The achievement of ignition from an Inertial Confinement
Fusion capsule will require a detailed understanding of
a wide range of high energy density phenomena. This paper
presents some recent work aimed at improving our knowledge
of the strength and equation of state characteristics of
low-Z materials, and outlines data which will
provide quantitative benchmarks against which our predictive
radiation hydrodynamics capabilities can be tested. Improvements
to our understanding in these areas are required if reproducible
and predictable fusion energy production is to be achieved
on the next generation of laser facilities.
In particular, the HELEN laser at AWE has been used to create
a thermal X-ray source with 140 eV peak radiation temperature
and 3% instantaneous flux uniformity to allow measurements
of the Equation of State of materials at pressures up to
20 Mbar to an accuracy of <±2% in shock velocity.
The same laser has been used to investigate the onset of
spallation upon the release of a strong shock at a metal-vacuum
boundary, with dynamic radiography used to image the spalled
material in flight for the first time. Finally, a range
of experiments have been performed to generate quantitative
radiation hydrodynamics data on the evolution of gross
target defects, driven in both planar and imploding geometry.
X-ray radiography was used to record the evolving target
deformation in a system where the X-ray drive and unperturbed
target response were sufficiently characterized to permit
meaningful analysis. The results have been compared to
preshot predictions made using a wide variety of fluid
codes, highlighting substantial differences between the
various approaches, and indicating significant discrepancies
with the experimental reality. The techniques developed
to allow quantitative comparisons are allowing the causes
of the discrepancies to be identified, and are guiding
the development of new simulation techniques.
