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We investigate the Cherenkov radiation by a charge uniformly moving inside a dielectric cylindrical channel in a homogeneous medium. The expressions for the Fourier components of the electric and magnetic fields are derived by using the electromagnetic field Green tensor. The spectral distribution of the Cherenkov radiation intensity in the exterior medium is studied for the general case of frequency dispersion of the interior and exterior dielectric functions. It is shown that, under certain conditions on the dielectric permittivities, strong narrow peaks appear in the spectral distribution. The spectral locations of those peaks are specified and their heights and widths are estimated analytically on the base of the dispersion equation for the electromagnetic eigenmodes of the cylinder., Comment: 11 pages, 2 figures, Discussions added

We investigate the electromagnetic radiation from a chain of relativistic charged particles uniformly rotating along equatorial orbit around a dielectric ball. For weak absorption of radiation in the ball material, at certain rotation frequency the radiation intensity becomes significantly higher than the corresponding value for a chain of charges rotating in free space or in a transparent medium with the same dielectric constant as that for the ball material. In the case of an equidistant distribution of charged particles along the orbit we determine the values of parameters of the problem for which the charges in the chain emit coherently. It is shown that the radiation intensity on a given harmonic increases in proportion to the square of the number of emitting charges. We also show that the relative shifts in the particles locations up to 10\% do not destroy the coherence properties of the radiation. It is demonstrated that the coherence effects may also dominate in the radiation intensity for chains with non-equidistant distributions of particles. The numerical results obtained for different dielectric balls have revealed the emitted radiation to be in the GHz/THz frequency ranges. The high-power radiation of the chain propagates in the angular range with respect to the rotation plane determined by the Cherenkov condition for the velocity of the chain projection onto the ball surface., Comment: 15 pages, 4 figures, discussion of peaks and references added

We analytically analyse the motion of a nonrelativistic charged particle in a cylindrical single capillary. The effective potential for interaction of a charged particle with the inner surface of a capillary is derived as a sum of the averaged atomic potential of the capillary wall surface and the induced potential defined by collective surface excitations. We have shown that under certain conditions this potential becomes attractive and may hold a particle in a bound state due to the surface excitations that defines a so-called surface channeling regime of motion. For the first time we have evaluated the induced potential revealing two limits to form either a well or a barrier that are delineated by the ratio of the insulator plasmon frequency to the frequency defined by the particle motion in a capillary., Comment: 9 pages, 3 figures

In this paper we simulate the emission by charged particles in complex structures with help of Geant4. We take into account Cherenkov radiation, transition radiation, bremsstrahlung, pair production and other accompanying processes. As an application we investigate the full size electromagnetic calorimeter for the muon g-2 experiment at Fermilab. A calorimeter module (24 are expected in the experiment) consists of a Delrin front panel for installation of the laser calibration system, 54 PbF2 Cherenkov crystals wrapped by the black Millipore paper, and silicon photo-multiplier sensors. We report here on a simulation of radiation from positrons passing through the calorimeter system. We carry out the simulation using Geant4 toolkit, which provides a complete set of tools for all areas of detector simulation: geometry, tracking, detector response, run, event and track management, and visualization. We consider Cherenkov photons expansion when a positron moves down through the calorimeter at the arbitrary angle of incidence. Both spectral and angular distributions of Cherenkov optical photons in different parts of the calorimeter system have been evaluated as well as the transition radiation and pre-shower distributions from the panel and from the Al vacuum chamber of the storage ring. (The paper is in progress)., Comment: The 7th International Conference "Channeling 2016 - Charged & Neutral Particles Channeling Phenomena"/ in progress

First computer experiment results on proton beam deflection by the crystal miscut surface are presented. The phenomenology of proton channeling and quasichanneling has been applied to describe new features of the beam deflection. The analysis predicts efficient beam deflection by the acute crystal end due to repelling miscut potential.

The question on X-ray extreme focusing (smallest reachable spot size) brings us to the idea for using the wave features of X-ray propagation in media. As known, wave features are revealed at propagation in ultra-narrow collimators as well as at glancing reflection from smooth flat and/or strongly curved surfaces. All these phenomena can be described within the general formalism of X-ray channeling., Comment: by the invited lecture at ISRP-10

A new CAD program, PolyCAD, designed for X-ray photon tracing in polycapillary optics is described. To understand the PolyCAD code and its results, the theoretical basis of X-ray transmission by a single cylindrical channel (monocapillary) is discussed first. Then the simplest cases of cylindrically and conically shaped polycapillary optics are examined. PolyCAD allows any type of X-ray source to be used: an X-ray tube of finite beam dimensions or an astrophysical object can be simulated in combination with the polycapillary optics. The radiation distribution images formed on a screen located at various focal distances are discussed. The good agreement of some of the PolyCAD results with those reported in earlier papers validate the code. This is the first paper of a series dedicated to the development of an exhaustive CAD program, work is in progress to develop the code to include other polycapillary-optics shapes, such as semi-lenses and full-lenses., Comment: Submitted to Applied Optics

Effects of orientational x-ray scattering have been experimentally examined in a film of vertically aligned multiwall carbon nanotubes (CNs). Additional contribution to the x-ray fluorescence intensity was revealed at angles close to the film normal. Theoretical considerations suggest the intensity enhancement to be caused by propagation of C K$_{\alpha}$-radiation mainly along the channels of CNs., Comment: 5 pages, 3 figures

In this work X-ray propagation in micro- and nano-size capillaries has been considered in the frame of a simple unified wave theory. It is shown that the diminishing of the channel sizes completely changes the mode of beam transportation, namely, we obtain the transformation of surface channeling in microcapillaries to bulk channeling in nanocapillaries (nanotubes)., Comment: 16 pages, 4 figures, Keywords: X-ray channeling, nanotubes, capillary optics, submitted to Phys. Lett. B