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To rapidly prototype novel mm-wave and THz sources there is a requirement to create intricate structures to produce and radiate electromagnetic fields. The motivation for this work is to create improved electron-beam-driven, vacuum electronic mm-wave and sub-THz sources by exploiting dispersion engineering. Although such structures can be manufactured by other techniques, additive manufacturing has...
Periodic surface lattice (PSL) structures have been fabricated and measured. When the required conditions are met, volume and surface waves can couple to form a cavity eigenmode at a frequency determined by the PSL's parameters. The formation of such eigenmodes is relevant to the realization of high-power mm-wave and THz coherent sources.
Periodic structures used for high power millimetre and sub-millimetre sources that implement relativistic beam — wave interactions have historically involved the implantation of a dielectric layer around the inner wall of the interaction region or a periodic corrugated structure that serves to reduce the velocity of an internal electromagnetic wave. Moving towards the THz regime, the physical dimensions...
Theoretical and modelling studies of periodic surface lattice (PSL) structures have been complemented by experiments. A cavity eigenmode can be formed, as a result of volume and surface wave coupling under certain conditions. The formation of such eigenmodes is relevant to the realization of high-power mm-wave and THz coherent sources.
Numerical finite difference time domain and Particle-In-Cell simulations have demonstrated an electron wave interaction in a Cherenkov maser utilizing a cylindrical two-dimensional (2D) Periodic Surface Lattice (PSL) as a mode selective cavity [1-8]. Optimization of this structure's physical properties resulted in the design of a cavity with 16 longitudinal periods of 1.6 mm length, 7 azimuthal variations...
Structures based on a periodic surface lattice (PSL) of planar geometry have been studied. It is shown that volume and surface fields can couple to form a cavity eigenmode, demonstrating the potential for novel mm-wave sources when combined in appropriate configurations with an electron beam.
Numerical FDTD and PiC simulations demonstrate the successful electron wave interaction in a Cherenkov maser utilizing a cylindrical 2D PSL as a mode selective cavity. Optimization of this structure's physical properties results in the design of a cavity with 16 longitudinal periods of 1.6 mm length, 7 azimuthal variations and an unperturbed inner radius of 4 mm. In numerical simulations this design...
Numerical 3D PIC code simulations show that Slow-Wave-Structures SWSs demonstrate excellent potential as a virtual dielectric in a Cherenkov based Backward Wave Oscillator (BWO). CST Microwave Studio confirms internal mode coupling between a volume TM0,6 and surface HE20,1 modes resulting in the creation of a high-Q cavity, necessary for the Cherenkov mechanism to be exploited. MAGIC 3D demonstrates...
Cavities based on a periodic-surface-lattice (PSL) of cylindrical topology have been studied. The lattice perturbations have an amplitude much smaller than the operating wavelength of the structure, allowing the PSL to be described as an effective metadielectric or high impedance surface. Dispersive plots describing the electromagnetic (EM) properties of the PSL are presented and the potential for...
Using a cavity based on a periodic-surface-lattice (PSL) the concept of a high-power, 200GHz Cherenkov source is developed. If the PSL satisfies certain defined conditions single mode operation is observed.
A Ka-band cavity based on a two-dimensional periodic lattice is studied. The apparatus designed to excite the cavity is discussed. Coupling between the surface and volume fields is demonstrated and pulse propagation through the cavity is investigated. The measurements agree well with simulations.
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