For the first time to the best of our knowledge, a simultaneous 10.6 mum CO(2) laser pulse has been used to enhance the Laser Induced Breakdown Spectroscopy (LIBS) emission from a 1.064 mum Nd:YAG laser induced plasma on a hard target. The enhancement factor was on the order of 25 to 300 times, depending upon the emission lines observed. For an alumina ceramic substrate the Al emission lines at 308 nm and Fe impurity line at 278 nm showed an increase of 60x and 119x, respectively. The output energy of the Nd:YAG laser was 50 mJ/pulse focused to a 1 mm diameter spot to produce breakdown. The CO(2) laser pulse had a similar energy density of 40 mJ/mm(2). Timing overlap of the two laser pulses within 1 microsecond was important for enhancement to be observed. An observed feature was the differential enhancement between different elemental species and also between different ionization states, which may be helpful in the application of LIBS for multi-element analysis.
A deep UV 266 nm laser induced LIBS plasma has been enhanced by using a simultaneous 10.6 microm CO(2) laser pulse at standoff ranges up to 55 m for several targets including metals, ceramics and plastics. The LIBS plasma emission was produced, for the first time, by a 266 nm laser and was enhanced by several orders of magnitude using the CO(2) laser pulse. The temperature of the enhanced LIBS plasma was measured, for the first time, and was observed to increase by about 3000K due to the addition of the CO(2) laser pulse.
A fully integrated UV Townsend Effect Plasma Spectroscopy (TEPS)-Raman Explosive Detection System (TREDS-2) system has been constructed for use of standoff detection. A single 266nm Q-Switched Nd:YAG laser was used for Raman excitation and TEPS plasma ignition. A nearly simultaneous 10.6μm CO 2 laser was employed for the signal enhancement in the TEPS measurements. TEPS and Raman spectra have been measured for a wide variety of energetic samples on several different substrates. Chemometric techniques are presented for analysis and differentiation between benign and energetic samples. Since these techniques are orthogonal, data fusion algorithms can be applied to enhance the results. The results of the TEPS and Raman techniques along with their algorithms are discussed and presented.
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