Non-parametric inference of impurity transport coefficients in the ASDEX Upgrade tokamak

Nuclear Fushion

article

T. Nishizawa¹  R. Dux¹  R.M. McDermott¹  F. Sciortino¹  M. Cavedon¹  C. Schuster¹  E. Wolfrum¹  U. von Toussaint¹  A.Jansen Van Vuuren⁴  D.J. Cruz-Zabala⁴  P. Cano-Megias⁵  C. Moon² 

[1] Max Planck Institute for Plasma Physics;Research Institute for Applied Mechanics, Kyushu University;Physik-Department E28, Technische Universität München;Dept. of Atomic, Molecular and Nuclear Physics, University of Seville;Centro Nacional de Aceleradores;Dept. of Energy Engineering, University of Seville

关键词: tokamak;    impurity;    Bayesian inference;    charge exchange recombinationspectroscopy;   

DOI  :  10.1088/1741-4326/ac60e8

来源: Institute of Physics Publishing Ltd.

【 摘 要 】

We present a non-parametric inference of impurity transport coefficients by using charge exchange recombination spectroscopy measurements of Ne X, Ne VIII, O VIII, and C VI lines. Due to their close atomic numbers, neon, oxygen and carbon impurity ions are assumed to have the same diffusion coefficientDand convection velocityv . Unlike conventional techniques that modulate or perturb the impurity contents, we employ a quasi-stationary plasma with static impurity profiles. Since the ratio ofvtoDonly describes the equilibrated profile of the sum of all impurity charge states, steady-state measurements can still decoupleDandvif different charge states are simultaneously observed. We have formulated a non-parametric analysis framework based on the Bayesian probability theory and conducted transport coefficient measurements for a Type III ELMy H-mode plasma at ASDEX Upgrade. The charge exchange reactions with the background neutrals, which are known to affect the impurity charge state balance, are taken into account by introducing additional free parameters. WhileDat the pedestal is close to the neoclassical level ( 1 m s⁻²), a large diffusion coefficient and a strong outward convection are inferred right inside the pedestal top.

【 授权许可】

Unknown