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.