AWE experimental laser plasma program

The achievement of ignition from an Inertial Confinement Fusion capsule wil l require a detailed understanding of a wide range of high energy density p henomena. This paper presents some recent work aimed at improving our knowl edge of the strength and equation of state characteristics of low-Z materia ls, and outlines data which will provide quantitative benchmarks against wh ich our predictive radiation hydrodynamics capabilities can be tested. Impr ovements to our understanding in these areas are required if reproducible a nd predictable fusion energy production is to be achieved on the next gener ation of laser facilities. In particular, the HELEN laser at AWE has been used to create a thermal X-r ay source with 140 eV peak radiation temperature and 3% instantaneous flux uniformity to allow measurements of the Equation of State of materials at p ressures 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 releas e of a strong shock at a metal-vacuum boundary, with dynamic radiography us ed to image the spalled material in flight for the first time. Finally, a r ange 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 ev olving target deformation in a system where the X-ray drive and unperturbed target response were sufficiently characterized to permit meaningful analy sis. The results have been compared to preshot predictions made using a wid e variety of fluid codes, highlighting substantial differences between the various approaches, and indicating significant discrepancies with the exper imental reality. The techniques developed to allow quantitative comparisons are allowing the causes of the discrepancies to be identified, and are gui ding the development of new simulation techniques.