Plasma and Warm Dense Matter

The construction of a short-pulse, tunable x-ray laser source will be a watershed for plasma-based and warm dense matter research. The area of warm dense matter refers to that part of the density-temperature phase space where the standard theories of condensed matter physics and/or plasma statistical physics are invalid. Warm dense matter defines a region between solids and plasmas, a regime that is found in planetary interiors, cool dense stars, and in every plasma device where one starts from a solid, e.g., laser-solid-matter-produced plasma, as well as all inertial fusion schemes. Experiments in the warm dense matter regime represent the most straightforward application of the Linac Coherent Light Source (LCLS), as it uses the beam to directly serve as the heating mechanism in a manner that is elegant yet unachievable with other sources such as high-power infrared and visible light lasers. The LCLS beam will also be used to measure local plasma conditions, by means of Thomson scattering. The LCLS x-ray beam is uniquely suited to probing the dense plasmas that it can create, since it can penetrate very dense plasmas that are opaque to infrared, visible or UV light. As plasma becomes denser, the LCLS will reach regimes where plasma theory has never been tested. The entire field of high-Z plasma kinetics from laser-produced plasma will then be available to study with the tunable source. As an example, one can study the underlying mechanisms that are currently used to produce soft x-ray lasers. Probing the kinetics of ion stages to test the gain of a potential laser scheme represents one of the most exacting tests of our ability to understand the kinetics of ions embedded in plasmas.

Adapted from : LCLS: The First Experiments - Plasma and Warm Dense Matter (pdf)
R.W. Lee, R.C. Cauble and O.L. Landen, Lawerence Livermore National Laboratory, Livermore, CA
J.S. Wark, Oxford University, Oxford, UK
A. Ng, University of British Columbia, British Columbia, Canada
S.J. Rose, Rutherford Appleton Laboratory, Chilton, Oxon, UK
C. Lewis and D. Riley, Queen's University Belfast, Belfast, Northern Ireland
J.-C. Gauthier and P. Audebert, Laboratoire pour l'Utilisation des Lasers, Paris, France