Experimental Research of the Diffraction and Vavilov-Cherenkov Radiation Generation in a Teflon Target

Geometry of Vavilov-Cherekov (VChR) radiation when an electron moves close to a dielectric target is in analogy to diffraction radiation (DR) geometry. In this case we may expect DR generation from the upstream face of the target besides that VChR. The joint observation of these booth types of radiation is very interesting from the pseudo-photon viewpoint, which is applicable for relativistic electrons. Unexpected results obtained in our experiment insist on reflection about nature both DR and VChR. The experiment was performed on the relativistic electron beam of the microtron of Tomsk Polytechnic University.Comment: This article will be published in Journal of Physic

A generalized framework towards structural mechanics of three-layered composite structures

Three-layered composite structures find a broad application. Increasingly, composites are being used whose layer thicknesses and material properties diverge strongly. In the perspective of structural mechanics, classical approaches to analysis fail at such extraordinary composites. Therefore, emphasis of the present approach is on arbitrary transverse shear rigidities and structural thicknesses of the individual layers. Therewith we employ a layer-wise approach for multiple (quasi-) homogeneous layers. Every layer is considered separately whereby this disquisition is based on the direct approach for deformable directed surfaces. We limit our considerations to geometrical and physical linearity. In this simple and familiar setting we furnish a layer-wise theory by introducing constraints at interfaces to couple the layers. Hereby we restrict our concern to surfaces where all material points per surface are coplanar and all surfaces are plane parallel. Closed-form solutions of the governing equations enforce a narrow frame since they are strongly restrictive in the context of available boundary conditions. Thus a computational solution approach is introduced using the finite element method. In order to determine the required spatially approximated equation of motion, the principle of virtual work is exploited. The discretization is realized via quadrilateral elements with quadratic shape functions. Hereby we introduce an approach where nine degrees of freedom per node are used. In combination with the numerical solution approach, this layer-wise theory has emerged as a powerful tool to analyze composite structures. In present treatise, we would like to clarify the broad scope of this approach

Experimental test of the shadowing effect in Smith-Purcell radiation

The observation of a shadowing effect of a relativistic electron Coulomb field for the Smith-Purcell radiation generation is presented in this paper. For this purpose the surface current from the closest surface of grating element to the electron beam was measured for a downstream one shadowed by upstream element. The experimental results showed that shadowing effect for Smith-Purcell radiation depends on grating geometry

Electromagnetic field features at interaction of relativistic electron with matter

The features of electromagnetic field of relativistic electrons passing through a hole in an absorbing screen as a function of the distance from the screen in the range of radiation formation length were investigated for the transversal and longitudinal field components. The analysis of the obtained results allows approving the existence of a semi-bare electron with a particularly deprived Coulomb field, which turns into the stable state of the usual electron at the distance of radiation formation length

Coherent Cherenkov radiation as an intense THz source

Diffraction and Cherenkov radiation of relativistic electrons from a dielectric target has been proposed as mechanism for production of intense terahertz (THz) radiation. The use of an extremely short high-energy electron beam of a 4th generation light source (X-ray free electron laser) appears to be very promising. A moderate power from the electron beam can be extracted and converted into THz radiation with nearly zero absorption losses. The initial experiment on THz observation will be performed at CLARA/VELA FEL test facility in the UK to demonstrate the principle to a wider community and to develop the radiator prototype. In this paper, we present our theoretical predictions (based on the approach of polarization currents), which provides the basis for interpreting the future experimental measurements. We will also present our hardware design and discuss a plan of the future experiment

“Shadowing” of the electromagnetic field of relativistic charged particles

VIII International Symposium Radiation from Relativistic Electrons in Periodic Structures (RREPS-09), Zvenigorod, Russia, Sept. 7-11, 2009International audienceIn radiation processes such as a transition radiation, diffraction radiation, etc. based on relativistic electrons passing through or near an opaque screen, the electron self-field is partly shadowed after the screen over a distance of the order of the formation length γ2λ. This effect has been investigated on coherent diffraction radiation (DR) by electron bunches. Absorbing and conductive half-plane screens were placed at various distances L before a standard DR source (inclined half-plane mirror). The radiation intensity was reduced when the screen was at small L and on the same side as the mirror. No reduction was observed when the screen was on the opposite side. It is worth noting that absorbing and conductive half-plane screens produce the same shadowing effect. The shadowing effect is responsible for a bound on the intensity of Smith-Purcell radiation

The coherent Vavilov-Cherenkov radiation for a bunch length diagnostic

Coherent Vavilov-Cherenkov radiation generated by a 6.1MeV bunched electron beam traveling in the vicinity of a solid dielectric target (PTFE and Paraffin) has been investigated experimentally. In addition, we have also demonstrated the simple scheme of the Cerenkov interferometer for non-invasive longitudinal electron bunch length diagnostics

Повышение эффективности работы автомобилей на основе транспортно-логистического взаимодействия

The author examines approaches to improvement of the efficiency of trucks’ operations on the basis of a concept of transition of a road carrier from pure physical movement of cargo to the system of transport and logistics services. The author proposes methods for structuring transport and logistics processes and suggests trends and directions of organization of their interaction.Автор рассматривает подходы к проблеме повышения эффективности работы автомобилей на основе концепции перехода автоперевозчика от чисто физического перемещения груза к системе транспортно-логистических услуг. Предлагает методы структуризации транспортно- логистических процессов и направления организации их взаимодействия