Detection of water by neutron scattering using a small Plasma Focus

Abstract

A compact Plasma Focus operated in deuterium which produces 2 10(8) neutrons per pulse, has been used as a radiation source for water detection by neutron scattering. The detecting system is composed by two silver activation sensors operated simultaneously on every shot. These detectors have quite different responses depending on whether the incoming neutrons are energetic or thermalised. Energetic neutrons come from the Plasma Focus itself, whereas those thermalized come, scattered, from the substance to be detected. The comparison between the readouts of each detector allows to reveal the presence of the blanket. The shot to shot variation of the Plasma Focus neutron yield does not preclude the detection. In practice shots with yields belonging to the 2 10(7)- 2 10(8)range, can be conveniently used. The obtained results indicate that the method is able to detect water contents of few percents in volume placed about 8.5 cm away from the Plasma Focus chamber. The presented method admits side-on as well as directional detection.