Direct evidence of departure from local thermodynamic equilibrium in a free-burning arc-discharge plasma

Non-LTE Argon-plasma Composition

“…The experimental results are plotted against two electron-number-density curves for the values T e /T h = 1 and 10. The best agreement is obtained with the experimental results of Nick et al [17], Snyder et al [18], de Regt et al [19] and Reiche et al [20], which are between the calculated curves of the electron number density. The results of Lim and Houk [21], Huang et al [22], Snyder et al [23], Zhu et al [24] and Snyder et al [25] are below the curve for T e /T h = 1 due to the interactions of the plasma with its surrounding, which decrease the measured electron number density by up to four orders of magnitude.…”

Effect of Anode Heat Transfer on Melted Penetration in Welding Process by Free-burning Argon Arc.

“…[1][2][3] Thus, understanding the relation among the temperatures of the arc plasma, the distributions of current and heat input on the anode, and the results is quite important for the materials processing by the free-burning arcs. However, experimental and theoretical investigations of the temperature of arc plasma, [3][4][5][6][7][8][9] the distributions of current and heat input, 10,11) and results, for example, the weld penetration [12][13][14][15][16] were separately conducted and the relation among them has not been made clear. For example, Nestor 10) measured the distributions of current and heat input on the anode of freeburning arc by using the water-cooled copper anode which consists of two separate blocks.…”

Number Density Distributions of Metal Vapor in Helium Gas Tungsten Arcs

“…The theory of Thomson scattering is explicated by many literatures [7][8][9][10][11]13]. Figure 2 shows the comparison between electron temperature for the pure helium arc with the water-cooled copper anode (left side) and that for the helium arc during welding (right side) under the same condition of 150 A in arc current and 5 mm in arc length.…”

“…Recently, some of non-LTE states in GTA plasma were showed in case of the pure argon. Snyder et al directly measured temperatures of electron and heavy particle in DC plasma jet [7] and free-burning arc [8] at atmospheric pressure by the method of laser scattering measurement which needs no assumption of LTE. They showed that electron temperature was different from heavy particle temperature.…”