New challenges create innovation

A counterterrorism test series paves the way for experimental breakthroughs.

By Jill Gibson | July 19, 2023

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The Dual-Axis Radiographic Hydrodynamic Test (DARHT) facility. Los Alamos National Laboratory

Los Alamos National Laboratory has wrapped up a groundbreaking series of experiments to determine how to safely detonate and disable terrorist weapons. Scientists say the test series, which concluded May 24, 2023, represents several significant technological advances.

“These tests were unlike any we have ever conducted at DARHT before,” says Jacob Mendez, who leads the Experiments and Diagnostics group at the Laboratory’s Dual-Axis Radiographic Hydrodynamic Test (DARHT) facility. “This series forced us out of our comfort zone, creating challenges that led to innovation in several areas.” 

The Tier Threat Modeling Archive-Validation (TTMA-V) series began in 2013 in response to a presidential national security directive. It consisted of 2 campaigns and 10 experiments. Each experiment considered different terrorism approaches and different types of threat devices. The findings will be used to train Nuclear Emergency Support Team responders. “Terrorists don’t give us examples of their devices so we can practice with them,” Mendez says. “These tests give us information to be prepared.”

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The volume of this 6-foot spherical confinement vessel was increased by installing a "top hat."

Scientists carried out the experiments at DARHT, which uses two linear accelerators to create high-powered x-ray pulses that image the detonation of mock weapons inside a steel containment vessel. The x-ray images, or radiographs, allow scientists to “see” materials inside the vessel that are moving at more than 2.5 miles per second.

Among the numerous innovations prompted by TTMA-V was the installation of a rail system that allowed scientists to adjust the position of DARHT’s x-ray sources. This new capability enabled a variable and expanded field of view, which greatly enhanced data quantity and reduced uncertainty when recording images.  

Mendez says the TTMA-V test series also pushed his team to develop new diagnostics, shielding methods, and dimensions for the vessels containing the experiments. In one case, scientists increased a vessel’s volume by installing a 2.5-foot-tall “top hat” extension in what was dubbed the “mad hatter” test. 

Test results were also analyzed using a groundbreaking method. Scientists in the Laboratory’s Theoretical division devised a new modeling technique that can reconstruct highly accurate 3D models of detonations. This will provide previously unavailable data that can be applied in multiple ways. “We have been developing this technique for several years,” says scientist Marc Klasky. “Using machine learning natural language processing architectures similar to those found in Chat GPT, we can create accurate models of dynamic events and increase our ability to apply our data.”

The TTMA-V series was a collaborative effort between Los Alamos and Lawrence Livermore national laboratories, the National Nuclear Security Administration, and the Defense Threat Reduction Agency. Mendez says all parties benefited from such a unique experimental series. “We’ve learned a lot that we otherwise wouldn’t have learned,” he says, “and we’ve shown DARHT is the place to do this kind of work.” ★