  We show that in perfectly quasi-isodynamic magnetic fields, which are
generally non-quasisymmetric and which can approximate fields of experimental
interest, neoclassical calculations can be carried out analytically more
completely than in a general stellarator. Here, we define a quasi-isodynamic
field to be one in which the longitudinal adiabatic invariant is a flux
function and in which the constant-B contours close poloidally. We first derive
several geometric relations among the magnetic field components and the field
strength. Using these relations, the forms of the flow and current are obtained
for arbitrary collisionality. The flow, radial electric field, and bootstrap
current are also determined explicitly for the long-mean-free-path regime.
