Negative Ion Plasmas

点击翻译按钮获取中文摘要

Negative ion plasmas have new features in plasma physics and its applications, which are to be investigated from both theoretical and experimental points of view. Here our recent experiments on negative ion plasmas are presented, including a brief review of the previous experiments. In our experiments, negative ion plasmas are produced by introducing a small amount of SF6 gas into a single-ended Q-machine plasma. The density ratio of negative (SF_6^-) to positive (K^+) ions, n_-/n_+, is controlled continuously in the range up to 0.9999. Our main interests are in effects of an existence of negative ions on characteristics of typical plasma waves and instabilities, i.e., electron plasma waves, ion waves, electrostatic ion cyclotron wave instability, and drift wave instability in negative ion plasmas. Their properties observed are consistent with theoretical predictions. It is also shown that some of these waves and instabilities are quite useful in determining the ratio n_-/n_+, especially in case of (n_+-n_-/n_+<< 1.