  We investigate the influence of the vacuum fluctuations of a background
electric field over a charged test particle in the presence of a perfectly
reflecting flat wall. A switching function connecting different stages of the
system is implemented in such a way that its functional dependence is
determined by the ratio between the measuring time and the switching duration.
The dispersions of the velocity components of the particle are found to be
smooth functions of time, and have maximum magnitudes for a measuring time
corresponding to about one round trip of a light signal between the particle
and the wall. Typical divergences reported in the literature and linked with an
oversimplification in modeling this system are naturally regularized in our
approach. Estimates suggest that this sort of manifestation of quantum vacuum
fluctuations over the motion of the particle could be tested in laboratories.
