Radiography codes and standards require that single wall exposure techniques be utilized whenever practical. Pipeline field radiography currently utilizes film or computed radiography (CR) for single wall viewing of pipeline welds, whereby each technology exhibits tradeoffs for image artifacts and time to image. Flexible digital detector arrays (DDAs) produce images with acceptable quality and minimal artifacts, in the shortest time to image possible. Application of flexible DDA technology to pipeline welds is new to the industry. Examples of single view radiographs are presented as part of this paper.

Industrial x-ray imaging is dominated by the interplay of critical factors defined by the source of x-rays and the detection medium. One of these factors is the x-ray spot size which causes blurring in the final image while also being directly proportional to source output due to heat deposition on the target. X-ray spot size directly impacts the maximum resolution an imaging system can achieve while also impacting required facility and subtler imaging system characteristics like scatter rejection and detector efficiency. As a result of these considerations a source with a spot size smaller than the detector resolution, called a micro-focus source, is desirable. Robust micro-focus x-ray sources with spot sizes down to a few micrometers (μm) have been limited to a maximum energy of 225keV as a practical limit of the source output vs. heat loading on the target while a few manufacturers have achieved sub 100 μm 450kV sources with improved heat handling via moving targets or more exotic materials. Above 450kV micro-focus x-ray sources are not commercially available. At the same time the advent of additive manufacturing of denser materials like refractory metals has resulted in a demand for higher resolution x-ray inspection of thick components. It is now possible to create features on the scale of a few hundred μm inside a meter scale objects with no access for inspection. This changing landscape in manufacturing provides a strong motivator for high-resolution MeV x-ray computed tomography. Numerous methods to improve detector resolution ranging from custom optical systems to super-resolution imaging methods have seen some success but retain significant compromises.
This talk describes a different approach with the development of a micro-focus MeV x-ray source using a laser driver to generate x-rays instead of a direct electron beam. The work described is the result of a collaboration led by Los Alamos National Lab researchers working with a team at Colorado State University’s ALEPH laser. The generation of high energy x-rays from a highly focused short-pulse laser has been known and published for a number of years but the primary focus has been on target physics and single shot imaging. This project instead used a simple metal conversion target and the ALEPH laser at Colorado State University in the USA to engineer a target system that can support the thousands of images required for computed tomography. With multiple successful CT scans this system sits at technology readiness level 4-5. This talk reviews advantages of a micro-focus MeV imaging system, basics
of the laser source, the setup used, results to date and remaining challenges to create a robust industrial source.

Cargo is inspected for contraband, e.g., explosives, at private air cargo facilities. Often, items from multiple vendors and of varying content are consolidated onto single units called skids. Commonly, existing x-ray scanners either do not penetrate dense cargo placed on the skids or produce images that are too cluttered for contraband detection. This requires unpacking the skids, scanning more manageable individual packages as “break bulk” cargo, and then re-consolidating the cargo. This is labor intensive and time consuming. To get similar levels of detection as Explosives Detection Systems (EDS) for checked luggage, tomographic scanners were recently scaled up by manufacturers for air cargo skids. These systems operate up to a potential of 450kV. LLNL has developed a high-potential, 3 MV, tomographic scanner that allows further penetration for dense air cargo with similar spatial resolution as EDS at an operational of throughput of 20 skids/hour. The system can also detect general contraband for customs purposes. The basic system design will be described, and preliminary results will be presented.

This work was funded under Department of Homeland Security Science and Technology Directorate contract 70RSAT20KPM000110

Prepared by LLNL under Contract DE-AC52-07NA27344
LLNL-ABS-2012870

High-speed X-ray and Microwave Interferometry diagnostics fielded on High-Explosive Experiments
Andrew Townsend*, R. Owen Mays, Joshua Ruelas, Steven Saavedra, Casey Banergard

Lawrence Livermore National Laboratory
7000 East Ave,
Livermore CA 94550
(925) 583-4225; *email townsend10@llnl.gov

Document number LLNL-ABS-2013030.

