  We present the first detailed study of the effect of a strong magnetic field
on single-electron pumping in a device utilising a finger-gate split-gate
configuration. In the quantum Hall regime, we demonstrate electron pumping from
Landau levels in the leads, where the measurements exhibit pronounced
oscillations in the lengths of the pumping plateaus with the magnetic field,
reminiscent of Shubnikov-de Haas oscillations. This similarity indicates that
the pumping process is dependent on the density of states of the 2D electron
gas over a narrow energy window. Based on these observations, we develop a new
theoretical description of the operation of single-electron pumps which for the
first time allows for the determination of the physical parameters of the
experiment; such as the capture energy of the electrons, the broadening of the
quantised Landau levels in the leads, and the quantum lifetime of the
electrons.
