Determination of charge on vertically aligned particles in a complex plasma using laser excitations

Abstract

Experimental studies on vertical oscillations of few particle vertical structures are described. One and two particle strings were subjected to two types of vertically driven oscillations. The first was electrode driven, which excites the structure as a whole, while the second was laser driven, which excites one particle in the structure only. The latter experiments are highly original, enabling us to excite two vertical resonances in our two particle structures. From the close agreement between our experimental data and theoretical model, several important physical parameters have been estimated, including the charge ratio and the Debye length.

Dust Particle Alignments in a Plasma Sheath

“…In Fig. 14 The strong influences of the wake on the charge of the second grain located downstream with respect to the first particle was also proved by experimental measurements of the charges on two vertically aligned particles in ICP argon plasma [36]. It was found that the charge on the bottom particle is 0.7 of the charge on the top particle.…”

“…The measurements of Ω z were performed using the standard procedure of determining the resonance frequency of the vertical oscillations [35] by applying the sinusoidal modulated voltage of the 1 V amplitude to the ring electrode. The measurements of Ω x were obtained from an analysis of the horizontal oscillations of the particle driven by a modulated laser beam [36]. The values of the confining strength γ z (vertical) and γ x (horizontal) were calculated using the given mass of the particles and the measured Ωz, Fig.…”

Measurement of electric field and gradient in the plasma sheath using clusters of floating microspheres

“…Therefore, q can only be determined accurately from in situ measurements. One way in which q has been measured is by combining a determination of the particle's vertical resonance frequency v with an estimate of the electric-field gradient E z Ј at the particle's position, [8][9][10][11] which quantities are related by…”

Wake Pairing of Dust Particles

“…The ion wake also influences the charge of the downstream particle which is different from the charge of the top one even in the case of identical particles. The latter has been shown by molecular dynamic simulations [1] as well as by experimental measurements of the charges on two vertically aligned particles in ICP argon plasma [2]. Thus the force that couples dust particles in the ion flow is a complex function of the dust and plasma parameters.…”