  Transverse energy distributions at midrapidity have been measured by the
PHENIX experiment at the BNL Relativistic Heavy Ion Collider (RHIC) for Au+Au,
U+U, Cu+Au, Cu+Cu, He+Au, d+Au, and p+p collisions over a wide energy range
from $\sqrt{s_{NN}}$ = 7.7 GeV to $\sqrt{s_{NN}}$ = 200 GeV as a function of
centrality. For central Au+Au collisions, it is observed that the midrapidity
Bjorken energy density demonstrates a power law behavior from $\sqrt{s_{NN}}$ =
7.7 GeV to $\sqrt{s_{NN}}$ = 2.76 TeV. At a given collision energy, the data
presented as a function of $N_{part}$ are independent of the size of the
collision system. For Au+Au, Cu+Au, and Cu+Cu collisions, the
centrality-dependent data are better described by scaling with the number of
constituent quark participants than scaling with the number of nucleon
participants.
