Accumulation Process of Negative Ions in a Hollow-Type Magnetized Plasma

1)利用电子回旋共振放电产生了CF4气体的磁化等离子体，并在等离子体下游区域利用盘状障碍物产生了跟踪型磁化等离子体。在中空型等离子体内部，氟正离子和负离子积累，产生离子-离子等离子体。通过探针测量，负离子密度与电子密度之比大于20。这一现象可以用电子和负离子径向扩散速度的差异来解释。由于径向扩散速度由与中性粒子碰撞的频率和步长(拉莫尔半径)决定，负离子的扩散速度远大于电子的扩散速度。结果，正离子和负离子优选地扩散到中空等离子体内的真空区。另一方面，电子和离子沿磁场方向自由运动。在端板上，高能电子倾向于…S更要流入板块之外的一道鞘势屏障。否则，负离子被鞘势垒反射，并被很好地限制在端板之间。通过这一过程，负离子有效地积累在中空等离子体中。2)通过多孔型障碍物，在磁化等离子体的下流区从CF4气体中产生多串等离子体。在这种情况下，负离子聚集在弦等离子体周围。在这里，以相同的间隔产生多个弦等离子体，并且可以产生大量的负离子积累。结果成功地产生了截面为30cm2的大面积负离子源。利用磁滤光片，可以从该等离子体源中引出负离子束，用于大面积负离子处理和中性束处理。3)利用紫外光脉冲激光，测量了跟随等离子体中的负离子量，并与探针数据进行了比较。较少

1) A magnetized plasma from CF_4 gas is generated by the electron cyclotron resonance discharge and a follow-type magnetized plasma is produced by use of a disk-type obstacle at the downstream region of the plasma. Inside the hollow-type plasma, fluorine positive and negative ions are accumulated, generating an ion-ion plasma. By means of a probe measurement, the ratio of negative ion density to electron density becomes more than 20. This phenomenon can be explained by a difference of radial diffusion speeds of electrons and negative ions. As the radial direction diffusion speed is decided by the collision frequency with neutral particles and a step length (a Lamor radius), the negative ions have much larger diffusion speed than that of electrons. As a result, positive and negative ions are preferably diffused into the vacuum region inside the hollow plasma. On the other hand, along the line of magnetic field, electron and ions freely move. At the end plates, high energy electrons tend … More s to flow into the plates beyond a barrier of sheath potential. Otherwise, the negative ions are reflected by the sheath barrier potential and well confined between the end plates. By this process, negative ions are effectively accumulated inside the hollow plasma2) By means of a multi-hole type obstacle, a multi-string plasma is produced at the down-flow region of the magnetized plasma from CF_4 gas. In this case, negative ions accumulate around the string plasmas. Here, many string plasmas are generated with same interval and large volume negative-ion accumulation can be produced. As a results, the large area negative ion source with cross-section of 30 cm^2 has been successfully generated. By use of a magnetic filter a negative ion-beam can be extracted from this plasma source and can be used for the large-area negative ion processing and the neutral beam processing.3) By means of a UV-range pulsed laser, amount of negative ions inside the follow plasma is measured and it is compared with the probe data. Less