[en] Large amplitude oscillations in the expansion of a cylindrical electron–positron plasma layer are investigated. The cold fluid equations and the Poisson's equation are solved non-perturbatively in order to allow for very large amplitude oscillations. It is found that oscillations are self-excited during the expansion and can grow to very large amplitudes as the expansion slows down with time and the plasma density decreases. The kinetic energy of the expansion is thereby converted into that of the oscillations. (paper)