In this paper, PHYSICS OF PLASMAS 20, 070501 (2013), "Progress towards ignition on the National Ignition Facility", and this paper, PHYSICS OF PLASMAS 20, 056318 (2013), "Detailed implosion modeling of deuterium-tritium layered experiments on the National Ignition Facility", they report densities near 1000 g/cm^3. These are number densities between 1E26 and 1E27 cm^-3. I'm not sure if it is the highest achieved, but it might be. Densities in hydrogen bombs might be higher, do they count?
Does quark-gluon plasma count? Densities there approach hadronic. I believe, something like tens of MeV/fm³ has been achieved, and that's over 1016kg/m³.
Does quark-gluon plasma count? Densities there approach hadronic. I believe, something like tens of MeV/fm³ has been achieved, and that's over 1016kg/m³.