Hybrid dielectric and iris-loaded periodic accelerating structure

Abstract

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 s /E 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 s /E 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.

Physical calculation for an X -band hybrid dielectric-iris-loaded accelerator

“…Typically this ratio of Es/Ea is more than 2. A hybrid dielectric and iris loaded periodic structure can reduce Es/Ea to near unity, while maintaining high acceleration efficiency as measured by r/Q compares favourably with conventional metallic structures [1] and the r/Q values of dipole modes for the new accelerating structure are much lower than those for the iris-load accelerating structure [2] . The device is shown in Fig.…”

Перспективные Технологии Для Прикладных Резонансных Ускорителей Заряженных Частиц И Примеры Их Использования (Обзор)

“…Другой альтернативой гладким диэлектрическим структурам является структура со вспомогательным диэлектриком (DAA) [226], в которой и кольцо, и диафрагма изготовлены из диэлектриков [227]…”

Dielectric assist accelerating structures for compact linear accelerators of low energy particles in hadrontherapy treatments

“…However, disk-loaded metallic structures were more successful in that time due to their high quality factor and field holding capabilities. Recently, thanks to a remarkable progress in new ceramic materials with high dielectric permittivity (ε r > 20), low loss (tan δ < 10 -4 ) [28][29][30], and ultra-low loss (tan δ < 10 -5 ) [31-33], DLA structures are again being studied for multiple applications such as dual-layered DLA structure [34], a hybrid dielectric and iris-loaded accelerating structure [35], and a DDA structure [36]. Some examples of these dielectrics are fused silica, chemical vapor deposition (CVD) diamond or alumina, among other ceramics, some of which have been experimentally tested with high-power wakefield at Argonne National Laboratory [37,38].…”