Measurements of negative hydrogen ions and mutual neutralization process by optical emission spectroscopy

本计画的目的是发展一种新的侦测电浆中负氢离子密度的诊断方法。诊断的原理是基于正负氢离子之间的相互中和。通过该反应产生处于激发态的氢原子。负氢离子通过测量由相互中和产生的激发氢原子的可见光发射来检测。为了实现这一目标，我们研究了以下项目：1）通过飞行时间质谱测量离子组成，2）通过激光光剥离测量负离子密度，3）由于相互中和而产生的光发射的检测，4）通过激光诱导荧光测量氢原子密度，以及5）氢等离子体的速率方程分析。在高密度氢等离子体的余辉中观察到的Hα和Hβ发射强度具有长衰减时间常数的尾部分量。发射强度随时间的变化与正负氢离子密度的乘积一致，说明可见光发射是由正负氢离子的相互中和作用产生的。因此，它已被本项目表明，简单的光学发射光谱可以用于监测等离子体中的负氢离子。

The purpose of the present project is to develop a novel diagnostic method for monitoring negative hydrogen ion density in plasmas. The principle of the diagnostics is based on mutual neutralization between positive and negative hydrogen ions. Hydrogen atoms at excited states are yielded by this reaction. Negative hydrogen ions are detected by measuring visible optical emission from excited hydrogen atoms produced by mutual neutralization. To achieve the goal, we have investigated the following items : 1) the measurement of the ion composition by time-of-flight mass spectrometry, 2) the measurement of the negative ion density by laser photodetachment, 3) the detection of optical emission due to mutual neutralization, 4) the measurement of the hydrogen atom density by laser-induced fluorescence, and 5) the rate-equation analysis of hydrogen plasmas. The intensities of Hα and Hβ emissions observed in the afterglow of high-density hydrogen plasmas had tail components with long decay time constants. The temporal variation of the emission intensity was consistent with the product of the positive and negative hydrogen ion densities, indicating that the visible optical emissions are originated from mutual neutralization between positive and negative hydrogen ions. Therefore, it has been shown by the present project that simple optical emission spectroscopy can be used for monitoring negative hydrogen ions in plasmas.