Recombination of Neon-Like and Adjacent Ions in Plasmas

The neon-like and sodium-like ions of medium Z elements, chromium and nickel are identified as abundant or strongly radiating species in the transport dominated region of the JET plasma. Also in plasma produced by laser ablation of multilayer targets stimulated emission has been identified from neon-like selenium. For both observations accurate theoretical electronic recombination rate coefficients contribute to spectral interpretation, to unambiguous separation of diffusive and atomic processes in impurity transport and to derivation of metal concentrations from VUV lines.

A new calculation is presented of recombination of fluorine-like, neon-like and sodium-like ions of chromium, iron, nickel and selenium. Radiative recombination and dielectronic recombination rates to angularly resolved energy levels of both low and high principal quantum number are determined using combination of multiconfiguration perturbation theory and Correspondence Principle techniques. The modifying effects of collisional redistribution in finite density plasma are evaluated and effective net recombination coefficients and effective recombination coefficients to excited levels leading to radiative emission obtained.

The theoretical radial distribution of nickel ions across the JET torus is obtained by combining the recombination results with a transport model.