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High-pressure research in the regime 10 - 100 Mbar

The project concerns the structure of highly compressed matter, in particular insulator-metal transitions, and applies to astrophysics, big planets, and inertial fusion. It goes beyond dynamical detonation methods limited to pressures of about 10 Mbar.

Very uniform shock waves at 5 - 10 Mbar pressure have been achieved in indirect drive experiments, using the LABYRINTH hohlraum developed at MPQ. They allowed observation of the optical signals occurring during shock break-out at the rear side of planar samples, both the self-emission and reflected light. The data obtained for aluminum and silicon samples are of unprecedented quality and time resolution (less than 10 ps). In semiconducting silicon, shock emission could be measured for a period of 200 ps prior to breakout, revealing a temperature of 300 K (room temperature) for the material in front of the shock. This means absolutely no preheat and represents a world record for laser driven shocks. In supplementary direct-drive and indirect-drive experiments, the principle Hugoniot of copper was determined up to pressures of 40 Mbar. The only data available so far in this regime were from underground nuclear explosions. The laser experiments are presently continued, and pressures up to 80 Mbar in gold have been achieved. These results give new insight into shock structure, material and transport properties of matter at pressures inaccessible so far in laboratory experiments. For future developments, a numerical study on low entropy compression of hydrogen has been performed. Refinements of the experiments will allow the metallic state of condensed hydrogen to be reached for the first time in the laboratory. Metallic hydrogen is of great interest for fundamental physics as well as astrophysics. The giant planets such as Jupiter are believed to consist of metallic hydrogen.

Reported by

Max-Planck Gesellschaft zur Förderung der Wissenschaften eV
Hans-Kopfermann-Str. 1
85740 Garching
Germany
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