Partial and total dielectronic recombination rate coefficients for W73+ to W56+

Preval, S. P. and Badnell, N. R. and O'Mullane, M. G. (2016) Partial and total dielectronic recombination rate coefficients for W73+ to W56+. Physical Review A, 93 (4). ISSN 1094-1622

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    Dielectronic recombination (DR) is a key atomic process which affects the spectroscopic diagnostic modelling of tungsten, most of whose ionization stages will be found somewhere in the ITER fusion reactor: in the edge, divertor, or core plasma. Accurate DR data is sparse while complete DR coverage is unsophisticated (e.g. average-atom or Burgess General Formula) as illustrated by the large uncertainties which currently exist in the tungsten ionization balance. To this end, we present a series of partial final-state-resolved and total DR rate coefficients for W$^{73+}$ to W$^{56+}$ Tungsten ions. This is part of a wider effort within {\it The Tungsten Project} to calculate accurate dielectronic recombination rate coefficients for the tungsten isonuclear sequence for use in collisional-radiative modelling of finite-density tokamak plasmas. The recombination rate coefficients have been calculated with {\sc autostructure} using kappa-averaged relativistic wavefunctions in level resolution (intermediate coupling) and configuration resolution (configuration average). The results are available from OPEN-ADAS according to the {\it adf09} and {\it adf48} standard formats. Comparison with previous calculations of total DR rate coefficients for W$^{63+}$ and W$^{56+}$ yield agreement to within 20\% and 10\%, respectively, at peak temperature. It is also seen that the J\"{u}ttner correction to the Maxwell distribution has a significant effect on the ionization balance of tungsten at the highest charge states, changing both the peak abundance temperatures and the ionization fractions of several ions.