The Extreme Light Infrastructure ERIC

Warm Dense Matter

Warm Dense Matter (WDM) is the study of matter under extreme conditions of pressure. It is a particular sub-field of high-energy density physics.

This field of research is relevant to an understanding of the following:

  • Inertial confinement fusion
  • Planetary cores
  • The fundamentals of the quantum nature of matter
  • The physics of shock waves in dense material
  • The non-equilibrium and phase-transition aspects of matter.

The main goal of WDM is to gain an understanding of the equation for determining the states and opacities of compressed matter. Of particular interest are conditions where there is very high-density matter (tens of grams per cubic-centimeter) but moderate and therefore warm temperatures (a few eV to a few tens of eVs). Simulating matter in these conditions is challenging, and effective simulation methods are still under development. The difficulties arise from the fact that matter under these conditions is a system of strongly interacting particles.

The complexity arises from the fact that in this state the potential energy between the interacting electrons and the nuclei is of a similar order to the kinetic energy of the electrons, as opposed to a plasma state where the kinetic energy of the electrons is much greater than the potential energy between the interacting electrons and the nuclei. Well-defined experiments can help to distinguish between conflicting theoretical models. The kilojoule laser, which is available in P3, L4n, will allow important research to be performed in WDM. Having the use of a local betatron as a diagnostic tool for exploiting the highly energetic electrons and the X-rays simultaneously will be a step forward in diagnosing the state of WDM. Even what occurs when hydrogen, the simplest atom, is exposed to extreme pressures is not yet fully understood. Although Wigner suggested in the 1930s that hydrogen has a phase transition to a metallic state, this has still not been fully confirmed.


  1. Y. Ping et al. Warm dense matter created by isochoric laser heating, HEDP 6, 246 (2010).
  2. S. H. Glenzer et al. X-ray Thomson Scattering in High Energy Density Plasmas, Rev. Mod. Phys. 81, 1625 (2009).
  3. F.Graziani, M.P. Desjarlais, R. Redmer, S.B. Trickey (Eds.) et al. Frontiers and Challenges in Warm Dense Matter, Springer Verlag, (2014).
  4. R.W. Lee et al. Warm Dense Matter: an overview, Report UCRL-TR-203844, Lawrence Livermore 2004.
Stefan Weber