  We study the stability of cylindrical Taylor-Couette flow in the presence of
combined axial and azimuthal magnetic fields, and show that adding an azimuthal
field profoundly alters the previous results for purely axial fields. For small
magnetic Prandtl numbers Pm, the critical Reynolds number Re_c for the onset of
the magneto-rotational instability becomes independent of Pm, whereas for
purely axial fields it scales as Pm^{-1}. For typical liquid metals, Re_c is
then reduced by several orders of magnitude, enough that this new design should
succeed in realizing this instability in the laboratory.
