Ramp compression of diamond to five terapascals

New laboratory techniques for applying enormous pressures allow diamond to be compressed to 50 million atmospheres, providing insight into the interiors of planets and theoretical implications. Journey to the centre of Jupiter Knowledge of the behaviour of matter under conditions of extreme pressure is essential for describing the interior state of giant planets such as Jupiter and many extrasolar planets. The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory in California is pursuing laboratory astrophysics with shock-free dynamic (ramp) compression up to 50 million atmospheres pressure. Working with the NIF at temperatures below those used in fusion experiments, Raymond Smith and colleagues have achieved a new experimental benchmark in the replication of conditions deep within giant planets. They describe properties of carbon compressed to an unprecedented density of 12 g cm −3 . These results also provide some of the most direct experimental tests of quantum-statistical theories developed in the early days of quantum mechanics. The recent discovery of more than a thousand planets outside our Solar System 1 , 2 , together with the significant push to achieve inertially confined fusion in the laboratory 3 , has prompted a renewed interest in how dense matter behaves at millions to billions of atmospheres of pressure. The theoretical description of such electron-degenerate matter has matured since the early quantum statistical model of Thomas and Fermi 4 , 5 , 6 , 7 , 8 , 9 , 10 , and now suggests that new complexities can emerge at pressures where core electrons (not only valence electrons) influence the structure and bonding of matter 11 . Recent developments in shock-free dynamic (ramp) compression now allow laboratory access to this dense matter regime. Here we describe ramp-compression measurements for diamond, achieving 3.7-fold compression at a peak pressure of 5 terapascals (equivalent to 50 million atmospheres). These equation-of-state data can now be compared to first-principles density functional calculations 12 and theories long used to describe matter present in the interiors of giant planets, in stars, and in inertial-confinement fusion experiments. Our data also provide new constraints on mass–radius relationships for carbon-rich planets.