The Experts below are selected from a list of 285 Experts worldwide ranked by ideXlab platform
Shunjiro Shinohara - One of the best experts on this subject based on the ideXlab platform.
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Performance of RF Plasma Thruster for Various Magnetic Field Configurations by Permanent Magnets
2020Co-Authors: Takahiro Nakamura, Hiroyuki Nishida, Shunjiro ShinoharaAbstract:In order to realize a long-lived and high-powered electric propulsion system, we have been investigating an electrodeless electric propulsion concept utilizing a RF plasma source and a Magnetic nozzle. In this study, the thrust performance of the RF plasma thruster is investigated under various Magnetic Field Configurations by changing operational conditions. From the measurements of the thrust force and the total ion flux, the thrust force, specific impulse, and plasma utilization efficiency monotonically increased with an applied RF power. The discharge mode transition points, where dramatic improvement of these performance, were found. These points were varied depending on the Magnetic Field configuration. In the case of same plasma flow rate, higher thrust force was obtained in the thruster with the higher Magnetic flux density (290 mT) than the lower Magnetic flux density (52 or 140 mT). The position of the Magnetic cusp in the discharge vessel could change a propellant utilization efficiency. After the discharge mode transition, this efficiency in the case that the Magnetic cusp was at the center of the RF antenna was higher than that in the case of no Magnetic cusp.
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characteristics of radio frequency wave propagation in bounded plasma under the various Magnetic Field Configurations
Physics of Plasmas, 2001Co-Authors: Shunjiro Shinohara, Akira FujiiAbstract:Detailed characteristics of radio frequency (rf) waves with pulsed modes in the whistler wave range were studied in a cylindrical rf-produced plasma, where the plasma boundary lay in the intermediate regime between infinite whistler wave propagation and bounded geometry helicon wave propagation. Excited Magnetic Field amplitudes and phases with three components in two-dimensional space were measured for different experimental conditions. Three Magnetic Field Configurations were used and the diameter of the excitation loop antenna was also varied. Numerical calculation by the finite element method, which has been demonstrated to be a powerful means for this analysis, showed good agreement with the observed results, satisfying the dispersion relation and wave structures of helicons in the semisteady state and also satisfying the dispersion of whistlers with a short pulsed mode. The excited waves propagated nearly along the Magnetic Field lines within a small angle of less than 10°. Furthermore, in the low (...
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rf wave propagation in bounded plasma under divergent and convergent Magnetic Field Configurations
Japanese Journal of Applied Physics, 1999Co-Authors: Seiji Takechi, Shunjiro ShinoharaAbstract:Radio frequency (RF) wave propagation in a bounded plasma (cylindrical shape with a large diameter of 45 cm) produced by a planar, spiral antenna was investigated under divergent and convergent Magnetic Field Configurations. The measured excited Magnetic Field amplitude and the phase were examined based on helicon wave characteristics, and were consistent with the computed results using the Transport Analyzing System for tokamaK/Wave analysis by Finite element method (TASK/WF) code. The wave propagation region was broadened (focused) in the radial direction with increasing distance from the antenna under the divergent (convergent) Field.
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characteristics of rf wave propagation in large diameter plasma with cusp Magnetic Field Configurations
Japanese Journal of Applied Physics, 1999Co-Authors: Seiji Takechi, Shunjiro Shinohara, Andatsushi FukuyamaAbstract:RF wave propagation, in the large-diameter (45 cm) plasma produced by a planar, spiral antenna, was investigated with the cusp Magnetic Field Configurations. Measurements of the excited Magnetic Field amplitude and the phase were examined by a helicon wave dispersion relation, and the obtained results were consistent with the calculated ones by Transport Analyzing System for tokamaK/Wave analysis by Finite element method (TASK/WF) code. The wave characteristics depended on the gradient and the magnitude of the Magnetic Field near the line cusp position, and in the neighborhood of this position, this wave showed different behavior from the helicon wave observed in a uniform Field.
Akira Fujii - One of the best experts on this subject based on the ideXlab platform.
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characteristics of radio frequency wave propagation in bounded plasma under the various Magnetic Field Configurations
Physics of Plasmas, 2001Co-Authors: Shunjiro Shinohara, Akira FujiiAbstract:Detailed characteristics of radio frequency (rf) waves with pulsed modes in the whistler wave range were studied in a cylindrical rf-produced plasma, where the plasma boundary lay in the intermediate regime between infinite whistler wave propagation and bounded geometry helicon wave propagation. Excited Magnetic Field amplitudes and phases with three components in two-dimensional space were measured for different experimental conditions. Three Magnetic Field Configurations were used and the diameter of the excitation loop antenna was also varied. Numerical calculation by the finite element method, which has been demonstrated to be a powerful means for this analysis, showed good agreement with the observed results, satisfying the dispersion relation and wave structures of helicons in the semisteady state and also satisfying the dispersion of whistlers with a short pulsed mode. The excited waves propagated nearly along the Magnetic Field lines within a small angle of less than 10°. Furthermore, in the low (...
