  We present evidence for strong radiative cooling in a pulsed-power-driven
magnetic reconnection experiment. Two aluminum exploding wire arrays, driven by
a 20 MA peak current, 300 ns rise time pulse from the Z machine (Sandia
National Laboratories), generate strongly-driven plasma flows ($M_A \approx 7$)
with anti-parallel magnetic fields, which form a reconnection layer ($S_L
\approx 120$) at the mid-plane. The net cooling rate far exceeds the Alfv\'enic
transit rate ($\tau_{\text{cool}}^{-1}/\tau_{\text{A}}^{-1} > 100$), leading to
strong cooling of the reconnection layer. We determine the advected magnetic
field and flow velocity using inductive probes positioned in the inflow to the
layer, and inflow ion density and temperature from analysis of visible emission
spectroscopy. A sharp decrease in X-ray emission from the reconnection layer,
measured using filtered diodes and time-gated X-ray imaging, provides evidence
for strong cooling of the reconnection layer after its initial formation. X-ray
images also show localized hotspots, regions of strong X-ray emission, with
velocities comparable to the expected outflow velocity from the reconnection
layer. These hotspots are consistent with plasmoids observed in 3D radiative
resistive magnetohydrodynamic simulations of the experiment. X-ray spectroscopy
further indicates that the hotspots have a temperature (170 eV) much higher
than the bulk layer ($\leq$ 75 eV) and inflow temperatures (about 2 eV), and
that these hotspots generate the majority of the high-energy (> 1 keV)
emission.
