| Laser-induced breakdown spectroscopy (LIBS), which uses focusing a powerful pulsed laser beam onto a sample to create a plasma, by spectrally analyzing the optical emission from the plasma, the element composition and content of the sample could be deduced. The significant attributes of LIBS technique are:ability to detect all elements, simultaneous multi-element detection capability, no need to vacuum, little or no sample preparation, non-destructive to the sample, real-time analysis, in situ diagnosis and remote detection. Therefore, since it was appeared, LIBS technique has been drew widespread attention, and it is developing to one of a valuable spectral analysis technique. Now, successful applications of LIBS has been found in many areas, such as chemical and biological hazards analysis, geological survey, artwork detection and space exploration.However, the poor limit of detection, low precision of analysis, lead to the low detection sensitivity of LIBS, has become the bottleneck of its further development, how to improve the LIBS detection sensitivity, which has become an important research subject in future. The main study of this thesis is using new-style space confinement, magnetic field and space confinement combination, dual-pulse excitation, and dual-pulse excitation and space confinement combination to further improve the optics emission intensity and accuracy of analysis from laser-induced plasma. After lot of research work, the following achievements and points of innovation:(1) The spatial confinement effects using a new-style of aluminium hemispherical cavity in single LIBS analysis were investigated for the first time, for the purpose of realization of three-dimensional uniform compression to the laser-induced plasmas. This hemispherical cavity not only can be used to enhance the atom spectra from high composition elements in the sample, but also used to enhance the low concentration elements. The best enhancement factor for the emission intensities from laser-induced plasmas by using the two-dimensional cylindrical confinement was about9, while a significant enhancement factor of about12was achieved when using three-dimensional hemispherical cavity.(2) The spectral enhancement scheme by combination magnetic field and spatial confinements in LIBS was investigated for the first time, both a magnetic mirror and a hemispherical cavity were designed and made as a magnetic and spatial confinement. The experimental results show that this double confinement can be used simultaneously to magnetically and spatially confine plasmas, and the maximum enhancement factor about24was obtained.(3) The enhancement effects of optical emission and scattering from laser-induced plasma using double-pulse excitation with different interpulse delay time were investigated, the point of the suspended particles on crater was condensed by the plasmas which excited by the first laser pulse was bring forward. By reheating the aluminium particles which formed by the A1plasmas, not only improve the resolution of Al atomic spectra, but also the self-absorption effect of Al amtomic spectra was disappeared.(4) The enhancement scheme of optical emission in Dual-pulse (DP-LIBS) LIBS with spatial confinement was bring forward for the first time, and a pair of plate walls were successfully used to spatially confine the plasmas produced in DP-LIBS, by the optimization of the distance between two Al walls and the interpulse delay time, the maximum enhancement factor about168.6was obtained.The OES of the plasma have been significantly enhanced with the aluminum hemispherical cavity, the magnetic-spatial confinement or the DP-LIBS with spatial confinement. These confinement are easy design, making and with low cost, so they Have a very broad space for development and application prospects. The results of this study provide a series of new pathways in improving the sensitivity of LIBS.
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