Planet formation, star evolution, and earthquakes all involve matter experiencing extreme pressure. It is possible to reproduce similar conditions in the lab by using a high-powered laser to initiate a shock wave and stress matter to millions of atmospheres of pressure. Under such high impact, solids exhibit plastic properties, causing the shock wave to split into the elastic precursor and plastic shock wave.

Though this phenomenon is well described by theoretical models, there is a lack of accurate direct observational data to discriminate and validate models. The high speed, submicron scale, and low contrast of shock wave propagation make it difficult to observe directly.

Makarov et al. applied X-ray free-electron lasers (XFELs) to directly capture and trace the evolution of wave splitting in diamonds at pressures comparable to those at Earth’s core. They used their first-of-a-kind measurements to calibrate a 2D failure model.

“In our work, we implement the unique capabilities of XFEL radiation together with a coherent phase-contrast radiography approach to probe and visualize the evolution of elastic-plastic shock wave structure,” said author Sergey Makarov.

Diamond is the ideal medium for tracking shock wave evolution because it can withstand ultra-high strain rates and is transparent to XFEL radiation.

“We traced the evolution of wave structure from the appearance of the elastic precursor to the disappearance of the plastic shock with submicron resolution,” said Makarov. “We found excellent agreement between the experimental data and simulations and demonstrated that the combined experimental-theoretical approach enables the study of high-speed failure dynamics and unusual stress-induced solid-state phase transitions.”

This approach enables the construction and verification of equations of state of matter and aids the design of next-generation materials.

Source: “Direct imaging of shock wave splitting in diamond at Mbar pressure,” by Sergey Makarov, Sergey Dyachkov, Tatiana Pikuz, Kento Katagiri, Hirotaka Nakamura, Vasily Zhakhovsky, Nail Inogamov, Victor Khokhlov, Artem Martynenko, Bruno Albertazzi, Gabriel Rigon, Paul Mabey, Nicholas J Hartley, Yuichi Inubushi, Kohei Miyanishi, Keiichi Sueda, Tadashi Togashi, Makina Yabashi, Toshinori Yabuuchi, Takuo Okuchi, Ryosuke Kodama, Sergey Pikuz, Michel Koenig, and Norimasa Ozaki, Matter and Radiation at Extremes (2023). The article can be accessed at