Nonlinear magnetohydrodynamic (MHD) simulations on relaxation phenomena in a spherical tokamak and a helical plasma, including three-dimensional (3D) equilibrium computations, are executed in full toroidal geometries. For a spherical tokamak, two-step evolution of the medium-n ballooning instabilities and a successive excitation of an internal n=1 crash has been observed. A similar process has ...

The nonlinear three-wave interaction process at the heart of the parametric decay process is studied by launching counterpropagating Alfvén waves from antennas placed at either end of the Large Plasma Device. A resonance in the beat wave response produced by the two launched Alfvén waves is observed and is identified as a damped ion acoustic mode based on the measured dispersion relation. Other...

A profile is a relationship between a response variable and one or more independent variables being controlled during the time. Process Capability Indices (PCI) are measured to evaluate the performance of processes in producing conforming products. Despite frequent applications of profile and a variety of available methods to monitor its different types, little researches have been carried out ...

A mathematical model is formulated to catch the dynamics hidden in the plasma-sheath transition layer and the inner sheath layer for planar motion of a plasma. It is shown that the rescaled potential in the plasma-sheath transition layer and inner layer is governed by a perturbed KdV equation, through which some of the complex interactions and couplings among physical mechanisms acting in the p...

This paper presents a brief discussion of ultra-short laser pulse propagation and laser wakefield acceleration in plasma channels. An envelope equation for the perturbed laser beam radius is given, including finite-pulse length and nonlinear effects. Angular distribution of electrons generated by the process of laser ionization and ponderomotive acceleration (LIPA) is also discussed. An example...

We show that higher-order nonlinear indices (n(4), n(6), n(8), n(10)) provide the main defocusing contribution to self-channeling of ultrashort laser pulses in air and argon at 800 nm, in contrast with the previously accepted mechanism of filamentation where plasma was considered as the dominant defocusing process. Their consideration allows us to reproduce experimentally observed intensities a...

in this paper, thermal effect of plasma arc welding is investigated, and temperature field of ferrite stainless steel is acquired. thermal effect of plasma arc and subsequently the generated temperature field in the work piece is the key for analysis and optimization of this welding process, which is the main goal of this paper. finite element simulation of welding process by simplec method and...

Nonlinear solitary structures of electron plasma waves have been investigated by using nonlinear quantum fluid equations for electrons with an arbitrary temperature. It is shown that the electron degeneracy parameter has significant effects on the linear and nonlinear properties of electron plasma waves. Depending on its value both compressive and rarefactive solitons can be excited in the mode...