Department of Engineering Physics, University of Wisconsin, Madison, Madison, Wisconsin 53706, USA.
Phys Rev Lett. 2010 Jun 4;104(22):225003. doi: 10.1103/PhysRevLett.104.225003. Epub 2010 Jun 2.
Recent experiments have shown that ions in weakly collisional plasmas containing two ion species of comparable densities nearly reach a common velocity at the sheath edge. A new theory suggests that collisional friction between the two ion species enhanced by two stream instability reduces the drift velocity of each ion species relative to each other near the sheath edge and finds that the difference in velocities at the sheath edge depends on the relative concentrations of the species. It is small when the concentrations are comparable and is large, with each species reaching its own Bohm velocity, when the relative concentration differences are large. To test these findings, ion drift velocities were measured with laser-induced fluorescence in argon-xenon plasmas. We show that the predictions are in excellent agreement with the first experimental tests of the new model.
最近的实验表明，在含有两种密度相当的离子物种的弱碰撞等离子体中，离子在鞘层边缘几乎达到共同速度。一种新的理论表明，由两流不稳定性增强的两种离子物种之间的碰撞摩擦会降低每种离子物种相对于彼此的漂移速度，并且发现在鞘层边缘的速度差异取决于物种的相对浓度。当浓度相当时，速度差异较小，而当相对浓度差异较大时，每种物种都会达到自己的玻姆速度。为了验证这些发现，使用激光诱导荧光在氩-氙等离子体中测量了离子漂移速度。我们表明，这些预测与新模型的首次实验测试非常吻合。
