In this paper, the effect of cathode geometry on the radial characteristics of a downstream plasma column is presented for a cold cathode type of hollow cathode system. It is observed that when an axial magnetic field is applied to a cylindrical cathode, the downstream plasma exhibits an off-centered peak in the plasma density. However, as the magnetic field increases, the discharge extinguishes rapidly above a critical value, due to the suppression in secondary electron emission from the cylindrical cathode surface. On the other hand, by replacing the hollow cylinder with a cone-shaped cathode an oblique sheath is formed with respect to the axial magnetic field. This configuration helps in sustaining the discharge at twice the magnetic field than in the cylindrical case. It is also found that the downstream plasma exhibits a peak plasma density at the center for the case of the conical cathode. The above experimental observations for each hollow cathode setup has been qualitatively explained with the help of a phenomenological model.

中文翻译：

---

冷空心阴极几何形状对下游磁化等离子体柱径向特性的影响

在本文中，针对冷阴极型空心阴极系统，介绍了阴极几何形状对下游等离子体柱径向特性的影响。观察到当轴向磁场施加到圆柱形阴极时，下游等离子体表现出等离子体密度的偏心峰。然而，随着磁场增加，由于抑制了圆柱形阴极表面的二次电子发射，放电在临界值以上迅速熄灭。另一方面，通过用锥形阴极代替空心圆柱体，形成相对于轴向磁场的倾斜护套。这种配置有助于在两倍于圆柱形情况下的磁场下维持放电。还发现对于锥形阴极的情况，下游等离子体在中心处表现出峰值等离子体密度。在现象学模型的帮助下，对每个空心阴极设置的上述实验观察结果进行了定性解释。