Measurement of beam currents downstream from strong electric field
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摘要: 针对强电场中电场渗透的问题，采用特殊的法拉第筒法测量脉冲束流强度：在法拉第筒入口处用栅网屏蔽强电场，并用在收集板上加正压的方式抑制二次电子。采用解析计算和数值模拟方式对栅网的形状进行了选择，在同样的栅网丝宽和透过率的前提下，通过正六边形栅网的渗透电场最弱，因此选择正六边形栅网。将设计的法拉第筒用于一台真空弧离子源的束流强度测量，获得了该离子源的束流强度波形，其峰值流强约为550 mA；利用测量结果计算了混合离子束在Cu收集板上的二次电子发射系数，约为2.0。Abstract: A Faraday cup used for measuring the beam currents downstream from strong electric fields was designed. The strong electric field was screened by a grid. The electrons were prohibited by the positive voltage on the collector. The shape of the grid was equilateral hexagon distributed because of its lowest saturation electric field at the same grid widths and the same grid transmission rates. The beam current of a vacuum arc ion source was measured by the designed beam current measuring device and the peak value of the beam current was about 550 mA. The secondary electron yield of the Cu collector bombarded by the hybrid ion beams was calculated to be 2.0.
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Key words:
- strong electric field /
- pulsed ion beam current /
- Faraday cup /
- grid /
- secondary electron
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