Relationship Between the DC Bias and the Debye Length in a Complex Plasma

Abstract

Abstract-The levitation height of a dust particle layer within a RF discharge plasma sheath is known to be related to the DC bias, the background pressure, and the Debye length. In this paper, a new experimental technique for measurement of the Debye length is introduced. This technique is based on the relationship between an externally applied DC bias and the particle levitation height and shows that under appropriate conditions, the addition of an externally applied DC bias provides a mechanism for evaluation of the Debye length. When compared with existing techniques, this new method appears to be simpler to implement in some cases.

Measurement of the Vertical Nonuniformity of the Plasma Sheath in a Complex Plasma

“…5, where µ = |y 2 -y 1 | / λ D , and λ D is the Debye length. In the experiment above, the measured Debye length is λ D = 100 µm [17], the average interparticle separation distance is approximately 240 µm and the highest peak to peak oscillation amplitude is 240 µm. This yields a fitting range of µ = 240 /100, 2∆µ = ± 240 / 100.…”

“…5, calculated residuals indicate that for the current case a linear force approximation is indeed valid. Additionally, both simulation and experiment [15], [16], [17] have shown the primary conditions necessary for the appearance of nonlinear effects, such as superharmonics, subharmonics, and/or hysteresis, to be low neutral gas pressures and high oscillation amplitudes. Since for the current experiment, both of these were carefully controlled and Fig.…”

Vertical Dust Particle Chains - Mass and Charge Measurements

“…2, the vertical layers of the cluster can be clearly seen where these particles are illuminated employing a 660 nm, 80mW diode laser. Once the chain stabilized, an externally modulated DC bias was provided to the cell's lower electrode via a KEPCO operational power supply [9] as shown in Figure 3. The filter shown only allows signals below 500 Hz to pass, optimizing the DC modulation technique used in these experiments.…”

The effect of dust charge variation, due to ion flow and electron depletion, on dust levitation

“…The experiment was performed in argon at 25 Pa.experiment. In this case, the distance between the layers is decreased to half a millimeter, which is the approximate Debye length for this discharge [2]. Even though the intent of the experiment, namely to influence the inter-layer distance, was achieved, upon further investigation, the levitation height of the particles could not be analytically reproduced using Orbital Motion Limited (OML) theory [3] and the usual assumption of a linear electric field [4].In order to insure the above results were not due to any bi-layer interaction, the experiment was repeated for different sizes separately, at a pressure of 20 Pa.…”

“…experiment. In this case, the distance between the layers is decreased to half a millimeter, which is the approximate Debye length for this discharge [2].…”