  Phase diagrams of the micromaser system are mapped out in terms of the
physical parameters at hand like the atom cavity transit time, the atom-photon
frequency detuning, the number of thermal photons and the probability for a
pump atom to be in its excited state. Critical fluctuations are studied in
terms of correlation measurements on atoms having passed through the micromaser
or on the microcavity photons themselves. At sufficiently large values of the
detuning we find a ``twinkling'' mode of the micromaser system. Detailed
properties of the trapping states are also presented.
