High-Pressure Astro- and Planetary Physics
In the last years more and more exoplanets in a “habitable” distance to stars were discovered. Similar to our earth live would be possible due to the existence of liquid water and air to breath.
A lot of these planets are much bigger than earth and as classified as super-earths. Most probably the surface is somehow influence by the inner core. For better understanding it is necessary to explore the composition and structure of the inner core, the outer mantle and the surface. But even the inner of the earth cannot be explored directly. The deepest existing drilled hole is only 12 km and so still 6000 km away from the center of earth.
Therefore the condition are simulated in laboratory experiments. By the use of diamond anvil cell, the sample under investigation is in between two diamond and pressed together mechanically. By this pressures up to 3.7 Mega-bar (1 bar is atmospheric pressure) and 4500°C by infrared heating lasers are reached. X-Rays allow to investigate and identify the materials as well as to determinate fundamental physical properties.
Double-stage diamond anvil cell
Even by this technique it wasn’t possible to reach the pressure and temperature region of super earths. A further development is the so called double-stage diamond anvil cell, which reached pressures up to 10 Mbars. But at higher temperature the inner second stack of diamond anvil fails on a short time scale, in which no data collection can be performed. This problem can be overcome by the use of the European XFEL with its extreme short and very intense X-Rays flashes.
Dynamic diamond anvil cell
Another exiting topic is the investigation of neptun-like planets, which mainly consist of water (H2O and ice), Ammonia (NH3), Methane (CH3) and Hydrogen (H2), but got a solid rocklike core. Bu this component high pressure cannot be reached compared to solid samples, because water is under these conditions very reactive and destroy the diamond anvils. In so-called dynamic diamond anvil cell the pressure is increased so rapidly to 3 Mbars that water cannot diffuse into the diamonds and weaken them. But the measurement itself must be performed in an extremely small time window, was can be only fulfilled by the European XFEL
Further details can be found here.