Spontaneous transition rates near the focus of a parabolic mirror with identification of the vectorial modes involved

Each natural mode of the electromagnetic field within a parabolic mirror exhibits spatial localization and polarization properties that can be exploited for the quantum control of its interaction with atomic systems. The region of localization is not restricted to the focus of the mirror leading to a selective response of atomic systems trapped on its vicinity. We report calculations of the spontaneous emission rates for an atom trapped inside the mirror accounting for all atomic polarizations and diverse trapping regions. It is shown that electric dipole transitions can be enhanced near the focus of a deep parabolic mirror with a clear identification of the few vectorial modes involved. Out of the focus the enhancement vanishes gradually, but the number of relevant modes remains small. Ultimately this represents a quantum electrodynamic system where internal and external degrees of freedom cooperate to maximize a selective exchange and detection of single excitations.

Improved and simplified design of the relativistic helitron resonator

One of the main trends in microwave electronics is the ultra-large power production. The electron stream energy is converted inside vacuum systems, where the key moment is increasing output power of microwave devices, which is possible only when using more and more powerful electron streams. Increasing electron stream power is possible due to either enhancing the carried currents or as a result of increasing the electron energy. Given the law that connects currents and voltages in electronic systems operating when the current is limited by a spatial charge, the production of ultra-high-power electron flows is associated with the usage of relativistic velocity electrons, i. e. approaching the light speed. Likewise, at present, relativistic electrovacuum devices (traveling-wave lamps and backward-wave lamps) use magnetic focusing for linear relativistic streams, which prevents the implementation of simple superconducting electrodynamic systems, because highfrequency metal superconductivity disappears in constant magnetic fields. Meanwhile, simplified ultra-highpower superconducting device structures can significantly increase the device energy due to the strong ohmic loss reduction, which just limits the device energy, destroying the working electrodynamic system surface by increasing power or pulse duration of the generator. The article outlines the modernized design of a new-type microwave generator – the relativistic helitron. The paper considers a simpler coaxial resonator design, obtained by using the supercritical narrowing of the inner conductor radius by the Hn1l mode of the electromagnetic field, rather than a coaxial resonator with notch filters.

Tunable resonator of power system

The article is devoted to issues related to the development of the electrodynamic system of a relativistic klystron, built on the basis of a linear electron accelerator. It is given a description of a frequency tunable resonator developed by the authors and used for energy extraction of large microwave power.

A case study of a loaded rectangular resonator with circular holes under the cavity perturbation theory

In this paper, a detailed description of a case study carried out for a specific electrodynamic system is given: a rectangular resonator made on a section of the WR90 waveguide, excited by a diaphragm and loaded onto round holes cut in its narrow wall. Considered structure has a certain practical significance, especially within the limits of restoring the electrophysical parameters of the samples placed in the cavity of the resonator by through holes. Thus, this case study, among other things, touches upon the main provisions of the resonator’s cavity perturbation method. The considered device was studied both in the natural experiment installation and in the process of model studies, which were carried out in various eigenfrequencies and eigenmodes numerical solvers for an electrodynamic system. The article provides a full description of the structure under consideration, its practical significance; the study of the waveguide inner surface roughness influence on the main parameters of the resonator is given; describes the technique for the experimental determination of the resonator Q-factor from the circuit haracteristics. An algorithm for the loaded resonator Q-factor calculating is proposed and experimentally verified. Additionally, the specific situation of inserting a cylindrical perturbation into the cavity of the resonator is considered. We provide the value of the sample shape factor, and outline the applicability boundaries of the perturbation method in this case study.

GRANULATION OF RAW MATERIALS DURING THE DIELECTRIC HEATING PROCESS

The aim of the work is to develop and justify the parameters of the installation for the granulation of non-food waste of animal and vegetable origin in the process of dielectric heating. Objectives of the study: to develop microwave installations with volumetric resonators of different configurations, providing high electric field strength and continuity of the process of granulating raw materials; calculate the parameters of the electrodynamic system of the generator (electric field strength, the intrinsic Q factor of the resonator) and visualize the distribution pattern of the electromagnetic field in the resonators of different configurations. The studies were based on the dielectric heating theory and the theory of forming granules from multicomponent raw materials. The parameters of the electrodynamic system of the microwave generator were studied in the CST Microwave Studio program. The structural performance of volume resonators is analyzed from the point of view of the implementation of the requirements imposed by microwave devices and granulators intended for use in farms. Analyzed devices with a toroidal resonator and a disk matrix and with ellipsoid resonators and gear ring matrices are analyzed. The electromagnetic field distributions are visualized in the developed design versions of resonators combined with the working chamber of granulators. The values of the self-quality of the resonators and the electric field strength in them are calculated.

The Noether current in Maxwell's equations and radiation under symmetry breaking

Symmetries in physical systems are defined in terms of conserved Noether Currents of the associated Lagrangian. In electrodynamic systems, global symmetry is defined through conservation of charges, which is reflected in gauge symmetry; however, loss of charges from a radiating system can be interpreted as localized loss of the Noether current which implies that electrodynamic symmetry has been locally broken. Thus, we propose that global symmetries and localized symmetry breaking are interwoven into the framework of Maxwell's equations which appear as globally conserved and locally non-conserved charges in an electrodynamic system and define the geometric topology of the electromagnetic field. We apply the ideas in the context of explaining radiation from dielectric materials with low physical dimensions. We also briefly look at the nature of reversibility in electromagnetic wave generation which was initially proposed by Planck, but opposed by Einstein and in recent years by Zoh. This article is part of the theme issue ‘Celebrating 125 years of Oliver Heaviside's ‘Electromagnetic Theory’’.