On the verification of atomic data for K _α radiation spectra from the TEXTOR tokamak

Abstract

High-resolution spectra from the Ar¹⁶⁺ and Ar¹⁵⁺ ions measured at the TEXTOR tokamak are used to verify atomic data necessary for simulation and diagnostics of a hot coronal plasma with an accuracy of about 5%. A self-consistent approach based on solving the inverse problem by the Bayesian iteration method in the framework of the proposed semiempirical “spectroscopic” model is used. The perturbation calculations of the atomic characteristics for [He] and [Li] argon ions by means of the ATOM and MZ codes require 10% correction of the ratios of the effective excitation rates for the intercombination line of the [He] ion and the group of dielectronic satellites corresponding to the 1s2p3l — 1s ²3l′ transitions in the [Li] ion to the resonance line of the [He] ion. The spectra calculated with this correction are in agreement with the measured spectra within the measurement accuracy ≲10% in the wide ranges ∼0.8–2.5 keV and ∼10¹³–10¹⁴ cm⁻³ of the central electron temperature and density, respectively. It is found that the central temperature value can be determined in the framework of the spectroscopic model with an accuracy of ∼5%, and the abundances of the [Li] and [II] argon ions with respect to the [He] ions can be determined with an accuracy of ∼20 and 50%, respectively. It has been shown that the use of the isothermal approximation when measuring the temperature from the ratio of the intensities of the dielectronic satellites to the resonance line can lead to a large error of ∼20% in the presence of gradients typical for tokamak plasmas.