  A fully relativistic description of the electron energy loss and the induced
radiation emission in arbitrary arrays of non-overlapping metallic cylinders is
presented in terms of the multiple scattering method on the basis of vector
cylindrical waves. Numerical analysis is given for dilute and dense arrays of
Aluminum cylinders with a nanoscale diameter. The results of the electron
energy loss spectrum are well correlated with the dispersion relation of
coupled surface plasmon polaritons, and can be interpreted with an effective
medium approximation when the electron runs inside the arrays. In addition, the
cavity modes localized in the grooves between the cylinders can affect strongly
the electron energy loss spectrum.
