517 research outputs found
Nonlinear behavior of magnetohydrodynamic modes near marginally stable states. II. Application to the resistive fast interchange mode
No full textNoriyoshi Nakajima and Satoshi Hamaguchi, Physics of Fluids B: Plasma Physics 2, 1184 (1990) https://doi.org/10.1063/1.859254With the use of the general formulation developed in an earlier paper, the nonlinear evolution of the resistive fast interchange mode near the marginally stable state is obtained analytically. The nonlinear amplitude equation of the mode is shown to be of the Landau type. It is also shown that there is a stable equilibrium bifurcating from the initial equilibrium. Comparing this analytical result to numerical simulations, it is confirmed that the saturation level and the saturation time are well estimated by this Landau type of nonlinear amplitude equation. © 1990 American Institute of Physics
Fluctuation spectrum and transport from ion temperature gradient driven modes in sheared magnetic fields
No full textSatoshi Hamaguchi and Wendell Horton, Physics of Fluids B: Plasma Physics 2, 1833 (1990) https://doi.org/10.1063/1.859455The ion temperature gradient driven mode or ηi-mode turbulence is reinvestigated based on two-component compressible fluid equations with the polarization drift velocity and adiabatic electrons. The scaling of the anomalous ion heat conductivity with magnetic shear s = Ln/L s and the excess of ηi over the critical value ηi,c for marginal stability is found to vary as χi = g(ρs/Ln)(cTi/eB) (ηi - ηi,c)exp(-as), where g≃1 and α≃5. © 1990 American Institute of Physics
Ion temperature gradient driven turbulence in the weak density gradient limit
No full textSatoshi Hamaguchi and Wendell Horton, Physics of Fluids B: Plasma Physics 2, 3040 (1990) https://doi.org/10.1063/1.859371The anomalous heat transport arising from the ion temperature gradient driven mode or ηi-mode turbulence is extended to the range of the weak density gradient limit (ηi = Ln/ L T→ ∞ ), which is appropriate for H-mode dishcarges. It is shown that the anomalous ion heat conductivity χi with L n→ ∞ scales as χi = g(ρs/ LT) (cTi/eB) exp( - βσ) with σ = (T e/Ti) (LT/Ls), β≃4, and g≃1. This χi scaling is the natural extension for high ηi of the scaling of χi for K = (T i/Te) (1 + ηi) ≲ 4 obtained [Phys. Fluids B 2, 1833 (1990)] from analytical and numerical studies. © 1990 American Institute of Physics
Anomalous transport arising from nonlinear resistive pressure-driven modes in a plasma
No full textSatoshi Hamaguchi, Physics of Fluids B: Plasma Physics 1, 1416 (1989) https://doi.org/10.1063/1.858972Anomalous transport caused by fluctuations of resistive pressure-driven modes is discussed within the framework of magnetohydrodynamics (MHD). The nonlinear-reduced equations describing fluctuations localized near a particular magnetic field line are derived for tokamak and reversed-field-pinch (RFP) plasmas, taking into account nonzero viscosity and heat conductivity. For an ideally stable but resistively slightly unstable plasma, the anomalous transport is caused particularly by convective motions. The convection is studied as bifurcation from the linearly unstable equilibrium and the expression of the anomalous transport in a tokamak plasma is obtained as a function of the mean pressure gradient near the critical point. In order to evaluate the effects of the convection on the anomalous transport under various conditions, the reduced equations are also solved numerically. It is found that Nusselt number, that is, the ratio of the total heat conductivity including the anomalous heat transport to the classical collisional heat conductivity, is significantly large under some conditions. This partially accounts for the large heat losses in controlled thermonuclear fusion devices. © 1989 American Institute of Physics
Self-limiting processes in thermal atomic layer etching of nickel by hexafluoroacetylacetone
No full textAbdulrahman H. Basher, Ikutaro Hamada, and Satoshi Hamaguchi. Jpn. J. Appl. Phys. 59 090905.In thermal atomic layer etching (ALE) of Ni, a thin oxidized Ni layer is removed by a hexafluoroacetylacetone (hfacH) etchant gas at an elevated surface temperature, and etching ceases when a metallic Ni surface appears (self-limiting step). However, atomistic details of the self-limiting step was not well understood. With periodic density-functional-theory calculations, it is found that hfacH molecules barrierlessly adsorb and tend to decompose on a metallic Ni surface, in contrast to the case of a NiO surface, where they can form volatile Ni(hfac)2. Our results clarify the origin of the self-limiting process in the thermal ALE
Molecular dynamics simulation of the formation of sp3 hybridized bonds in hydrogenated diamondlike carbon deposition processes
No full textYasuo Murakami, Seishi Horiguchi, and Satoshi Hamaguchi, Physical Review E 81, 041602, 2010The formation process of s p3 hybridized carbon networks (i.e., diamondlike structures) in hydrogenated diamondlike carbon (DLC) films has been studied with the use of molecular-dynamics simulations. The processes simulated in this study are injections of hydrocarbon (CH3 and CH) beams into amorphous carbon (a-C) substrates. It has been shown that diamondlike s p3 structures are formed predominantly at a subsurface level when the beam energy is relatively high, as in the "subplantation" process for hydrogen-free DLC deposition. However, for hydrogenated DLC deposition, the presence of abundant hydrogen at subsurface levels, together with thermal spikes caused by energetic ion injections, substantially enhances the formation of carbon-to-carbon s p3 bonds. Therefore, the s p3 bond formation process for hydrogenated DLC films essentially differs from that for hydrogen-free DLC films. © 2010 The American Physical Society
