Abstract: In order to study the high ionization efficiency of helicon discharge， and reveal the deposition mechanism of RF power to plasma in helicon plasma thruster， a numerical simulation was made on the variation characteristics of coupling mode of m=+1 helicon wave and TG mode and its influence rule on wave magnetic field， electric field and current density with the external magnetic field. The results show that， at low magnetic field below 500G the configuration of helicon and TG waves is similar and shows strong coupling. Most of the RF power is coupled into the TG mode by helicon wave and then deposited into the plasma within 0.2～0.4m downstream of the antenna with the strong damping of the TG mode. The coupling efficiency of the helicon wave to the TG wave declines at high magnetic field. Part of the RF energy is transported to the downstream by helicon wave and continuously coupled to the TG wave. This part of RF energy is then deposited into the plasma for the damping effect of the TG wave. Thus， the distribution characteristics of the axial power deposition density are characterized by the eigenmode of the helicon wave. With the increase of the applied magnetic field， the distribution of the partial components of wave magnetic field and the electric field along the z-axis changes from the amplitude attenuation states to the quasi-periodic fluctuating states. The variation characteristics of current density are similar to those of power deposition density.

Key words: Helicon wave；TG wave；Coupling mode；Power deposition；Eigenmode；Magnetic field

摘要： 为了研究螺旋波放电的高电离效率，揭示螺旋波等离子体推力器射频功率向等离子体的沉积机制，对m=+1型螺旋波与TG波耦合模式随磁场的变化特征，以及对波磁场、电场、电流密度的影响规律进行了数值模拟研究。计算结果显示:B_0≤500G的低磁场条件下，螺旋波与TG波构型相似，耦合较强，大部分射频功率由螺旋波耦合到TG波内，并经TG波的强阻尼作用，在天线下游0.2～0.4m距离内沉积到等离子体中；高磁场下，螺旋波向TG波的耦合效率降低，螺旋波将一部分射频能量输运到下游并持续向TG波耦合，由TG波的阻尼作用沉积到等离子体中，轴向的功率分布特征就表现为螺旋波的本征模式；随着外加磁场强度的增大，波磁场、电场的部分分量沿z轴的分布由幅值衰减状态变为准周期性波动状态，电流密度的变化特征与功率沉积密度较为相似。

关键词: 螺旋波；TG波；耦合模式；功率沉积；本征模式；磁场