Numerical analysis of ion temperature effects to the plasma wall transition using a one-dimensional two-fluid model. II. Asymptotic two-scale limit

作者：Gyergyek T^*; Kovacic J

来源：Physics of Plasmas, 2017, 24(6): 063506.

DOI：10.1063/1.4984787

A one-dimensional, steady state, two fluid model, presented in Part I [T. Gyergyek and J. Kovacic, Phys. Plasmas 24, 063505 (2017)] is extended to the asymptotic two-scale limit. Separate solutions in the pre-sheath and in the sheath region are presented. Ion temperature is treated as an independent parameter, which is included in the model as a boundary condition. For the pre-sheath solutions, it is shown that when the ion temperature is increased, the ion flow velocity at the boundary of the system must also be increased. A simple relationship between ion temperature and ion flow velocity at the boundary is found. This relationship is the same as the corresponding relationship found in Part I. If ion temperature is increased, both the potential drop and the density drop in the pre-sheath decrease. The same is true for the pre-sheath length. As for the solutions in the sheath scale, it is shown that the ion velocity, electron velocity, and electric field at the sheath edge must all be above a certain minimum value in order to obtain physically acceptable monotonic solutions. It is proposed to select the ion velocity at the sheath edge equal to the ion sound velocity. If, at the same time, the zero electron flow velocity at the sheath edge is selected, the electric field at the sheath edge must be larger than roughly 3 x 10(-6), in order to obtain monotonic solutions of the model. The selection of the electron velocity at the sheath edge is elaborated extensively. It is concluded that increased ion temperature improves the shielding of the plasma from the electrode. Published by AIP Publishing.

• 出版日期2017-6