Simulation Of Thermal Coupling Plasma Density In Rubidium Vapor Laser

Diode-pumped Alkali Laser(DPAL)is one of the most potential megawatt high energy laser alternatives,which has the characteristics of full electric energy operation,light compact structure,fluidity heat dissipation and high quantum efficiency.At present,the kilowatt class power output has been achieved internationally,but with the increase of the pump power,the high energy level transitions and ionization effects accompanying the DPAL during the operation will be enhanced,and thus the DPAL will form plasma inside.The production of plasma will reduce the number of effective atoms of the generated laser,which will affect the propagation of the laser and bring additional thermal effect,which brings difficulties to the high power DPAL output.In the face of the engineering problem of high power output of DPAL,this paper will simulate the interaction of plasma and plasma and provide some reference for understanding and solving the problem.This dissertation first introduces the working principle of DPAL and the basic characteristics and parameters of plasma.Then from the perspective of plasma particle collision,the plasma collision frequency and the high energy reaction,ionization reaction and compound reaction in Rb DPAL are explained.The expression of plasma collision frequency and the rate equation of energy level particles are deduced and simulated,and verify the correctness of solving plasma density through the rate equation.Then the diffusion equation of the plasma in the rubidium DPAL is derived,and it is applied to the simulation of the two-dimensional plasma density.At last,using the multi physical field coupling software COMSOL,the coupling simulation of the number density and collision frequency of each energy level is carried out in the case of the temperature variable T.The distribution of the temperature and plasma density in the rubidium DPAL with time and space is obtained.The study of the multi physical field simulation of the plasma in rubidium DPAL shows that after a period of pumping,a large number of plasma at the pump center of DPAL will be gathered at the same time and the temperature rises sharply,which coincide with the phenomenon of the heat damage of the rubidium vapor absorption pool in the experiment.