  The RHIC Beam Energy Scan focuses on mapping the QCD phase diagram and
pinpointing the location of a possible critical end point. Bose-Einstein
correlations and event-by-event fluctuations of conserved quantities, measured
as a function of centrality and collision energy, are promising tools in these
studies. Recent lattice QCD and statistical thermal model calculations predict
that higher-order cumulants of the fluctuations are sensitive indicators of the
phase transition. Products of these cumulants can be used to extract the
freeze-out parameters (1) and to locate the critical point (2). Two-pion
interferometry measurements are predicted to be sensitive to potential
softening of the equation of state and prolonged emission duration close to the
critical point (3). We present recent PHENIX results on fluctuations of
net-charge using high-order cumulants and their products in Au+Au collisions at
\sqsn = 7.7 - 200 GeV, and measurement of two-pion correlation functions and
emission-source radii in Cu+Cu and Au+Au collisions at several beam energies.
The extracted source radii are compared to previous measurements at RHIC and
LHC in order to study energy dependence of the specific quantities sensitive to
expansion velocity and emission duration. Implications for the search of a
critical point and baryon chemical potentials at various collision energies are
discussed.
