尘埃等离子体棘轮中尘埃涡流研究

Study on the dust vortex in a dusty plasma ratchet

尘埃涡流是芯片刻蚀工艺和微重力及地面尘埃等离子体实验中普遍存在的一种现象,研究其形成机制具有重要意义.由于实验上很难诊断带电尘埃颗粒所处鞘层的等离子体参量,因此尘埃涡流的形成机制仍不清楚.本文在一个全新的尘埃等离子体棘轮实验中观察到了单个尘埃涡流的运动,并探讨了放电条件对其运动规律的影响.通过建立三维尘埃等离子体棘轮模型,数值模拟研究了棘轮通道内的等离子体参量分布特征,并利用Langevin模拟重现了实验现象.实验与模拟结果表明,尘埃颗粒所在的锯齿槽内的电势分布具有不对称性,进而造成锯齿槽内离子流的旋度不为零,非平衡离子拖拽力是驱动尘埃颗粒产生涡流运动的根本原因.

A dust vortex is a common phenomenon in the chip etching process and microgravity-and ground-based dusty plasma experiments.Therefore,it is of great significance to study the dust-vortex formation mechanism,which remains unclear due to difficulties in determining plasma parameters in the sheath where the charged dust particles reside.In this work,we observed the motion of a single dust vortex in a new experiment on dusty plasma ratchets and studied its motion patterns under various discharge conditions.By establishing a three-dimensional dusty plasma ratchet model,we numerically investigated the distribution characteristics of the plasma parameters in the saw channel and reproduced the observed experimental phenomenon in a Langevin simulation.The experimental and simulation results revealed asymmetry in the potential distribution within the saw channel wherein dust particles are suspended,resulting in a nonzero ion flow vorticity in the sawtooth.This nonequilibrium ion drag is the fundamental force driving the dust particles to generate the vortex motion.