The smuggling of special nuclear materials (SNM) through international borders could enable nuclear terrorism and constitutes a significant threat to global security. This paper presents the experimental demonstration of a novel radiographic technique for quantitatively reconstructing the density and type of material present in commercial cargo containers, as a means of detecting such threats. Unlike traditional techniques which use sources of bremsstrahlung photons with a continuous distribution of energies, multiple monoenergetic gamma radiography (MMGR) utilizes monoenergetic photons from nuclear reactions, specifically the 4.4 and 15.1 MeV photons from the 11 B(d,nγ) 12 C reaction. By exploiting the Z-dependence of the photon interaction cross sections at these two specific energies it is possible to simultaneously determine the areal density and the effective atomic number as a function of location for a 2D projection of a scanned object. The additional information gleaned from using and detecting photons of specific energies for radiography substantially increases the resolving power between different materials. This paper presents results from the imaging of mock cargo materials ranging from Z ≈ 5-92, demonstrating accurate reconstruction of the effective atomic number and areal density of the materials over the full range. In particular, the system is capable of distinguishing pure materials with Z 70, such as lead and uranium -a critical requirement of a system designed to detect SNM. This methodology could be used to screen commercial cargoes with high material specificity, to distinguish most benign materials from SNM, such as uranium and plutonium.
Neutron resonance transmission analysis (NRTA) is a spectroscopic technique that uses the resonant attenuation of epithermal neutrons to infer the isotopic composition of an object. NRTA is particularly well suited for applications requiring nondestructive analysis of objects containing mid-and high-Z elements. To date, NRTA has required large expensive accelerator facilities to achieve precise neutron beams and has not been suitable for on-site applications. In this study, we provide an experimental demonstration showing that NRTA can be performed using a compact low-cost deuterium-tritium (DT) neutron generator to analyze neutron resonances in the 1-50-eV range. The neutron transmission spectra for five single-element targets-silver, cadmium, tungsten, indium, and depleted uranium-each show uniquely identifiable resonant attenuation dips in measurement times on the order of tens of minutes. Closely spaced resonances of approximately 1-cm-thick multielement targets can be easily differentiated with 1-eV resolution up to neutron energies of 10 eV and 5-eV resolution up to neutron energies of 30 eV. These results demonstrate the viability of compact NRTA measurements for isotopic identification and have the potential to significantly broaden the applicability of the technique across materials science, engineering, and nuclear security.
Abstract. Although the graphics processing unit (GPU) was originally designed to accelerate the image creation for output to display, today's general purpose GPU (GPGPU) computing offers unprecedented performance by offloading computing-intensive portions of the application to the GPGPU, while running the remainder of the code on the central processing unit (CPU). The highly parallel structure of a many core GPGPU can process large blocks of data faster using multithreaded concurrent processing. A game engine has many "components" and multithreading can be used to implement their parallelism. However, effective implementation of multithreading in a multicore processor has challenges, such as data and task parallelism. In this paper, we investigate the impact of using a GPGPU with a CPU to design high-performance game engines. First, we implement a separable convolution filter (heavily used in image processing) with the GPGPU. Then, we implement a multiobject interactive game console in an eight-core workstation using a multithreaded asynchronous model (MAM), a multithreaded synchronous model (MSM), and an MSM with data parallelism (MSMDP). According to the experimental results, speedup of about 61x and 5x is achieved due to GPGPU and MSMDP implementation, respectively. Therefore, GPGPU-assisted parallel computing has the potential to improve multithreaded game engine performance.
Smuggling of special nuclear materials and nuclear devices through borders and ports of entry constitutes a major risk to global security. Technologies are needed to reliably screen the flow of commerce for the presence of high-Z materials such as uranium and plutonium. Here, we present an experimental proof-of-concept of a technique that uses inelastic (p, p 0 ) nuclear reactions to generate monoenergetic photons, which provide means to measure the areal density and the effective-Z (Z eff ) of an object with an accuracy surpassing that achieved by current methods. We use an ION-12 SC superconducting 12 MeV proton cyclotron to produce 4.4, 6.1, 6.9, and 7.1 MeV photons from a variety of nuclear reactions. Using these photons in a transmission mode, we show that we are able to accurately reconstruct the areal densities and Z eff of a test object. This methodology could enable mobile applications to screen commercial cargoes with high material specificity, providing a means of distinguishing common cargo materials from high-Z materials that include uranium and plutonium.
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