Boundary conditions in wall-stabilized arc columns

Abstract

Conduction and breakdown have been studied in the boundary regions of wall-stabilized arc columns for arc currents up to 50 A in N2, Ar, He, air and SF6 at atmospheric pressure, and for stabilizing hole diameters of 5 and 4 mm. In the case of SF6 no electrons could be drawn to a positively charged disk, and this is shown to be due to the unusual property of an SF6 plasma below 4000°K, namely that it comprises only positive and negative ions (S+ and F−). Estimates of temperature on the plasma side of the boundary layer, based on the magnitudes of the positive-ion currents, vary from 2800°K in SF6 to 4800°K in N2 for 25 A arcs in 5 mm diameter holes. Some characteristics of unipolar arcs, which are defined as arcs which join a metallic electrode to a plasma, are given for Ar and SF6.

On the Double-Arcing Phenomenon in a Cutting Arc Torch

“…Also note that no ion saturation current was found. This behaviour is similar to those presented in wall-stabilized arc experiments with (Hill & Jones, 1979) or without externally imposed axial gas flow (George & Richards, 1968) …”

The effect of an aldosterone antagonist on the protective action of carbenoxolone on the gastric mucosal barrier

“…The residual volume was assumed to be constant in the calculating of net fluxes. This residual volume was determined before the series of experiments by a phenol red dye dilution technique using the mean of 20 replicate estimations (George, 1968).…”

Electrical conductance time constants for freely decaying arcs

“…The method of current collection of the probes was discovered to be diffuse, rather than that due to localized spot collection. Thus the finite probe thickness caused it to collect a net electron current at voltages lower then the floating potential [20].…”

“…Primarily, one must be certain that the electron current portions of the probe characteristics have equal slopes through their respective points of floating potential up to the value of electron current drawn from the pair. The single probe characteristics can also tell one the maximum value of electron current which can safely be drawn without causing the probe plasma sheath to break down [20].…”

“…Rather than measure the characteristic of each probe, a point at, a time, at a given current level [16], the characteristics were found dynamically [18,20]. With the arc operating at constant current, the voltage of a probe is raised to its point of floating potential.…”