Development and high-power testing of an X -band dielectric-loaded power extractor

Abstract

Dielectric-loaded structures are promising candidates for use in structure wakefield acceleration. They could be useful for both the collinear wakefield and the two-beam acceleration (TBA) approaches, due to their low fabrication cost, low radio-frequency (rf) losses, and potential to withstand high gradients. A short rf pulse ($\le 20\mathrm{ns}$) TBA program is currently being developed at the Argonne Wakefield Accelerator (AWA) facility, where dielectric-loaded structures are being used for both the power extraction and transfer structure (PETS) and the accelerator. In this study, an $X$-band 11.7 GHz dielectric PETS was developed and tested at AWA to demonstrate high-power, short-pulse wakefield generation. The PETS was driven by a 1.3 GHz train of eight electron bunches separated by 769.2 ps (9 times the $X$-band rf period) in order to achieve coherent wakefield superposition. A total train charge of 360 nC was passed through the PETS structure to generate $\sim 200\mathrm{MW}$, $\sim 3\mathrm{ns}$ flat-top rf pulses without rf breakdown. A future experiment is being planned to increase the generated rf power to approximately $\sim 1\mathrm{GW}$ by optimizing the structure design and improving the drive beam quality.