Sheath expansion effect of double flush mounted probe in weakly ionized plasma

Abstract

Sheath expansion is a distinctive feature of the double flush mounted probe because of the embedded configuration. Previously, the sheath expansion effect was usually neglected in weakly ionized plasma dominated by collisions between charged particles and neutrals. In this work, we investigated the sheath expansion effect of the double flush mounted probe in weakly ionized plasma. Results indicate that measurements using the double flush mounted probe were also influenced to a certain extent by the sheath expansion effect in weakly ionized plasma. To eliminate the influence, an empirical analytical formula has been presented to eliminate the influence of sheath expansion. In addition, a fitting curve is given based on experimental data, which indicates that sheath expansion should be considered in processing the measured data when the plasma pressure is lower than 200 Pa. In summary, this work indicates that the ion–neutral collision is a crucial factor that affects sheath expansion in addition to the radius parameter and probes' bias, which can be extended to double flush mounted probe diagnostics in collisional plasma such as the reentry plasma sheath and high-powered plasma thruster.

Diagnosing ratio of electron density to collision frequency of plasma surrounding scaled model in a shock tube using low-frequency alternating magnetic field phase shift

“…Equations ( 13) and (16) show that no matter whether the enveloping plasma is spherical or cylindrical, the attenuation and phase shift of the LF alternating magnetic field relate to n e /v e . The rectangular enveloping plasma in Fig.…”

“…The electrostatic probe method [15][16][17][18] is straightforward and portable and has a time resolution better than 1 µs and a measurement dynamic range spanning nearly three orders of magnitude. The electron density and electron temperature can be calculated through measuring the voltammetry characteristic curve by using probes, and the collision frequency can be obtained from an empirical formula.…”

Determining sheath edge electric field around cylindrical pins of a DC-biased hairpin resonator probe

“…The interaction of sheathaccelerated, unidirectional positive ions determines the anisotropic etching on silicon substrates [2]. The charging of satellites in zero-gravity conditions [7], plasma thrusters [8,9], surface creation of negative ions in neutral beam sources [10], plasma diagnostics [11][12][13][14][15], plasma confinement [16], and dust particle interaction [17,18] are other examples where sheath physics finds relevance. As a result, a number of theoretical [19][20][21][22][23][24][25][26][27][28] and experimental investigations [29][30][31][32][33] have been carried out to understand the nature of the sheath regions that are typically formed in low-temperature laboratory plasmas.…”