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Swift, Alicia L.

Publications and source records attributed to Swift, Alicia L..

10 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Neutron Imaging at LANSCE—From Cold to Ultrafast

In recent years, neutron radiography and tomography have been applied at different beam lines at Los Alamos Neutron Science Center (LANSCE), covering a very wide neutron energy range. The field of energy-resolved neutron imaging with epi-thermal neutrons, utilizing neutron absorption resonances for contrast as well as quantitative density measurements, was pioneered at the Target 1 (Lujan center), Flight Path 5 beam line and continues to be refined. Applications include: imaging of metallic and ceramic nuclear fuels, fission gas measurements, tomography of fossils and studies of dopants in scintillators. The technique provides the ability to characterize materials opaque to thermal neutrons and to utilize neutron resonance analysis codes to quantify isotopes to within 0.1 atom %. The latter also allows measuring fuel enrichment levels or the pressure of fission gas remotely. More recently, the cold neutron spectrum at the ASTERIX beam line, also located at Target 1, was used to demonstrate phase contrast imaging with pulsed neutrons. This extends the capabilities for imaging of thin and transparent materials at LANSCE. In contrast, high-energy neutron imaging at LANSCE, using unmoderated fast spallation neutrons from Target 4 [Weapons Neutron Research (WNR) facility] has been developed for applications in imaging of dense, thick objects. Using fast (ns), time-of-flight imaging, enables testing and developing imaging at specific, selected MeV neutron energies. The 4FP-60R beam line has been reconfigured with increased shielding and new, larger collimation dedicated to fast neutron imaging. The exploration of ways in which pulsed neutron beams and the time-of-flight method can provide additional benefits is continuing. We will describe the facilities and instruments, present application examples and recent results of all these efforts at LANSCE.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2017

Development and Characterization of a High-Energy Neutron Time-of-Flight Imaging System

We present that Los Alamos National Laboratory has developed a prototype of a high-energy neutron time-of-flight imaging system for the non-destructive evaluation of dense, massive, and/or high atomic number objects. High-energy neutrons provide the penetrating power, and thus the high dynamic range necessary to image internal features and defects of such objects. The addition of the time gating capability allows for scatter rejection when paired with a pulsed monoenergetic beam, or neutron energy selection when paired with a pulsed broad-spectrum neutron source. The Time Gating to Reject Scatter and Select Energy (TiGReSSE) system was tested at the Los Alamos Neutron Science Center’s (LANSCE) Weapons Nuclear Research (WNR) facility, a spallation neutron source, to provide proof of concept measurements and to characterize the instrument response. This paper will show results of several objects imaged during this run cycle. In addition, results from system performance metrics such as the Modulation Transfer Function and the Detective Quantum Efficiency measured as a function of neutron energy, characterize the current system performance and inform the next generation of neutron imaging instrument.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Antigovernment Groups. A Growing Threat to US Security

Domestic terrorism is a growing threat in the United States, particularly from the 998 right-wing antigovernment (AG) groups in existence in 2015. In the years since the September 11, 2001 attacks in New York City, right-wing anti-government acts have oc- curred more often and killed more people in the United States than Muslim extremists. Such AG group members are often in uenced by racist, anti-Semitic, or anti-Islamic views, believe conspiracy theories about the government, and often refuse to pay taxes or participate in frivolous lawsuits in order to intentionally waste the government's time. There is, however, a violent element to these groups which participates in events ranging from the armed take-over of federal land in Oregon, to an armed stand-o with federal agents in Nevada, to the bombing of the Oklahoma City building which killed 168 people. Such acts may be conducted by a few individuals, as is the case of the Oklahoma City bombing, or an entire group. Such groups have a wide range of capabilities, with typical weapons including legal and illegal rearms, with a focus on purchasing fully automatic weapons; hand grenades, with some homemade; deadly tox- ins, like ricin (in multiple cases) and sodium cyanide (in one case); transportation, such as all-terrain vehicles (ATVs); arson, with the intent of destroying federal property; and explosives, often in large numbers and including pipe bombs, truck bombs, IEDs, and other homemade explosives. The growing acceptance of these violent methods by Republican congressmen and governors, however, only increases visibility of such groups and encourages their behavior. Coupled with the removal of the Department of Homeland Security's division responsible for monitoring such groups, the result could prove disastrous for the safety of United States citizens.

98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL P↗
DOE OSTI2015

Neutron Imaging Developments at LANSCE [PowerPoint]

Thermal, epithermal, and high-energy neutrons are available from two spallation sources at the 800-MeV proton accelerator. Improvements in detectors and computing have enabled new capabilities that use the pulsed beam properties at LANSCE; these include amorphous Si (aSi) detectors, intensified charge-coupled device cameras, and micro-channel plates. Applications include water flow in living specimens, inclusions and fission products in uranium oxide, and high-energy neutron imaging using an aSi flat panel with ZnS(Ag) scintillator screen. images of a metal/plastic cylinder from photons, low-energy and high-energy neutrons are compared.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

A Verification of MCNP6 FMESH Tally Capabilities

This work serves to verify the MCNP6 FMESH capability through comparison to two types of data. FMESH tallies, binned in time, were generated on an ideal detector face for neutrons undergoing a single scatter in a graphite target. For verification, FMESH results were compared to analytic calculations of the nonrelativistic TOF for elastic and inelastic single neutron scatters (TOF for the purposes of this paper is the time for a neutron to travel from its scatter location in the graphite target to the detector face). FMESH tally results were also compared to F4 tally results, an MNCP tally that calculates fluence in the same way as the FMESH tally. The FMESH tally results agree well with the analytic results and the F4 tally; hence, it is believed that, for simple geometries, MCNP6 FMESH tallies represent the physics of neutron scattering very well.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

UT-NE Radiation Instrumentation Research Group Meeting: An Update on Progress

The purpose of this project is to design a system to image large and/or thick objects with high dynamic ranges using an intensified, charge coupled device (CCD) camera and a fast-pulsed, high energy neutron source; Improve image resolution by reducing scatter; and Design ultra-fast scintillator using nanotechnology to allow for better timing (and thus better scatter rejection).

07 ISOTOPE AND RADIATION SOURCES↗