Rapid development of many scientific and technical disciplines, especially in material science and material engineering increases a demand for quick, accurate and cheap techniques of materials investigations. The EPR spectroscopy meets these requirements and it is used in many fields of science including biology, chemistry and physics. For proper work, the EPR spectrometer needs a microwave source, which are reviewed in this paper. Vacuum tubes as well as semiconductor generators are presented such as magnetron, klystron, traveling wave tube, backward wave oscillator, orotron, gyrotron, Gunn and IMPATT diodes. In this paper main advantages of gyrotron usage, such as stability and an increased spectral resolution in application to EPR spectroscopy is discussed. The most promising and reliable microwave source is suggested.

A dynamic development of the spectroscopic tech- niques at different wavelengths and the development of promising sources of the microwave radiation create many new opportunities for utilizing these techniques in this field. One of sources of the high frequency electromagnetic radiation is gyrotron. In this paper its main advantages, such as stability and an increased spectral resolution in application to the EPR spectroscopy is discussed.

Using the orbital angular momentum of light for the development of a vortex interferometer, the underlying physics requires microwave/RF models,1 as well as quantum mechanics for light1,2 and fluid flow for semiconductor devices.3,4 The combination of the aforementioned physical models yields simulations and results such as optical lattices,1 or an Inverse Farday effect.5 The latter is explained as the absorption of optical angular momentum, generating extremely high instantenous magnetic fields due to radiation friction. An algorithmic reduction across the computational methods used in microwaves, lasers, quantum optics and holography is performed in order to explain electromagnetic field interactions in a single computational framework. This work presents a computational model for photon-electron interactions, being a simplified gauge theory described using differentials or disturbances (photons) instead of integrals or fields. The model is based on treating the Z-axis variables as a Laplace fluid with spatial harmonics, and the XY plane as Maxwell's equations on boundaries. The result is a unified, coherent, graphical computational method of describing the photon qualitatively, quantitatively and with proportion. The model relies on five variables and is described using two equations, which use emitted power, cavity wavelength, input frequency, phase and time. Phase is treated as a rotated physical dimension under gauge theory of Feynmann's QED. In essence, this model allows the electromagnetic field to be treated with it's specific crystallography. The model itself is described in Python programming language.

The article presents a microwave vacuum tube called gyrotron. Its applications, construction and principle of operation are briefly described. It is also discussed the issue of an appropriate electron beam generation and formation.

Short history of gyrotron is presented with its main applications. The principles of operation are briefly discussed with emphasis on the cavity. The classical cavity is presented in the context of subTHz and Ths wavelength generation. The new concepts for THz gyrotrons are presented such as double-beam and planar gyrotrons. The novel concept for the use of planar magnet is presented.

The paper summarizes the investigation of field electron emission properties of plasma sprayed layers. The tested layers were Cr2O3+SiO2, Al2O3+TiO2, TiO2, Cr3C2+NiCr and Cr3C2+NiCrAlY. The deposition methods were APS and SPS. The Cr2O3+SiO2, Al2O3+TiO2 and TiO2 layers were laser engraved after deposition. Structure investigations of the deposited layers revealed them as composite. The obtained results show, that field electron emission from plasma sprayed layers is comparable with emission from DLC and other carbon-based layers. The best turn-on field was 12 V/μm and has been obtained for laser engraved Al2O3+13 wt.% TiO2 layers. Investigation of temperature dependence of emission showed a remarkable influence of hot (Schottky) emission. The emission of Al2O3+TiO2 layers decreased in elevated temperatures. This has been attributed to the temperature dependence of TiO2 permittivity, which increases with temperature. Computer calculations supported this explanation. The emission parameters suggested very high local electric fields. This probably was the result of field enhancement due to presence of dielectric–conductor–vacuum junction points in addition to that caused by the surface topography.

A temperature dependence of field electron emission from composite layers has been investigated. Air plasma spraying associated with laser engraving and suspension plasma spraying has been used for preparation of composite field electron emitters. The deposited materials were fine sized TiO2 and TiO2∕Al2O3 powders. The sprayed titanium oxide layers contained rutile, anatase, and Magneli phases as well as alumina and alumina-titania spinel. Field emission from these layers was strongly influenced by the emitter temperature. A decrease of emission with temperature rise was observed. This effect has been explained as a result of rutile grain permittivity and conductivity increase with temperature. Model calculations supported this explanation. The plots of low-level current emission as a function of temperature have been used for identification of emission mechanism in this range. The presence of low-current tail in Fowler-Nordheim plot has been attributed to hot electrons. An absence of such tail should indicate a metal-like conduction mechanism in the emitting layer. As the penetration of external electric field into the bulk of emitter material creates conditions for generation of hot electrons, the temperature dependence of electron emission current may be used for indication of carrier transport mechanism in the composite layers.

Simulation results of multibeam gun for coupled-cavity travelling wave tube have been presented. The code used was the OmniTrak (Field Precision). The results show, that space-charge induced asymmetry together with magnetic field distribution cause slight corkscrewing of the beamlets.

