  We developed an experimental platform for studying magnetic reconnection in
an external magnetic field with simultaneous measurements of plasma imaging,
flow velocity, and magnetic-field variation. Here, we investigate the
stagnation and acceleration in counter-streaming plasmas generated by
high-power laser beams. A plasma flow perpendicular to the initial flow
directions is measured with laser Thomson scattering. The flow is,
interestingly, accelerated toward the high-density region, which is opposite to
the direction of the acceleration by pressure gradients. This acceleration is
possibly interpreted by the interaction of two magnetic field loops initially
generated by Biermann battery effect, resulting in a magnetic reconnection
forming a single field loop and additional acceleration by a magnetic tension
force.
