弱磁场低频驱动高功率低气压感应耦合等离子体源放电机理研究

The high-power low-pressure inductively coupled plasma (ICP) ion source driven by a low frequency source is one of the crucial parts for the neutral beam injection system, and it is very important for the neutral beam heating to make the discharge mechanism in the ICP ion source clear. A self-consistent multiphysics coupled model is established to describe the behavior of plasma and neutral gases in the discharge of the ICP ion source, and it is studied by a three-dimensional hybrid simulation (Fluid/PIC/MC/DSMC). The Langmuir probe is used to measure the density and temperature of electrons, and the optical emission spectroscopy is used to measure the density and temperature of neutral gases. By comparing the results of experiments and simulations, the rationality of the physics model is tested. We focus on the influence of the factors, such as the ponderomotive force, the second harmonic electric current, the neutral gas heating and depletion, the structure of magnetic field, and so on, on the space uniformity of distributions of electron density, electron temperature, ion flux, ion energy. The optimal parameters for the design of the large-area-uniform high-density ICP ion source are hoped to obtain from the results of simulations and experiments.

弱磁场低频驱动高功率低气压感应耦合等离子体（ICP）源是中性束注入系统的关键部分之一，弄清其中的放电机理对于实现磁约束核聚变所需的中性束加热有非常重要的意义。通过建立描述ICP离子源中等离子体和中性气体运动行为的自洽的多物理场耦合模型，采用三维混合模拟（流体/粒子模拟/直接蒙特卡洛模拟），对ICP离子源中的放电过程进行研究，并通过发射光谱、Langmuir探针等诊断手段，对电子密度、电子温度、中性气体密度、中性气体温度等物理量进行诊断，来检验理论模拟的可靠性。着重研究有质动力、二次谐波、中性气体加热与损耗、磁场位形等因素对电子密度、电子温度、离子通量、离子能量等物理量空间分布均匀性的影响。提出可引出大面积均匀高密度离子束的ICP离子源的优化设计方案，为ICP离子源的研制提供理论支持。

我们建立了自洽的描述弱磁场低频驱动高功率低气压ICP 放电过程的物理模型，通过流体方法、粒子模拟方法(Particle-In-Cell,PIC)、蒙特卡罗Monte Carlo(MC)、直接蒙特卡洛方法direct simulation Monte Carlo(DSMC)对等离子体放电和中性气体流场热场相互耦合的过程进行混合模拟，研究了低频驱动引起的多种非线性效应、中性气体加热与损耗和外加磁场位形对ICP 放电过程的影响。并自主设计并搭建了低频高功率小型化的射频感应耦合负氢离子源装置，同时通过Langmuir探针对等离子体密度、温度及电子能量分布函数的随着控制参数的演化规律进行了诊断测量。本项目开发的PIC/MC/DSMC算法和程序不仅揭示了了弱磁场低频驱动高功率低气压ICP 放电过程的各种物理过程和机制，也具有普适性，能够用于一大类跟气体放电相关的问题，包括低温等离子体、聚变等离子体、空间等离子体等。