Equilibrium mode distribution

About: Equilibrium mode distribution is a research topic. Over the lifetime, 928 publications have been published within this topic receiving 14939 citations.

Intermediate nonlinear regimes of line-tied g mode and ballooning instability

Abstract: A theoretical framework has been developed to describe the nonlinear regimes of line-tied g modes in slab geometry and ballooning instabilities in toroidal configurations. Recent experimental observation and numerical simulations demonstrate a persistence of ballooning-like filamentary structures well into the nonlinear stage of edge localized mode (ELM) activity in H-mode plasmas. Our theory is based on an expansion using two small scale lengths, the mode displacement across magnetic flux surfaces and the mode width in the most rapidly varying direction, both normalized by the equilibrium scale length. When the mode displacement across the magnetic flux surface is much less than the mode width in the most rapidly varying direction, the mode is in the linear regime. When the mode displacement grows to the order of the mode width in the rapidly varying direction, the plasma remains incompressible to lowest order, and the Cowley–Artun regime is obtained. The detonation regime, where the nonlinear growth of the mode could be finite-time singular, is accessible when the system is sufficiently close to marginal stability. At higher levels of nonlinearity, the system evolves to the intermediate nonlinear regime, when the mode displacement across the magnetic flux surface becomes comparable to the mode width in the same direction. During this phase, the nonlinear growth of the mode in the parallel and perpendicular directions are coupled, and sound wave physics contributes to nonlinear stability. The governing equations for the line-tied g mode and the ballooning instability in the intermediate nonlinear regime have been derived. A remarkable feature of the nonlinear equations is that solutions of the associated local linear mode equations continue to be valid solutions into the intermediate nonlinear regime in a Lagrangian reference frame. This property has been confirmed in the full ideal MHD simulations of both the line-tied g mode in a shearless slab and the ballooning instability in a tokamak, and may help explain the growth and persistence of the filamentary structures observed in ELM experiments well into the nonlinear phase.

Characteristic evaluation method, device and program of single mode optical fiber

Abstract: PROBLEM TO BE SOLVED: To provide a characteristic evaluation device of a single mode optical fiber capable of evaluating nondestructively and highly accurately a distribution characteristic in the longitudinal direction between connected optical fibers, in an optical fiber transmission path constituted of a plurality of single mode optical fibers. SOLUTION: This device has a back-scattering light intensity measuring device 11 for measuring back-scattering light intensity S (λ, z) on a position z of the single mode optical fiber 13 on both ends, when pulse light having the wavelength λ is allowed to enter the single mode optical fiber 13 having an optional length L; and a back-scattering light intensity waveform analyzer 12 for operating a specific refractive index difference Δ(z) on an optional position z of the single mode optical fiber 13 by using a normalization structure inconsistency loss component In (λ, z) on the position z of the single mode optical fiber 13 operated from the back-scattering light intensity S (λ, z), and a mode field diameter 2W (λ, z 0 ) and the specific refractive index difference Δ(z 0 ) at its optional reference point z 0 . COPYRIGHT: (C)2008,JPO&INPIT

Waveguide type wavelength measuring apparatus

Abstract: A waveguide type wavelength measuring apparatus is provided with a single mode channel type optical waveguide formed on a waveguide substrate, in which the light to be measured is inputted, a double mode waveguide connected to the single mode channel type optical waveguide, waveguide branches for branching the light output from the double mode waveguide, and photodetectors for detecting independently the light branched by the waveguide branches. The wavelength of the inputted light is measured on the basis of the output signals from the photodetectors. Hence it is possible to perform precise real-time measurement of the wavelength of the incident light with a compact and extremely miniaturized structure.

Method and device for stabilizing the light power carried by an optical fibre

Abstract: 1. Method of stabilizing the light power carried by an optical fiber in which the output power of the light source is controlled by means of a control signal derived from the light beam radiated by a light source, characterized in that as a control signal is used the Rayleigh scattered radiation emanating in a reverse direction from a section of the optical fiber which can be determined according to location and length, in which the Rayleigh scattered radiation is directly proportional to the light power guided in the optical fiber itself.