  We demonstrate magnetic confinement of an ultracold neutral plasma (UCNP)
created at the null of a biconic cusp, or quadrupole magnetic field. Initially,
the UCNP expands due to electron thermal pressure. As the plasma encounters
stronger fields, expansion slows and the density distribution molds to the
field. UCNP electrons are strongly magnetized over most of the plasma, while
ion magnetization is only significant at the boundaries. Observations suggest
that electrons and ions are predominantly trapped by magnetic mirroring and
ambipolar electric fields respectively. Confinement times approach 0.5 ms,
while unmagnetized plasmas dissipate on a timescale of a few tens of
microseconds.
