scattering act (i.e. lower speed v of scattered neutrons) will result in a later time of arrival of the scattered neutrons to a detector -in our case it is a photomultiplier with plastic scintillator (PMT+S) -compared with the arrival time of "direct" neutrons coming to the detector from the source without scattering [1,8]. Taking into consideration these time lags, amplitudes of pulses and corresponding cross-sections of scattering it is possible to reconstruct an elemental content of the material under interrogation from an oscilloscope trace [1,8,9,11].…”

“…lower speed v of scattered neutrons) will result in a later time of arrival of the scattered neutrons to a detector -in our case it is a photomultiplier with plastic scintillator (PMT+S) -compared with the arrival time of "direct" neutrons coming to the detector from the source without scattering [1,8]. Taking into consideration these time lags, amplitudes of pulses and corresponding cross-sections of scattering it is possible to reconstruct an elemental content of the material under interrogation from an oscilloscope trace [1,8,9,11]. However, as one may see from figure 2, this difference between energy of direct neutrons coming from the source to the detector and elastically scattered by the nuclei becomes negligible for heavy nuclei comprising fissile materials (elements like Th, U, etc.…”

“…In principle these methods can exploit a number of sources with long-pulse or continuous neutron radiation such as isotopes and classical neutron generators (direct-type accelerators generating 10 8 neutrons per pulse having duration ∼ 10 µs) or low-power sources like the Van de Graaff accelerator irradiating 10 3 neutrons during a pulse of duration of 2 ns [1][2][3][4][5][6][7].…”

“…To reach a high value of SNR in those techniques it is necessary to integrate over many pulses with the above neutron sources (for generators ->10 6 pulses) or to ensure a long operation time (for isotope sources -> half an hour). This leads to high activation and to a long period of the interrogation of objects [1][2][3][4][5][6][7].…”