Nuclear track methodology for the analysis of isotropic components in a plasma focus neutron yield

The average angular distributions of neutron emissions have been measured in the Fuego Nuevo II (FN-II) dense plasma focus device (5kJ) by means of CR-39 plastic nuclear track detectors. When pure deuterium is used as the filling gas, the data can be adjusted to a Gaussian function, related to anisotropic emission, superposed on a constant pedestal, related to isotropic emission. When deuterium-argon admixtures are used, the anisotropic contribution is best represented by a parabola. The neutron flux at these two angles are used, along with the angular distribution obtained from the track detectors, in order to estimate the absolute neutron yield of both the isotropic and the anisotropic contributions. From examining different groups of shots, it is found that the shape of the angular distribution is important in the estimation of anisotropy, and that the value usually reported, as the ratio of the neutron flux head on and side on, as measured by activation counters, may be misleading.