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

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