The Concept

By sending bunches of high energy electrons through a specially designed "tube," microwaves can be generated!

Think of a bell: When you hit a bell sharply with a mallet, it rings at a particular, resonant frequency. Similarly, when you "hit" the tube with a bunch of electrons the tube "rings," but rather than emitting sound, it emits microwaves.

My Research

My work in this area was focused on the design of these tubes, attempting to optimize the type and amount of microwaves generated. This specific tube, which can be seen in the images above, is designed to generate a 6 ns pulse of 11.7 GHz microwaves at the gigawatt power level.  The burst of microwaves generated by my device could then be used to accelerate particles in a wakefield accelerator. The design was successfully tested in 2021 with the 65 MeV electron beam at the Argonne Wakefield Accelerator (AWA) in Illinois. 

Pulses of up to 565 MW of X-band power have been generated using this structure, which is the highest power to-date at the AWA facility. My presentation on this work won the 2022 Best Student Paper Award at the International Vacuum Electronics Conference in Monterey, CA.

What Makes It a "Metamaterial"?

The structure is build from a set of alternating copper plates that form a "metamaterial" when stacked together. Metamaterials are materials that contain "sub-wavelength" dimensions. This means while the material may look like a set of discrete pieces to us, light sees the material as smooth and homogeneous. The key is that that we can easily tailor how light interacts with the metamaterial in a substantial way by making relatively simple changes in the metal plates.

Relevant Papers

J. Picard, et al., "Generation of 565 MW of X-Band Power using a Metamaterial Power Extrator for Structure-Based Wakefield Acceleration", Phys. Rev. Accel . Beams 25, 051301 (2022).

X. Lu, J. Picard, et al., "Coherent high-power RF wakefield generation by electron bunch trains in a metamaterial structure", Applied Physics Letters, 116, 264102 (2020).

X. Lu et al., “Generation of high-power, reversed-Cherenkov wakefield radiation in a metamaterial structure,” Phys. Rev. Lett. 122, 014801 (2019).

This project builds off of the work of a previous graduate student, Xueying Lu.