Standoff LIBS measurements of energetic materials using a 266nm excitation laser

Waterbury, Robert D.; Pal, Avishekh; Killinger, Dennis K.; Rose, Jeremy; Dottery, Edwin L.; Ontai, G. P.

doi:10.1117/12.778668

Cited by 11 publications

(5 citation statements)

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“…In these experiments temperature increases on the order of a few hundred Kelvin were observed over 100 s, far exceeding the time scales achievable with MD simulations. Spectroscopy techniques that measure laser-induced decomposition products use much higher pulse energies, , which can reach into the megawatt power range. These powers, if confined to a volume of 20 μm 3 would approximately match the lowest power density used in this study.…”

Section: Simulation Detailsmentioning

confidence: 99%

Coupled Thermal and Electromagnetic Induced Decomposition in the Molecular Explosive αHMX; A Reactive Molecular Dynamics Study

2014

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We use molecular dynamics simulations with the reactive potential ReaxFF to investigate the initial reactions and subsequent decomposition in the high-energy-density material α-HMX excited thermally and via electric fields at various frequencies. We focus on the role of insult type and strength on the energy increase for initial decomposition and onset of exothermic chemistry. We find both of these energies increase with the increasing rate of energy input and plateau as the processes become athermal for high loading rates. We also find that the energy increase required for exothermic reactions and, to a lesser extent, that for initial chemical reactions depend on the insult type. Decomposition can be induced with relatively weak insults if the appropriate modes are targeted but increasing anharmonicities during heating lead to fast energy transfer and equilibration between modes that limit the effect of loading type.

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Section: Simulation Detailsmentioning

confidence: 99%

Coupled Thermal and Electromagnetic Induced Decomposition in the Molecular Explosive αHMX; A Reactive Molecular Dynamics Study

2014

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“…Examples of advantages of multipulse excitation include an increase of the plasma volume or plasma reheating by the second pulse, in turn, enhancement of detection limits for LIBS 10-to 100-fold and/or a decrease in relative standard deviation when comparing single-with double-pulse bursts [3]. Following short-pulse UV-excitation a CO 2 laser may be used to enhance detection from a distance of atomic and molecular species [4][5][6]. Some applications are also designed with eye-safety in mind, required for remote and/or field-safe LIBS systems [7,8].…”

Section: Introductionmentioning

confidence: 99%

Time-Resolved Spectroscopy Diagnostic of Laser-Induced Optical Breakdown

Parigger

Hornkohl

Nemes

2010

International Journal of Spectroscopy

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Transient laser plasma is generated in laser-induced optical breakdown (LIOB). Here we report experiments conducted with 10.6-micron CO2 laser radiation, and with 1.064-micron fundamental, 0.532-micron frequency-doubled, 0.355-micron frequency-tripled Nd:YAG laser radiation. Characterization of laser induced plasma utilizes laser-induced breakdown spectroscopy (LIBS) techniques. Atomic hydrogen Balmer series emissions show electron number density of 1017 cm−3 measured approximately 10 μs and 1 μs after optical breakdown for CO2 and Nd:YAG laser radiation, respectively. Recorded molecular recombination emission spectra of CN and C2 Swan bands indicate an equilibrium temperature in excess of 7000 Kelvin, inferred for these diatomic molecules. Reported are also graphite ablation experiments where we use unfocused laser radiation that is favorable for observation of neutral C3 emission due to reduced C3 cation formation. Our analysis is based on computation of diatomic molecular spectra that includes accurate determination of rotational line strengths, or Hönl-London factors.

