  The plastic response of beryllium was investigated during loading by
laser-induced shock waves, using surface velocimetry and in-situ x-ray
diffraction. Results from loading by thermal x-rays (hohlraum) were consistent
with more extensive studies using laser ablation. Strong elastic waves were
observed, up to ~1 km/s in free surface speed, with significant structure
before the arrival of the plastic shock. The magnitude and shape of the
precursor could be reproduced with a plasticity model based on dislocation
dynamics. Changes in lattice spacing measured from the x-ray diffraction
pattern gave a direct measurement of uniaxial compression in the elastic wave,
triaxial flow from the decay of the precursor, and triaxial compression in the
plastic shock; these were consistent with the velocity data. The dynamic
strength behavior deduced from the laser experiments was used to help interpret
surface velocity data around the onset of shock-induced melting. A model of
heterogeneous mixtures is being extended to treat anisotropic components, and
spall.
