轴向磁场下感应耦合放电模式转换的实验研究

为探究轴向磁场对纯Ar感应耦合等离子体放电模式转换的影响，设计并搭建一整套等离子体产生装置展开实验研究，引入阻抗分析法对放电模式转换进行判断，并得到了朗缪尔探针法的验证。实验发现，当气压为10 Pa时，轴向磁场强度的增加使得E-H和H-E模式转换的阈值功率增大；同时，随着轴向磁场的增强，放电中心区域的电子密度不断降低。初步分析认为，这是由于带电粒子在洛伦兹力作用下做回旋运动，导致高能电子在垂直磁场方向上的碰撞减少，降低了电子密度以及感应耦合效率。进一步分析电子能量概率函数(EEPF)发现，在E模式下，轴向磁场对电子运动的约束作用更加明显，高能电子(>27 eV)所占比例增多，电子能量分布更加均匀。

Experimental investigation on mode transition of inductively coupled plasma discharge under axial magnetic field

In order to investigate the problem of mode transition of radio frequency Ar inductively coupled plasma under the influence of axial magnetic field, a small inductively coupled plasma generator experimental system was designed and built. The impedance analysis method was used in the experiment, also verified correct by Langmuir probe method. It is found out that, when the pressure is 10 Pa, the increase of axial magnetic field intensity will increase the discharge power of E-H and H-E mode transitions. At the same time, the stronger the magnetic field is, the lower the electron density at the center of discharge area is. According to some preliminary analysis, charged particles make cyclotron motion at the influence of Lorentz force, which leads to the reduced collisions of high-energy electrons in the direction perpendicular to the magnetic field. Accordingly, electron density decreases and power coupling efficiency decreases. Further analysis on electron energy probability function (EEPF) has suggested that axial magnetic field has stronger restriction on electronic motion under E mode than H mode. As a result, the reduced collisions lead to a higher high-energy (>27 eV) proportion and a more uniform electron energy probability function under E mode, which has conformed with aforementioned analysis.