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High-sensitive laser spectroscopic method using atomic interference to measure microscopic electric field in plasmas

利用原子干涉测量等离子体微观电场的高灵敏激光光谱法

基本信息

批准号：
12680479
负责人：
TAKIYAMA Ken
金额：
$ 1.92万
依托单位：
HIROSHIMA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

项目摘要

We have proposed a sensitive method to directly measure the electric field in plasmas by using a laser-induced fluorescence (LIF) of a helium atom. In this LIF technique the electric field can be measured by observing only the linear polarization of the allowed fluorescence (4^1D→2^1P) subsequent to the forbidden excitation of metastable He atoms (2^1S→4^1D) due to the Stark-induced electric dipole and the electric quadrupole (QDP) transitions. In the case of the magnetized plasma a new high sensitive LIF method will be possible. The crossed magnetic field to electric field can induce the interference between the Stark and QDP amplitudes. The forbidden excitation generates anisotropic population between magnetic sublevels with opposite sign of quantum number (orientation), e.g. m_l = +1 and -1. The anisotropy appears as the dichroism in circular polarization components of LIF.The electric field dependence of the degree of circular polarization induced by the interference was theoretica … More lly calculated based on the selection rules of the transitions involved in the LIF process. It showed that the circular dichroism has high sensitivity (the minimum detectable electric field : 10 V/cm) and wide dynamic range as compared with the linear one. A model-type experiment was performed with a cylindrical hollow cathode discharge with the magnetic field applied perpendiculany to the electric field in the cathode dark space. We observed simultaneously both the circularly polarized components of LIF from the plasma along the magnetic field direction. The observed LIF was strongly polarized in the sheath. The degree of the polarization agreed with a theoretically calculated value. It should be noted that in the plasma the interference effect was observed for the first time. From the facts described above we may conclude that the use of the circular that the use of the circular dichroism will make it possible to measure the microscopic electric field of the plasma separately to the macroscopic one. Less

我们提出了一种利用氦原子的激光诱导荧光（LIF）直接测量等离子体电场的灵敏方法。在这种LIF技术中，由于stark诱导的电偶极子和电四极子（QDP）跃迁，亚稳He原子（2^1S→4^1D）被禁止激发后，通过观察允许荧光（4^1D→2^1P）的线性极化，可以测量电场。在磁化等离子体的情况下，一种新的高灵敏度LIF方法将成为可能。磁场与电场的交叉会诱发斯塔克振幅与QDP振幅之间的干扰。禁止激发在量子数（方向）符号相反的磁亚能级之间产生各向异性的人口，例如m_l = +1和-1。这种各向异性表现为LIF圆偏振分量的二色性。干涉引起的圆极化程度与电场的依赖关系是理论上的，更多的是根据LIF过程中涉及的跃迁选择规则进行计算。结果表明，与线性二色性相比，圆二色性具有高灵敏度（最小可检测电场为10 V/cm）和宽动态范围。采用圆柱形空心阴极放电，在阴极暗空间中垂直施加磁场与电场，进行了模型实验。我们同时观察到等离子体沿磁场方向的圆偏振分量。观察到的LIF在鞘层中呈强极化。偏振度与理论计算值一致。值得注意的是，在等离子体中首次观察到干涉效应。从上面所描述的事实我们可以得出这样的结论：圆二色性的使用将有可能分别测量等离子体的微观电场和宏观电场。少