Abstract
We present the design of avolumetric metamaterial (MTM) structure and its interaction with a relativistic electron beam. This novel structure has promising applications in particle beam diagnostics, acceleration, and microwave generation. The volumetric MTM has a cubic unit cell allowing structures of arbitrary size to be configured as an array of identical cells. This structure allows the exploration of the properties of a metamaterial structure without having to consider substrates or other supporting elements. The dispersion characteristics of the unit cell are obtained using eigenmode simulations in the HFSS code and also using an effective medium theory with spatial dispersion. Good agreement is obtained between these two approaches. The lowest-order mode of the MTM structure is found to have a negative group velocity in all directions of propagation. The frequency spectrum of the radiation from a relativistic electron beam passing through the MTM structure is calculated analytically and also calculated with the CST code, with very good agreement. The radiation pattern from the relativistic electron beam is found to be backward Cherenkov radiation, which is a promising tool for particle diagnostics. Calculations are also presented for the application of a MTM-based wakefield accelerator as a possible all-metal replacement for the conventional dielectric wakefield structure. The proposed structure may also be useful for MTM-based vacuum electron devices for microwave generation and amplification.
Highlights
Metamaterials (MTMs) have been intensively studied in the microwave frequency range in recent years
In the area of passive microwave devices, MTMs are applied to cloaking [4], “perfect” lens [5,6], antenna design [7], etc., and these MTMs are often based on 2D planar split ring resonators (SRRs) [2]
In MTMs with negative group velocities, backward Cherenkov radiation (CR) can be observed as first suggested by Veselago [1], and planar MTM structures aimed at generating backward radiation were developed [22] first in 2002
Summary
Metamaterials (MTMs) have been intensively studied in the microwave frequency range in recent years. In MTMs with negative group velocities, backward CR can be observed as first suggested by Veselago [1], and planar MTM structures aimed at generating backward radiation were developed [22] first in 2002 Both theoretical and experimental work [23,24,25,26] have verified backward CR using a phased antenna array to mimic a traveling current. The radiated field profile changes with different bunch lengths; their discovery indicates a possible application of measuring beam bunch length and velocity using CR in MTMs. In Sec. II, we will present the design of a unit cell with 3D negative group velocity.
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