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Development of laser-induced polarization fluorescence spectroscopy for measuring electric fields in magnetic confinement fusion plasma edges

开发用于测量磁约束聚变等离子体边缘电场的激光诱导偏振荧光光谱

基本信息

批准号：
16340183
负责人：
TAKIYAMA Ken
金额：
$ 10.37万
依托单位：
Hiroshima University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2006
项目状态：
已结题

项目摘要

We have developed a high-sensitive method for measuring the electric field in plasmas, which relies on polarization of laser-induced fluorescence (LIF) by the excitation of He atoms through forbidden transitions (e.g. 2^1S→4^1D). Purposes of this work are to elucidate the effect of collisional disalignment due to electrons in plasmas on the LIF polarization method and to examine whether the method utilizing the interference between Stark and electric quadrupole (QDP) amplitudes can be available or not under such high magnetic field as in magnetic confined fusion plasmas.Time decay of LIF linear polarization was measured as a function of electron d ensity ne in a Penning discharge plasma. The disalignment rates obtained were proportional to ne. From the linear dependence the rate coefficient for disalignment due to electronic collisions w as deduced to be (4.9±0.5)x10^<-11> m^3/s. The upper limit of elect ron densities for application of the polarization method was discussed.Excitation spectra of circularly polarized LIF were observed by scanning the laser wavelength covering the Zeeman splitting under high magnetic fields (500 G< B< 1500 G) perpendicular to the electric field in the sheath of a magnetron plasmas. It was found that the anisotropic population (orientation) was formed among magnetic sublevels with opposite sign in 4^1D. This shows that the Stark-QDP interference takes place even under the cond ition of the selective excitation to each sublevel by a laser with a narrow spectral width as compared to the Zeeman splitting.

我们开发了一种高灵敏度的等离子体电场测量方法，该方法依赖于通过禁止跃迁（例如 2^1S→4^1D）激发 He 原子而产生的激光诱导荧光 (LIF) 偏振。这项工作的目的是阐明等离子体中电子引起的碰撞错位对 LIF 极化方法的影响，并检验在磁约束聚变等离子体这样的高磁场下，利用斯塔克和电四极 (QDP) 振幅之间的干涉的方法是否可行。测量了 LIF 线性极化的时间衰减作为潘宁放电等离子体中电子密度 ne 的函数。获得的错位率与ne 成正比。根据线性相关性，电子碰撞引起的错位速率系数推导出为(4.9±0.5)x10^<-11>m^3/s。讨论了偏振法应用时电子密度的上限。在垂直于磁控管等离子体鞘层的电场的高磁场(500G<B<1500G)下，通过扫描覆盖塞曼分裂的激光波长，观察了圆偏振LIF的激发光谱。发现4^1D中符号相反的磁子能级之间形成各向异性布居（取向）。这表明，即使在用比塞曼分裂窄光谱宽度的激光选择性激发每个子能级的条件下，斯塔克-QDP干涉也会发生。