ISSN 0869-6632 (Print)
ISSN 2542-1905 (Online)

Innovations in applied physics

Relativistic TWT and BWO on irregular waveguides with cathode filter-modulator

Results of development of the nonlinear theory of relativistic TWT and BWO on irregular hollow waveguides with cathode filter-modulator with the account as propagating, and beyond cut-off waves are given. The results of optimization on efficiency of variants relativistic Cherenkov oscillators are given. The rigorous theory of excitation of an irregular electrodynamic system is used to solve the problem of determining the profile of output horn of Cherenkov oscillators that provides a required mode structure at the output and an optimum directivity pattern.

Terahertz gyrotrons at high cyclotron harmonics

The results of first experiments and future trends in advancing to sub-THz and THz frequency ranges with self-oscillators working at high cyclotron harmonics and gyromultipliers are discussed. In both varieties of gyrotrons, selective excitation of high harmonics can be simplified by the use of electron beams describing helical trajectories whose centers are close to the cavity axis (the configuration of Large Orbit Gyrotron).

Induced waves scattering in cyclotron-resonance masers

For masers on cyclotron resonance it is researched a possibility of induced scattering of the opposite feedback wave on relativistic electron beam to the following wave of higher frequency. This effect can be used for powerful TGz-radiation receipt in a generator of millimeter range of wavelengths.

Prospective field emitters made from carbon nanotubes, graphene and semiconductors recent developments

The article presents the latest published in the literature data on the development and research of promising field emitters made from carbon nanotubes, graphene and semiconductors. The possibilities of obtaining high densities and currents of field emission, as well as opportunities to ensure long-term operation of emitters in high-voltage electron devices are analyzed. 

X-band magnetron electronic conductivity

Some results of the X-band magnetron research are presented. Its active conductivity and the reactive one are measured in dependence both on anode voltage and RF voltage of the oscillatory systems. Approximating formulas are built for these dependences. This is necessary for transient processes calculation in microwave systems of X-band electron accelerators. The comparison is carried out with the known relations for the S-band magnetron.

On secondary-ion photoeffect

A secondary ion yield change from photoconducting semiconductors under influence of illumination has been established (secondary-ion photoeffect). The classification of this phenomenon is given: the normal and the anomalous secondary ion photoeffects are defined. The normal photoeffect is found in reducing of cadmium positive secondary ion yield from CdS-PbS sample under illumination as a result of electron work function decrease.

Field emitters with fullerene coatings and their activation

Methods of fullerene-coated tip field emitter creation were worked out and investigated. Basic rules and mechanisms of the microstructure origin on the fullerene surface during coverage formation and treatment (thermal and field) were determined. The emitters with fullerene coatings were made that secure stable currents from the single submicron tip up to 150 µA at static regime and up to 1.5–2 mA at pulsed one. Activation of the fullerene-coated field emitter by potassium atom and ion flows was studied.

Statistical characteristics of nonstationary emission process

An analytical Markov nonstationary model of electron emission is suggested. The model is determined by having limited life time of cathode. Some relations between probabilistic characteristics of emissivity and reliability of an emitter are obtained.

Wave equations for the pockels effect description in crystals and their analysis on the example of lithium niobate

Theoretical description of the Pockels effect is offered in which statement of a problem in the form of Maxwell equations allows to go on to wave equations directly and to find their solutions. Analytical expressions determining phase velocities and polarization of the optical plane waves, propagating in crystal of lithium niobate in principal crystallographic directions, for different cases of influence of an exterior static electric field are gained.

Development of methods of gyrotrons electron-optics systems with axial symmetry distortion

The simulation technique of helical beam formation system of gyrotrons with typical axial symmetry distortion is presented. The simulation of the second harmonic magnetron-injection gun for 260 GHz band gyrotron with 0.5 mm beam axis displacement was made. It was shown that displacement of axis beam has a significant effect upon the angular distribution of pitch-factor.