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Regarding the importance of the stability in a miniature pinch plasma generator in repetitive and strong plasma pinch, the stable operation of a 3J miniature plasma focus device in two single-shot and repetitive discharge modes (at 0.5Hz and 5Hz discharge frequencies) and the factors in creation of switch misfire was demonstrated. Then, the device efficiency and strength of the plasma pinch for four different coaxial electrode configurations were studied, upon scanning argon gas pressure ranged from 0.6 to 1.5 mbar via the study of the charging voltage variation from 8.3 to 9.3 kV. It was observed that the strength and efficient pinching is appropriately produced for the tapered anode configuration over an expanded operating pressure ranged from 0.6 to 1.5 mbar. After the calculation of the speed factor and pinch sensitivity for the optimum electrodes geometry, it was shown that the best plasma compression at the pinch phase was associated with 0.88±0.8 mbar argon gas pressure and 8.3-8.5 kV charging voltage, respectively. From the viewpoint of the stability assessment of the device, it was observed that the stable operation of the device was for the charging voltage of 8.3 to 8.7 kV in the operating pressure of 0.6 to 1.1 mbar.

In this article, after a brief introduction of MTPF-1 plasma focus device, some of the related experimental data are presented. These data show that it is possible to select the proper gas pressure and discharge voltage in order to have a specified pinch time interval. In addition, the effects of gas pressure and discharge voltage on the current sheath’s mean velocity have also been studied. This study showed that, in the case of argon, the maximum value of the current sheath’s mean velocity is about 5 cm/µs, where it can be obtained under various combinations of the pressures and discharge voltages. By using the speed factor concept, the velocity of the current sheath at the pinch time was also examined. It was determined that in two separate experiments with different gas pressures and discharge voltages, the equality of the pinch times means the approximate equality of the current sheath radial velocities.

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In this paper, after reviewing the history of plasma focus devices, the plasma focusing issue is raised and then the results of comparisons between two new Mather type plasma focus devices are presented. The main aim of this investigation was to study the effect of the energy bank capacitance , and the circuit inductance , on the energy of the hard X-ray of Mather type devices. This invetigation showed that the effect of the reduction, on the increment of the hard X-ray energy, is much more than the effect of the discharge energy variation. That is, in spite of 55% discharge energy decrement, a 40% reduction of the , leads to 227% increment of the hard X-ray energy. That is observed in a Mather type device designing. It should be mentioned that the more energy consumption is not a neccesary condition for a more energetic hard X-ray emission.

Copyright of Archives of Mining Sciences is the property of Polish Academy of Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The diurnal cycle of surface heat flux in summer fair weather conditions at mid- or low latitudes is known to affect wind-driven flow. The present study investigates diurnal cycle effects in various wind and weather conditions, with variable heating time, heating rate and cooling rate over a period of 1 day, using large-eddy simulations (LESs). Emphasis is given to the speed factor and deflection angle of the wind-driven flow at the surface, which have been observed to vary seasonally in the Tsushima Strait. The LES results show that diurnal cycle effects on the surface speed factor and deflection angle are considerable, even in non-fair weather conditions. The effects are particularly significant when the sea surface is heated during the daytime, while the daily mean heating rate is large and negative (strong cooling), which is typical in winter seasons. For example, the LES results show that the winter diurnal cycle in the Tsushima Strait doubles the speed factor relative to that without this cycle, even with the same imposed daily mean surface heat flux. The LES results also show that observed seasonal variations in speed factor and deflection angle can be explained by these diurnal cycle effects. Analytical solutions of the wind-driven flow are also sought under the diurnal cycle of surface heat flux in order to clarify the mechanism of the wind-driven flows under diurnal heat flux cycles. These results demonstrate the importance of the diurnal cycle of surface heat flux for wind-driven flow under a wide range of weather conditions. [ABSTRACT FROM AUTHOR]

Weigh-in-motion (WIM) systems differ in terms of sensing technology, sensing element, installation procedure, structural design, and material, which make them respond differently to equivalent loading conditions. The research objective was to investigate the performance of three types of piezoelectric WIM sensors in a medium strength asphalt concrete pavement of stone mastic design under different vehicle speeds and cold and warm air temperature factors using the factorial experiment method. A multiple-sensor WIM system was installed at the test site and included different types of sensors such as quartz, polymer, and ceramic piezoelectric sensors. The quartz sensors showed insensitivity to speeds higher than 30 km/h and air temperature; whereas, the effects of air temperature and speed on the ceramic sensors were significant. The polymer sensors demonstrated sensitivity to the speed (on auto-calibrated sensors specifically for lower than 30 km/h) and air temperature factors. Acquired knowledge about the effects of major climate and traffic factors on performance of the least expensive piezoelectric sensors will assist in developing an effective auto-compensation algorithm specifically for improving estimation of polarized piezoelectric sensors. [ABSTRACT FROM AUTHOR]

This paper reports the results of characterization and optimization experiments carried out on a newly developed NX-3 dense plasma focus device (20 kJ at 20 kV, a quarter time period of \sim\!\!3\ \mu\s, and 10 kJ/600 kA at 14 kV) at the Plasma Radiation Source Laboratory, NIE, Nanyang Technological University, Singapore. Initial experiments were conducted with an electrode assembly configuration having anode radius and length of 20 and 160 mm, respectively, for detailed neutron emission characterization of NX-3 device followed by further optimization of neutron yield using various other electrode configurations designed using the Lee Code. At \geq10-kJ operation, the average neutron yield on the order of 10^9 neutrons/pulse in 4\pi\sr was obtained for the deuterium filling gas pressure range of 6–8 mbar. The neutron yield of \sim\!\!4.6 \times 10^9 neutrons/pulse at 10 kJ/6 mbar is the highest ever reported for a device with the same stored energy. The neutron anisotropy measurements point to the beam–target mechanism as the dominant neutron production mechanism for NX-3 plasma focus device. Further optimization of neutron yield in NX-3 was achieved with the peak average neutron yield being enhanced from \sim\!\!(2.38 \pm 0.31) \times 10^9 neutrons/shot for the initial electrode configuration to about \sim\!\!(3.40 \pm 0.43) \times 10^9 neutrons/shot for the electrode configuration with anode radius and length of 26 and 140 mm, respectively. The analysis of neutron yield results for various electrode assembly configurations demonstrates the speed factor as a key optimization tool for maximization of neutron yield. [ABSTRACT FROM PUBLISHER]