Kevin L. Linker

Integrated explosive preconcentrator and electrochemical detection system for 2,4,6-trinitrotoluene (TNT) vapor

This article reports on an integrated explosive-preconcentration/electrochemical detection system for 2,4,6-trinitrotoluene (TNT) vapor. The challenges involved in such system integration are discussed. A hydrogel-coated screen-printed electrode is used for the detection of the thermally desorbed TNT from a preconcentration device using rapid square wave voltammetry. Optimization of the preconcentration system for desorption of TNT and subsequent electrochemical detection was conducted yielding a desorption temperature of 120 degrees C under a flow rate of 500 mL min(-1). Such conditions resulted in a characteristic electrochemical signal for TNT representing the multi-step reduction process. Quantitative measurements produced a linear signal dependence on TNT quantity exposed to the preconcentrator from 0.25 to 10 microg. Finally, the integrated device was successfully demonstrated using a sample of solid TNT located upstream of the preconcentrator.

Trace detection and discrimination of explosives using electrochemical potentiometric gas sensors

In this article, selective and sensitive detection of trace amounts of pentaerythritol tetranitrate (PETN), 2,4,6-trinitrotoluene (TNT) and cyclotrimethylenetrinitramine (RDX) is demonstrated. The screening system is based on a sampling/concentrator front end and electrochemical potentiometric gas sensors as the detector. Preferential hydrocarbon and nitrogen oxide(s) mixed potential sensors based on lanthanum strontium chromite and Pt electrodes with yttria stabilized zirconia (YSZ) solid electrolyte were used to capture the signature of the explosives. Quantitative measurements based on hydrocarbon and nitrogen oxide sensor responses indicated that the detector sensitivity scaled proportionally with the mass of the explosives (1-3 μg). Moreover, the results showed that PETN, TNT, and RDX samples could be discriminated from each other by calculating the ratio of nitrogen oxides to hydrocarbon integrated area under the peak. Further, the use of front-end technology to collect and concentrate the high explosive (HE) vapors make intrinsically low vapor pressure of the HE less of an obstacle for detection while ensuring higher sensitivity levels. In addition, the ability to use multiple sensors each tuned to basic chemical structures (e.g., nitro, amino, peroxide, and hydrocarbon groups) in HE materials will permit the construction of low-cost detector systems for screening a wide spectrum of explosives with lower false positives than present-day technologies.

Explosives detection portal for high-volume personnel screening

We discuss a trace explosive detection portal for high-volume personnel screening, which has been developed recently at Sandia National Laboratories (SNL), using funding provided by the Federal Aviation Administration (FAA) and the Department of Energy (DOE) Office of Safeguards and Security (OSS). This portal screens individuals for explosives using noninvasive means to collect explosive residue in the forms of vapor and particulate contamination. The portal combines a commercially available ion mobility spectrometer (IMS) with a preconcentrator developed at SNL to perform detection of explosives. The prototype portal has undergone one series of tests at the Albuquerque International Airport, and we are now proceeding to develop an improved, second-generation portal, and to find a company to market the portal.

Miniaturized explosives preconcentrators for use in man-portable explosives detection systems

This paper describes the function and testing of miniaturized chemical concentrating devices that are designed to enhance the capabilities of portable trace explosive detection systems, such as those based on ion mobility spectrometry (IMS). These preconcentrators are based upon a patented design first developed for use in personnel portals, in which explosive vapor and/or residue is adsorbed onto a high density metal screen, and subsequently desorbed into the detector.

Explosives Detection Personnel Portals

Publisher Summary This chapter provides a brief review about explosive detection personnel portals. The presence of an explosive on a body can be characterized by two individual forms — by bulk and trace. The bulk form is an amount of actual explosives of some macroscopic mass quantity located on the person or on the area. A trace form explosive consists that remains on the person when he or she has been next to an explosive or has some mass of explosive concealed on his or her person. The main detection group is locating the ultimate bulk explosive by methods, such as a physical search or X-ray backscatter, millimeter-wave, and low-power microwave. The subsequent exposure category offers notification that outlines explosive remains existing on the person. This information can be offered to personnel; one can question the person and execute a corporeal hunt to conclude the position of the real explosive. Some detection technique such as a physical search presents an elevated possibility of recognizing the existence of an explosive, but suffers from being invasive and time-consuming.

Development of a trace explosives detection portal for personnel screening

We discuss the development, design and operation of a walk-through trace detection portal designed to screen personnel for explosives. Developed at Sandia National Laboratories (SNL) with primary funding from the Federal Aviation Administration (FAA) and additional support from the Department of Energy Office of Safeguards and Security, this portal is intended primarily for use in airport terminals and in other localities where a very high throughput of pedestrian traffic is combined with stringent security requirements. The portal is capable of detecting both vapor and particulate contamination, with the collection of explosive material being based upon the entrainment of that material in air flows over the body of the person being screened. This portal is capable of detecting high explosives of interest to the FAA. We discuss the results of field testing of the portal in the Albuquerque International Airport in September, 1997 and more recent steps towards commercialization of the portal.

Microfabricated Chip for Calibration of Field Instruments

Accurate, periodic calibration is required to operate IMS, GC, and portal security systems with maximum efficiency, surety, and operator confidence. To this end, we are presently developing a microfabricated device for on-demand calibration of fieldable contraband detection instruments. Using robotically-assisted picoliter dispensing methods, precise nanogram or larger amounts of calibration compound(s) are placed on micron-sized bridge structures. Resistively heating these structures delivers precisely quantified low-levels of calibration compounds to the detector systems. This provides reliable calibration for identification and quantification of explosives, narcotics, and other contraband.

Transportable, modular, high security vault utilizing pin connections

A rapid deployment access delay system (RAPADS) has been designed to provide high security protection of valued assets. The author presents the RAPADS concept, design, fabrication, and construction. The system or vault is transportable, is modular, and utilizes a pin connection design. Individual panels are attached together to construct the vault. The pin connection allows for quick assembly and disassembly, and makes it possible to construct vaults of various sizes to meet a specific application. Because of the unique pin connection and overlapping joint arrangement, a sequence of assembly steps is required to assemble the vault. As a result, once the door is closed and locked, all pin connections are concealed and inaccessible. This provides a high level of protection in that no one panel or connection is vulnerable.<<ETX>>