高电流存储环中束流急停过程的瞬态束流负载效应对能量损失的影响
Transient beam loading effects on energy loss during beam abort in high-current storage ring
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中文总结 AI 辅助
该研究针对高电流存储环束流急停过程，测量3-400mA下的急停圈数，发现瞬态束流负载是能量损失增强的主因，其圈数行为呈饱和特性，可通过数值方式预测，为急停保护系统设计提供依据。
中文摘要 AI 辅助
通过关闭射频（rf）腔实现束流急停，是现代衍射极限同步辐射光源存储环中广泛应用的机器保护方案。该过程中，存储的束流会逐圈损失能量，直至被专用吸收体拦截。对于束流尺寸放大急停方案而言，急停过程中从射频关闭到后续束流损失的圈数是关键参数，尽管该参数对急停保护系统设计至关重要，但尚未在高存储电流下得到表征。我们在3GeV的NanoTerasu存储环中，对3至400mA宽电流范围内的急停圈数进行了测量，结果显示存在明显的电流依赖性：高存储电流下束流损失显著更快，束流损失前的圈数从3mA时的435圈减少至400mA时的187圈。我们的结果表明，急停束流在空载射频腔中诱导的瞬态束流负载是导致能量损失增强的主要机制。高电流下圈数行为并非简单与束流负载成正比，而是呈现饱和特性。时间分辨的腔拾取信号结合跟踪模拟与解析建模，可定量复现观测到的趋势。我们的实验结果与理论建模表明，瞬态束流负载会显著影响高电流第四代存储环的急停动力学，强调需将该效应纳入机器保护系统设计。我们将稳态腔-束流响应近似扩展至束流急停瞬态过程，可良好复现实验结果，表明束流急停过程中的圈数可通过纯数值方式预测。
英文摘要
Beam abort by shutting off the rf cavities is a widely used machine-protection scheme in modern diffraction-limited synchrotron light source storage rings. In this process, the stored beam loses energy turn by turn until it is intercepted by a dedicated absorber. A key parameter in this process is the number of turns after the rf shutdown until the subsequent beam loss, especially for the beam-size blow-up abort scheme. Despite its importance for designing an abort protection system, this quantity has not been characterized at high stored currents. We report measurements of abort turns over a broad current range from 3 to 400 mA in the 3-GeV NanoTerasu storage ring. The results show a clear current dependence: the beam is lost significantly faster at higher stored currents, with the number of turns until beam loss reduced from 435 at 3 mA to 187 at 400 mA. Our results indicate that transient beam loading induced by the aborting beam in empty rf cavities is the primary mechanism responsible for the enhanced energy loss. The number-of-turns behavior is not simply proportional to the beam loading at high current but saturates. Time-resolved cavity pickup signals, together with tracking simulations and analytical modeling, quantitatively reproduce the observed trend. Our experimental results and theoretical modeling demonstrate that transient beam loading significantly influences abort dynamics in high-current fourth-generation storage rings, emphasizing the need to incorporate this effect into machine-protection system design. Our approximate extension of the steady-state cavity-beam response to beam-abort transients reproduces experimental results well, indicating that the number of turns during a beam abort can be predicted purely numerically.
