电子理想吸收体近似下的等离子体壁
Plasma walls beyond the perfect absorber approximation for electrons
摘要：
等离子体壁比离子更有效地积累电子，导致相对于等离子体电势为负的壁电势。理论上，壁通常被视为电子和离子的完美吸收体，这意味着粒子完美地粘附到壁，并且粘附到壁的粒子的解吸时间无限长。对于电子，我们质疑完美的吸收体模型和计算，特别是对于平面电介质壁，电子粘附系数$s_e$和电子解吸时间$τ_e$。对于不带电的壁，我们发现$s_e\ll 1$和$τ_e\approx 10^{-4}s$。因此，在壁电势建立的早期阶段，当壁基本上不带电时，壁不是电子的理想吸收体。对于带电壁，我们发现$τ_e^{-1}\approx 0$。因此，$τ_e$接近理想的吸收体值。但$s_e$仍然只是$10^{-1}$的量级。计算$s_e$作为壁电位的函数，并将此表达式与电子和离子表面密度的准定态平衡方程相结合，我们发现自洽壁电位，包括表面效应，是理想吸收体值的30%。
英文摘要：
Plasma walls accumulate electrons more efficiently than ions leading to wall potentials which are negative with respect to the plasma potential. Theoretically, walls are usually treated as perfect absorber for electrons and ions implying perfect sticking of the particles to the wall and infinitely long desorption times for particles stuck to the wall. For electrons we question the perfect absorber model and calculate, specifically for a planar dielectric wall, the electron sticking coefficient $s_e$ and the electron desorption time $τ_e$. For the uncharged wall we find $s_e\ll 1$ and $τ_e\approx 10^{-4}s$. Thus, in the early stage of the build-up of the wall potential, when the wall is essentially uncharged, the wall is not a perfect absorber for electrons. For the charged wall we find $τ_e^{-1}\approx 0$. Thus, $τ_e$ approaches the perfect absorber value. But $s_e$ is still only of the order of $10^{-1}$. Calculating $s_e$ as a function of the wall potential and combining this expression with the quasi-stationary balance equations for the electron and ion surface densities we find the selfconsistent wall potential, including surface effects, to be 30% of the perfect absorber value.
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