FIRST ORBIT LOSSES OF CHARGED FUSION PRODUCTS IN TOKAMAK: FLUX CALCULATION

A.O. Moskvitin, V.O. Yavorskij, V.Ya. Goloborod’ko, Yu.K. Moskvitina

Full Text :   (1400 kB, Eng.) 

Abstract
Technique of calculation the pitch-angle, energy and poloidal distributions of the flux of charged fusion products (CFPs) lost to the first wall of axisymmetric tokamak due to first orbit (FO) loss mechanism is developed. This technique extends the approach for evaluation the poloidal distributions of FO loss of CFPs in tokamaks proposed by [Kolesnichenko Ya.I. et al. Sov. J. Plasma Phys 2 (1976) 506]. The upgraded technique enables to calculate distributions of lost fast ions in wide class of tokamak magnetic configurations. Analytical model of the magnetic field used in this study [Yavorskij V.A. et al. Plasma Phys. Control. Fusion 43 (2001) 249] takes into account Shafranov shift, elongation, triangularity and up-down asymmetry. Usage of the drift constant of motion space allows substantial reducing the computational efforts for simulation the lost particles flux at a given point of the first wall. The developed approach is useful for simulation the pitch- angle and energy distributions of fast ions lost to the scintillator detector [Zweben S.J. et al. Nucl.Fusion 30 (1990) 1551] in present-day tokamaks [Kiptily V.G. et al. Nucl.Fusion 49 (2009) 065030] as well as for calculation of the CFP fluxes to the plasma-facing wall in future tokamak-reactors.

KEY WORDS: first orbit losses, charged fusion product, axisymmetric tokamak, non-circular flux surface, scintillator detector.

ABOUT PARAMETERS OF REACTOR-STELLARATOR IN THE CONDITIONS OF AMBIPOLARITY OF NEOCLASSICAL TRANSPORT FLUXES

V.A. Rudakov

Full Text :   (470 kB, Rus.) 

Abstract
Parameters of reactor-stellarator with the use of one-dimensional spatio-temporal numerical code are calculated in the conditions of ambipolarity of neoclassical transport fluxes. The steady- state modes of the self supported thermonuclear reaction are got at the pellet-injection of DT-fuel. The variants of the magnetic system with the different sizes of helical field's ripples are considered. The technical parameters of reactors appear executable and have fusion power, comparable with the power of already operating nuclear reactors.

KEY WORDS: reactor-stellarator, ambipolar electric field, neoclassic transport, power and plasma density balance

REGULARIZATION OF THE NONLINEAR THEORY OF DRIFT WAVES IN THE INHOMOGENEOUS MAGNETIZED COLLISIONAL PLASMA

A.A. Vodyanitskii

Full Text :   (470 kB, Rus.) 

Abstract
Nonlinear oscillations of the magnetized non-uniform collisional plasma are studied. Basic nonlinear equation is got for waves and regularization of the theory of perturbation is considered. It consists in the inclusion of dissipative terms into normal functions and in an account of their derivatives with respect to the the non-unifrm coordinate This procedure supplies with the crucial non-linearities which determine the nonlinear stabilization of drift-dissipative instability and anomalous transfer of plasma.

KEY WORDS: nonlinear theory, magnetized plasma, drift-dissipative instability

INVESTIGATION OF AXIAL STRUCTURE OF DC GLOW DISCHARGE IN NITROGEN BY LANGMUIR PROBE METHOD

V.A. Lisovskiy, V.A. Koval, E.A. Kravchenko

Full Text :   (1630 kB, Rus.) 

Abstract
This work studies with a Langmuir probe axial profiles of such plasma parameters as electron temperature, plasma potential and concentration of the direct current glow discharge in nitrogen for various gas pressure values. The electric field strength is shown to be small in the negative glow whereas axial profiles of plasma concentration and electron temperature possess maxima. These parameters approach their minima near the interface separating the negative glow and the dark Faraday space. The strata are observed in the positive column at low gas pressure whereas at higher pressure (above 0.5 Torr) the column becomes uniform. The axial profile of plasma concentration in the dark Faraday space is found to attain a maximum that may exceed the average plasma concentration in the positive column. Increased ionization in the dark Faraday space may be caused by a step-like ionization of metastable nitrogen molecules by electrons having acquired the sufficient energy in the increasing electric field. It is expedient not to relate the dark Faraday space to cathode parts of the glow discharge but regard this space as a starting (preliminary) form of the positive column.

KEY WORDS: glow discharge, Langmuir probe, dark Faraday space, positive column, nitrogen

AMBIPOLAR DIFFUSION IN A PLASMA CONSISTING OF ELECTRONS, NEGATIVE IONS AND TWO TYPES OF POSITIVE IONS

V.A. Lisovskiy

Full Text :   (840 kB, Rus.) 

