Karino Takahiro
Graduate School of Engineering, Utsunomiya University, Utsunomiya 321-8585, Japan.
Rev Sci Instrum. 2020 Mar 1;91(3):033316. doi: 10.1063/1.5129170.
In a laser ion source using solenoid field confinement, it is known that an ion beam becomes unstable in the certain range of a magnetic field. Although it is essential to quantify the instability when discussing the unstable region of the beam, it is difficult to evaluate the beam instability by peak current or the amount of charge because an irregular change of temporal profile occurs in addition to the shot-by-shot fluctuation of amplitude. In this study, I propose the most appropriate method to evaluate the beam instability using the difference from an average waveform. The validity of the new method was evaluated by comparing three evaluation methods (variation of maximum value, variation of integral of waveforms, and the proposed evaluation method) with the experimentally obtained waveforms with the stable and unstable regions of a solenoid field. The proposed method was verified to best represent the beam instability by laser-induced plasma.
在使用螺线管场约束的激光离子源中，已知离子束在磁场的特定范围内会变得不稳定。尽管在讨论束流的不稳定区域时量化不稳定性至关重要，但由于除了幅度的逐次脉冲波动外还会出现时间轮廓的不规则变化，因此难以通过峰值电流或电荷量来评估束流不稳定性。在本研究中，我提出了一种最合适的方法，即利用与平均波形的差异来评估束流不稳定性。通过将三种评估方法（最大值的变化、波形积分的变化以及所提出的评估方法）与通过实验获得的具有螺线管场稳定和不稳定区域的波形进行比较，评估了新方法的有效性。结果验证了所提出的方法能够最好地体现激光诱导等离子体产生的束流不稳定性。
