GSCCM Biennial Meeting

Dr. Craig Tarver, LLNL

Craig Tarver was born in Syracuse, New York and attended Syracuse Central Technical High School. He then attended Clarkson University and graduated with a B.S. in Chemistry in 1968. Next he enrolled at Johns Hopkins University earning a Ph.D in Chemistry in 1973. Craig then joined the SRI International in 1973. In 1976, he joined the Chemistry Department at Lawrence Livermore National Laboratory, where he worked for 45 years before retiring in 2019.

Title: Calculating Overdriven Detonation for Reaction Product Shock States at Pressures Higher than those for Steady Detonation Waves

Abstract: When detonation waves impact high impedance materials, are overdriven in gas gun or laser experiments, enter a converging geometry, etc., shock pressures much higher than steady, Chapman-Jouguet (C-J) detonation can be generated. Such measurements have steadily improved over the past 50 years as spacial and time resolution have improved.¹ So has reaction product equation of state modeling. The Jones-Wilkins-Lee (JWL) reaction product equations of state were originally fit only to product expansion below C-J and were too compressible at higher pressures. Urtiew and Hayes² showed that by raising R₁, R₂, and ω, they could improve fits to overdriven data, while still matching product expansion data below the C-J state.

In the 1990s, Nellis, Mitchell, et al³ measured high-pressure Hugoniots of dissociating liquid nitrogen, ionization of water, and CO/CO₂ equilibrium as functions of shock pressure. The shock temperatures of individual dimers and trimers are higher than those for detonation C-J waves, which distribute their internal energy over more product vibrational modes. Thus more N₂ dissociation, more H₂O ionization, and different CO₂/CO ratios occur in the Nellis experiments compared to detonation. The large dissociation energy of N₂ has the greatest effect on the CHEETAH chemical equilibrium calculations, as shown by Tarver¹­­ for HMX and TATB overdriven detonation waves.

References

1. Tarver, C.M., Journal of Physical Chemistry A, 124, 1399 (2020).
2. A. Urtiew and B. Hayes, Combustion, Explosion, and Shock Waves 27, 505–514(1991)
3. J. Nellis et al. J. Chem. Phys. 94, 2244–2257 (1991)

Dr. Shawn McGrane

Shawn joined Los Alamos National Laboratory as a postdoc in 2001 after receiving a PhD in Physical Chemistry from the University of Minnesota. His postdoc work began on the High Explosive Reaction Chemistry via Ultrafast Laser Excited Spectroscopies (HERCULES) project, and he has been working with lasers and explosives ever since. His research efforts have focused on ultrafast shock physics and chemistry, dynamic thermometry in explosives, explosives detection, and femtosecond laser techniques. He has been author or co-author on over 45 journal articles, 3 book chapters, 1 patent, and numerous conference proceedings. He served as a Team Leader in the Shock and Detonation Physics Group at LANL for 5 years before becoming the Deputy Group Leader in 2019 and has been Group Leader since late 2020.

Title: Shedding light on shock-induced chemistry

Abstract: Rapid shock-induced chemistry is an essential characteristic of high explosives. The effect of these chemical reactions is apparent in a variety of measurements, such as embedded gauge, front curvature, and “Pop” plot run to detonation data used to calibrate reactive burn models. However, these techniques measure the effects of chemistry without any consideration of molecules, bonds, or temperature! Molecular dynamics simulations of shocked explosives provide all of this information, but how do we know the results are adequate reflections of the real materials? We need to experimentally see the reactions happening inside shocked explosives and the temperature that drives these reactions. This talk will detail the development and application of several interferometric and spectroscopic diagnostics to the problem of shock induced chemistry in high explosives, discuss what has been learned, the practical limitations of each technique, and the prospect of validating chemical predictions with experimental data.

Dr. Rachel Husband, DESY

Rachel is a scientist at the Deutsches Elektronen-Synchrotron (DESY), where she primarily works on the implementation of static and dynamic diamond anvil cell (DAC) techniques at the European X-ray Free Electron Laser (EuXFEL) in the framework of the HIBEF consortium. After completing her Master’s degree and PhD at the University of Edinburgh, she was a postdoctoral fellow at Harvard University before moving to the PETRA III synchrotron source at DESY. Her research is mainly focused on time-resolved studies of dynamic processes in the DAC, where she utilizes a range of X-ray based techniques including diffraction, imaging, and X-ray heating. Most recently, she co-led a DAC community proposal which used XFEL heating to induce high temperature states in low Z planetary materials.

