Recombination of open-f-shell tungsten ions

Krantz, C and Badnell, N R and Müller, A and Schippers, S and Wolf, A (2017) Recombination of open-f-shell tungsten ions. Journal of Physics B: Atomic, Molecular and Optical Physics, 50 (5). 052001. ISSN 0953-4075

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    We review experimental and theoretical efforts aimed at a detailed understanding of the recombination of electrons with highly charged tungsten ions characterised by an open 4f sub-shell. Highly charged tungsten occurs as a plasma contaminant in ITER-like tokamak experiments, where it acts as an unwanted cooling agent. Modelling of the charge state populations in a plasma requires reliable thermal rate coefficients for charge-changing electron collisions. The electron recombination of medium-charged tungsten species with open 4f sub-shells is especially challenging to compute reliably. Storage-ring experiments have been conducted that yielded recombination rate coefficients at high energy resolution and well-understood systematics. Significant deviations compared to simplified, but prevalent, computational models have been found. A new class of ab initio numerical calculations has been developed that provides reliable predictions of the total plasma recombination rate coefficients for these ions.