A cold-cathode source of low-energy low-divergent broad ion beams
A cold-cathode source of low-energy low-divergent broad ion beams
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DOI：
10.1063/1.1313795
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发表时间：
2000-09
影响因子：
1.6
通讯作者：
N. Gavrilov;D. Emlin;S. Kuleshov
中科院分区：
文献类型：
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作者：
N. Gavrilov;D. Emlin;S. Kuleshov
本文研究了辉光放电离子源中磁场（5-30 mT）和放电等离子体与加速-减速离子光学屏电极之间的电位差对离子等离子体发射器性能和离子束参数的影响。在实验中使用的是改进的潘宁电离计电极系统，其中离子沿着磁场被提取，并且放电在低气压（10 - 2 Pa）下以10 - 1 A的电流稳定地操作。它已被证明，在径向分布的离子束流密度（1-10 mA/cm ~ 2）的变化，随着磁场的增加是由于在等离子体中的电子温度的径向梯度的增加。当最佳B场强为15 mT时，在150 cm ~ 2的面积上获得了几乎均匀（在10%以内）的电流密度分布。已经证明低能的角发散（0.5-1 keV）离子束可以随着等离子体和屏电极之间的电势差以及离子光学器件的加速间隙中的电场的同时增加而减少;然而，最大束流密度，这是由于在加速间隙中的电场接近击穿值的条件下等离子体密度的增加而实现的，随着电势差的增加而下降。根据改变等离子体与离子光学屏电极之间的离子空间电荷鞘层参数时等离子体边界的位置和形状的变化，定性地解释了所获得的实验结果。
This article presents a study of the effect of a magnetic field (5–30 mT) and the potential difference between the discharge plasma and the screen electrode of the accelerating–decelerating ion optics on the performance of the ion plasma emitter and on the parameters of the ion beam in a glow-discharge-based ion source. Used in the experiment was a modified Penning ionization gauge electrode system in which ions are extracted along the magnetic field and the discharge operates stably with a current of ∼1 A at low gas pressures (∼10 −2 Pa ). It has been shown that the changes in the radial distribution of the ion beamcurrent density (1–10 mA/cm2) with increasing magnetic field are due to an increase in the radial gradient of the electron temperature in the plasma. With an optimal B field strength of ∼15 mT, a nearly uniform (within ∼10%) current density distribution has been obtained over an area of ∼50 cm2. It has been demonstrated that the angular divergence of low-energy (∼0.5–1 keV) ion beams can be reduced with a simultaneous increase in the potential difference between the plasma and the screen electrode and in the electric field in the acceleration gap of the ion optics; however, the maximum beam current density, which is achieved thanks to the increase in the plasma density under conditions when the electric field in the accelerating gap approaches the breakdown value, drops with growing potential difference. The experimental results obtained are explained qualitatively based on the changes of the position and shape of the plasma boundary on varying the parameters of the ion space charge sheath between the plasma and the screen electrode of the ion optics.