  A microscopic version of the Continuum Discretized Coupled Channel (CDCC)
method is used to investigate $^{6}$He scattering on $^{27}$Al, $^{58}$Ni,
$^{120}$Sn, and $^{208}$Pb at energies around the Coulomb barrier. The $^{6}$He
nucleus is described by an antisymmetric 6-nucleon wave function, defined in
the Resonating Group Method. The $^{6}$He continuum is simulated by
square-integrable positive-energy states. The model is based only on well known
nucleon-target potentials, and is therefore does not depend on any adjustable
parameter. I show that experimental elastic cross sections are fairly well
reproduced. The calculation suggests that breakup effects increase for high
target masses. For a light system such as $^{6}$He+$^{27}$Al, breakup effects
are small, and a single-channel approximation provides fair results. This
property is explained by a very simple model, based on the sharp-cut-off
approximation for the scattering matrix. I also investigate the $^{6}$He-target
optical potentials, which confirm that breakup channels are more and more
important when the mass increases. At large distances, polarization effects
increase the Coulomb barrier, and provide a long-tail absorption component in
the imaginary part of the nucleus-nucleus interaction.
