Turbulent-convective block for the ASTRA transport code
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Turbulent-Convective Block for the ASTRA Transport Code A. Yu. Dnestrovskij, V. P. Pastukhov*, and N. V. Chudin National Research Center Kurchatov Institute, Moscow, 123182 Russia *e-mail: [email protected] Received August 25, 2016; in final form, November 17, 2016
Abstract―A physical model for the enhanced transport code is presented, which explicitly takes into account the contribution of turbulent convection to the processes of particle and heat transport in the hot core of the tokamak plasma. The model is based on the specially developed CONTRA-A turbulent block, while an adapted version of the existing ASTRA transport code is used as a transport envelope. The CONTRA-A turbulent block, based on the adiabatically reduced quasi-2D magnetohydrodynamic equations, calculates the generation and self-consistent evolution of low-frequency turbulence, including the spatiotemporal structure of turbulent fluctuations of the plasma velocity, density, and temperatures of electrons and ions. Using the obtained data on fluctuations, the CONTRA-A block calculates the turbulent-convective particle and heat fluxes and transfers them to the modified ASTRA code, which computes the evolution of quasi-equilibrium plasma parameters. To illustrate the capabilities of the enhanced transport model, the results of simulations of turbulent plasma evolution in two discharge scenarios with nonstationary auxiliary plasma heating in the T-10 and T-15MD tokamaks are presented. DOI: 10.1134/S1063780X1704002X
1. INTRODUCTION The problem of particle, heat, and toroidal and poloidal momentum transport in tokamaks remains among the most important issues of plasma physics and ITER project research. As a rule, cross-field fluxes of heat and particles observed in tokamaks and other magnetic confinement systems significantly exceed their neoclassical values. Anomalous transport processes are usually associated with the turbulence initiated by plasma instabilities. There are a vast amount of works dedicated to developing various transport models and codes with allowance for anomalous transport processes in magnetized plasma, as well as codes for direct simulation of turbulence (see, e.g., review [1], presented at the 23rd IAEA Fusion Energy Conference). Many existing transport codes allow one to describe global nonstationary transport processes in different regions of tokamak plasmas with account of a real structure of magnetic surfaces. Due to the use of flux coordinates, these codes, in essence, are onedimensional in terms of the radial flux coordinate. Among this class are such well-known codes as ASTRA [2], TRANSP [3], TOPICS-IB [4], CRONOS [5], JINTRAC [6], etc. To describe particle and heat fluxes in these codes, the diffusive approximation with local empirical transport coefficients is commonly used. At the same time, many experiments carried out in tokamaks (e.g., [7– 9]) and other magnetic confinement systems (stellara-
tors [10, 11], tandem mirrors [12, 13], etc.) show that the diffusive approximation with local empirical transport
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