Figure 2 shows photographs of several ARL LIBS systems: (a) a laboratory LIBS setup, (b) a commercial LIBS system by Ocean Optics, Inc., (c) a prototype man-portable LIBS device, and (d) a prototype standoff LIBS system developed for 100+ m detection and discrimination of explosive residues. ARL has used LIBS for the detection of Halon alternative agents (19,20), tested a field-portable LIBS system for the detection of lead in soil and paint (10), studied the spectral emission of aluminum and aluminum oxide from bulk aluminum in different bath gases (21), performed kinetic modeling of LIBS plumes (22) (23)(24)(25), and demonstrated the detection and discrimination of geological materials (18,(26)(27)(28)(29)(30)(31), plastic landmines (32,33), explosives (34)(35)(36)(37)(38)(39)(40)(41)(42), and chemical and biological warfare agent surrogates (43)(44)(45)(46)(47). Army Research Laboratory (ARL) in the Weapons and Materials Research Directorate (WMRD) have been developing LIBS for a variety of applications since the early 1990s. Beyond the practical interest of this study for LIBS, it provides also insights to the kinetics of the AlO molecule formation in laserinduced plasma So the thesis also studied the condition for the formation of the molecules in the plasma. While the plasma cools down in air, molecules are formed, AlO for instance. Furthermore, in order to understand the effects of these parameters on the properties of the plasma, the microscopic mechanisms during post ablation and the propagation of the plasma are also studied. Following the thesis of Qianli Ma which has studied the effect of laser wavelength on the behavior of the plasma induced in an ambient gas of argon, the present thesis has used the same diagnostic techniques (time- and space-resolved emission spectroscopy and fast spectroscopic images) together with 1064 nm ns laser pulse ablation of a target of aluminum to investigate the effects of other parameters, such as the fluence and the duration of laser pulse, the effect of different ambient gases (argon and air), on the morphology and internal structure of the plasma. Evolutions of the morphology and the internal structure of the ablation plasma are considered as the consequence of its hydrodynamic expansion into the ambient gas. The determination of the morphology as well as the internal structure of the plasma together with their evolution during plasma expansion into the ambient gas is therefore crucial for the optimization of the use of ablation plasma as a spectroscopic emission source. Although time-resolved and gated detection can greatly improve the performance of the LIBS technique especially that of calibration-free LIBS (CF-LIBS) with a better determination of plasma temperature, the temporal evolution of the plasma is correlated to its morphology and its spatial inhomogeneity. However, the laser-induced plasma exhibits a transient behavior. LIBS uses the ablation plasma as a light source that contains the elemental composition information of the sample. Recently, LIBS technique has been well developed and applied in different domains, for example oceanic exploration, pollution monitoring in the environment. Laser-induced breakdown spectroscopy (LIBS) has been invented for more than 50 years, which analyzes the spectrum of the laser-induced plasma to determine the elemental composition of the ablated sample.

M100700 air conditioner