Study Of The Effect Of Background Gas On The Laser-produced Al Plasma State Using Emission Spectroscopy

The laser-produced plasma generated by a high-energy nanosecond pulse laser acting on the surface of a solid target has the characteristics of rapid spatial and temporal evolution,high temperature and high density,large spatial gradient of parameter distribution,wide radiation band and frequent interaction between microscopic particles.The formation,radiation and dynamic evolution characteristics of such laser-produced plasma are closely related to the experimental conditions such as laser wavelength,pulse width,intensity,target type and shape,background gas and pressure.The background gas and pressure will have an important influence on the distribution and evolution of the electron temperature and electron density of the plasma.In this paper,the laser-produced Al plasma emission spectra of different background gases and background pressures were measured by a high spatial and temporal resolution laser-produced plasma emission spectrum measurement device.The state was diagnosed by emission spectroscopy,and the temporal and spatial evolution information of electron temperature and electron density was obtained.At the same time,the temporal and spatial evolution information is simulated by the laser-produced plasma radiation hydrodynamics program,which verifies the applicability of the program in laserproduced plasma simulation.The following work has been carried out:(1)The experimental conditions of spatial and temporal resolved spectral measurement of laser-produced plasma spectra were optimized,and the optimal focusing position of laser was determined.The spatial and temporal resolved spectra of laserproduced Al plasma in Air and Ar background gases and under 760 Torr,76 Torr and 7.6Torr background pressures were measured,and the spectral line information in the spectrum was identified.(2)Based on the assumption of optically thin and local thermodynamic equilibrium,the electron temperature of the laser-produced Al plasma at different background gases and background pressures was diagnosed using the Saha-Boltzmann method,and the electron density was diagnosed using the Stark spreading method.Finally,the information on the distribution of electron temperature and electron density of laser-produced Al plasma in air and argon at 1 atm and in air with different pressures at different delay times and different spatial positions were obtained.The physical mechanisms of the effects of different background gases and background pressures on the distribution and evolution of the laser-produced plasma state parameters are analyzed.(3)The evolution of the distribution of electron temperature and electron density under the same time conditions has been simulated using the laser-produced plasma radiation hydrodynamics program RHDLPP,and the results show good agreement between the simulation and experimental results,completing the calibration of the program.It is shown that our RHDLPP program can be used in the study of the distribution of laser-produced plasma state parameters for different background gases and background pressures.