Beam-breakup instability theory for energy recovery linacs
Beam-breakup instability theory for energy recovery linacs
复制标题
能量回收直线加速器的光束破碎不稳定性理论
DOI：
10.1103/physrevstab.7.054401
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发表时间：
2004
影响因子：
--
通讯作者：
I. Bazarov
中科院分区：
文献类型：
--
作者：
G. Hoffstaetter;I. Bazarov
在这里，我们将推导出一般理论的束分裂不稳定性在循环直线加速器，其中聚束不一定是在相同的RF相位在每个再循环圈。这对于描述能量回收直线加速器（ERL）（其中聚束在RF波的减速阶段进行再循环）以及对于其他再循环器布置（其中不同RF阶段具有优势）非常重要。此外，它还可用于分析再循环束团的相位误差。它示出了如何为一个给定的直线加速器的阈值电流可以计算和一个显着的协议与跟踪数据证明。然后分析了几种解析可解情况下的一般公式，这些情况表明：（a）为什么一个腔中的不同高阶模（HOM）不耦合，以便可以单独考虑最危险的模式。(b)为了单独考虑它们，HOM频率必须有多大不同。(c)任何光学器件都不能使两个腔的高阶矩相消。(d)光学器件如何避免两个腔的不稳定性的增加。(e)多匝再循环器中的HOM如何干扰自身。此外，还介绍了一种计算腔体失调引起的轨道偏差的简单方法。结果表明，BBU不稳定性总是发生在轨道漂移变得很大之前。
Here we will derive the general theory of the beam-breakup instability in recirculating linear accelerators, in which the bunches do not have to be at the same RF phase during each recirculation turn. This is important for the description of energy recovery linacs (ERLs) where bunches are recirculated at a decelerating phase of the RF wave and for other recirculator arrangements where different RF phases are of an advantage. Furthermore it can be used for the analysis of phase errors of recirculated bunches. It is shown how the threshold current for a given linac can be computed and a remarkable agreement with tracking data is demonstrated. The general formulas are then analyzed for several analytically solvable cases, which show: (a) Why different higher order modes (HOM) in one cavity do not couple so that the most dangerous modes can be considered individually. (b) How different HOM frequencies have to be in order to consider them separately. (c) That no optics can cause the HOMs of two cavities to cancel. (d) How an optics can avoid the addition of the instabilities of two cavities. (e) How a HOM in a multiple-turn recirculator interferes with itself. Furthermore, a simple method to compute the orbit deviations produced by cavity misalignments has also been introduced. It is shown that the BBU instability always occurs before the orbit excursion becomes very large.