Satellite lines from autoionizing states of Fe XVI and the problems with the X-ray Fe XVII lines

Abstract We present new calculations of atomic data needed to model autoionizing states of Fe xvi. We compare the state energies, radiative and excitation data with a sample of results from previous literature. We find a large scatter of results, the most significant ones in the autoionization rates, which are very sensitive to the configuration interaction and state mixing. We find relatively good agreement between the autoionization rates and the collisional excitation rates calculated with the R-matrix suite of programs and autostructure. The largest model, which includes J-resolved states up to n = 10, produces ab-initio wavelengths and intensities of the satellite lines which agree well with solar high-resolution spectra of active regions, with few minor wavelength adjustements. We review previous literature, finding many incorrect identifications, most notably those in the NIST database. We provide several new tentative identifications in the 15-15.7 Å range, and several new ones at shorter wavelengths, where previous lines were unidentified. Compared to the previous CHIANTI model, the present one has an increased flux in the 15–15.7 Å range at 2 MK of a factor of 1.9, resolving the discrepancies found in the analysis of the Marshall Grazing Incidence X-Ray Spectrometer (MaGIXS) observation. It appears that the satellite lines also resolve the long-standing discrepancy in the intensity of the important Fe xvii 3D line at 15.26 Å.</jats:p

Dielectronic recombination of lanthanide and low ionization state tungsten ions: W-1(3+)-W1+

The experimental thermonuclear reactor, ITER, is currently being constructed in Cadarache, France. The reactor vessel will be constructed with a beryllium coated wall, and a tungsten coated divertor. As a plasma-facing component, the divertor will be under conditions of extreme temperature, resulting in the sputtering of tungsten impurities into the main body plasma. Modelling and understanding the potential cooling effects of these impurities requires detailed collisional-radiative modelling. These models require a wealth of atomic data for the various atomic species in the plasma. In particular, partial, final-state resolved dielectronic/radiative recombination (DR/RR) rate coefficients for tungsten are required. In this manuscript, we present our calculations of detailed DR/RR rate coefficients for the lanthanide-like, and low ionization stages of tungsten, spanning charge states W13+–W1+. The calculations presented here constitutes the first detailed exploration of such low ionization state tungsten ions. We are able to reproduce the general trend of calculations performed by other authors, but find significant differences between ours and their DR rate coefficients, especially at the lowest temperatures considered

R-matrix Electron-impact Excitation Data for the H- and He-like Ions with Z = 6−30

Abstract Plasma models built on extensive atomic data are essential to interpreting observed cosmic spectra. H-like Lyman series and He-like triplets observable in the X-ray band are powerful diagnostic lines to measure the physical properties of various types of astrophysical plasmas. Electron-impact excitation is a fundamental atomic process for the formation of H-like and He-like key diagnostic lines. Electron-impact excitation data adopted by the widely used plasma codes (AtomDB, CHIANTI, and SPEX) do not necessarily agree with each other. Here we present a systematic calculation of electron-impact excitation data of H-like and He-like ions with the atomic number Z = 6–30 (i.e., C to Zn). A radiation-damped R-matrix intermediate-coupling frame transformation calculation was performed for each ion with configurations up to n = 6. We compare the present work with the above three plasma codes and the literature to assess the quality of the new data, which are relevant for current and future high-resolution X-ray spectrometers.</jats:p

Electron and neutral interactions with impurities in divertor plasmas

With the current focus on the characteristics and effective operation of divertor configurations in fusion plasma research, a reassessment of the atomic database available for divertor modeling and diagnosis is taking place. The quest for ideal materials for divertor targets and for impurities that can be used to promote optimum working conditions has exposed some gaps in the database. In addition, for the finer spectroscopic diagnostic and modeling tools now being promoted, existing data may be organized inappropriately or may be at unsuitable precisions. In this paper, some examples that emphasize electron collisions and collisions with neutrals, are used to demonstrate these points. Then, a case study is presented, based on experience at SET Joint Undertaking, of tailoring atomic data and their manipulation for experiment support

Electron and neutral interactions with impurities in divertor plasmas

With the current focus on the characteristics and effective operation of divertor configurations in fusion plasma research, a reassessment of the atomic database available for divertor modeling and diagnosis is taking place. The quest for ideal materials for divertor targets and for impurities that can be used to promote optimum working conditions has exposed some gaps in the database. In addition, for the finer spectroscopic diagnostic and modeling tools now being promoted, existing data may be organized inappropriately or may be at unsuitable precisions. In this paper, some examples that emphasize electron collisions and collisions with neutrals, are used to demonstrate these points. Then, a case study is presented, based on experience at SET Joint Undertaking, of tailoring atomic data and their manipulation for experiment support.</p