Partial and total dielectronic recombination rate coefficients for W 55+ to W 38+

Dielectronic recombination (DR) is the dominant mode of recombination in magnetically confined fusion plasmas for intermediate to low-charged ions of W. Complete, final-state resolved partial isonuclear W DR rate coefficient data is required for detailed collisional-radiative modelling for such plasmas in preparation for the upcoming fusion experiment ITER. To realise this requirement, we continue The Tungsten Project by presenting our calculations for tungsten ions ${{\rm{W}}}^{55+}$ to ${{\rm{W}}}^{38+}$. As per our prior calculations for ${{\rm{W}}}^{73+}$ to ${{\rm{W}}}^{56+}$, we use the collision package autostructure to calculate partial and total DR rate coefficients for all relevant core-excitations in intermediate coupling (IC) and configuration average (CA) using κ-averaged relativistic wavefunctions. Radiative recombination rate coefficients are also calculated for the purpose of evaluating ionisation fractions. Comparison of our DR rate coefficients for ${{\rm{W}}}^{46+}$ with other authors yields agreement to within 7%–19% at peak abundance verifying the reliability of our method. Comparison of partial DR rate coefficients calculated in IC and CA yield differences of a factor $\sim 2$ at peak abundance temperature, highlighting the importance of relativistic configuration mixing. Large differences are observed between ionisation fractions calculated using our recombination rate coefficient data and that of Pütterich et al (2008 Plasma Phys. Control. Fusion 50 085016). These differences are attributed to deficiencies in the average-atom method used by the former to calculate their data.