An electron beam is used to excite a unique electromagnetic response from a complementary split ring resonator (CSRR) metasurface loaded waveguide and investigate it as a backward propagating Cherenkov radiation source. This novel structure comprises of a metallic WR-284 waveguide loaded with four layers of CSRR-metasurface 1 mm thick, with sufficient spacing between the metasurface layers for electron beam propagation. The loaded waveguide exhibits left handed behaviour around 5.86 GHz where a TM-like mode exists. The transverse confinement of this mode between the closely lying metasurface layers and the strong electrical response of the CSRRs leads permeability and permittivity to be simultaneously negative. The structure has been optimised to reduce the surface current on the metasurface, improve the fabrication suitability and minimise the effect of hybrid modes.
The structure is suitable for beam-based applications as it exhibits strong beam coupling parameters and excitation of longitudinal wake impedance at the frequency of the TM-like mode. The beam coupling parameters exhibited are high with R/Q of 36 Ω and shunt impedance of 177 kΩ. Strong excitation of the longitudinal wake impedance of 10 kΩ, with minimal transverse wake impedance and minimal beam disruption, has been observed for this mode. Results from particle-in-cell simulations will be shown to verify that backward propagating Cherenkov is radiated when a suitable electron beam propagates between the central layers of the waveguide. This investigation can lead to new solutions for non-destructive beam detection and wakefield acceleration which can potentially be scaled to higher frequency ranges.