New RF Design of Externally Powered Dielectric-Based Accelerating Structures

This project will develop a broadband coupling section for the high-gradient dielectric loaded accelerator (DLA). The coaxial-type, DLA coupler design will avoid vacuum gaps between the dielectric sections and thus eliminate any points for potential radio frequency (RF) breakdown. It will allow the construction of a new type of dielectric-based accelerator structure that provides accelerating gradients exceeding 100 MV/m. Instead of using a TE-TM mode converter plus a tapered dielectric matching section, the approach will utilize a coaxial-type coupler, which simultaneously can provide the required mode conversion and the impedance matching transition without using a tapered dielectric and without RF breakdown at the dielectric-vacuum gaps. In Phase I, two coaxial-type, X-band coupler solutions ¿ an alumina-based coupler and a coupling section loaded with MCT-20 ceramic ¿ will be designed, developed, and tested The two designs will assure compatibility with DLA structures already built and demonstrated. The coupling sections will be bench tested and the results will be used to validate simulations. A high power test of the coupling section and a high gradient DLA demonstration are planned for Phase II. Commercial Applications And Other Benefits as described by the Applicant: The coaxial-type, ceramic-based coupling section for the dielectric based accelerator should be a key enabling technology for high-gradient Dielectric Loaded Accelerator operation.