  We study electron pumps in the absence of interference effects paying
attention to the spin degree of freedom. Electron-electron exchange
interactions combined with a variation of external parameters, such as magnetic
field and gate potentials, affect the compressibility-spin-tensor whose
components determine the non-coherent parts of the charge and spin pumped
currents. An appropriate choice of the trajectory in the parameter space
generates an arbitrary ratio of spin to charge pumped currents. After showing
that the addition of dephasing leads to a full quantum coherent system
diminishes the interference contribution, but leaves the non-coherent
(classical) contribution intact, we apply the theory of the classical term for
several examples. We show that when exchange interactions are included one can
construct a source of pure spin current, with a constant magnetic field and a
periodic variation of gate potentials only. We discuss the possibility to
observe it experimentally in GaAs heterostructures.
