Abstract: For the purpose of revealing the underlying mechanism of power coupling in the plasma source of plasma thruster，a three-parameter pressure function ([fa]，[sp]，[tp]) as well as a three-parameter temperature function ([fa]，[st]，[tt]) is employed to study the effects of the radial pressure gradient and electron temperature gradient on the power deposition，wave field，and current density in Helicon plasma，focusing on the steady-state process of the gas with RF heating after being ionized and accounting the uniformity of the plasma density. Three kinds of gradient are taken into consideration including positive gradient，negative gradient and zero gradient. The results show that the positive pressure gradient weakened the power deposition near the boundary of the plasma，but the penetration depth of the RF wave increases，due to the lower plasma density near the tube wall and the radial energy attenuation less per unit length. The negative temperature gradient strengthens the power deposition near the core of cylinder plasma，due to the higher density and electric temperature making the deposition stronger near the plasma core. The configuration of wave field and current density distribution on different transverse profile almost remain the same，which confirms the robustness of the m=1 mode.

Key words: Radial pressure gradient；Radial temperature gradient；Helicon wave；Plasma；Power deposition

摘要： 为了揭示螺旋波等离子体推力器中的等离子体源功率耦合机理，针对气体工质电离后被射频加热的稳态过程，考虑等离子体密度非均匀分布条件，采用三参数压力函数 ([fa]，[sp]，[tp]) 和温度函数([fa]，[st]，[tt]) 表示柱状等离子体内压力和温度的径向分布，分析了径向压力梯度、温度梯度对螺旋波等离子体内功率沉积、波电场、波磁场和电流密度的影响。考虑梯度为正，梯度为负和梯度为零三种梯度类型。结果发现:压力梯度为正时，螺旋波在等离子体临近壁面处的功率沉积减弱，但射频波透入深度增加，原因是靠近管壁处等离子体密度较低，RF波径向单位长度衰减较少，透入深度增加。温度梯度为负时，柱状等离子体中心处能量沉积变强，原因是管中心位置等离子体密度较大，电子温度较高，与RF波能量耦合增强；横向截面的电磁场、电流密度分布在不同压力和温度梯度下基本不变，证明了m=1模式的稳定性。

关键词: 径向压力梯度；径向温度梯度；螺旋波；等离子体；功率沉积