Investigations into X-band dielectric disk accelerating structures for future linear accelerators

TL;DR

This paper presents a numerical investigation of X-band dielectric disk accelerating structures operating at TM02 mode, achieving high efficiency, quality factor, and bandwidth, offering a promising alternative for future linear accelerators.

Contribution

The study introduces a novel optimized dielectric disk accelerating structure with significantly improved RF efficiency, quality factor, and bandwidth compared to conventional designs.

Findings

Achieved a high quality factor Q_0=111064.

RF-to-beam efficiency of 46.6%, surpassing previous structures.

Supported up to 73 regular cells with 1.0 MHz frequency separation.

Abstract

Dielectric disk accelerating (DDA) structures are being studied as an alternative to conventional disk-loaded copper structures. This paper investigates numerically an efficient X-band DDA structure operating at a higher order mode of TM02-{\pi}. This accelerating structure consists of dielectric disks with irises arranged periodically in a metallic enclosure. Through optimizations, the RF power loss on the metallic wall can be significantly reduced, resulting in an extremely high quality factor Q_0=111064 and a very high shunt impedance R_shunt=605 M{\Omega}/m. The RF-to-beam power efficiency reaches 46.6% which is significantly higher than previously-reported CLIC-G structures with an efficiency of only 28.5%. The optimum geometry of the regular and the end cells is described in detail. Due to the wide bandwidth from the dispersion relation of the accelerating mode, the DDA structure is allowed to have a maximum number of 73 regular cells with a frequency separation of 1.0 MHz, which is superior to that of conventional RF accelerating structures. In addition, the DDA structure is found to have a short-range transverse wakefield lower than that of the CLIC-G structure.