  To reveal the effect of secondary electron emission on the charging
properties of a surface covered by micron-sized insulating dust particles and
the migration characteristics of these particles, for the first time, we used a
laser Doppler method to measure the diameters and velocities of micron-sized
anorthite particles under electron beam irradiation with an incident energy of
350 eV. Here, anorthite particles are being treated as a proxy for lunar
regolith. We experimentally confirm that the vertical transport of anorthite
particles is always dominant, although the horizontal transport occurs. In our
experiments, some anorthite particles were observed to have large vertical
velocities up to 9.74 m~s$^{-1}$ at the measurement point. The upper boundary
of the vertical velocities $V_{\rm{z}}$ of these high-speed anorthite particles
are well constrained by its diameter $D$, that is, $V_{\rm{z}}^2$ linearly
depends on $D^{-2}$. These velocity-diameter data provide strong constraints on
the dust charging and transportation mechanisms. The shared charge model could
not explain the observed velocity-diameter data. Both the isolated charge model
and patched charge model appear to require a large dust charging potential of
$-$350 to $-$78 V to reproduce the observed data. The micro-structures of the
dusty surface may play an important role in producing this charging potential
and in understanding the pulse migration phenomenon observed in our experiment.
The presented results and analysis in this paper are helpful for understanding
the dust charging and electrostatic transport mechanisms in airless celestial
bodies such as the Moon and asteroids in various plasma conditions.
