Experiments at New X-Ray Facility May Lead to Better Explosive Modeling

Credit: Los Alamos National Laboratory.

The detonation of carbon-rich high explosives yields solid carbon as a major constituent of the product mixture, as well as a variety of carbon allotropes and morphologies may form and evolve.

Now for the first time, researchers at the Los Alamos National Laboratory (LANL) are using time-resolved small-angle x-ray scattering (TRSAXS) to observe ultra-fast carbon clustering and graphite and nanodiamond production in Plastic Bonded Explosive (PBX) 9502, potentially leading to better computer models of explosive performance.

PBX 9502 is an insensitive high explosive that is widely used in the U.S. nuclear deterrent. High explosives are used to drive the nuclear “primary” to a critical mass, initiating a nuclear detonation. Insensitive high explosives are very difficult to detonate accidentally, and are considered extremely safe. However, the exact chemical process of energy transfer is still largely unknown.

“Carbon clusters are produced during the chemical process of detonation in high explosives,” said Dana Dattelbaum, of Explosive Science and Shock Physics Division. “The carbon particle size, shape, composition and their evolution in time helps us understand how explosives deliver energy over a given time frame.”

The researchers found that the creation of carbon clusters happens much faster than previously thought, and the composition of the carbon is very different than had been assumed.

“An unexpected and significant finding of this research was the ratio of graphite to diamond inferred by the x-ray contrast from the scattering measurements,” said Dattelbaum. “In detonating TATB-based PBX 9502, we found that approximately 80 percent graphite and 20 percent diamond was formed when we were expecting to see a much higher percentage of diamond-like carbon.”

The products of detonation, the particle size dynamics and type of carbon produced can correlate directly to the type of explosive, and improving computer models of explosive performance, leading to better predictive capability in assuring the safety, security, and effectiveness of the U.S. nuclear deterrent.

The research is funded by the National Nuclear Security Administration as part of Science Campaign 2 in support of the Stockpile Stewardship Program. User facilities include the Center for Integrated Nanotechnologies and the Dynamic Compression Sector of the Advanced Photon Source at Argonne.

Read the paper at the Journal of Physical Chemistry: Evolution of Carbon Clusters in the Detonation Products of the Triaminotrinitrobenzene (TATB)-Based Explosive PBX 9502.