Mendoza Sean, Gharib Morteza
Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA, 91125, USA.
Sci Rep. 2025 Mar 26;15(1):10494. doi: 10.1038/s41598-025-88250-7.
In this work, we investigate the anomalous appearance of bright visible light from a toroidal argon plasma generated through extreme hydrodynamic shear. In ambients of nitrogen or helium, the spectral content is easily correlated to the plasma's color. In an argon ambient however, infrared spectral lines dominate the spectrum, while the plasma appears light blue, nearly white, to the naked eye. We determine that this luminescence is a visible broadband continuum emitted by electrons scattering off neutral argon atoms, a form of radiation called bremsstrahlung radiation ([Formula: see text]). Using multispectral imaging, we calculate the temperature, T, of bremsstrahlung-producing electrons spatially throughout the plasma, up to the ionization energy of argon atoms 15.76 eV. We further provide a method of calculating electron density, n, from the same data. We find that in both the T and n fields, two distinct phases appear; a small inner ring of high T, low n, and an outer diffusive region with low T, high n. The boundary between these disparate phases is extremely small, less than 10 µm, indicating an element of self-confinement intrinsic to this plasma configuration.
在这项工作中，我们研究了通过极端流体动力学剪切产生的环形氩等离子体发出明亮可见光的异常现象。在氮气或氦气环境中，光谱成分很容易与等离子体的颜色相关联。然而，在氩气环境中，红外光谱线在光谱中占主导地位，而等离子体肉眼看起来呈浅蓝色，近乎白色。我们确定这种发光是电子从中性氩原子散射发出的可见宽带连续谱，这是一种称为韧致辐射（[公式：见正文]）的辐射形式。使用多光谱成像，我们在整个等离子体中空间计算产生韧致辐射的电子温度(T)，直至氩原子的电离能(15.76)电子伏特。我们还提供了一种从相同数据计算电子密度(n)的方法。我们发现，在(T)和(n)场中都出现了两个不同的阶段；一个高(T)、低(n)的小内环和一个低(T)、高(n)的外扩散区域。这些不同阶段之间的边界极小，小于(10)微米，表明这种等离子体构型具有自约束特性。
