Melinda has a Ph.D. in physics from the University of California at Davis, specializing in experimental particle physics. As a graduate student she participated in dark matter searches using a xenon time projection chamber and air Cherenkov telescope. She also participated in the development of neutron and antineutrino detection in water Cherenkov detectors. Since joining Sandia in 2013, she has completed further work on antineutrino detector R&D for nuclear reactor monitoring, and participated in a variety of neutron imaging projects.
- Adaptive masks for time-encoded imaging systems: SNL recently completed a 1 year feasibility project exploring the ability to create time-varying coded apertures in hydrogenous media to image fission energy neutron sources. Time-encoded imaging is analogous to coded-aperture imaging: rather than the mask pattern modulating in space, it is modulated in time. While 1D imaging was demonstrated in the lab, plenty of research and development remains, and the benefits of creating a mask pattern on the fly has not been fully explored. For instance, the open fraction and mask pattern can be adapted to optimize the signal to noise of a particular source distribution as it is discovered. The scope of this project is to develop a 2D system, characterize its performance in the lab, and use predictive modeling to fully explore the benefits of an adaptable mask. Alternatively, a short-term project could improve upon the 1D design and use predictive modeling to characterize its expected performance.
- Material Identification through Resonant Attenuation: We have just completed a project proving the feasibility of an explosive detection and imaging system based on the measurement of the energy-dependent attenuation of neutrons in the 1-10 MeV range that have been down-scattered by scintillation detectors from a D-T neutron source. This attenuation “fingerprint” is sensitive to the number densities of many low-Z elements. Based on the relative ratios of Hydrogen, Carbon, Nitrogen, Oxygen, and others, an inspected item can be categorized as contraband, explosives, or benign. The scope of this project is both to advance the development of this technology and to explore signatures relevant to arms control. Specifically, the presence of conventional high explosives is an attribute of warheads that has not been given much attention. There are a large range of remaining computational and technical challenges associated with this system.