Department of Physics, ITA (Technological Institute of Aeronautics), São José dos Campos 12228-900, Brazil.
Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Avenida Rovisco Pais, 1049-001 Lisboa, Portugal.
Phys Rev E. 2018 Jan;97(1-1):013201. doi: 10.1103/PhysRevE.97.013201.
In this work we compute the main features of a surface-wave-driven plasma in argon at atmospheric pressure in view of a better understanding of the contraction phenomenon. We include the detailed chemical kinetics dynamics of Ar and solve the mass conservation equations of the relevant neutral excited and charged species. The gas temperature radial profile is calculated by means of the thermal diffusion equation. The electric field radial profile is calculated directly from the numerical solution of the Maxwell equations assuming the surface wave to be propagating in the TM_{00} mode. The problem is considered to be radially symmetrical, the axial variations are neglected, and the equations are solved in a self-consistent fashion. We probe the model results considering three scenarios: (i) the electron energy distribution function (EEDF) is calculated by means of the Boltzmann equation; (ii) the EEDF is considered to be Maxwellian; (iii) the dissociative recombination is excluded from the chemical kinetics dynamics, but the nonequilibrium EEDF is preserved. From this analysis, the dissociative recombination is shown to be the leading mechanism in the constriction of surface-wave plasmas. The results are compared with mass spectrometry measurements of the radial density profile of the ions Ar^{+} and Ar_{2}^{+}. An explanation is proposed for the trends seen by Thomson scattering diagnostics that shows a substantial increase of electron temperature towards the plasma borders where the electron density is small.
在这项工作中，我们计算了大气压下氩气中表面波驱动等离子体的主要特征，以期更好地理解收缩现象。我们包括了氩的详细化学动力学动力学，并求解了相关中性激发态和带电物种的质量守恒方程。通过热扩散方程计算气体温度径向分布。通过假设表面波在 TM_{00}模式下传播，直接从麦克斯韦方程组的数值解计算电场径向分布。该问题被认为是径向对称的，忽略轴向变化，并且以自洽的方式求解方程。我们考虑了三种情况来探测模型结果：（i）通过玻尔兹曼方程计算电子能量分布函数（EEDF）；（ii）EEDF 被认为是麦克斯韦分布；（iii）从化学动力学动力学中排除离解复合，但保持非平衡 EEDF。从这个分析中，可以看出离解复合是表面波等离子体收缩的主要机制。结果与离子 Ar^{+}和 Ar_{2}^{+}的径向密度分布的质谱测量进行了比较。提出了一种解释，用于说明 Thomson 散射诊断所显示的趋势，即在电子密度较小的等离子体边界处，电子温度会显著升高。
