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arXiv 1502.04150physics.acc-ph
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相干同步辐射尾场和共振的观测

Observation of Wakefields and Resonances in Coherent Synchrotron Radiation

B. E. Billinghurst, J. C. Bergstrom, C. Baribeau, T. Batten, L. Dallin, T. E. May, J. M. Vogt, W. A. Wurtz, R. Warnock, D. A. Bizzozero, S. Kramer

摘要:

我们报告在加拿大光源(CLS)的相干同步辐射(CSR)的光谱共振的高分辨率测量。共振以$0.074 ~\textrm{cm}^{-1}$的波数间隔穿透光谱,并且在机器设置变化(能量、桶填充模式、突发或连续模式下的CSR)下高度稳定。很久以前,在一个理想化的理论中,类似的共振被预测为光滑环形真空室的本征模,该真空室由在圆形轨道上运动的聚束驱动。在频谱中的峰值的一个推论是在明确定义的空间间隔的聚束的尾场中的脉冲的存在。通过实验和进一步的计算,我们阐明了CLS真空室中的共振和尾场机制,它具有与光滑环面有很大不同的凹槽形状。在30-110 GHz范围内通过RF二极管直接观察尾流场,在THz范围内通过干涉仪间接观察尾流场。由二极管发现的尾流脉冲序列比环形模型中的不太规则,并且取决于观察点,但是在凹槽室中的场的模拟中被考虑。注意所观察到的领域的极化,并可能在相邻的弯曲磁铁产生的领域的相干性。低频尾流场的产生似乎主要是局部的一个单一的弯曲,但多弯曲的影响不能完全排除,并可能在高频谐振中发挥作用。已经开发了新的模拟技术,这对今后的工作应该是非常宝贵的。

英文摘要:

We report on high resolution measurements of resonances in the spectrum of coherent synchrotron radiation (CSR) at the Canadian Light Source (CLS). The resonances permeate the spectrum at wavenumber intervals of $0.074 ~\textrm{cm}^{-1}$, and are highly stable under changes in the machine setup (energy, bucket filling pattern, CSR in bursting or continuous mode). Analogous resonances were predicted long ago in an idealized theory as eigenmodes of a smooth toroidal vacuum chamber driven by a bunched beam moving on a circular orbit. A corollary of peaks in the spectrum is the presence of pulses in the wakefield of the bunch at well defined spatial intervals. Through experiments and further calculations we elucidate the resonance and wakefield mechanisms in the CLS vacuum chamber, which has a fluted form much different from a smooth torus. The wakefield is observed directly in the 30-110 GHz range by RF diodes, and indirectly by an interferometer in the THz range. The wake pulse sequence found by diodes is less regular than in the toroidal model, and depends on the point of observation, but is accounted for in a simulation of fields in the fluted chamber. Attention is paid to polarization of the observed fields, and possible coherence of fields produced in adjacent bending magnets. Low frequency wakefield production appears to be mainly local in a single bend, but multi-bend effects cannot be excluded entirely, and could play a role in high frequency resonances. New simulation techniques have been developed, which should be invaluable in further work.

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