On Detection of a Global Mode Structure in Experiments by Use of Turbulence Diagnostic Simulator

Abstract

Development of experimental diagnostics in fusion plasmas has made possible to measure plasma fluctuations with high spatial and temporal resolution. To detect a global mode, which contributes to global transport phenomena, it is helpful to use simulation data as a test field for the measurements. The turbulence diagnostic simulator is an assembly of codes for turbulence simulations and numerical diagnostics. Using the turbulence diagnostic simulator, a time series of turbulence data is obtained, on which numerical diagnostics are carried out to demonstrate how global modes to be observed. There exist modes, which are broad in the radial direction, and correlation analyses reveal the characteristic structures with a finite number of local observations in the radial direction, as in experiments.

Selective formation of streamers in magnetized cylindrical plasmas

“…This turbulent structure is sustained by the energy transfer between modes, which have neighbouring m by means of the mediator mode (1,2). We have carried out calculations with other paths for energy transfer by nonlinear couplings for comparison, and found that the streamer is selectively formed in spite of the other possible energy exchange paths [27]. In addition, our analyses have shown in this paper that the streamer is formed and its lifetime is longer, even in a less unstable case with ν in close to the critical value for mode excitation.…”

“…Numerical simulations of drift wave turbulence in linear devices have been carried out to understand the fundamental mechanism of structural formation by comparison with experiments [24][25][26][27][28][29]. We have developed a three-dimensional numerical simulation code, which simulates the resistive drift wave turbulence in magnetized cylindrical plasmas [24].…”

“…The streamer is formed when the ionneutral collision frequency is larger than the critical value. Numerical simulations showed that the energy path to form the streamer is selected within several kinds of coupling paths by changing the number of modes included in simulations [27]. In addition to the previous research near the critical point of the bifurcation between the zonal flow and the streamer, the turbulent behaviour near the stability boundary of the drift wave is studied in this paper.…”

Simulation Science at the National Institute for Fusion Science

“…(4) "Fluid turbulence transport simulation group" studies physics issues related to turbulent transport in toroidal plasmas by using the theory and simulation based on fluid model. Turbulence Diagnostic Simulator has been developed for understanding the mechanism of the turbulence structure formation based on the demonstration of experimental measurement and the correlation analysis [19]. By using a set of reduced two-fluid model the excitation of the macro-MHD mode has been demonstrated owing to the multi-scale interaction in a quasi-steady equilibrium formed by the balance between micro-turbulence and zonal flow [20].…”

Dynamical Response of Turbulent Structures in Cylindrical Magnetized Plasmas

“…Recently, turbulent diagnostic simulator (TDS) project has been started [17], which has played an important role to find the turbulent structures [10]. Here we apply TDS to the problem of dynamical evolution of the streamer in a cylindrical plasma.…”