P A Sturrock - One of the best experts on this subject based on the ideXlab platform.
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maximum energy of semi infinite Magnetic Field Configurations
The Astrophysical Journal, 1991Co-Authors: P A SturrockAbstract:This article addresses the conjecture by Aly J. J. (1984, ApJ, 283) that the maximum-energy state of Magnetic Field Configurations that have a given flux distribution on a given surface is the open-Field configuration. It is shown that the existence of a maximum-energy configuration depends upon the topology of the source surface: for a multiply connected surface there is no maximum-energy state. However, the Magnetic energy is known to be bounded above for a wide class of simply connected surfaces, and it is shown that in this case there must be a Field configuration that has maximum energy
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maximum energy of semi infinite Magnetic Field Configurations
LNP, 1991Co-Authors: P A SturrockAbstract:In solar physics and many other areas of astrophysics, one is interested in the properties of Magnetic-Field Configurations that extend out from a given surface that may be termed the "source surface." (See, for instance, Parker 1979; Priest 1982.) I f the Field is assumed to extend to infinity, we may refer to such Configurations as "semi-infinite." For instance, the Magnetic Field of a solar active region maybe considered to extend upwards from a planar source surface.
W Gonzalezvinas - One of the best experts on this subject based on the ideXlab platform.
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pattern formation in spin coating of hybrid colloids in different Magnetic Field Configurations
Journal of Physics D, 2019Co-Authors: Raheema Aslam, W GonzalezvinasAbstract:This work was partially supported by the Spanish AEI (Grant Nos. FIS2014-54101-P and FIS2017-83401-P).
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spin coating of moderately concentrated superparaMagnetic colloids in different Magnetic Field Configurations
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2017Co-Authors: Raheema Aslam, W GonzalezvinasAbstract:Abstract Spin-coating technique is very fast, cheap, reproducible, simple and needs less material to fabricate films of particulate systems/colloids. Their thickness and uniformity may be controlled by means of external Fields. We apply Magnetic Fields during the spin-coating of a moderately concentrated superparaMagnetic colloid (made of silica coated magnetite particles). We study the influence of different Magnetic Field Configurations (homogeneous and inhomogeneous) on the resulting spin-coated deposits and compare experimental results under various conditions. SuperparaMagnetic colloids behave as, non-Newtonian, magnetorheological fluids. Their viscosity vary significantly under applied Magnetic Fields. We measure and compare the effect of uniform and non-uniform Magnetic Fields on their relative effective viscosity, using the spin-coated deposits and a previously existing model for simple colloids. The mechanisms involved in the deposits formation under different experimental conditions are also discussed. In particular, we show that the magnetophoretic effect plays an important role in the spin-coating of Magnetic colloids subjected to non-uniform Magnetic Fields. We characterize an effective magnetoviscosity in non-uniform Magnetic Fields that is largely influenced by the magnetophoretic effect that enhances the flow of the Magnetic fluid.
Y M Wang - One of the best experts on this subject based on the ideXlab platform.
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Magnetic Field Configurations associated with fast solar wind
Solar Physics, 1991Co-Authors: N R Sheeley, Y M WangAbstract:In this paper, we consider the implications of the observed inverse correlation between solar wind speed at Earth and the expansion rate of the Sun-Earth flux tube as it passes through the corona. We find that the coronal expansion rate depends critically on the large-scale photospheric Field distribution around the footpoint of the flux tube, with the smallest expansions occurring in tubes that are rooted near a local minimum in the Field. This suggests that the fastest wind streams originate from regions where large coronal holes are about to break apart and from the facing edges of adjacent like-polarity holes, whose Field lines converge as they transit the corona. These ideas lead to the following predictions: (1) Weak holes and fragmentary holes can be sources of very fast wind. (2) Fast wind with steep latitudinal gradients may be generated where the Field lines from the polar hole and a lower-latitude hole of like polarity converge to form a mid-latitude ‘apex’. (3) The fastest polar wind should occur shortly after sunspot maximum, when trailing-polarity flux converges onto the poles and begins to establish the new polar Fields.
