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Title: Absolute Hugoniot measurements from a spherically convergent shock using x-ray radiography

Here, the canonical high pressure equation of state measurement is to induce a shock wave in the sample material and measure two mechanical properties of the shocked material or shock wave. For accurate measurements, the experiment is normally designed to generate a planar shock which is as steady as possible in space and time, and a single state is measured. A converging shock strengthens as it propagates, so a range of shock pressures is induced in a single experiment. However, equation of state measurements must then account for spatial and temporal gradients. We have used x-ray radiography of spherically converging shocks to determine states along the shock Hugoniot. The radius-time history of the shock, and thus its speed, was measured by radiographing the position of the shock front as a function of time using an x-ray streak camera. The density profile of the shock was then inferred from the x-ray transmission at each instant of time. Simultaneous measurement of the density at the shock front and the shock speed determines an absolute mechanical Hugoniot state. The density profile was reconstructed using the known, unshocked density which strongly constrains the density jump at the shock front. The radiographic configuration and streakmore » camera behavior were treated in detail to reduce systematic errors. Measurements were performed on the Omega and National Ignition Facility lasers, using a hohlraum to induce a spatially uniform drive over the outside of a solid, spherical sample and a laser-heated thermal plasma as an x-ray source for radiography. Absolute shock Hugoniot measurements were demonstrated for carbon-containing samples of different composition and initial density, up to temperatures at which K-shell ionization reduced the opacity behind the shock. Here we present the experimental method using measurements of polystyrene as an example.« less
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  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Washington State Univ., Pullman, WA (United States)
  3. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Univ. of Rochester, Rochester, NY (United States)
  4. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)
  5. Atomic Weapons Establishment, Berkshire (United Kingdom)
  6. Univ. of California, Berkeley, CA (United States); Helmholtz Zentrum, Dresden (Germany)
  7. Univ. of California, Berkeley, CA (United States)
Publication Date:
Grant/Contract Number:
AC02-76SF00515; AC52-07NA27344
Accepted Manuscript
Journal Name:
Review of Scientific Instruments
Additional Journal Information:
Journal Volume: 89; Journal Issue: 5; Journal ID: ISSN 0034-6748
American Institute of Physics (AIP)
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
Country of Publication:
United States
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1437674