One disadvantage of conventional iris-loaded accelerating structures is the high ratio of the peak surface electric field to the peak axial electric field useful for accelerating a beam. Typically this ratio E{sub}s/E{sub}a ≥ 2. The high surface electric field relative to the accelerating gradient may prove to be a limitation for realizing technologies for very high gradient accelerators. In this paper, we present a scheme that uses a hybrid dielectric and iris loaded periodic structure to reduce E{sub}s/E{sub}a to near unity, while the shunt impedance per unit length r and the quality factor Q compare favorably with conventional metallic structures. The analysis based on MAFIA simulations of such structures shows that we can lower the peak surface electric field close to the accelerating gradient while maintaining high acceleration efficiency as measured by r/Q. Numerical examples of X-band hybrid accelerating structures are given.
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机译：传统的虹膜加速结构的一个缺点是峰面电场与可用于加速梁的峰值轴向电场的高比率。通常，该比率E {Sub} S / E {Sub}A≥2。相对于加速梯度的高表面电场可能被证明是实现非常高梯度加速器技术的限制。在本文中，我们介绍了一种使用混合电介质和虹膜加载的周期性结构的方案来减少靠近统一的E {Sub} S / E {Sub}，而每单位长度R和质量因子Q比较有利地比较用传统的金属结构。基于MAFIA模拟的这种结构的分析表明，我们可以降低靠近加速梯度的峰面电场，同时保持通过R / Q测量的高加速效率。给出了X波段混合加速结构的数值例子。
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