Atomic structure and radiative data calculations for heavy elements of interest in fusion plasma research. Theoretical challenges and recent advances

In the present contribution, we discuss some recent advances concerning the determination of radiative parameters (transition probabilities, oscillator strengths, radiative lifetimes) in lowly ionized heavy atoms (Z ≥ 37). Some emphasis is put on the procedures followed to obtain the new results but also on the difficulties associated with their experimental and theoretical determination. Among the heavy elements considered, tungsten deserves a particular attention. Indeed, it is well known that spectroscopic parameters of W ions are essential for exploring the physical conditions in Tokamak plasmas such as ITER in which tungsten is currently considered to be a primary candidate for the plasma-facing material in the divertor region. In fusion reactors, tungsten will be sputtered from the wall as a neutral element and the determination of the W influx rate to the core plasma will depend on a calculation of transport from the wall surface through the srape-off layer. Consequently, the identification of emission lines and the knowledge of radiative parameters from all ionization stages of tungsten will greatly aid modelling of the plasma edge and scrape-off layer transport and facilitate the analysis of net tungsten influx rates. In this context, the new sets of atomic data obtained in our work for the first ionization stages of tungsten will be extremely useful for future fusion plasma analyses. (author)