碰撞等离子体中电中性条件对单探针测量的约束

在碰撞等离子体中使用单探针测量系统测得的伏安特性曲线会发生畸变. 实验中分别测量了非碰撞条件下(20 Pa)和碰撞条件下(400 Pa)氩气(Ar)电感耦合等离子体的单探针伏安特性曲线, 并进一步通过在400 Pa下测量不同位置处的单探针伏安特性曲线和引入干扰电极调节整体电中性约束的程度的方法来分析研究曲线的畸变现象. 结果表明碰撞等离子体中整体电中性约束条件会对非碰撞探针测量系统进行约束, 并通过理论分析和实验证明:在单探针测量过程中, 以真空室壁为电位参考点, 等离子体将通过改变自身等离子体电位来满足整体电中性的要求, 此时, 单探针测得的伏安特性曲线就不是理论上的单探针的鞘层伏安特性.

The electrical-neutrality constraint of single Langmuir probe measurement in collisional plasma

The volt-ampere (V-I) characteristic curve obtained using single probe diagnostic system for collisionless plasma will be distorted when the system is applied to collisional plasma. The V-I characteristic curves of collisionless and collision inductively coupled plasma is obtained at the gas pressure of 20 Pascal and 400 Pascal, respectively. The distortion phenomenon was studied by measuring the V-I characteristic curves at different positions of the probe and introducing interference electrode to adjust the level of overall electrical-neutrality constraint. The inferential and experimental results show that the overall electrical neutrality in collisional plasma will compose constraint on the single probe diagnostic system for collisionless plasma. Moreover, it is concluded from experiments that the plasma will adjust the potential of itself, which makes the potential of vacuum chamber wall as reference, in order to satisfy the overall electrical neutrality, and that the V-I characteristic curve obtained by single probe is not the V-I characteristic of probe sheath predicted by theory.