Mahjour-Shafiei M, Noori H, Ranjbar A H
Department of Physics, University of Tehran, Tehran 1439955961, Iran.
Rev Sci Instrum. 2011 Nov;82(11):113502. doi: 10.1063/1.3658201.
A cold-cathode penning-type ion source has been developed in our laboratory to study the electric breakdown in this type of sources. The breakdown voltage was measured as a function of axial magnetic field, in the range of 440-600 G, and anode length, in steps of 14, 20, and 24 mm. The measurement was performed with stainless steel cathodes in argon gas at pressure of 4 × 10(-2) mbar. Furthermore, a model was developed to explain the breakdown voltage data. In the construction of the model, the first Townsend coefficient was not directly used to avoid difficulties originating from the non-uniformity of the electric field. The empirical parameters of the model were obtained using the experimental data. The equation γ = c × (E(z)/N)(n), expressing the effective secondary emission coefficient in terms of reduced electric field, which was needed in the modeling process, was inspired from previous works. The parameters c and n were then calculated from the empirical parameters of the model. The n parameter turned out to be 0.59, which differs from the value reported by other authors merely by 1.6%. Three values, 0.010, 0.013, and 0.017 corresponding to the three anodes were obtained for the c parameter. These numbers are in good agreement with 0.01, which has been reported in the previous works. It was also found that the value of n has a decisive impact on the breakdown voltage curve in the high breakdown voltage region.
我们实验室研发了一种冷阴极潘宁型离子源，用于研究此类离子源中的电击穿现象。在440 - 600 G的轴向磁场范围内，以及分别以14、20和24 mm为步长的阳极长度条件下，测量了击穿电压与轴向磁场及阳极长度的函数关系。测量是在氩气压力为4×10(-2) mbar的条件下，使用不锈钢阴极进行的。此外，还开发了一个模型来解释击穿电压数据。在构建模型时，未直接使用第一汤森德系数，以避免因电场不均匀性产生的困难。模型的经验参数通过实验数据获得。在建模过程中所需的、以折合电场表示有效二次发射系数的方程γ = c × (E(z)/N)(n)，是受先前研究启发得到的。然后从模型的经验参数中计算出参数c和n。结果发现n参数为0.59，与其他作者报道的值仅相差1.6%。对于c参数，得到了分别对应三个阳极的0.010、0.013和0.017这三个值。这些数值与先前研究中报道的0.01非常吻合。还发现，在高击穿电压区域，n值对击穿电压曲线有决定性影响。