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“…Thus, Waterbury et al (60) used an 80-mJ laser, emitting at 266 nm for ionization, to minimize damage to the eye. (Still, eye damage can occur even in this case when the eye is accidentally and directly hit by the laser beam.)…”

Section: Laser-induced Breakdown Spectroscopymentioning

confidence: 99%

“…Thus, a CO 2 laser is additionally used, which hits the target about 0.5 μs after the 266-nm pulse. An increase of the LIBS signal by a factor of 100-300 is the additional benefit of this technique (Townsend-effect plasma spectroscopy (61) ) which extends the useful investigation range to 40 m. (60,62) Recently, femtosecond (750 fs) fiber-laser-induced LIBS has been applied to detect explosive materials involving higher scanning speeds (40 mm s −1 ), pulse energies of 3 μJ, repetition rates of 225 kHz, and a wavelength of 1030 or 800 nm (Ti:sapphire). (48,63 -65) As usual, elemental constituents included C, H, N, and O; in addition, molar emissions from CN and C 2 are observed.…”

Section: Laser-induced Breakdown Spectroscopymentioning

confidence: 99%

Laser‐ and Optical‐Based Techniques for the Detection of ExplosivesUpdate based on the original article by David L. Monts, Jagdish P. Singh and Gary M. Boudreaux,Encyclopedia of Analytical Chemistry, © 2000, John Wiley & Sons, Ltd

Hummel

Dubroca

2013

Encyclopedia of Analytical Chemistry

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A wide variety of optical‐ and laser‐based techniques have been and are currently being investigated as means of identifying and characterizing explosive materials. These efforts are hampered by the very low volatility of explosive compounds at room temperature and their tendency to ignite at higher temperatures where their vapor pressures are beginning to reach a regime where the species can be readily detected. Traditional, condensed‐phase absorption spectroscopy (both infrared (IR) and ultraviolet/ visible (UV/VIS)) requires larger samples than are frequently available and, although useful as confirmatory techniques, do not provide signatures that enable unique identification of species. The choice of nontraditional techniques for analysis of explosive materials is dependent upon the amount of sample available, the sample matrix, and sample‐imposed constraints upon the measurement. Raman spectroscopy can identify and quantify condensed phase explosive materials, but the detection limit depends upon substrate, excitation wavelength, and illumination area: limits of detection (LODs) vary from 0.05 ng for 2,4,6‐trinitrotoluene (TNT) on glass to 10 µg for nitroglycerin (NG) on silica gel. The other detection techniques considered require volatilization of either the explosive compound itself or more often of characteristic decomposition products, such as NO, NO 2 , or N 2 O. Using IR irradiation, researchers have demonstrated that photoacoustic spectroscopy (PAS) has detection limits ranging from 0.55 ppb (parts per billion) for vapor‐phase NG with 9 mm excitation to 220 ppm (parts per million) for vaporphase 2,4‐dinitrotoluene (DNT) with 6‐µm excitation. IR laser differential absorption detection of dissociation products NO, NO 2 , and/or N 2 O can achieve detection limits of a few picograms. Laser‐induced fluorescence (LIF) detection of the photofragments (typically NO) of explosive compounds yields detection limits in the tens to hundreds of ppb (by weight) range. Low LODs can be achieved using ion detection techniques: resonance‐enhanced multiphoton ionization (REMPI) spectrometry is capable of LODs for detecting vapor‐phase explosives compounds in the hundredths to tens of ppb range; ion mobility spectrometry (IMS) has vapor‐phase detection limits for common explosive compounds of typically 200 pg, but for some species can be significantly lower: for example, 1 pg for TNT.

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Standoff LIBS measurements of energetic materials using a 266nm excitation laser

Cited by 11 publications

References 0 publications

Coupled Thermal and Electromagnetic Induced Decomposition in the Molecular Explosive αHMX; A Reactive Molecular Dynamics Study

Coupled Thermal and Electromagnetic Induced Decomposition in the Molecular Explosive αHMX; A Reactive Molecular Dynamics Study

Time-Resolved Spectroscopy Diagnostic of Laser-Induced Optical Breakdown

Laser‐ and Optical‐Based Techniques for the Detection of ExplosivesUpdate based on the original article by David L. Monts, Jagdish P. Singh and Gary M. Boudreaux,Encyclopedia of Analytical Chemistry, © 2000, John Wiley & Sons, Ltd

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