Neutron anisotropy and X-ray production of the FN-II dense plasma focus device

Abstract

The FN-II Dense Plasma Focus is a small (< 5kJ) Mather type device, where the dependence of neutron yield and its anisotropy, in terms of deuterium filling pressure, and the neutron emission angular distribution have been studied. Two different electrode configurations have been tested, showing that their geometry plays an important role both on neutron yield and anisotropy. Time integrated anisotropy has been measured with silver activation counters, on a shot to shot basis. CR-39 nuclear track detectors are used to determine the angular distribution of neutrons, averaged over tens of shots, showing that an isotropic pedestal accounts for 70% of the emission, while the anisotropy component accounts for the remaining 30%. The neutron yield shows a tendency to increase with anisotropy, as well as with the emission of hard X-rays observed on-axis. Scintillator-photomultiplier detectors show a slight Doppler shift in the neutron energy at backward angles, supporting the beam-target mechanism. Additional information has been obtained from time integrated X-ray diagnostics, which include filtered multi-pin-hole cameras.