  We report new experimental results on the generation and dynamics of multiple
double layers in front of a positively biased electrode immersed in a
DP-machine plasma. Depending on the geometry or the dimensions of the
electrode, this complex space charge configuration can appear in two different
modes. If the electrode is small with respect to the plasma size, the
phenomenon appears as a set of concentric luminous shells with different
intensities. If the electrode has large dimensions, or a one-dimensional
geometry, the spherical double layers appear adjacent to each other, as equally
separated luminous plasma blobs. Our experimental investigations prove that in
both of cases we deal with almost the same phenomenon. The same elementary
processes, namely electron-neutral impact excitations and ionizations, play the
key role in the generation and dynamics of each structure. This is emphasized
in the static current-voltage characteristic of the electrode, which shows
similar jumps of the current, associated with hysteresis.
