High Gradient Excitation and RF Power Generation Using Dielectric Loaded Wakefield Structures

Dielectric loaded wakefield structures are being developed to be used as high gradient accelerator components. The high current electron beam at the Argonne Wakefield Accelerator Facility (AWA) was used to excite wakefields in cylindrical dielectric loaded wakefield structures in the frequency range of 8 to 14 GHz, with pulse duration of a few nanoseconds. Short electron bunches (13 ps FWHM) of up to 86 nC drove these wakefields, and accelerating fields as high as 100 MV/m were reached. Similar structures were used to extract RF power from the electron beam; however, in this case they were traveling-wave structures, driven by electron bunch trains of up to 16 bunches. RF pulses of up to 40 MW were measured at the output coupler of these structures. The AWA electron beam was also used to drive the cavity modes in a metallic standing-wave structure designed and built by SLAC / KEK (originally meant to be powered by a klystron).