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.

La distribución angular promedio de la emisión de neutrones ha sido medida en el foco del Dispositivo de Plasma Denso (5kJ) Fuego Nuevo II (FNII) mediante detectores plásticos de Trazas Nucleares (CR-39). Cuando se usa deuterio puro como gas de llenado en el dispositivo, los datos se pueden ajustar a una funcion Gaussiana, relacionando la emisión anisotrópica, superpuesta sobre un pedestal. Cuando se usa una mezcla de deuterio-argón, la contribución anisotrópica está mejor representada por una parábola. Se usó el flujo de neutrones a dos ángulos, a lo largo con la distribución angular obtenida por los detectores de trazas, con objeto de estimar el campo absoluto de neutrones en ambas contribuciones, isotrópica y anisotrópica. Examinando los diferentes grupos de disparos del FNII, se encuentra que la distribución angular es importante en la estimación de la anisotropía, y que el valor usualmente reportado, es una relación de los flujos principales y secundarios de neutrones, como los medidos con contadores por activación.

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 diferent 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 inte- grated X-ray diagnostics, which include filtered multi-pin-hole cameras.