ABSTRACT
A thorough understanding of the mechanisms responsible for explosive ignition and detonation is essential for ensuring the safety of explosive systems. Most non-fire-related explosive accidents result from low-speed impacts; however, studying these events is challenging due to the opaque confinement of explosives and obscuration by smoke and flames, which limit the effectiveness of conventional optical imaging. This work utilizes a high-speed X-ray imaging system developed at LLNL, combined with microwave interferometry to confirm detonation events, to investigate the conditions leading to ignition and detonation. The integration of few-view computed tomography and virtual-reality visualization techniques will be discussed.

Keywords: High-speed X-ray video, Microwave interferometry, Explosive safety, Few-view Computed Tomography, virtual-reality visualization

INTRODUCTION
Most explosive incidents and accidents that are not related to fire are caused by low-speed impacts. To ensure the safety of explosive systems, it is crucial to understand how initiation and detonation occur under various mechanical and thermal stresses. However, observing these events in real time is challenging because explosives are typically confined during tests or obscured by smoke and flames. Furthermore, the way explosives break apart and fragment under mechanical stress can significantly influence how the reaction progresses after ignition.
Collecting experimental data on explosive impact conditions and the resulting reactions is essential for supporting LLNL’s modeling and simulation efforts. This data directly informs the development and analysis within HERMES (High Explosive Response to MEchanical Stimulus), which is a component of the ALE3D multi-physics simulation software.
To address these challenges, we use a high-speed X-ray radiography system—also known as cineradiography—developed at LLNL. By combining this imaging technique with synchronized microwave Doppler interferometry to track the detonation front, we can gain valuable insights into the conditions that lead to explosive ignition and detonation.

EXPERIMENTAL SYSTEM
The experimental setup consists of a target assembly housed within a steel box, which serves to shield both the X-ray source and the camera from detonation fragments. The X-ray source is a rotating-anode medical unit, providing the necessary flux for high-speed imaging. Image capture is performed by a Phantom v2512 high-speed camera, which has been modified with a Gadolinium Oxysulfide scintillator to convert X-rays into visible light. The scintillator is attached to a glass fiber-optic taper, with the narrow end positioned directly against the camera’s CMOS sensor. The system’s field of view, measured at the midpoint between the X-ray source and the scintillator, is a circular area with a diameter of 40 mm.
The cineradiography system achieves sub-millimeter spatial resolution and operates at acquisition speeds up to 100,000 frames per second. The design ensures sufficient X-ray flux to image through containment vessels rated for safely confining detonations of up to 100 grams of explosives. This configuration enables detailed imaging of projectile impacts, such as bullets, on the target assembly.
Additionally, a microwave antenna is positioned above the impact area. This diagnostic tool distinguishes between true detonations and non-detonating violent explosions, and measures the velocity of the detonation front as it propagates through the explosive column.

TEST METHODOLOGY, RESULTS AND DISCUSSION
The initial commissioning of the imaging system involved capturing high-speed radiographs of standard 4.5 mm diameter lead pellets, fired from an air rifle at velocities near 300 m/s. Early explosives breakup experiments were conducted at the Energetic Materials Research and Testing Center (EMRTC) in Socorro, New Mexico. The current experimental work was performed at the High Explosives Applications Facility (HEAF) at Lawrence Livermore National Laboratory (LLNL) in Livermore, California.

This paper presents results from two distinct impact experiment configurations. In the first configuration, a bullet impacts and penetrates a test plate positioned in front of a column of explosive material, with a fixed metal anvil located behind the column. The second configuration replaces the plate with a metal punch; the punch is struck by a metal projectile with a hemispherical head, pinching the explosive between the punch face and the anvil.

High-speed video recordings of the impact events, along with synchronized Doppler microwave interferometer data, will be discussed. Additionally, the system’s capability for high-speed, few-view X-ray computed tomography (see Figure 1), as well as the use of virtual-reality tools for data visualization, will be highlighted.

ACKNOWLEDGEMENTS
Document number LLNL-ABS-2013030.
This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52–07NA27344.