  At the high $n_{e}$ proposed for high-field fusion reactors, it is uncertain
whether ionization, as opposed to plasma transport, will be most influential in
determining $n_{e}$ at the pedestal and separatrix. A database of Alcator C-Mod
discharges is analyzed to evaluate the impact of source modification via
cryopumping. The database contains similarly-shaped H-modes at fixed $I_{p} =$
0.8 MA and $B_{t} =$ 5.4 T, spanning a large range in $P_\mathrm{net}$ and
ionization. Measurements from an edge Thomson Scattering system are combined
with those from a midplane-viewing Ly$_{\alpha}$ camera to evaluate changes to
$n_{e}$ and $T_{e}$ in response to changes to ionization rates,
$S_\mathrm{ion}$. $n_{e}^\mathrm{sep}$ and $T_{e}^\mathrm{ped}$ are found to be
most sensitive to changes to $S_\mathrm{ion}^\mathrm{sep}$, as opposed to
$n_{e}^\mathrm{ped}$ and $T_{e}^\mathrm{sep}$. Dimensionless quantities, namely
$\alpha_\mathrm{MHD}$ and $\nu^{*}$, are found to regulate attainable pedestal
values. Select discharges at different values of $P_\mathrm{net}$ and in
different pumping configurations are analyzed further using SOLPS-ITER. It is
determined that changes to plasma transport coefficients are required to
self-consistently model both plasma and neutral edge dynamics. Pumping is found
to modify the poloidal distribution of atomic neutral density, $n_{0}$, along
the separatrix, increasing $n_{0}$ at the active X-point. Opaqueness to
neutrals from high $n_{e}$ in the divertor is found to play a role in mediating
neutral penetration lengths and hence, the poloidal distribution of neutrals
along the separatrix. Pumped discharges thus require a larger particle
diffusion coefficient than that inferred purely from 1D experimental profiles
at the outer midplane.
