Laser Induced Copper Plasma Characteristics With Combined Confinement Of Magnetic And Spatially

Laser-induced breakdown spectroscopy(LIBS)is a very promising analytical technique for the detection of chemical constituents.The LIBS has some advantages of simple,rapid and simultaneous analysis of multi-elements for the element detection of the solid,liquid and gas.However,there are some shortcomings such as strong continuous background,self-absorption phenomenon and low detection sensitivity in the actual detection process.The LIBS spectral enhancement can be achieved by using the combined confinement of magnetic and spatially to improve the detection sensitivity of LIBS.In this thesis,the characteristics of Cu plasma with combined confinement of magnetic and spatially are studied.The expansion processes of Cu plasma with combined confinement of magnetic and spatially are studied by optical shadow graph and fast photography,and the enhancement of Cu plasma spectrum is realized.The experimental results show that the displacement,velocity and pressure of the plasma shock wave are increased with combined confinement of magnetic and spatially.At the early expansion,the plasma pressure is larger than the magnetic pressure,the displacement of the plasma plume is not changed obviously.But at large delay time,the plasma pressure is smaller than the magnetic pressure,the displacement of the plasma plume obviously becomes smaller.The pulse energy and the position of the target have effect on the expansion characteristics of the Cu plasma.The lifetime of the plasma plume induced by high pulse energy laser is longer,and the displacement of the plasma plume increases continuously.With magnetic-spatial combined confinement the Cu I 521.8 nm plasma spectrum shows two peaks structure.Spectral enhancement arises from magnetic confinement at small delay time,while at large delay time it is generated by spatial constraints.Combined with optical shadow graph and fast photography,the action time of shock wave to plasma plume is the same as that of spectrum enhancement time.By the research and analysis,we have a deeper understanding of Cu plasma dynamic characteristics and spectral enhancement mechanism with combined confinement of magnetic and spatially,and it provides a powerful theoretical basis for improving the detection sensitivity of LIBS.