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arXiv physics/0010002physics.acc-ph
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加速器结构中RF击穿的等离子体模型

A Plasma Model for RF Breakdown in Accelerator Structures

P. B. Wilson

摘要:

提出了一个等离子体模型,用于在强直流电场存在下,在铜表面上的场发射位点附近形成"阴极斑点“和随后的弹坑发展。添加到以前发表的模型,我们建议,双流等离子体不稳定性与等离子体密度的尺寸。参数表明,这种等离子体斑点的形成和动力学基本上是相同的现象,直流和射频场。加速结构的结果是,当存在这样的等离子体斑点时,它们以每库仑离子轰击电流约300微克的速率侵蚀铜表面。在高梯度下处理几百小时后,这种侵蚀速率可以对加速结构的射频特性产生可测量的影响。

英文摘要:

A plasma model is presented for the formation of ``cathode spots'' and subsequent crater development near field emission sites on a copper surface in the presence of a strong dc electric field. Adding to previously published models, we propose that the two-stream plasma instability relates the plasma density to its dimensions. Arguments are presented that suggest that the formation and dynamics of such plasma spots are essentially the same phenomenon for both dc and rf fields. A consequence for accelerating structures is that, when such plasma spots are present, they erode the copper surface at a rate on the order of 300 micrograms per Coulomb of ion bombardment current. This erosion rate can have a measurable effect on the rf properties of an accelerating structure after processing at high gradients for a few hundred hours.

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