Abstract:

Recent progress in a single-pulse technique of interrogation of hidden objects will be presented. The method uses very bright neutron pulses having duration of about 10ns, which are generated by Dense Plasma Focus (DPF) devices PF-10 (Institute of Theoretical and Experimental Physics, RF) and PF-6 (Institute of Plasma Physics and Laser Microfusion, Poland). This powerful and short pulse is irradiated from the source having a size of about 1cm as a shell propagating in space almost spherically and having a thickness of about 20 cm. This neutron pulse has a quite high energetic monochromaticity with ΔE_n⁄E₀∼2-3×10⁻², where E₀ is energy of neutrons at their peak in the energy distribution function – EDF (2.45 MeV in a side-on direction to the longitudinal Z-axis of the DPF chamber and about 2.7 MeV in the directions close to the Z-axis) and ΔE_n is a full width at half maximum of this EDF. Such a small size occupied by the neutron flash, its intensity and the above-mentioned monochromaticity ensure an opportunity to use a time-of-flight (TOF) technique with flying bases of about a few metres. During previous researches we used a DPF chamber counted on the DPF bank energy of about 7 kJ and generated a neutron yield on the level of 10⁹ neutrons per pulse having duration 15 ns (i.e. the length of the neutron pulse in a space was 30 cm). TOF base in those tests was 18.5 m. In the trials currently presented we have experienced an opportunity to use much lower bank energy (~2-3 kJ), smaller DPF chamber, decreased neutron yield (~10⁸ n/shot), and TOF base as well (7 m). In this case it appeared that the neutron pulse duration became 7-8 ns, space occupied by the pulse is about 15 cm, and the above-mentioned new TOF base is fitted to distinguish different elements composing the substance (H₃PO₄ in this case) under interrogation by means of measuring of the elastically scattered neutrons. It is achievable in particular in the case when the wavelet technique is applied to “clean” experimental data. Moreover this pulse duration gives a principal opportunity to estimate a size of lengthy objects by means of a single pulse of neutrons irradiated by our Dense Plasma Foci with the spatial precision of these measurements equal to the neutron pulse “length” (15 cm in this case).