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

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 (<= 20 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 similar to 200 MW, similar to 3 ns flat-top rf pulses without rf breakdown. A future experiment is being planned to increase the generated rf power to approximately similar to 1 GW by optimizing the structure design and improving the drive beam quality.