  Divertor plasma detachment is likely needed for the function of magnetically
confined nuclear fusion. It greatly reduces the particle and heat flux incident
on a target, and thus reduces the sputtering and heat loading on the target. It
is therefore advantageous to have accurate simulations of plasma behaviour in
the divertor to design future Tokamak divertors. A common simulation package
used for this purpose is SOLPS-ITER, which has previously been observed to be
underestimating the contribution of molecular effects to plasma detachment. To
correct this, its reaction rate for molecular charge exchange was altered. This
alteration resulted in a significant increase in the density of $D_2^+$ ions
within the divertor. The particle balance and $D\alpha$ emission data was then
computed from the simulation outputs. These were compared to experimental data
and a set of post-processing routines for the original simulations that
predicts the effect of a corrected charge exchange rate. In comparison to the
post-processing predictions: the increase in Molecular activated Recombination
and the depth of the target flux rollover was less than predicted. This is due
to the post-processing not being self consistent and it does not account for
how the alterations in reaction rate would affect the background plasma.
Compared to the experimental data: the correction showed a significant
improvement in the agreement of general trends, such as the increased MAR
reaction rate and the rollover of target flux. However, there were still
significant disagreements in the magnitudes of various reaction rates,
suggesting further improvements to SOLPS-ITER are still needed.
