Observations of continuum depression in warm dense matter with x-ray Thomson scattering

L B Fletcher; A L Kritcher; A Pak; T Ma; T Döppner; C Fortmann; L Divol; O S Jones; O L Landen; H A Scott; J Vorberger; D A Chapman; D O Gericke; B A Mattern; G T Seidler; G Gregori; R W Falcone; S H Glenzer

doi:10.1103/PhysRevLett.112.145004

Observations of continuum depression in warm dense matter with x-ray Thomson scattering

Phys Rev Lett. 2014 Apr 11;112(14):145004. doi: 10.1103/PhysRevLett.112.145004. Epub 2014 Apr 10.

Authors

L B Fletcher¹, A L Kritcher², A Pak², T Ma², T Döppner², C Fortmann², L Divol², O S Jones², O L Landen², H A Scott², J Vorberger³, D A Chapman⁴, D O Gericke⁵, B A Mattern⁶, G T Seidler⁶, G Gregori⁷, R W Falcone⁸, S H Glenzer⁹

Affiliations

¹ SLAC National Accelerator Laboratory, 2575 Sand Hill Road, MS 72 Menlo Park, California 94025, USA and Physics Department, University of California, Berkeley, California 94720, USA.
² L-399, Lawrence Livermore National Laboratory, University of California, P.O. Box 808, Livermore, California 94551, USA.
³ Max-Planck-Institut für die Physik Komplexer Systeme, 01187 Dresden, Germany.
⁴ Plasma Physics Group, AWE plc, Aldermaston, Reading RG7 4PR, United Kingdom and Centre for Fusion, Space and Astrophysics, Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom.
⁵ Centre for Fusion, Space and Astrophysics, Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom.
⁶ Physics Department, University of Washington, P.O. Box 351560, Seattle, Washington 98195, USA.
⁷ University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom.
⁸ Physics Department, University of California, Berkeley, California 94720, USA.
⁹ SLAC National Accelerator Laboratory, 2575 Sand Hill Road, MS 72 Menlo Park, California 94025, USA.

PMID: 24765979
DOI: 10.1103/PhysRevLett.112.145004

Abstract

Detailed measurements of the electron densities, temperatures, and ionization states of compressed CH shells approaching pressures of 50 Mbar are achieved with spectrally resolved x-ray scattering. Laser-produced 9 keV x-rays probe the plasma during the transient state of three-shock coalescence. High signal-to-noise x-ray scattering spectra show direct evidence of continuum depression in highly degenerate warm dense matter states with electron densities ne>1024 cm-3. The measured densities and temperatures agree well with radiation-hydrodynamic modeling when accounting for continuum lowering in calculations that employ detailed configuration accounting.