LIBS System

This paper explores the trade-offs of gem damage during LIBS analysis and data quality under a variety of analytical conditions. Two lasers, a Big Sky Laser Technology (now Quantel USA) Nd-YAG nano-second laser operated at its fundamental wavelength of 1064 nm, and a Raydiance, Inc., pico-second laser operated at its fundamental wavelength of 1552 nm as well as harmonics at 776, 517.2, and 388 nm, are used in separate LIBS systems. Furthermore, the use of inert gas environment (He or Ar) is explored to increase peak intensities at lower laser power and sample damage. 

The pico-second laser causes significantly less damage to the stone than the nanosecond laser however, fewer trace element peaks may be observed in the pico-second LIBS spectra (Fig. 1). The sensitivity of the pico-second LIBS system to trace elements may be enhanced in Ar or He, with a better lens system than currently employed, or by using the harmonic wavelengths. These parameters are under investigation. 

This paper presents an overview of the current research issues and commercialization efforts related to laser ablation for chemical analysis, discusses several fundamental studies of laser ablation using time-resolved shadowgraph and spectroscopic imaging, and describes recent data using nanosecond laser pulsed ablation sampling for ICP-MS and LIBS. Efforts towards commercialization of field based LIBS systems also will be described. 

Fig. 9. Single-shot laser-induced breakdown spectroscopy (LIBS) spectra collected with man-portable LIBS system of (a) RDX residue on aluminum under argon, (b) RDX on aluminum in ambient atmosphere, and (c) plain aluminum in ambient atmosphere. Carbon (C), Hydrogen (H), Nitrogen (N), and Oxygen (O) are shown...

Fig. 10. Laser-induced breakdown spectroscopy (LIBS) spectrum of RDX collected at 20m with ARL standoff LIBS system. The elements present due to RDX are labeled.

Here F is the Faraday constant and z the ion transported charge in the electrolyte. In the LIB system, Li+ is the ionic conductor, which means that z=l for the LIB... 

Understanding how nanoenergetic materials are both made and consumed requires the ability to monitor these processes widi real time in-situ diagnostic techniques. Laser Induced Breakdown Spectroscopy (LIBS) is an optical technique that can detect all the elements simultaneously from very small sanq>les of material. Only four elements are needed to implement this technique an excitation source, delivery and collecting optics, a detector with wavelength dispersion capability, and a conqtuter for control and anal is. Because of these relatively sinq>le requirements, a conq>lete LIBS system can be made contact, rugged, and fairly ine q>ensively. Spectrometers are now becoming commercially... 

Because the dielectric constant (relative permittivity) of TFP is lower than that of EC (e, 11 for TFP, 90 for EC), the ionic conductivity of LiPFg solution decreases when adding TFP to mixed EC h-EMC solvent in the wide temperature range [115]. Also the higher concentration of TFP tends to deaease the rechargeability of the graphite-based negative electrode. Thus, about 40 % of the TFP component in the electrolyte satisfies both the nonflammability and the reversibility of the electrode in the LIB system. 

A schematic of a modem LIBS system is shown in Figure 7.51. The components required are a high-peak-power Q-switched laser, optics to focus the laser onto the sample surface, laser pulse... 

Spectrometer designs are similar to those already discussed, including broadband diode array, echelle, Czerny-Turner, and Paschen-Runge spectrometers, with miniature echelle and CCD array systems most suited to portable LIBS systems. The LIBSCAN 25+ (Applied Photonics Ltd.) uses up to 6 compact CCD array spectrometers covering the 185-900 nm range. Figure 7.53 shows the field-portable LIBSCAN 25-I-. 

Remote (standoff) LIBS systems have been built by Applied Photonics Ltd. with a range capability of >100 m for defense departments. They also built a transportable standoff LIBS with a 20 m range to characterize radioactive materials in a hot cell at the Sellafield, UK, high-level nuclear waste vitrification plant by directing the laser beam through the lead-glass window of the cell. LIBS is an excellent tool for remote and in situ detection of uranium oxide fuel located in hard-to-reach... 

Companies that make commercial LIBS systems or custom-made devices include Applied Photonics Ltd. (www.appliedphotonics.co.uk) Applied Spectra, Inc. (www.appliedspectra.com) Bertin Technologies (www.bertin.fr) Energy Research Co. (www.er-co.com) IVEA (www. ivea-solution.com/libs/) LTB Lasertechnik Berlin (www.ltb-berlin.de) Marwan (www.marwan-technology.com) Ocean Optics, Inc. (www.oceanoptics.com) TSI, Inc. (www.tsi.com). Photon Machines, Inc. (www.photon-machines.com) and StellarNet (www.stellamet-inc.com). Applications notes, videos, and technical information on LIBS are available on most of these companies websites. 

Soon after commercialization, the Li-ion battery (LIB) system became a popular choice because of its high-energy density, good performance, and no memory effect as occurred with nickel-cadmium (Ni-Cd) or nickel-metal hydride (Ni-MH) batteries. LIBs have been primarily used for portable electronics, especially cellular phones and notebook computers. Recently, the application area has been extended to power tools, electric bikes, and energy storage systems. Several companies are now working toward adapting the lithium-ion system for use in electric drive vehicle (EDV) applications. 

LIBS system provided the elemental composition measurement with accuracy within 15% and it was tested olf-line at a power plant on three dilferent coals. Field results indicated a satisfactory average relative error when compared to an ASTM standardised protocol and good precision figures. 

It is not trivial to define or select substructures that should be considered for this purpose. For the STIRS system, considerable effort has gone into the search for substructures that can be successfully classified by the implemented spectral similarity search. The Mass-Lib system uses a predefined set of 180 binary molecular descriptors to characterize the similarity of structures. In most investigations a more or less arbitrary set of substructures, functional groups or more general structural properties (compound classes) has been considered. Self-adapting methods that automatically analyse the molecular structures in the hitlist (for instance by searching for frequent and large substructures) have not been used up to now in MS. 

Garcia etal. [41] developed a two-dimensional porous electrode model and accounted for potential and charge distributions in the electrolyte. They employed transport equations derived from dilute solution theory, which is generally not adequate for LIB systems. The stress generation effect is built into the 2D DNS modeling framework with a simplified, sphere-packed electrode microstmcture description. 

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