Experimental verification of complete LTE plasma formation in hydrogen pellet cloud
Experimental verification of complete LTE plasma formation in hydrogen pellet cloud
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DOI：
10.1088/0741-3335/49/8/005
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发表时间：
2007-08
影响因子：
2.2
通讯作者：
M. Goto;R. Sakamoto;S. Morita
中科院分区：
文献类型：
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作者：
M. Goto;R. Sakamoto;S. Morita
在大型螺旋装置（LHD）中，氢粒子被注入等离子体。从一个致密的等离子体周围形成的弹丸，所谓的“弹丸云”的强辐射，观察和它的光谱进行了分析。中性氢的发射谱线呈现斯塔克加宽轮廓，电子密度通过与理论数据（例如2.1 × 1023 m−3）比较来评估。连续辐射由两个分量占主导地位，这两个分量分别对应于辐射复合和辐射电子附着，后者产生负离子。根据连续辐射的绝对强度及其与波长的关系，确定了电子温度（1.02 eV）、原子密度（1.7 × 1025 m−3）和观测到的等离子体体积（1.6 × 10−5 m3）。这些结果表明等离子体状态接近于完全的局部热力学平衡。由于重吸收效应，巴耳末-α谱线轮廓发生了变形。通过一维辐射输运计算，估算了观测方向上的等离子体厚度（2.4 × 10−3 m）。结果表明，弹丸云在垂直于观测方向上呈各向异性扩展。
A hydrogen pellet is injected into a plasma in the Large Helical Device (LHD). Strong radiation from a dense plasma formed around the pellet, the so-called ‘pellet cloud’, is observed and its spectrum is analysed. Emission lines of neutral hydrogen exhibit Stark broadening profiles and the electron density is evaluated through comparison with theoretical data (e.g. 2.1 × 1023 m−3). The continuum radiation is dominated by two components which correspond to radiative recombination and radiative electron attachment, respectively, the latter of which yields negative ions. From the absolute intensity and its dependence on the wavelength of the continuum radiation, the electron temperature (1.02 eV), the atom density (1.7 × 1025 m−3) and the observed plasma volume (1.6 × 10−5 m3) are determined. These results indicate that the plasma state is close to complete LTE (local thermodynamic equilibrium). The Balmer-α line profile is deformed owing to the reabsorption effect. With the help of one-dimensional radiation transport calculation, the plasma thickness in the direction of the observation (2.4 × 10−3 m) is estimated. The result suggests that the pellet cloud is extended anisotropically in the direction perpendicular to the observation.