Observation of defects in shocked diamond below the HEL

Diamond is well established to have strong resistance to plastic deformation and it’s Hugoniot Elastic Limit (HEL) is large relative to other materials. Canonically, the propagation of shock waves through a single crystal involves an initial defect-free elastic wave followed by a plastic wave with defects. This study focuses on the defects and strain gradients generated below and at the HEL in <110> oriented single crystal diamond. This laser driven dynamic compression X-ray topography experiment was conducted at the Materials at Extreme Conditions beamline at the Linac Coherent Light Source. X-ray topography is a near field imaging technique that images defects by observing contrast in the intensity of the diffracted X-ray beam. By using a line focused X-ray beam coupled with a thick diffracting region, we generate 2D images where defect derived intracrystalline rotations generate a diffraction intensity contrast compared to the defect free regions. We shock <110> oriented diamonds that are type Ib and IIa over a range of stresses to view defects and strain gradients to visualize the physics at and below the HEL.

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 through LDRD project 21-ERD-032.