  With construction of ITER progressing and existing tokamaks carrying out
ITER-relevant experiments, accurate fundamental and derived atomic data for
numerous ionization stages of tungsten (W) is required to assess the potential
effect of this species upon fusion plasmas. The results of fully relativistic,
partially radiation damped, Dirac $R$-matrix electron-impact excitation
calculations for the W$^{44+}$ ion are presented. These calculations use a
configuration interaction and close-coupling expansion that opens-up the
3d-subshell, which does not appear to have been considered before in a
collision calculation. As a result, it is possible to investigate the arrays,
[3d$^{10}$4s$^2-$3d$^9$4s$^2$4f] and [3d$^{10}$4s$^2-$3d$^9$4s4p4d], which are
predicted to contain transitions of diagnostic importance for the soft x-ray
region. Our $R$-matrix collision data are compared with previous $R$-matrix
results by Ballance and Griffin as well as our own relativistically corrected,
Breit-Pauli distorted wave and plane-wave Born calculations. All relevant data
are applied to the collisional-radiative modelling of atomic populations, for
further comparison. This reveals the paramount nature of the 3d-subshell
transitions from the perspectives of radiated power loss and detailed
spectroscopy.
