Development of a Tunable Dielectric Loaded Accelerating Structure

Dielectric structures driven by wakefields or external radio frequency (RF) are presently being considered as a promising technique for next generation linear colliders. This project will develop dielectric-loaded wakefield accelerating structures that can be adjusted in frequency using a bias electric field. This technique can be used to compensate for nonuniformities in dielectric structures, which are intrinsic to the manufacturing process and limit the utility of these devices. The method will be inexpensive and easy to implement without affecting beam quality. The tuning will be accomplished by incorporating a thin film layer of ferroelectric material. The nonlinear change in the permittivity of the ferroelectric material under an applied DC electric field will be used to vary the frequencies of the cavity modes in the structure. In Phase I, the ferroelectric material to be used as an additional layer in the accelerating structures will be improved, and the required loss factor will be achieved. A thin, cylindrical ferroelectric layer for a prototype, tunable, dielectric-loaded accelerator (DLA) structure will be developed and bench tested. In Phase II, the tunable DLA structure will be beam- and high-power tested. Commercial Applications and other Benefits as described by the awardee: In addition to the application for efficient cost effective future electron accelerators, the technology should be directly applicable to the communications industry with respect to microwave power sources and switches, passive microwave resonators, filters, and phase-shifters.