Engineering topics

Azevedo, Stephen G.

Publications and source records attributed to Azevedo, Stephen G..

6 records

DOE OSTI2022

Livermore tomography tools: Accurate, fast, and flexible software for tomographic science

Livermore Tomography Tools (LTT) is a customizable scientific software package that enables a broad range of research and development efforts into computed tomography (CT). Here, it was developed to process x-ray and neutron CT data accurately and rapidly from raw detector counts to reconstructed volumes with the flexibility to handle many special cases. LTT fulfills long-term CT software goals to provide quantitatively accurate results reported in physical units (e.g., mm -1 or cm -1 ) while exploiting all available computational advantages to maximize speed. Written in C/C++ with support for multiple CPUs and GPUs, LTT runs on many computing platforms (Linux/Unix, Windows, and Mac; laptops to supercomputers). As a result, LTT can:process data acquired from various custom-built and commercially available CT scanners, model and simulate x-ray and neutron interactions to encourage algorithm prototyping, and allow for rapid insertion of the latest algorithms.We describe LTT’s software architecture, user interfaces, and its 88 algorithms (as of this writing) for pre-processing, reconstruction, post-processing, and simulation that support many scanner geometries (parallel-, fan-, cone-beam, and custom). Several applications are presented that illustrate LTT’s accuracy, speed, and flexibility relative to other solutions.

36 MATERIALS SCIENCE↗

DOE OSTI2019

System-independent characterization of materials using dual-energy computed tomography

A system for characterizing the material of an object scanned via a dual-energy computed tomography scanner is provided. The system generates photoelectric and Compton sinograms based on a photoelectric-Compton decomposition of low-energy and high-energy sinograms generated from the scan and based on a scanner spectral response model. The system generates a Compton volume with Compton attenuation coefficients from the Compton sinogram and a photoelectric volume with photoelectric attenuation coefficients from the photoelectric sinogram. The system generates an estimated effective atomic number for a voxel and an estimated electron density for the voxel from the Compton attenuation coefficient and photoelectric coefficient for the voxel and scanner-specific parameters. The system then characterizes the material within the voxel based on the estimated effective atomic number and estimated electron density for the voxel. This information can be used to provide a mapping of known effective atomic numbers and known electron densities to known materials.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2019

Method to Extract System-Independent Material Properties From Dual-Energy X-Ray CT

In 2016, we published a method for processing dual-energy computed tomography (DECT) data called system-independent rho-e/Z-e (ρ e /Z e ) or SIRZ. Using data from multiple DECT systems and spectra, SIRZ estimated the electron density ρ e and effective atomic number Z e (based on published X-ray cross sections), for a set of known specimens. However, the decomposition process required complex spectral modeling of the DECT system, which made SIRZ difficult to implement and automate. This paper describes the subsequent work on “SIRZ-2” to simplify the spectral modeling, automate the process, and improve its range and versatility. The SIRZ-2 basis functions are more accurate for the X-ray energy range (<;200 keV) and materials that are common to DECT applications in security and nondestructive characterization. To evaluate the SIRZ-2 performance, eight well-characterized specimens (with Z e of 6-20) were scanned with multiple spectral pairs (up to 200 keV) on seven different DECT systems, including a commercial airport luggage scanner. For these varied tests, the average SIRZ-2 relative errors for ρ e estimates were four times lower (0.7% compared to 3.0% for SIRZ), while average Z e relative errors were comparably low for both methods (<;1.5%). Average precision errors were also low (<;2.3% for both). SIRZ-2 produces accurate, repeatable, and system-independent material property estimates of (ρ e , Z e ) that can be directly compared across DECT systems and over time.

42 ENGINEERING↗

DOE OSTI2018

An Overview of Nondestructive Evaluation and Characterization at Lawrence Livermore National Laboratory

For more than 60 years, Lawrence Livermore National Laboratory (LLNL) has developed and employed advanced technologies in both nondestructive evaluation (NDE) and nondestructive characterization (NDC) to enhance national security. Additonally, the Laboratory established an extensive array of NDC capabilities that enable the inspection and characterization of virtually every element on the periodic table. This allows for the evaluation of structures of interest with densities ranging from ~20 mg/cm 3 to approximately 20 g/cm 3 , across length scales from nanometers to meters, and over time scales ranging from microseconds to decades. This paper provides an overview of the NDE and NDC activities at LLNL, illuminating current research and development interests in well-established areas such as weapons and explosives research, and in new areas such as additive manufacturing. Traditional NDC techniques, such as X-ray radiography and computed tomography, are also discussed. Furthermore, new approaches, such as X-ray phase-contrast imaging and X-ray ptychography, are examined.

36 MATERIALS SCIENCE↗

DOE OSTI2016

System-independent characterization of materials using dual-energy computed tomography

In this study, we present a new decomposition approach for dual-energy computed tomography (DECT) called SIRZ that provides precise and accurate material description, independent of the scanner, over diagnostic energy ranges (30 to 200 keV). System independence is achieved by explicitly including a scanner-specific spectral description in the decomposition method, and a new X-ray-relevant feature space. The feature space consists of electron density, ρ e , and a new effective atomic number, Z e , which is based on published X-ray cross sections. Reference materials are used in conjunction with the system spectral response so that additional beam-hardening correction is not necessary. The technique is tested against other methods on DECT data of known specimens scanned by diverse spectra and systems. Uncertainties in accuracy and precision are less than 3% and 2% respectively for the (ρ e , Z e ) results compared to prior methods that are inaccurate and imprecise (over 9%).

42 ENGINEERING↗

DOE OSTI2013

ZeCalc Algorithm Details

This report documents the implementation of the Java application ZeCalc (as released in version 3 on October 18, 2012), which calculates “Z e ”, a newly-defined “effective atomic number” for mixtures and compounds. Z e differs from the traditional Z eff in that it is based upon the x-ray cross section of the material, so it is more amenable to radiographic applications. Additionally, ZeCalc calculates ρ e , the volumetric electron density (with units of electron‐mol/cm 3 ), for materials with a specified composition and volumetric mass density, ρ m with units of g/cm 3 ).

42 ENGINEERING↗