Title: Probing phase transitions at intermediate compression rates using time-resolved X-ray diagnostics

Abstract:Fast compression using dynamic diamond anvil cells (dDACs) allows for the study of materials at intermediate strain rates that are not accessible using traditional static and dynamic compression techniques. These devices utilize piezo actuators to achieve compression timescales ranging from ~1 ms to several minutes, allowing for the study of phase transition kinetics at compression rates spanning over 7 orders of magnitude (~10^-2-10^5 GPa/s). Characterization of material behavior under dynamic compression requires time-resolved diagnostics compatible with the compression timescale. X-ray diffraction measurements at synchrotron sources provide structural information at kHz repetition rates, while X-ray phase contrast imaging allows for the visualization of samples as they undergo structural phase transitions such as melting and crystallization. More recently, the implementation of the dDAC at the European X-ray Free Electron Laser (EuXFEL) has allowed for structural studies to be extended to µs timescales. In this talk, I will discuss how these recent developments have allowed for the study of pressure-induced structural transitions in a range of different elemental materials, paving the way for future studies of phase transition kinetics at previously inaccessible compression rates.

Dr. Mathew Cherukara, Argonne National Laboratory

Mathew Cherukara leads the Computational X-ray Science (CXS) group at the Advanced Photon Source (APS) at Argonne National Laboratory. The group develops algorithms, computational tools and AI/ML models to analyze and interpret data from the various x-ray characterization techniques performed at the APS. His personal research is in AI-enabled materials characterization and AI-accelerated materials modeling.  He has particular interest in the development of novel x-ray and electron imaging capabilities that are only made possible because of AI. Mathew received his Ph.D from Purdue University in 2015 and his bachelors from the Indian Institute of Technology (IIT) Madras in 2010, both in computational materials science. He has 4 patent applications and has published over 50 peer-reviewed papers.

Title: AI-Enabled X-ray Science at the Advanced Photon Source

Abstract: The capabilities provided by next generation light sources such as the APSU along with the development of new characterization techniques and detector advances are expected to revolutionize materials characterization by providing the ability to perform scale-bridging, multi-modal materials characterization under in-situ and operando conditions. For example, providing the ability to image in 3D large fields of view (~mm³) at high resolution (<10 nm), while simultaneously acquiring information about structure, strain, elemental composition, oxidation state, photovoltaic response etc.

However, these novel capabilities dramatically increase the complexity and volume of data generated by instruments at the new light sources. Conventional data processing and analysis methodologies become infeasible in the face of such large and varied data streams. The use of AI/ML methods is becoming indispensable for real-time analysis, data abstraction and decision making at advanced synchrotron light sources such as the APS. I will describe the use high-performance computing (HPC) along with AI on edge devices to enable real-time analysis of streaming data from x-ray characterization instruments at the APS.

Prof. Sarah Stewart, UC Davis

Sarah specializes in the study of collisions in the solar system. She is widely known for proposing a new model for the origin of the Moon, where the Moon grows within a new type of planetary object known as a synestia, which was featured in a popular TED talk. Sarah’s experimental program on planetary materials focuses on measurements of thermodynamic properties and calculating the mass of melt and vapor produced during planetary impact events. Sarah directs the Shock Compression Laboratory at UC Davis, a light gas gun facility, and conducts experiments on laser and pulsed power platforms. Sarah received her AB in Astrophysics and Physics from Harvard in 1995 and her PhD in Planetary Science from the California Institute of Technology in 2002. Sarah has received a Presidential Early Career Award for Scientists and Engineers, the Urey Prize from the American Astronomical Society’s Division for Planetary Sciences, and a MacArthur Fellowship.

Title: The Collisional Accretion of Earth: A Shock Physics Story

Abstract: Collisions play a central role in the growth of rocky planets from planetesimals. As the bodies grow, the mutual impact velocities increase from a subsonic mechanical regime to a shock-induced vaporization regime at 10’s km/s. Today, the most extreme natural impact pressures can be reached at high energy facilities such as the Z machine, the Omega and Omega EP lasers, and the National Ignition Facility, and I will summarize recent advances and challenges in experimental work on probing the shock Hugoniots and phase boundaries of planetary materials using these facilities. The irreversible work deposited by the shock-and-release thermodynamic path induces widespread melting and vaporization in the colliding bodies. I will highlight recent insights on the effects of shock-induced phase changes on planetesimals, which survive as bodies in the asteroid belt, and on the origin of the Earth and Moon.

Public-friendly summary: Collisions play a central role in the growth of Earth and Earth-like planets. Today, all of the impact velocities during planet formation can be reached in laboratory experiments. From shock experiments, we determined when shock waves generated by these collisions led to melting and vaporization of growing planets. I will highlight how impact vaporization changes the way we think about asteroids and meteorites and the origin of the Earth and Moon.