The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Experimental results from the operation of an electron beam driven, mm-wave, vacuum electronic source are reported. The aim of this work is to create improved electron-beam-driven, vacuum electronic mm-wave and sub-THz sources by exploiting dispersion-engineering. Dispersion-engineered structures can be manufactured by several techniques and in this work additive manufacturing has proven to be quick,...
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...
A two-dimensional (2D) periodic surface lattice (PSL) can be obtained by creating shallow periodic perturbations on a metal surface. When the individual lattice elements are synchronised by coupled volume and surface fields eigenmodes can be formed. Cavities based on a PSL of cylindrical topology have been studied and an analytical description of the dispersive properties of the cavity is presented...
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...
Two-dimensional (2D) Periodic Surface Lattices have been useful in producing distributed feedback in a Free-Electron Maser driven by an oversized electron beam of annular geometry [1]. The Periodic Surface Lattices in this case act as frequency selective mirrors allowing the production of narrow band microwave output. Such 2D periodic structures observed using a hollow, copper, cylindrical waveguide...
The design of an experiment to study a two-dimensional (2D) cylindrical lattice is presented. We illustrate the mode transformations inside the set-up and discuss planned experiments with the lattice. Investigations of a W-band periodic surface lattice are reported. This lattice is intended for use in a novel W-band surface field Cherenkov maser.
Studies of a periodic surface lattice and a surface field oscillator based on such a lattice, producing radiation at high-GHz frequencies are presented. The scalability of the oscillator is discussed. The influence of the structure's parameters on the Cherenkov device's performance is demonstrated.
Temperature and resuscitation profiles of 15 non-survivors were compared with matched survivors of major burns. All patients were intubated and ventilated for smoke inhalation injury, survived more than 3 days postburn and had a cutaneous burn greater than 15 per cent of the body surface area (mean 32.3 ± 11.0 per cent SD). Cases were matched for similar ages (within 10 years) and total body surface...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.