A normal-conducting, X-band traveling wave structure operating in the dipole mode has been systematically high-gradient tested to gain insight into the maximum possible gradients in these types of structure. Measured structure conditioning, breakdown behavior, and achieved surface fields are reported as well as a postmortem analysis of the breakdown position and a scanning electron microscope analysis of the high-field surfaces. The results of these measurements are then compared to high-gradient results from monopole-mode cavities. Scaled to a breakdown rate of ${10}^{-6}$, the cavities were found to operate at a peak electric field of $154\mathrm{MV}/\mathrm{m}$ and a peak modified Poynting vector $S_c$ of $5.48\mathrm{MW}/{\mathrm{mm}}^2$. The study provides important input for the further development of dipole-mode cavities for use in the Compact Linear Collider as a crab cavity and dipole-mode cavities for use in x-ray free-electron lasers as well as for studies of the fundamental processes in vacuum arcs. Of particular relevance are the unique field patterns in dipole cavities compared to monopole cavities, where the electric and magnetic fields peak in orthogonal planes, which allow the separation of the role of electric and magnetic fields in breakdown via postmortem damage observation. The azimuthal variation of breakdown crater density is measured and is fitted to sinusoidal functions. The best fit is a power law fit of exponent 6. This is significant, as it shows how breakdown probability varies over a surface area with a varying electric field after conditioning to a given peak field.

中文翻译：

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偶极子射频结构的高梯度行为

已经系统地测试了以偶极模式工作的正向导通X波段行波结构，以深入了解这些类型结构中的最大可能梯度。报告了测得的结构条件，击穿行为和获得的表面场，以及击穿位置的事后分析和高场表面的扫描电子显微镜分析。然后将这些测量结果与单极模腔的高梯度结果进行比较。缩放至故障率${10}^{-6}$，发现腔在峰值电场为 $154\mathrm{MV}/\mathrm{米}$ 和峰修饰的Poynting向量 ${\mathrm{小号}}_C$ 的 $5.48\mathrm{兆瓦}/{\mathrm{毫米}}^2$。该研究为进一步开发紧凑型线性对撞机中用作蟹形腔的偶极模腔以及用于X射线自由电子激光器的偶极模腔以及用于研究X射线的基本过程提供了重要的投入。真空电弧。与单极腔相比，偶极腔中独特的场模式尤其重要，在单极腔中，电场和磁场在正交平面中达到峰值，从而可以通过事后破坏观察来分离电场和磁场在击穿中的作用。测量击穿坑密度的方位角变化，并将其拟合为正弦函数。最佳拟合是指数6的幂律拟合。这很重要，