磁膨胀螺旋等离子体中空密度的形成
Hollow density formation in magnetically expanding helicon plasma
摘要：
对螺旋等离子体装置的源室和膨胀室径向密度分布的测量表明，源室的径向密度分布始终是中心峰值，而在发散磁场附近的膨胀室中，密度分布在磁场的临界值以上变为中空。这个值对应于电子和离子都被磁化的值。温度分布总是在轴外达到峰值，并且在源室和膨胀室中的峰值位置处都发现了尾电子。由于梯度B漂移，尾电子在膨胀室中的方位角方向上的旋转产生更多的离轴电离，并产生中空密度分布;然而，如果离子没有被磁化，则额外的电离不会导致中空。
英文摘要：
Measurement of radial density profile in both the source and expansion chambers of a helicon plasma device have revealed that it is always centrally peaked in the source chamber, whereas in the expansion chamber near the diverging magnetic field it becomes hollow above a critical value of the magnetic field. This value corresponds to that above which both electrons and ions become magnetized. The temperature profile is always peaked off- axis and tail electrons are found at the peak location in both the source and expansion chambers. Rotation of the tail electrons in the azimuthal direction in the expansion chamber due to gradient-B drift produces more ionization off-axis and creates a hollow density profile; however, if the ions are not magnetized, the additional ionization does not cause hollowness.
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