Exploring
High Energy Density Matter at Pressures Ranging
from a few Kilabar to
Several Gigabar
Gilbert W. Collins1, Raymond Smith1, Damien Hicks1, Jave Kane1, Jon Eggert1, Peter Celliers1, Marina Bastea1, Yogi Gupta2, James R. Asay2, Paul Loubeyre4, Stephanie Brygoo4, Tom Boehly5, David Meyerhoffer5, Raymond Jeanloz6, Ryan McWilliams6, David Bradley1, and Dan Kalantar1
1Lawrence Livermore
National Laboratory
2Washington State University
3Los
Alamos National Laboratory
4CEA, France
5Laboratory
for Laser Energetics
6University of California, Berkeley
A new generation of materials experiments at high pressures and densities is now possible due to a variety of high energy density (HED) facilities and new compression techniques. Shock and shockless compression experiments can now produce material states from kilobar to gigabar pressures with timescales ranging from picoseconds to microseconds. While the production of truly novel material states is well underway, the careful inspection of these states is still maturing. The marriage of these new HED capabilities with advanced light sources will enable the detailed characterization of these new states. Described first are several recent HED experiments to highlight the extreme material states produced with HED facilities. A few ways that advanced light sources can revolutionize the characterization of such HED matter are suggested.
Laser shock compression experiments have measured the insulator-conductor transition and the high-pressure equation of state of several low Z materials (C, H2O, SiO2, H2, D2, He) from Kbar to 10’s of Mbar. These experiments enable us to recreate the core states of giant planets and low mass stars in the laboratory. For example, recent experiments show shock compressed He becomes an electronic conductor at pressures significantly lower than expected albeit at higher shock pressures and temperatures than hydrogen. Another interesting example is diamond, whose compressibility has recently been measured to over 30 Mbar. The diamond melt curve was recently discovered to have a negative dP/dT along the Hugonoit. Moreover, shocked diamond transitions from an insulator to an electronic conductor upon crossing the melt. In addition to shock experiments, shockless compression experiments are being used to explore “low temperature and high pressure” multi-phase diagrams and phase transition kinetics with loading rates ranging from 106 to 108 s-1. This technique has been used to determine the quasi-isentrope of Al to near 1 Mbar and solid-solid phase boundaries and transition kinetics for Fe, Bi, and Ce.
X-ray diagnostics are often used to explore these HED states, ie the compressibility, lattice structure, temperature, and spatial structure. Often what limits the accuracy of these x-ray measurements is the brightness and spectral quality of the source. We show a couple of examples where an improved x-ray source could dramatically change the accuracy of such measurements.
