On $K\beta$ radiation of Ar$^{16+}$ ions in coronal plasma

The measured and calculated data obtained in this and earlier works for the intensity ratio $G_3= I[K_{\beta_2}]/I[K_{\beta_1}]$ of the intercombination and resonance $K_{\beta}$ lines corresponding to the $1s3p^3 P_1\to 1s^{21}S_0 (K_{\beta_2})$ and $1s3p^1 P_1\to 1s^{21}S_0 (K_{\beta_1})$ transitions in the coronal plasma spectrum of Ar$^{16+}$ ions were compared with each other. In this work, the $G_3$ ratio was measured on the TEXTOR (Julich, Germany) tokamak equipped with high-resolution Bragg spectrometers and other diagnostic instruments. The calculations carried out within the framework of the radiative-collision model using the ATOM, MZ, and GKU programs developed in the Lebedev Physical Institute, Russian Academy of Sciences, are in agreement, to the experimental accuracy, with all the data obtained on the PLT (Princeton, USA), ALCATOR-C (Cambridge, USA), and TEXTOR tokamaks. It is shown that the previously observed factor of 1.3-2 discrepancies between the measured and $G_3$ values calculated using the HULLAC code and appreciably exceeding the experimental error are caused by the use of inaccurate atomic data and simplified atomic kinetics in those works. The results presented in this work are evidence for the high accuracy of our atomic data (transition rates) and for the possibility of effectively using, on their basis, the $K_{\beta}$ lines of multicharged ions in X-ray spectrum diagnostics of electron temperature and density in laboratory and astrophysical coronal plasma sources.