  The problem of spontaneous radiation of the electron bunch grazing into a
charged metallic surface with randomly distributed needle shaped asperities is
considered. Distances between two neighboring asperities have been described by
gamma distribution. Being repealed by highly charged asperities the electrons
of the bunch move along non-regular periodical trajectories in the planes
parallel to the metallic surface. The spatial periods of the trajectories are
random quantities which are described by the same gamma distribution. The
radiation characteristics of the bunch have been obtained. It is shown that the
angular distributions of the number of photons radiated from the bunch and from
a single electron are the same but the frequency distribution of the bunch is
being drastically changed at the hard frequency region. It is proposed to
develop a new non-destructive method for investigation of the metal surface
roughness. The frequency distribution of the number of photons radiated under
the zero angle has been obtained. That allows to find the gain expression of
the stimulated radiation.
