Study On Effect Of Ablation Angle On Laser-induced Breakdown Spectroscopy

During the operation of the fusion device,the process of Plasma-Wall Interaction(PWI)will cause a series of interaction processes such as fuel retention,impurity deposition and material sputtering.The feasibility of using Laser Induced Breakdown Spectroscopy(LIBS)to diagnose the first wall material of tokamak in situ has been verified,including the composition and the content of the deposited layer,depth indexing,fuel retention and other processes.Tungsten material is one of the first wall materials.The study of the interaction between plasma and tungsten material is very important for understanding the physical mechanism of interaction between plasma and wall material.In addition,in the process of in-situ diagnosis of the first wall material by the fixed window,it is inevitable to involve the ground error caused by different laser ablation angles.Considering these aspects,this topic mainly carried out the research in the following aspects:The second chapter of this paper introduces the generation mechanism of laser induced plasma,the working principle of LIBS,the basic process of plasma radiation spectrum and the calculation method of plasma parameters including electron density and electron temperature.The LIBS device constructed in the laboratory was introduced,the timing delay between each experimental device was set,and the laser energy reaching the sample surface under different delays was tested.Make theoretical and experimental preparations for subsequent experimental research.In the third chapter of this paper,by studying the main existence forms of tungsten plasma and the representative tungsten plasma spectral lines under different time delays,the typical tungsten ion lines are determined.Under the same experimental conditions,the evolution of spectral line intensity with time and the evolution of the signal-to-back ratio with time were studied.The electron temperature and electron density of the plasma were calculated.The physical explanation of the evolution tungsten plasma with time was given.In the fourth chapter of this paper,by changing the delay laser energy,the evolution of laser ablated tungsten plasma with different laser energy over studied,and the change of the laser ablated tungsten atomic line with the delay of 120 ns.As the laser energy increases,the line intensity increases.Then the variation of the intensity of laser ablated tungsten atomic line with different ablation angles under 120 ns time delay is studied,and the laser energy under different ablation angles is studied.