Experimental verification of resonance instability bands in quadrupole doublet focusing channels
Experimental verification of resonance instability bands in quadrupole doublet focusing channels
复制标题
四极双合态聚焦通道共振不稳定带的实验验证
DOI：
10.1016/j.nima.2013.05.101
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
K. Fukushima
中科院分区：
文献类型：
--
作者：
Mayumi Aoki;et al.;K. Hosokawa;K. Fukushima
采用台式等离子体阱实验“S-POD”，探讨了一系列四极双极电池聚焦强带电粒子束的稳定性。S-POD是一个紧凑的线性保罗阱，在那里我们产生了一个单种非中性离子等离子体，它可以近似地重现由周期性线性力聚焦的强光束的集体运动。与传统的依赖于大规模输运通道和加速器的光束动力学实验不同，S-POD可以在大范围内控制四极光束聚焦的功能形式，从而探索各种四极聚焦晶格。我们系统地测量捕获粒子的损失率作为裸电子加速器调谐的函数，以定位等离子体变得不稳定的共振带。结果表明，随着光束强度的变化，会出现几个相干共振带。当水平聚焦和垂直聚焦之间存在不平衡时，这些不稳定带就会分裂。实验结果表明，在相当大的参数范围内，四极聚焦元件的相位对不稳定带相对不敏感。实验结果与使用Warp代码进行的细胞内横向切片粒子模拟结果进行了比较。
The tabletop plasma trap experiment named “S-POD” is employed to explore the stability of intense charged-particle beams focused by a series of quadrupole doublet cells. S-POD is a compact linear Paul-trap, where we generate a single-species non-neutral ion plasma that can approximately reproduce the collective motion of an intense beam focused by periodic linear forces. Unlike conventional beam-dynamics experiments relying on large-scale transport channels and accelerators, it is straightforward in S-POD to control the functional form of quadrupole beam focusing over a wide range of variation to explore a variety of quadrupole focusing lattices. We systematically measure the loss rate of trapped particles as a function of bare betatron tune to locate resonance bands in which the plasma becomes unstable. It is confirmed that a few bands of coherent resonances appear depending on the beam intensity. When there is an imbalance between the horizontal and vertical focusing, those instability bands split. Experimental results indicate that the instability band is relatively insensitive to the phase of quadrupole focusing element placement within the doublet configuration over a significant range of parameters. Experimental observations are compared with transverse slice particle-in-cell simulations carried out using the Warp code.