Plasma sprayed coatings have been investigated as field emission cathodes. The tested materials were Al2O3+13%TiO2, Al2O3+40%TiO2, TiO2. Some of these coatings were laser engraved. The samples used were initially prepared for purposes other than field emission and their components and structures were not optimised for electron emission. The emission properties were evaluated from current-voltage characteristics taken in a diode configuration in a vacuum chamber under a pressure of 1x10(-6) Pa. Preliminary results indicate that some layers are good field emitters (threshold field 1x10(7) V/m for Al2O3+13%TiO2). The emission stability was generally good and the emission curves were similar on repetition. No significant hysteresis in I-V plots for "up-and-down" measurements was noticed. A model of possible mechanism of low microscopic field emission is presented and microstructural investigations using techniques of XRD, Raman spectroscopy and SEM techniques of plasma sprayed and laser engraved layers enabled understanding of increase of field enhancement factor.

In this paper a multilevel traffic control system for medium and large urban agglomerations is discussed. It is based on a structural hierarchy resulting directly from tasks and functions of this system. Proposed approach to the traffic control system is a guiding framework which will be used as a start point to develop the Intelligent Transportation System for urban agglomeration. The functional requirements define the terms for specified levels to receive coordinates and issue influence variables.

The paper deals with investigation of electron field emission from plasma sprayed and laser engraved TiO2 and Al2O3–TiO2 coatings of two compositions (13 and 40 wt.% of TiO2). The coatings were plasma sprayed onto aluminum rolls coated initially with Ni20Cr alloy. Their technology included also grinding and polishing prior to CO2 laser treatment. The treatment was similar to that applied for anilox rolls manufacturing and allowed a production of three different patterns with the lines densities of 60, 100 and 200 cm−1 and depths of approximately 80, 50 and 10 μm correspondingly. The patterns were engraved under angle of 60° that results in a honeycomb geometry of cells. Measurements of emission current under macroscopic electric field up to 150 V/μm for all the samples were carried out. The SEM observations of engraved coating morphology were made in order to find the electron emission spots and XRD analysis allowed to identify the crystal phases present in the coatings. A tentative explanation of a field emission mechanism basing onto Fowler–Nordheim (FN) model is also presented.

Laser engraved surface of thick layer of plasma sprayed ceramic (mainly Cr2O3) covered with the thin Ti layer appeared to be an effective field electron emitter (Surf. Coat. Technol. J., submitted for publication; Patent pending: method of field electron emitters surface forming and field emitters, no. 20/Z/02 from 20 May 2002). In this paper we describe some calculations concerning emissive parameters i.e. electric field enhancement factor β, emission area α, radius of the emitting sites and their quantity. These calculations seem to confirm the previously stated conclusions that the crystalline forms arising from the material melted with laser beam are the main emitting sites.

Resistive sintered CrSi2/Si has been used as a model material for field electron emission experiments. The measured characteristics of emission current show some discrepancy from the standard plot calculated from the Fowler–Nordheim theory with experimentally determined coefficients. There are indications that electric field penetration into the emitter enhances electron emission. It is suggested that this enhancement is caused by ballistic emission.

The powders of alloys Al2O3+13wt.%TiO2 and Al2O3+40wt.% TiO2 were plasma sprayed onto aluminum rolls coated initially with Ni20Cr bond deposits. The coatings were subsequently ground, polished and submitted to laser engraving. The engraving, similar to that applied for anilox rolls manufacturing, enabled production of three different patterns with the line densities of 60, 100 and 200 1/cm and depths of about 80, 50 and 10 µm correspondingly. The patterns were engraved under angle of 60° that corresponds to a honeycomb geometry of cells. Emission current, for the electric fields up to 150 V/µm, was in the range of 10-7-10-4A for coatings containing 13 wt.% of titania and, in the range 10-11–10-9 A for that of 40 wt.% of titania. The SEM observations of engraved coating morphology was made in order to find the electron emission spots.

Plasma sprayed Cr2O3 coatings were engraved with the use of a CO2 c.w. laser in an installation for production of anilox rolls. The engraved cells had a ‘honeycomb’ geometry with different line densities and depths: 140 lines/cm with 35-μm depth, 180 lines/cm and 200 lines/cm, both 10 μm deep. The engraved surfaces were subsequently PVD coated with a Ti thin film. The microstructure of the coatings was characterized using scanning electron microscopy and optical microscopy. Finally, the measurements of the field emission current were carried out. It was found out that the greatest current was emitted from the surface engraved with the 34-μm deep cells. The emissions spots were presumably small, micrometer sized crystals generated at the solidification of laser molten Cr2O3.

This article presents some investigation results of GaN hexagonal crystals deposited on Si pyramids as field emitters. GaN is considered to be an interesting material for field emission cathodes due to its stability. This exceptional stability makes emitter shaping difficult work. Si is easily formed but GaN grown on Si substrate forms small, separate grains. The formation of such single crystals on Si pyramids may be an easy way for field emitter array formation. The obtained results show that this approach may be useful in practical application. There are some indications that the overheating of emitter tips may lead to decomposition of GaN and to release of metallic Ga.