Plasma polarization spectroscopy
Plasma polarization spectroscopy
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DOI：
10.1088/0741-3335/39/9/002
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发表时间：
1997
影响因子：
2.2
通讯作者：
Takashi Fujimoto;Sergei A Kazantsev
中科院分区：
文献类型：
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作者：
Takashi Fujimoto;Sergei A Kazantsev
在密度矩阵形式中，原子或离子的集合用粒子数以及激发能级和基态的排列来表示。激发能级的布居决定了源自该能级的发射线的强度，并且排列引起该线的线性偏振。空间各向异性碰撞会引起种群和排列之间的转变；例如，与基态布居的激发能级电子束一起产生布居排列。因此，各向异性等离子体产生偏振辐射，通过等离子体偏振光谱（PPS），我们可以研究等离子体的各向异性，从而研究非热特性。扰动速度的角分布以勒让德多项式形式展开。种群之间转变的扩展系数和相关横截面以及对齐产生这些转变的速率系数。对于浸没在等离子体中的原子或离子的集合，为粒子群和激发能级的排列构建了耦合速率方程。我们回顾了各种碰撞过程的碰撞截面知识的现状。回顾了迄今为止对 PPS 进行的一些实验观察，其中包括托卡马克等离子体、激光产生的等离子体、各种放电等离子体和太阳耀斑的实验观察。我们讨论可以从 PPS 获取哪些类型的信息。
In the density matrix formalism, the ensemble of atoms or ions is expressed in terms of population and alignment of excited levels and the ground state. The population of an excited level determines the intensity of an emission line originating from this level and the alignment gives rise to the linear polarization of this line. Spatially anisotropic collisions induce transitions between the populations and the alignments; for example, an alignment along with a population is produced by a beam of electrons in an excited level from the ground-state population. Thus, an anisotropic plasma produces polarized radiations, and by plasma polarization spectroscopy (PPS) we can investigate the anisotropic, and thus non-thermal, features of the plasma. The angular distribution of the perturber velocities is expanded in terms of Legendre polynomials. The expansion coefficients and the relevant cross sections for the transitions among the populations and the alignments yield the rate coefficients for these transitions. For the ensemble of atoms or ions immersed in the plasma, coupled rate equations are constructed for the populations and the alignments of excited levels. We review the present status of our knowledge of the collision cross sections for various collision processes. Several experimental observations of PPS performed so far are reviewed, which include those on a tokamak plasma, laser produced plasmas, various discharge plasmas and solar flares. We discuss what kind of information could be obtained from PPS.