Abstract
There are many kinds of ions in vacuum arc discharge plasma, which have different distributions in space. In this paper, a compact magnetic analyzer is developed for studying the spatial distribution of deuterium ions and metal ions in vacuum arc discharge with occluded deuterium electrode. When the arc current is about 100 A, the device can effectively transfer the ion beam with good secondary electron suppression, and can accurately obtain the ion current intensity. The spatial distribution of deuterium ions and titanium ions in the vacuum arc discharge with TiD electrode are measured by this device. The results show that both deuterium ions and Titanium ions are Gaussian distribution in the radial direction, but deuterium ions are evenly distributed, while titanium ions are relatively concentrated near the axis, resulting in the lowest proportion of deuterium ions near the axis. Along the axis, the number of all ions decreases as a natural exponential function, and the relative magnitudes are approximately equal, so the proportion of deuterium ions is almost constant. The results of this study not only help to understand the plasma expansion process of vacuum arc discharge, but also guide the design of vacuum arc ion source with occluded deuterium electrode and its ion extraction.
Highlights
Photos of the cross section of ion beam on fluorescent screen: (a) The fluorescent screen was set at the position of 3 mm after the grounding electrode; (b) the fluorescent screen was set at the position of the collectors
Typical waveforms of the ion current collected by each collector while the discharging current is 100 A
1) (Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621900, China) 2) (Graduate School of CAEP, Mianyang 621900, China) 3) (Sichuan XW Bank, Chengdu 610000, China)
Summary
Schematic of the transmission channel for ion beam extract from the ion source. 图 3 离子束轰击闪烁体形成的发光区域照片 (a) 闪烁体 放置在距离地电极后 3 mm 位置; (b) 闪烁体放置在收集极处 Fig. 3. Photos of the cross section of ion beam on fluorescent screen: (a) The fluorescent screen was set at the position of 3 mm after the grounding electrode; (b) the fluorescent screen was set at the position of the collectors. 二次电子能量大部分小于 50 eV, 所需负偏压并不 高 [21]. 图 4 收集极上的总平均电流随偏压的变化趋势 (偏压从 –30 到 30 V 变化) Fig. 4. Average total collected current versus bias voltage from –30 to 30 V. 图 5 收集极上的各离子电流信号波形 (放电弧流为 100 A) Fig. 5. Typical waveforms of the ion current collected by each collector while the discharging current is 100 A. s 该装置可以测得放电等离子体中氘离子、氢离 s 子及金属离子随时间变化规律. 子密度径向空间分布如图 6 所示, 横坐标 0 代表离 子源轴线位置, 正负数值代表偏离轴线距离. 从图 6 中可以看出, 氢和氘离子径向分布比较均匀, 而钛 离子在轴向上更集中. 由于放电点位于阴极边缘, 042901-4
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