Arc plasmas have been extensively studied, experimentally and by means of modeling, due to their wide range of applications. In this article, a calibration-free Boltzmann plot method was applied to measure the species composition and pressure in the arc plasmas based on the assumption of local thermodynamic equilibrium and only single ionization of atoms. Experiments were performed on the argon free-burning arcs at two different pressures. Firstly, several Ar I and Ar II spectral lines were utilized to draw the Boltzmann plot. Then, the plasma temperatures were obtained by three different methods, the Boltzmann plot method, two-line Saha–Boltzmann plot method, and the Fowler–Milne method. The species concentration was calculated using the intercepts with ordinate in the Boltzmann plot. Combined with the electron number density determined from the Stark broadening of Ar I 696.54 nm, arc pressures are calculated based on the equation of state. The measured species concentration and pressures are in good agreement with the theoretical results, indicating that the used method is reliable for further arc plasma applications.

中文翻译：

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免标定玻尔兹曼图法在氩自燃电弧成分和压力测量中的应用

由于其广泛的应用，电弧等离子体已经通过实验和建模进行了广泛的研究。在本文中，基于局部热力学平衡和原子仅单次电离的假设，应用免校准玻尔兹曼图方法测量电弧等离子体中的物质组成和压力。在两种不同压力下对氩无燃弧进行了实验。首先，利用几条Ar I 和Ar II 谱线绘制玻尔兹曼图。然后，通过三种不同的方法获得等离子体温度，即玻尔兹曼图法、两线萨哈-玻尔兹曼图法和 Fowler-Milne 法。使用玻尔兹曼图中纵坐标截距计算物质浓度。结合由 Ar I 696.54 nm 的斯塔克展宽确定的电子数密度，基于状态方程计算电弧压力。测量的物质浓度和压力与理论结果非常一致，表明所用方法对于进一步的电弧等离子体应用是可靠的。