Publications

This slide presentation outlines information on a technology acquisition strategy for the security of water distribution networks. The Department of Homeland Security (DHS) has tasked a multi-laboratory team to evaluate current and future needs to protect the nation's water distribution infrastructure by supporting an objective evaluation of current and new technologies. The primary deliverables from this Operational Technology Demonstration (OTD) are the following: establishment of an advisory board for review and approval of testing protocols, technology acquisition processes and recommendations for technology test and evaluation in laboratory and field settings; development of a technology acquisition process; creation of laboratory and field testing and evaluation capability; and, testing of candidate technologies for insertion into a water early warning system. The initial phase of this study involves the development of two separate but complementary strategies to be reviewed by the advisory board: a technology acquisition strategy; and, a technology evaluation strategy. Lawrence Livermore National Laboratory and Sandia National Laboratories are tasked with the first strategy, while Los Alamos, Pacific Northwest, and Oak Ridge National Laboratories are tasked with the second strategy. The first goal of the acquisition strategy is the development of a technology survey process that includes a review of current test programs and development of a method to solicit and select existing and emerging sensor technologies for evaluation and testing. The second goal is to implement the acquisition strategy to provide a set of recommendations for candidate technologies for laboratory and field testing.

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This work describes the design, simulation, fabrication and characterization of a microfabricated thermal conductivity detector to be used as an extension of the {micro}ChemLab{trademark}. The device geometry was optimized by simulating the heat transfer in the device, utilizing a boundary element algorithm. In particular it is shown that within microfabrication constraints, a micro-TCD optimized for sensitivity can be readily calculated. Two flow patterns were proposed and were subsequently fabricated into nine-promising geometries. The microfabricated detector consists of a slender metal film, supported by a suspended thin dielectric film over a pyramidal or trapezoidal silicon channel. It was demonstrated that the perpendicular flow, where the gas directly impinges on the membrane, creates a device that is 3 times more sensitive than the parallel flow, where the gas passed over the membrane. This resulted in validation of the functionality of a microfabricated TCD as a trace-level detector, utilizing low power. the detector shows a consistent linear response to concentration and they are easily able to detect 100-ppm levels of CO in He. Comparison of noise levels for this analysis indicates that sub part per million (ppm) levels are achievable with the selection of the right set of conditions for the detector to operate under. This detector was originally proposed as part of a high-speed detection system for the petrochemical gas industry. This system was to be utilized as a process monitor to detect reactor ''upset'' conditions before a run away condition could occur (faster than current full-scale monitoring systems were able to achieve). Further outlining of requirements indicated that the detection levels likely achievable with a TCD detector would not be sufficient to meet the process condition needs. Therefore the designed and fabricated detector was integrated into a detection system to showcase some technologies that could further the development of components for the current gas phase {micro}ChemLab as well as future modifications for process monitoring work such as: pressurized connections, gas sampling procedures, and packed columns. Component integration of a microfabricated planar pre-concentrator, gas-chromatograph column and TCD in the separation/detection of hydrocarbons, such as benzene, toluene and xylene (BTX) was also demonstrated with this system.