Study On The Charge State Of Highly Charged Ne And Xe Ions Penetrating Through Gaseous Argon Target And Hydrogen Plasma Target

Controllable nuclear fusion is the ultimate way to solve human energy problems,and it has attracted the attention of more and more scientists in the world.At present,it is mainly represented by magnetic confinement and inertial confinement.In the science of inertial confinement nuclear fusion,the energy deposition process of highly charged ions in dense plasma is the core research content of the target pellet alpha particle self-sustained combustion and particle fast ignition technology.The magnitude of the deposition energy is not only related to the collision process of the projectile–target,but also closely related to the charge state of the projectile ions.According to some theories,the energy loss is proportional to the quadratic power of the effective nuclear charge Z_effof the projectile.Therefore,the study of ion charge states in the interaction between highly charged ions and gas targets and plasma targets is of great significance for the in-depth exploration of the difference of ion charge–changing mechanism and the accurate description of the corresponding energy loss process in low temperature and high temperature plasma environments.High-precision experimental data can also provide key physical parameter data for the future intense heavy ion beam driving inertial confinement fusion science.Relying on the HIRFL accelerator device of the Institute of Modern Physics,Chinese Academy of Sciences,the author built a dedicated experimental terminal for the interaction between highly charged ions and target material on the 320 k V comprehensive research platform of highly charged ions.In the experiment,the charge state distributions of highly charged Ne⁷⁺and Xe²⁰⁺ions in the Bohr velocity energy region after passing through gaseous Ar targets of different densities were systematically measured,and the corresponding experimental data of charge state evolution were obtained.In theory,the cross section of electron loss and capture for Ne and Xe ions interacting with Ar gas in the Bohr velocity energy region are calculated accurately based on the available data and theoretical model of charge–changing cross section.Finally,the charge state distribution,the value of average charge states of the exited ions and their dependence on the target density are obtained.Combined with experimental measurement and theoretical calculation,we completed the following research work:(1)The evolution mechanism of the charge state in the interaction between Ne⁷⁺ions and Ar gas in the Bohr velocity energy region was systematically studied.Firstly,experimentally measured the charge state distribution of Ne⁷⁺ions passing through a gaseous Ar target with different pressure conditions(different areal densities),and obtained the experimental results that the ion charge state distribution as a function of target areal density.In order to reveal the dependence of charge state on charge–changing cross-section and evaluate the influence of multi-electron charge–changing process on the evolution of ion charge state,the experimental results are compared with theoretical predictions:one only considers the single-electron charge exchange process and the other additionally consider the double-electron charge–changing process.In the later stage of the equilibrium phase,the energy loss effect of the projectile begin to be significant,causing the charge state to decrease again,making the existing theories unapplicable.We propose an analytical model to predict the average charge state of the projectile when a significant energy loss happens.The Schiwietz's formula was used to test the validity of the model,and the results showed that the model can explain our experiments well.Based on the proposed analysis model,the influence of energy loss on the charge–changing cross section and the evolution of the charge state is quantitatively evaluated.(2)The evolution mechanism of the charge state in the interaction between Xe²⁰⁺ions and Ar gas in the Bohr velocity energy region is systematically studied.Firstly,the experiment measured the charge state distribution of Xe²⁰⁺ions after passing through gaseous Ar target with different areal density,and obtained the experimental results that the ion charge state distribution as a function of target areal density.In order to understand the charge–changing reaction mechanism of highly charged ions in a gaseous environment,we use two theoretical models(CTMC and semi-empirical law)of charge state based on charge–changing cross section to compare and analyze the collisional particles in the gaseous environment from a theoretical perspective.From a theoretical point of view,the impact of the electron shell structure,interaction mechanism,and energy loss of colliding particles in a gaseous environment on the charge–changing mechanism is comparatively analyzed.Finally,we qualitatively explained the influence of energy loss on the evolution of the charge state through experiments.(3)For the low-density plasma target,the author has completed the diagnosis of the key parameters of the plasma.Using the Monte Carlo calculation program that simulates the ion-plasma interaction,the highly charged Ne ions in the Bohr velocity energy region are calculated respectively.The charge state distribution after ions penetrating through the gaseous argon target and the hydrogen plasma target showed that the charge state of projectile ions under the plasma target condition increased significantly.The reason can be attributed to the existence of a large number of free electrons in the plasma,which caused a significant difference in the charge-changing mechanism.