DETECTION OF NUCLEAR-RELATED CHEMICALS AND OTHER THREAT MATERIALS USING LIBS

Prototype instruments for standoff detection and identification of CBRNE threat materials are being developed based on laser-induced breakdown spectroscopy (LIBS). Both man-portable (MP) and vehicle-portable (VP) instruments are required by the user. The MP instrument provides close analysis of 0.5 m whereas the VP instrument can access targets out to 40 m. While standoff detection of uranium and other SNM in the field is the primary goal of this effort, detection and identification of nuclear-related materials and explosives is also needed in field operations. These field instruments are being developed under DTRA/NTD sponsorship to satisfy identified user requirements. This paper will describe results of detailed laboratory studies supporting the development of field instruments for a variety of chemical compounds. Substances of interest include U compounds, tributyl phosphate (TBP), explosive compounds, various plastic materials, and amino acids and pollens as confusants. In contrast to the conventional use of the analytic LIBS technique for elemental detection, the ability to identify more complex compounds represents a special challenge for LIBS. Early results on explosives were obtained using chemometric algorithms developed by our partner, A3 Technologies. Reasonable fidelity was obtained when this algorithm was integrated in the control and data analysis system of the MP instrument. More recent investigations have used ARA-developed algorithms for identification of explosive and plastic materials. Very good discrimination among these organic materials and others has been achieved.