Nondestructive Characterization
Institute (NCI)

TSA Partnership

Nearly 3,000 improvised explosive device incidents occurred in the United States in 2017, killing 10 people and wounding dozens. The clear and present threat of homemade explosives continues to evolve in the United States as the nation’s enemies constantly adapt to the state-of-the-art in explosives detection with stealthier, deadlier tactics. To keep the nation ahead of emerging threats, the Department of Homeland Security (DHS) Science and Technology Directorate (S&T) takes on rigorous explosives threat detection research through its various dedicated labs and projects.

“Screening at checkpoints is a top priority for Congress and the Department. These labs support this activity and the wider DHS mission by rapidly delivering explosives data, helping us better prepare for any future threats that may arise,” said William N. Bryan, Senior Official Performing the Duties of the Under Secretary for DHS S&T.

The Tyndall Reactive Materials Group (TRMG) in Florida and the recently launched Detection Technology Center (DTC) in Alabama are two test facilities operated by S&T in support of transportation security equipment used by the Transportation Security Administration (TSA) and other DHS components. A third facility, S&T’s Transportation Security Laboratory in New Jersey is responsible for certifying the equipment tested at TRMG and DTC.

“DHS S&T uses data collected at those labs to inform and develop mitigation strategies and strengthen our detection and response capabilities in order to stop an attack,” said Elizabeth Obregon, DHS S&T Homemade Explosives Program Manager.

“The information generated from these facilities ensures screening equipment is attuned to detect threats before they can create tragedy, and the folks operating at these labs work tirelessly to keep families safe.” Obregon concluded. S&T works closely with Lawrence Livermore National Laboratory to analyze laboratory data for TSA.

Supporting Additive Manufacturing

Livermore and the Kansas City National Security Campus (KCNSC), which has decades of experience as a production facility for the NSE and in meeting the extremely rigorous qualification standards for stockpile component production, recognized the potential for AM polymers and began to explore an improved, concurrent design and development process. “When the AM team first came to the weapons program, we could print a 2D silicone doily. Now, we can print complex parts with completely arbitrary shapes, and we’re integrating machine learning and high-performance computing. It’s remarkable how far additive manufacturing has evolved in such a short time,” says program leader and materials scientist Bob Maxwell....

The most common method for producing polymer AM components is direct ink writing (DIW), which involves extruding a silicone resin ink through a nozzle onto a substrate creating a series of intricate lattice structures. The substrate or mandrel moves during the extrusion process following a digital design dictating its path. “Working with DIW is challenging. You can always design the ideal part, but you plug that design into a computer, push the button, and you might end up with spaghetti instead of a nice, cohesive 3D part,” says Tom Wilson, polymer scientist in Livermore’s Materials Science Division....

Once a part has been printed, researchers must examine it in a noninvasive manner for potential flaws that might compromise its integrity. Chuck Divin, a nondestructive evaluation (NDE) engineer at Livermore, has led a team of engineers and scientists at the Polymer Production Enclave in developing new NDE methods of inspection that allow researchers to determine the as-built structure and composition of a part with greater precision and accuracy, reducing uncertainties to less than 0.2 percent without disassembling a part. KCNSC and Livermore worked together to modify the NDE system to be more practical, robust, and user-friendly, ensuring that technicians can reliably evaluate parts.

National Ignition Facility uses lasers to generate x-rays

Lawrence Livermore National Laboratory has a rich history in laser research since the pursuit of inertial confinement fusion (ICF) began decades ago. In addition to Livermore’s December 2022 ignition achievement at the National Ignition Facility (NIF), the Laboratory’s laser science research has led to several significant technological advances, including designing and building ultraintense, high-average-power lasers. Recent developments using these short-pulse lasers involve efficiently generating beams of particles—electrons, protons, neutrons, x rays, and muons. The types of particles produced depend on the strength, shape, and pulse of the laser beam, the materials used in the laser target (a tiny capsule holding matter that is heated to more than 3 million degrees Celsius), and the interaction between the laser and those materials.

Laser-driven sources at Livermore support ICF research at NIF, which contains the Advanced Radiographic Capability (ARC), the world’s most energetic short-pulse laser. ARC provides a nondestructive, diagnostic tool to see through the fast moving, small feature, and dense NIF target, evaluating the shape of the target as it compresses and examining material response to stresses at extreme conditions.

Livermore researchers are using ARC to develop laser-based x-ray and neutron sources for radiography, an imaging technique that uses x rays, gamma rays, or similar ionizing or non-ionizing radiation to view the internal form of an object. Radiography is used to conduct x-ray imaging of humans and to inspect flaws or cracks within materials that may not be visible to the naked eye. Among other uses at Livermore, radiography using laser-produced particles offers new opportunities for non-destructive evaluation of weapons components and the complex internal structures of 3D-printed materials.

NDE researchers at LLNL make headway in situ monitoring to meet additive manufacturing advances

The integrity of components fabricated with advanced manufacturing techniques, such as laser powder bed fusion, is dependent upon rapid heating, melting, and solidification processes. New techniques are needed to provide in situ feedback of these processes, to ensure that builds are on track or can be reconfigured in case of error. Morales and team have created a laser-based ultrasonic technique to probe thermal effects induced by a high-power continuous wave laser in titanium samples.

Their paper, published in Nature Scientific Reports, shows that spatially uniform heating beam, laser-induced surface acoustic waves are strongly influenced by surface heating conditions, are dispersive in the case of rapid heating, and that abrupt velocity reduction happens upon the onset of surface melting. Their work involves a pulsed laser to generate high frequency surface acoustic waves that propagate through the laser-heated region and are detected using a photorefractive crystal-based interferometer. The upshot? Changes in the surface wave velocity can be used to track local heating and detect the onset of surface melting in real time, so that adjustments can be made to additive metal builds as needed.