Publications

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Sandia National Labs (SNL)-designed, portable chemical warfare agent (CWA) detection systems consist of three-stages: collection, separation, and detection. We use microfabrication technologies to miniaturize these stages and to reduce the overall size, weight, power, and (potentially) cost of the final system. Our newest system consists of a multi-dimensional separation stage and an miniature ion mobility spectrometer (IMS) detector for unprecedented system sensitivity, selectivity, and depth of target list.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Stress corrosion cracks (SCC) represent a major concern for the structural integrity of engineered metal structures. In hazardous or restricted-access environments, remote detection of corrosion or SCC frequently relies on visual methods; however, with standard VT-1 visual inspection techniques, probabilities of SCC detection are low. Here, we develop and evaluate an improved optical sensor for SCC in restricted access-environments by combining a robotically controlled camera/fiber-optic based probe with software-based super-resolution imaging (SRI) techniques to increase image quality and detection of SCC. SRI techniques combine multiple images taken at different viewing angles, locations, or rotations, to produce a single higher- resolution composite image. We have created and tested an imaging system and algorithms for combining optimized, controlled camera movements and super- resolution imaging, improving SCC detection probabilities, and potentially revolutionizing techniques for remote visual inspections of any type.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Neutron sensing is critical in civilian and military applications. Conventional neutron sensors are limited by size, weight, cost, portability and helium supply. Here the microfabrication of gadolinium (Gd) conversion material-based heterojunction diodes for detecting thermal neutrons using electrical signals produced by internal conversion electrons (ICEs) is described. Films with negligible stress were produced at the tensile-compressive crossover point, enabling Gd coatings of any desired thickness by controlling the radiofrequency sputtering power and using the zero-point near p(Ar) of 50 mTorr at 100 W. Post-deposition Gd oxidation-induced spallation was eliminated by growing a residual stress-free 50 nm neodymium-doped aluminum cap layer atop Gd. The resultant coatings were stable for at least 6 years, demonstrating excellent stability and product shelf-life. Depositing Gd directly on the diode surface eliminated the air gap, leading to a 200-fold increase in electron capture efficiency and facilitating monolithic microfabrication. The conversion electron spectrum was dominated by ICEs with energies of 72, 132 and 174 keV. Results are reported for neutron reflection and moderation by polyethylene for enhanced sensitivity, and γ- and X-ray elimination for improved specificity. The optimal Gd thickness was 10.4 μm for a 300 μm-thick partially depleted diode of 300 mm 2 active surface area. Fast detection (within 10 min) at a neutron source-to-diode distance of 11.7 cm was achieved with this configuration. All ICE energies along with γ-ray and K α,β X-rays were modeled to emphasize correlations between experiment and theory. Semi-conductor thermal neutron detectors offer advantages for field-sensing of radioactive neutron sources.

We have developed and characterized novel in-situ corrosion sensors to monitor and quantify the corrosive potential and history of localized environments. Embedded corrosion sensors can provide information to aid health assessments of internal electrical components including connectors, microelectronics, wires, and other susceptible parts. When combined with other data (e.g. temperature and humidity), theory, and computational simulation, the reliability of monitored systems can be predicted with higher fidelity.

Abstract not provided.

High-reliability components for high-consequence systems require detailed testing of operation after having undergone highly accelerated stress testing (HAST) under unusual conditions of high-temperature and humidity. This paper describes the design and operation of a system called "Wormwood" that is a highly multiplexed temperature measurement system that is designed to operate under HAST conditions to allow measurement of the temperature as a function of time and position in a HAST chamber. HAST chambers have single-point temperature measurements that can be traceable to NIST standards. The objective of these "Wormwood" measurements is to verify the uniformity and stability of the remaining volume of the HAST chamber with respect to the single traceable standard.

Neutron sensing is critical in civilian, military, industrial, biological, medical, basic research, and environmental applications. Conventional neutron sensors are limited by size, weight, cost, portability, and helium supply. Here the microfabrication of Gd conversion material-based heterojunction diodes is described for detecting thermal neutrons using electrical signals produced by internal conversion electrons (ICE). Films with negligible stress were produced at the tensile-compressive crossover point, enabling Gd coatings of any desired thickness by controlling the radiofrequency sputtering power and using the zero-point near p(Ar) of 50 mTorr at 100 W. Post-deposition Gd oxidation-induced spallation was eliminated by growing a residual stress-free 50 nm neodymium-doped aluminum cap layer atop Gd. Resultant coatings were stable for at least six years demonstrating excellent product shelf life. Depositing Gd on the diode surface eliminated air gap, leading to improved efficiency and facilitating monolithic microfabrication. The conversion electron spectrum was dominated by ICE with energies of 72, 132, and 174 keV. Results are reported on neutron reflection and moderation by polyethylene for enhanced sensitivity and γ- and X-ray elimination for improved specificity. Optimal Gd thickness was 10.4 μm with 300 μm thick partially depleted diode of 300 mm2 active surface area. Fast detection within 10 minutes at a neutron source-to-diode distance of 11.7 cm was achieved using this configuration. All ICE energies along with γ-ray and Kα X-ray were modeled to emphasize correlations between experiment and theory and to calculate efficiencies. Semiconductor thermal neutron detectors offer advantages for field-sensing of radioactive neutron sources.