Theoretical modeling of M-shell spectra of heavy ions

The study of radiation from multiply charged heavy ions and from tungsten ions (W, Z = 74) in particular is of great interest for plasma physics community. For example, many components of present-day, and planned future generation, Tokamaks are made of tungsten, and tungsten wire array implosions are being intensively studied at Sandia National Laboratories (SNL). The study of x-ray M-shell spectra of W ions is, in general, a very complicated problem even for low-density Tokamak plasmas because of the simultaneous contributions from numerous ionization stages. This work focuses on theoretical development of x-ray M-shell diagnostics of W ions in high temperature plasmas. The synthetic spectra calculated using a developed non LTE-kinetic model include ionization stages from Se- to Cr-like W ions and cover the broad spectral range from 3.5 to 7.5 A. All needed atomic data were calculated using the MCHF code developed by Cowan and the fully relativistic many-body perturbation theory code (RMBPT). The modeling of M-shell W spectra from 5 to 6 A was benchmarked with LLNL electron beam ion trap (EBIT) experimental data. In particular, modeling of eleven experimental EBIT spectra produced at different energies of electron beams leads to identification of 63 x-ray spectral features for the first time recorded in such details in the laboratory. Also the ionization balance of W ions was studied in detail, which is extremely important for validation of the model and for the knowledge of the distribution of W ions at certain plasma parameters. Upon analyzing the W spectra, it was noticed that Ni-like W transition lines were dominant in most of EBIT spectra. In order to further study the Ni-like W ions, RMBPT calculations were performed. This method included all second-order correlation corrections and corrections from negative energy states. Reduced matrix elements, oscillator strengths, and transition rates were calculated for electric-dipole (E1) and electric-quadrupole (E2) transitions and magnetic-dipole (M1) and magnetic-quadrupole (M2) transitions in Ni-like ions with nuclear charges ranging from Z = 30 to 100. The resulting transition energies and transition rates were compared with experimental values and with results from other recent calculations. The most significant results were the presented calculations for Ni-like and Cu-like ions as a benchmark for comparison with experiment and theory. In addition, the application of generated atomic data to modeling and interpreting of x-ray M-shell spectra of heavy ions.