The force exerted by a fireball

Abstract

The force exerted by a fireball was deduced both from the change of the equilibrium position of a pendulum and from the change in the pendulum oscillation period. That measured force was found to be several times larger than the force exerted by the ions accelerated across the double layer that is assumed to surround the fireball. The force enhancement that is expected by ion-neutral collisions in the fireball is evaluated to be too small to explain the measured enhanced force. Gas pressure increase, due to gas heating through electron-neutral collisions, as recently suggested [Stenzel et al., J. Appl. Phys. 109, 113305 (2011)], is examined as the source for the force enhancement. V C 2014 AIP Publishing LLC. [http://dx.

A model for the basic plasma parameter profiles and the force exerted by fireballs with non-isothermal electrons

“…(2) yields a potential drop of around 30 V in the DL, which is around 6 times higher than the potential drop calculated with the conventional formula (4.8 V). 3 This again strengthens the claim that ions can indeed gain enough kinetic energy in the potential drop, which is then available for neutral gas heating via inelastic collisions. The drop in the plasma potential of around 30 V indicates the possibility of the creation of Ar 2þ ions as the second ionization potential of argon is 28.6 eV, but these species are neglected here for simplicity.…”

“…Specifically, the assumption of isothermal electrons made in Ref. 3 is a simplification that is not congruent with experimental data, obtained by different authors such as Rubens and Henderson 4 who measured differences in T e of up to 250% between the interior of a FB and the bulk plasma. A more recent experimental study, which clearly shows that the assumption of isothermal electrons only holds within the FB and outside the double layer (but with very different values), was conducted by Weatherford et al 5 However, if only isothermal electrons are considered, the behavior of the electrons in the boundary region of the FB, which is formed by the DL, is completely neglected.…”

“…(2) and the equation suggested by Makrinich and Fruchtman. 3 The black squares in Fig. 4 denote the actually measured data.…”

“…It was argued by the latter authors that these gas flows were induced by fast electrons that heat the neutrals. This pioneering work was later supplemented by a theoretical model by Makrinich and Fruchtman 3 along with the partial comparison of the theoretical data with measurements. The aforementioned model is a good starting point for theoretical investigations.…”

Interaction of biased electrodes and plasmas: sheaths, double layers, and fireballs

“…This understanding has recently been advanced by new laser collision-induced fluorescence (LCIF) diagnostics and the first 2D particle-in-cell (PIC) simulations of fireball formation [30]. Fireballs have been proposed as a means to control flows in plasmas [31], as well as to generate thrust for plasma-based propulsion systems [32]. Section 7 concludes the review with a brief discussion of connections with related topics and open questions.…”