Year
2010
Abstract
Prototype instruments for standoff detection and identification of CBRNE threat materials are being developed based on laser-induced breakdown spectroscopy (LIBS). Supported by extensive lab experimentation, both man-portable (MP) and vehicle-portable (VP) prototypes have demonstrated detection of trace levels of uranium (U), explosives, and other materials at ranges between 0.4 and 40 meters. The shorter-range man-portable instrument has demonstrated the detection of U under operational conditions at the DOE Y-12 Complex foundry. These field instruments are being developed under DTRA/NTD sponsorship to satisfy identified user requirements. The detection of uranium and other SNM in the field is the primary goal of this effort. This paper will describe results of detailed laboratory studies of U and Th detection using LIBS, as well as work on other actinides. This work assisted the development of LIBS instruments for standoff detection of radiological and nuclear materials in bulk form and as surface contaminants. Studies included (1) monitoring U spectra at various pressures and in an argon atmosphere, (2) determining detection limits for U in different matrices, and (3) cataloging uranium emission lines in the 260-800 nm region. Detection limits for uranium in soil were 0.26%w/w (close range) and 0.5%w/w (30-m). Surface detection limits were substrate dependent and ranged from 13 to 150 µg/cm 2 . Double-pulse LIBS interrogation enhanced uranium signals up to a factor of 30 in some cases. This paper will also describe the VP and MP instruments. The VP instrument (~200 lbs; 3x5x2 feet) was built using commercial components including a 330- mJ/pulse Nd:YAG laser and a 12-inch telescope. Beam-scanning in an automated mode was implemented and trace levels of U and other elements were detected at 40 m. Automated reporting of detection results occurred within two seconds of interrogation. Several MP prototypes have been designed, fabricated, tested, and demonstrated. These units are based on compact Nd:YAG lasers and spectrometers and operate at standoff ranges of 0.4-0.8 m. A recent version has a backpack weight of 23 lbs and a handheld probe weight of 11 lbs. User-friendly reports are issued within 2 seconds of interrogation.