  The effects of reflecting boundaries on vacuum electric field fluctuations
are treated. The presence of the boundaries can enhance these fluctuations and
possibly lead to observable effects. The electric field fluctuations lead to
voltage fluctuations along the worldline of a charged particle moving
perpendicularly to a pair of reflecting plates, These voltage fluctuations in
turn lead to fluctuations in the kinetic energy of the particle, which may
enhance the probability of quantum barrier penetration by the particle. A
recent experiment by Moddel {\it et al} is discussed as a possible example of
this enhanced barrier penetration probability.
