[en] A new dense plasma focus device, named Fuego Nuevo II, has been built at the ICN-UNAM, its goal is to help to understand the physics of accelerated ion beams, x-ray, and their role in neutron pulse generation. The purpose of this report is to show the initial results, obtained at early operation. Soft x-rays emitted from a 13 kJ DPF are detected. Hydrogen or a mixture of hydrogen and argon are used as filling gas. The image of the emitting area (time integrated) is taken with a five hole x-rays pin hole camera. The visible light is filtered using Al foils of different thickness in each of the five holes. The image is a fine line (2 mm long) of the PF axis, into which several bright points can be observed. An estimation of the emitting zone temperature is performed through measurements of transmittance for each hole image using radiographic plate densitometry. The background plasma emission corresponds to a temperature between 1 and 2 keV

[en] The dense plasma focus is a coaxial plasma gun in which a high-density, high-temperature plasma is obtained in a focused column for a few nanoseconds. When the filling gas is deuterium, neutrons can be obtained from fusion reactions. These are partially due to a beam of deuterons which are accelerated against the background hot plasma by large electric fields originating from plasma instabilities. Due to a beam-target effect, the angular distribution of the neutron emission is anisotropic, peaked in the forward direction along the axis of the gun. The purpose of this work is to illustrate the use of CR-39 nuclear track detectors as a diagnostic tool in the determination of the time-integrated neutron angular distribution. For the case studied in this work, neutron emission is found to have a 70% contribution from isotropic radiation and a 30% contribution from anisotropic radiation. (author)

[en] Mixed crop-livestock farms are widely spread in different tropical regions in the world; they contribute to food security, rural development, sustainability and poverty alleviation. The effect of scale on performance of dual purpose (DP) cattle farms was evaluated in two Mexican ecological zones: dry (DT) and wet tropics (WT). In 2011, a questionnaire of 184 items distributed into technical and social characteristics was applied to a representative sample of 3,285 farms with 50 or less cows (0.97%). The farms were classified into three groups according to their dimension: very small (1-9 cows), small (10-19 cows) and medium (20-50 cows). A general linear model (GLM) with two factors and their interactions was applied. Significant effects in dimension and ecological zone were found as well as seven interactions between both factors (p<0.05). Native pastures were used in all farms for grazing. However, small farms’ herds frequently grazed on cultivated pastures and on crop residues (p<0.05). Medium farms showed the highest grazing surface, but in the WT silage and green fodder were used while in the DT dry fodders were used (p<0.001). The interactions between factors showed a bigger specialization in milk production in DT farms, whereas WT farms were more specialized in meat production. The mixed crop-livestock system in tropic region requires an increase in herd size according to farm’s own productive structure, which is strongly influenced by the ecological zone. The systems would improve with the active participation of smallholders to identify and achieve best practices, higher technological adoption level and with an effective support from public and private Institutions.

No abstract available

[en] Adsorption and desorption of impurities in the filling gas, by the electrodes, the insulator and chamber materials of plasma focus devices, have been suggested as probable causes for the fluctuations in their neutron yield. This work describes analysis of data, aimed at looking for evidence to support this hypothesis. Before starting each series of discharges, a vacuum around 10-6 torr, is achieved. The filling gas, pure deuterium, is maintained under static conditions. A sudden fall of the initial pressure, around 5%, is systematically observed after the first shot in each series, before creeping back at an almost constant rate, in successive shots. On the other hand, for the first shot with fresh filling gas, the neutron yield is always low, and systematically increases for the second one. Except for the first two shots, we find no evidence to support the hypothesis that the neutron yield fluctuations are related to an adsorption-desorption process. It is also observed that, as the number of shots increases for each series, the neutron yield variability tends to increase, as higher yields are obtained for a few shots

No abstract available

[en] Adsorption and desorption of the filling gas, by the electrodes, the insulator and chamber materials of plasma focus devices, have been suggested as probable causes for the fluctuations in their neutron yield. This work describes analysis of data, aimed at looking for evidence to support this hypothesis. Before starting each series of discharges, a vacuum around 10^-6 Torr is achieved. The filling gas, pure deuterium, is maintained under static conditions. A sudden fall of the initial pressure, around 5%, is systematically observed after the first shot in each series, before creeping back at an almost constant rate, in successive shots. On the other hand, for the first shot with fresh filling gas, the neutron yield is always low and systematically increases for the second one. The pressure evolution for the following shots shows no correlation with the neutron yield fluctuations. Thus, except for the first two shots, we find no evidence to support the hypothesis that the neutron yield fluctuations are related to an adsorption-desorption process. It is also observed that a tendency exists for the last shots of each series to yield a larger number of neutrons but with a larger dispersion. This study has been done with both solid and hollow anodes, showing qualitatively similar results in both cases

[en] This study aimed to obtain ceramic filters with bactericidal action for water disinfection. For this, aqueous suspensions of montmorillonite K10 clay were prepared at concentrations of 48%, 50%, and 52%. Later, these were impregnated into polymeric sponges in order to form the ceramic skeletons by using the replica technique. The ceramic filters were submerged in nickel resins doped with 0.25 and 0.50 mol% silver. These resins were obtained by the Pechini method and heat-treated at 600 and 700 deg C for 2 h. Moreover, techniques such as X-ray diffraction, particle size analysis, scanning electron microscopy, energy dispersive spectroscopy, compressive strength, water absorption, and apparent porosity were used to characterize the filters, and their performance was analyzed by a bactericidal test. The bactericidal test results showed that the filters impregnated with the resin containing 0.50 mol% of silver promoted the total elimination of the Staphylococcus aureus and Escherichia coli bacteria. (author)

No abstract available

[en] The average angular distributions of neutron emissions have been measured in the Fuego Nuevo II (FN-II) dense plasma focus device (SkJ) 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. (Author)