I'm more used to seeing colliders rated by the kinetic energy of the colliding particles, but just recently I've been seeing estimates of the ENERGY DENSITY to be expected right at the point of collision. This raises doubts about exactly what is meant. what is the nominal area of collision? what nominal volume is the kinetic energy spread out in? but there should be some way to give a plausible rough figure for the energy density. experimental physicists are good at that kind of guesstimation. So what do our experts in this department say? Would you say it is closer to 10 GeV per cubic fermi or to, say, 1016 GeV per cubic fermi?