Tuesday, May 8, 2018
Structure based wakefield acceleration is promising for achieving high accelerating gradient. In this talk, I will present the theory and experiment of a metamaterial wagon wheel structure for wakefield acceleration with a frequency of 11.4 GHz.
The structure was designed and fabricated at MIT, and tested recently at the Argonne Wakefield Accelerator at Argonne National Lab. The operating mode has a negative group velocity, so when an electron beam travels through, energy is extracted from the beam by reversed Cherenkov radiation, which was verified in the experiment.
Single bunches up to 45 nC were sent through the structure and generated microwave power up to 25 MW in a 2 ns pulse, in very good agreement with both the analytical wakefield theory and the numerical simulations. Two bunches with a total charge of 85 nC generated 80 MW of microwave power. The structure is scalable to a power extractor of over 1 GW by increasing the structure length from 8 cm to 22 cm.