  Magnetized laser-produced plasmas are central to many novel laboratory
astrophysics and inertial confinement fusion studies, as well as in industrial
applications. Here we provide the first complete description of the
three-dimensional dynamics of a laser-driven plasma plume expanding in a 20 T
transverse magnetic field. The plasma is collimated by the magnetic field into
a slender, rapidly elongating slab, whose plasma-vacuum interface is unstable
to the growth of the "classical", fluid-like magnetized Rayleigh-Taylor
instability.
