  The phase diagram of strongly interacting matter can be explored by analyzing
data of heavy-ion collisions at different center of mass collision energies.
For investigating the space-time structure of the hadron emission source, HBT
correlation measurements are among the best tools. In this paper we present the
latest results from the RHIC PHENIX experiment on such measurements in
$\sqrt{s_{\rm NN}}=$ 39 GeV and 62 GeV Au+Au collisions.
