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 work in this area is focused on the design of these tubes, attempting to optimize the type and amount of microwaves generated. My current project, which can be seen in the images above, is designed to generate a 6 ns pulse of 11.7 GHz microwaves at over 1 gigawatt of power. 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 February 2021 with the 65 MeV electron beam at the Argonne Wakefield Accelerator
in Illinois, generating the highest power to-date for structure-based wakefield acceleration.
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.
This project builds off of the work of a previous graduate student, Xueying Lu