Rapid breakdown mechanisms of open air nanosecond dielectric barrier discharges
No full textTsuyohito Ito, Tatsuya Kanazawa, and Satoshi Hamaguchi, Physical Review Letters 107, 065002, 2011The discharge initiation mechanism of nanosecond dielectric barrier discharges in open air has been clarified with time-dependent measurement of the discharge electric field by electric-field-induced coherent Raman scattering and optical emission. Our experimental observations have revealed that, in the prebreakdown phase of a nanosecond dielectric barrier discharge, the externally applied fast-rising electric field is strongly enhanced near the cathode due to large accumulation of space charge, which then strongly enhances ionization near the cathode. Once a sufficiently large number of ionizations take place, the location of peak ionization forms a front and propagates toward the cathode with strong optical emission, which establishes the discharge. This process is essentially different from the well-known Townsend mechanism for slower discharges. © 2011 American Physical Society
Chemically Reactive Species In Liquids Generated By Atmospheric-Pressure Plasmas And Their Roles In Plasma Medicine
No full text8th International Conference on Atomic and Molecular Data and Their Applications, ICAMDATA 2012; Gaithersburg, MD; United States; 30 September 2012 through 4 October 2012Satoshi Hamaguchi, AIP Conference Proceedings 1545, 214 (2013) https://doi.org/10.1063/1.4815857This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in AIP Conference Proceedings 1545, 214 (2013) and may be found at https://doi.org/10.1063/1.4815857.Plasmas whose gas temperatures are close to room temperature may be generated in ambient air or a gas at atmospheric pressure with the use of low-frequency high voltage or low-power radio-frequency (RF) or microwave power applied to electrodes. Such plasmas can serve as a powerful source of free radicals and/or chemically reactive species that arise from atoms and molecules of the ambient gas. Recently use of such plasmas for medical purposes has attracted much attention as they can be implemented in possible medical devices that can cause blood coagulation, heal wounds, facilitate angiogenesis, sterilize surgical devices as well as living tissues without harming healthy cells, and selectively inactivate cancer cells. Especially of interest among reactive species generated by atmospheric-pressure plasmas (APP) are reactive oxygen species (ROS) and reactive nitrogen species (RNS) that are generated in liquid phase. Since most living tissues and cells are immersed in liquids (such as blood or culture media), reactive species generated by APPs in the gas phase are transported to the liquid phase and possibly converted to different types of reactive species therein before causing some influence on the tissues or cells. In this study, the rate equations are solved to evaluate concentrations of various reactive species in pure water that are originated by plasma reactions in atmosphere and possible effects of such species (including ROS/RNS) on living tissues and cells are discussed
Oscar — 2022: Hamaguchi Ryūsuke
No full textThe article is devoted to the work of the famous Japanese film director Hamaguchi Ryūsuke — a representative of the new generation of Japanese cinematographers. He is the winner of many prestigious awards of the international film festivals in Locarno, Cannes, etc. His film Drive My Car received the prize of the American Film Academy, Oscar — 2022, as the best foreign film. The film is unusual and interesting in many of its features, which are described in detail in this paper. But, first of all, the author draws attention to the fact that the plot of this picture is based on the eponymous story by the popular Japanese novelist Murakami Haruki. At the same time, the director borrowed a lot from the play “Uncle Vanya”, written by Russian classic A. P. Chekhov, whose influence is quite evident in all the director’s recent works. Another key figure who determined the main vector of creativity of Hamaguchi is Andrei Tarkovsky. The Japanese director owes his acquaintance with Tarkovsky’s films to his teacher — a master of modern Japanese cinema Kurosawa Kiyoshi. Thus, the Russian theme is one of the most interesting aspects of his work. At the same time, the author seeks to analyze in details other literary and cinematic origins of Hamaguchi’s directorial career and comes to the conclusion that his work is a complex but harmonious synthesis of Western and Japanese culture with the latter’s pronounced national traditions
Structure of laboratory ball lightning
No full textTsuyohito Ito, Tomoya Tamura, Mark A. Cappelli, and Satoshi Hamaguchi, Physical Review E 80, 067401, 2009Trajectories of self-sustained laboratory ball lightning, generated by arc discharges with silicon, are investigated for understanding the possibility of buoyant flight. Extremely low apparent densities are found, nearly approaching that of standard air. The freely buoyant balls are observed to survive for about 0.1 s, with significantly buoyant balls surviving for several seconds. These ball lightning objects are found to have a density and size that can easily allow them to be carried by a gentle breeze of a few meters per second. The results are interpreted by a model that is an extension of that first proposed by Abrahamson and Dinniss. The buoyant behavior of ball lightning seen in our experiments is believed to arise as a result of the formation of a nanoparticle oxide network growing from a molten silicon core. © 2009 The American Physical Society
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