Thermal and Electrical Properties of an Argon Plasma

Abstract

Temperatures ranging from 10 000 to 25 000°K have been measured spectroscopically in thermal plasmas of atmospheric pressure argon arcs at currents in the range of 200 to 800 amp. Electrical properties of the plasmas have been derived from measured radial temperature distributions using Spitzer's theory for the temperature dependence of electrical conductivity of a completely ionized gas. Existence of local thermal equilibrium has been demonstrated by the agreement between excitation temperatures determined from both atomic and ionic spectral line intensities. Agreement between values of electrical quantities obtained by direct measurement and those derived from measured temperatures based on the assumption of thermal equilibrium demonstrates the internal consistency of the experimental and analytical methods.

Protection characteristics of a Faraday cage compromised by lightning burnthrough.

“…This design was based on a papers by Olsen and Nestor who employed it to examine the extent of a steady argon arc driven by currents ranging from 200 to 800 amps [26], [27], [10]. They used water-cooled, thin copper electrodes to measure the amount of current on each side of the split between two "D" electrodes and from that data backed out the radius of the plasma.…”

Quasi-neutrality and local thermodynamical equilibrium in atmospheric presure arc discharges

“…However, the partition functions and number densities of the species must be calculated, although the ratio N m (T)/Z m (T) is almost independent of the temperature, so that only a small uncertainty in T results (Murphy, 1994). As noticed by several authors (Olsen, 1959;and Thornton, 1993b) the method is limited to the lower measurable temperatures of 9,000-10,000 K for argon using Ar I lines. This is due to the abrupt decay of the normalized intensity above 10,000 K (Fig.…”

“…3 and consists of a Czerny-Turner monochromator (1 m focal length, 1200 g/mm, 0.1 Å spatial resolution) equipped with a CCD detector. The method employed for the temperature determination was initially proposed by Milne, 1923a and1923b) and employed among the others by Olsen (1959) and Thornton (1993a and1993b). For plasmas in LTE and at constant pressure, Equation 12 passes through a maximum at a temperature called the normal temperature.…”

“…These conditions determine the minimum concentration of charged particles that make the plasma. Using argon equilibrium data at atmospheric pressure (Olsen, 1959), n e -1/3 ≈λ D in the system under investigation (Fig. 1a).…”

“…In this paper, this idea is developed starting from experimental results in argon TIG arcs at currents of 100 and 200 A, investigated by optical emission spectroscopy (OES). Combining results of OES temperatures (and the consequently derived transport parameters) with the composition data available from the literature (Olsen, 1959), the Debye length and the corresponding Debye Number, and the degree of ionization are obtained. This information is used to show that quasi-neutrality is violated within these electrical discharges, revealing their current denomination of 'plasmas' as inappropriate.…”