Researches On The Plasma Expansion Dynamics Induced By Double Pulsed Laser In The Presence Of Magnetic Field

Confinement by magnetic field research is remarkable in the application of plasma. It is used to constrain the movement of the plasma charged particles in the field, the plasma confinement in a certain area by Lorentz force. It is widely used in laser-induced breakdown spectroscopy, magnetic confinement fusion technology, lithography technology and magnetron sputtering technology, researchers have been of great concern to all countries. Due to its physical process is very complex, so we need research magnetic field under the constraint of the laser-induced plasma expansion dynamics of in-depth.The thesis studies the behavior of plasma spectral characteristics of double laser-induced plasma under magnetic field confinement, the physical process of plasma plume expansion body shape, plasma shock wave expansion processes.Under the established field of laser-induced plasma atomic emission spectrometry constrained experimental system and comparison the single-pulse laser induced aluminum plasma spectral intensity with and without magnetic field confines. Also change the aluminum target position in a magnetic field, the radius of curvature and the gradient magnetic field, the magnetic field lines bending the degree of plasma spectrum of the influence of the plasma spectrum. Study different wavelengths in the magnetic field of spectral intensity under the constraint condition. Calculate the electron temperature and density with and without t magnetic field and the magnetic field.Study the single-pulse laser induced aluminum plasma expansion constraint dynamics with and without magnetic field confines. By fast photography and shadowgraph recorder the plasma image. Comparison the evolution time of shockwave expansion distance and velocity and pressure with and without magnetic field. Compare the photograph of the target in different location in the magnetic field, calculate the plasma expansion distance, fount the contrary of the expansion distance and spectral intensity in different location in magnetic field. This observation signifies that the same curvature and gradient of the magnetic field, the magnetic pressure increase, the rate of electron-ion collisional recombination increases and the ohmic heating is enhanced, and plasma expansion distance and velocity decreased, emission intensity increases. Calculate the shock wave velocity and pressure, found that under the condition of magnetic field constraint shock wave velocity and pressure were greater than without magnetic field constraint conditions.Under the established field of collinear double pulse laser-induced plasma experimental system, using a mirror microscope combined collimated beam, record the double pulse plume front evolution of plasma in different delay time in magnetic field by fast photographic method. Using spectroscopy to analysis of different delay double pulse laser induced plasma spectroscopy properties. Double pulse results once again proved the long-wavelength laser plasma enhanced shielding effect, reducing the laser-target coupling, and short-wavelengths reduces plasma shielding effect, increasing laser-target coupling. It also shows the influence of a magnetic field confines the plasma characteristics.