Resistive-wall impedance constitutes a significant percentage of the total beam-coupling impedance budget of an accelerator. A number of different reduction techniques have been proposed during the years depending on the specific applications, ranging from higher order modes damping to solutions entailing high electrical-conductivity coatings of the pipe. This article investigates the use of metamaterial-based absorbers for sensibly reducing or nearly canceling the beam-coupling impedance. We design and fabricate subwavelength 2-D metallic resonant structures based on the split-ring resonator (SRR) geometry that can be employed as mode dampers in accelerating structures. A number of prototypes have been fabricated and measured in a “test model” pillbox cavity. Experimental results, combined with full-wave electromagnetic simulations, prove the efficiency of the SRR-based metamaterials. This article opens up to the possibility of considering metamaterials as a valid alternative to other devices for impedance mitigation in experimental setups commonly operating along a particle beamline, such as accelerating cavities or collimators, and more in general for the development of filters with a large out-of-band signal rejection in specific applications.

中文翻译：

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用于降低加速器梁耦合阻抗的基于超材料的吸收器

电阻壁阻抗在加速器的总光束耦合阻抗预算中占很大比例。多年来，根据具体应用提出了许多不同的减少技术，范围从高阶模式阻尼到需要管道高导电涂层的解决方案。本文研究了使用基于超材料的吸收器来显着降低或几乎消除光束耦合阻抗。我们设计和制造基于裂环谐振器 (SRR) 几何结构的亚波长二维金属谐振结构，可用作加速结构中的模式阻尼器。已经在“测试模型”药丸腔中制造和测量了许多原型。实验结果，结合全波电磁仿真，证明了基于 SRR 的超材料的效率。本文提出了将超材料作为其他设备的有效替代方案的可能性，这些设备通常沿粒子束线运行，例如加速腔或准直器，以及更一般地用于开发具有大输出的滤波器。特定应用中的带外信号抑制。