  Non-central heavy ion collisions create an out-of-plane-extended participant
zone that expands toward a more round state as the system evolves. The recent
RHIC Beam Energy Scan at sqrt{s_{NN}} of 7.7, 11.5, and 39 GeV provide an
opportunity to explore the energy dependence of the freeze out eccentricity.
The new low energy data from STAR complements high statistics data sets at
sqrt{s_{NN}} of 62.4 and 200 GeV. Hanbury-Brown-Twiss (HBT) interferometry
allows to determine the size of pion emitting source regions. The dependence of
the HBT radius parameters on azimuthal angle relative to the reaction plane
have been extracted. These dependencies can be related to the freeze out
eccentricity. The new results from STAR are consistent with a monotonically
decreasing freeze out eccentricity and constrain any minimum, suggested by
previously available data, to lie in the range between 11.5 and 39 GeV. Of
several models UrQMD appears to best predict the STAR and AGS data.
