Development of Dielectric Disk Accelerators For Argonne 500MeV Short Pulse Two Beam Wakefield Accelerator Demonstrator

In the last two decades, the theoretical and experimental investigations of dielectric accelerating structures for application to wakefield acceleration have predominantly used a dielectric-lined waveguide, due to its simple geometry (i.e. low fabrication cost). However, in comparison with the prevailing metallic disk-loaded accelerators, the dielectric-lined waveguide suffers from a lower Q-factor and lower shunt impedance. Taking the opportunity of DoE SBIR Program, we plan to develop a new dielectric-disk loaded accelerator (DDLA). The preliminary simulation shows that, even with 5e-4 of loss tangent dielectric material (eps=50), we can achieve ~200Mohm/m shunt impedance at 26GHz traveling wave operation (the beam aperture keep the same in the comparison), which is 4 times higher than those of the conventional dielectric loaded accelerator. Under Phase 1 of the project, we will focus on the structure and rf coupling design. Through fabrication of numbers of testing cells we will determine the optimum fabrication procedures for a single-cell DDLA structure, including study of metallization, brazing or other fabrication techniques, frequency tuning, etc. In order to validate the dielectric-based short-pulse wakefield Two Beam Accelerator concept on a relatively large scale without a significant budget increase, the High Energy Physics Division of Argonne National Laboratory plans to demonstrate a ~500-MeV module in the current Argonne Wakefield Accelerator facility within the next 5 years. A new high shunt impedance dielectric wakefield accelerator is the key element for this experiment. The knowledge and experiences gained in the project will benefit the accelerator community in general.