Absolute measurement of the total ion-drag force on a single plasma-confined microparticle at the void edge under microgravity conditions

We present an absolute measurement of the total ion-drag force on one single microparticle at the edge of the dust free region in low pressure complex plasmas: the void. In order to do so, the particle confinement position was monitored as a function of the gas pressure for two particle sizes under normal gravity conditions and under microgravity conditions during parabolic flights. At the border of the void, the ion-drag force on a particle with a radius of 4.90 μm appeared to be $(3.6\pm 0.3)\times {10}^{-12}$ N.

Figure 1

Representation of a small particle ($r_p$${}_1$ = 2.45 ± 0.05 μm) under normal gravity conditions (Configuration 1) confined in the electric field in the plasma sheath at the same vertical position as a larger particle ($r_p$${}_2$ = 4.90 ± 0.09 μm) under microgravity conditions.

Figure 2

Particle position above the rf electrode of the $r_p$ = 4.90 μm particle as a function of time during the hyper- and microgravity phases of a parabola for three values of the gas pressure.

Figure 3

Particle position above the rf electrode as a function pressure for “configuration 1” (black squares) and “configuration 2” (red triangles) intersecting at $p$ = 0.18 ± 0.01 mbar.