Abstract
In this work we investigated the ambipolar diffusion in electronegative plasma. The case of a plasma containing electrons, one kind of negative ions and two kinds of positive ions is considered. The formulas for the coefficient of ambipolar diffusion are obtained, which in extreme cases (one kind of negative ions, electropositive plasma) give the well-known results. It is shown that in a plasma with a density of negative ions more than 10 times higher the density of electrons, it is necessary to take into account the mobility of positive and negative ions. It was found that in strongly electronegative plasmas diffusion is no longer ambipolar, the ambipolar diffusion coefficients of charged particles are approximately equal to their free diffusion coefficients.

KEY WORDS: ambipolar diffusion, negative ions, positive ions, electronegative plasma

COMPUTER SIMULATION OF EFFICIENCY ENHANCEMENT THROUGH PROFILING GUIDING MAGNETIC FIELD AT COAXIAL GYRO-BWO

V.M. Khoruzhiy

Full Text :   (330 kB, Eng.) 

Abstract
The gyro-BWO is a UHF powerful oscillator for cm and mm band of wavelength in which relativistic electrons beam is used for coupling with a backward wave on normal Doppler effect. The first research of gyro-devices was published in 60th. Possible applications of gyro-devices UHF radiation are the followings: electron cyclotron resonance heating of plasma for controlled fusion, communication, spectroscopic researches, high-resolution radars etc. Investigations of gyro-BWO confirm that an essential limitation of the considered device is the small efficiency. One of possibilities for efficiency enhancing is to use profiling guiding magnetic field along an interaction region. We investigated dependence of efficiency increasing under using optimal profiling guiding magnetic field by special law. As a result of effective process bunch formation under special conditions most electrons can be confined in the energy-losing phase HF field. Efficiency enhancement takes place from initial value η~0,1 for homogenous guiding field to η~0,3 for profiling one.

KEY WORDS: microwaves, gyro-devices, backward wave oscillators, guiding magnetic field, efficiency, computer simulation

FOCUSING OF ELECTRON BUNCHES WAKE FIELDS IN A PLASMA-DIELECTRIC WAVEGUIDE

R.R. Kniazev, .G.V. Sotnikov

Full Text :   (560 kB, Rus.) 

Abstract
The excitation of wake waves by the electron bunch in an isotropic plasma-dielectric waveguide is studied. It is shown that the excited field consists of two components: the field of the Langmuir wave and the field of eigenmodes of a dielectric waveguide. At a certain plasma density, the longitudinal component of the Langmuir waves is much smaller longitudinal component of the dielectric waves and transverse field components of the Langmuir wave is much larger transverse components of the dielectric waves. The periods of these two types of waves differ significantly. This allows to provide the acceleration of the test bunch by a field of the dielectric wave with its simultaneous focusing by the plasma wave field.

KEY WORDS: acceleration, focusing, wakefield, bunch, dielectric waveguide, plasma

DOSE MAPPING OF A GAMMA INDUSTRIAL RADIATION FACILITY USING A PRACTICAL AND COMPUTATIONAL DOSIMETRY

N. Boshnakova, V.T. Lazurik, V.M. Lazurik, G. Popov, Yu. Rogov

Full Text :   (460 kB, Eng.) 

Abstract
Comparison results for absorbed dose mapping of the Co⁶⁰ industrial radiation facility BULGAMMA of Sopharma PLC, Bulgaria using a practical and computational dosimetry are presented in the paper. The gamma radiation facility is based on JS-8500 Co⁶⁰ irradiator produced by MDS Nordian, Canada. The absorbed dose distributions of gamma rays in an irradiated product on JS- 8500 Co⁶⁰ irradiator have been calculated using the ModeGR Monte Carlo software. The software ModeGR was designed specially for simulation of the absorbed dose distribution within multi-layer packages irradiated with gamma ray from flat panoramic Co⁶⁰ source rack using a Monte Carlo method. Absorbed dose measurements into containers filled with material using Ethanol Chlorobenzene chemical dosimeters were carried out to validate the software ModeGR. The comparison results show that software ModeGR can be used as a predictive tool for detailed dose mapping in gamma irradiated product.

KEY WORDS: computational dosimetry, software ModeGR, Monte Carlo method, absorbed dose mapping, industrial gamma facility

NEUTRON RADIATION UNDER THE DRY STORAGE OF THE SPENT NUCLEAR FUEL

V.G. Rudychev, Y.V. Rudychev, S.A. Pismenetskiy, A.F. Shchus

Full Text :   (300 kB, Rus.) 

Abstract
To calculate the neutron radiation field around a ventilated container filled with spent nuclear fuel at ZNPP dry accumulated Monte Carlo simulation package used implemented in MCNP. It is shown that the main source of neutrons in the spent fuel is stored ²⁴⁴Cm, the contribution of (α,n) reactions is negligible. The neutron spectrum for the simulation was described by the Maxwell distribution. There is a significant difference between the neutron dose rate in the axial and radial directions due to the differences in the protective properties of the container in their respective areas. To strengthen the radiation protection from the neutron emission during storage of spent nuclear fuel with high burnup offered an additional shield, and its dimensions are optimized to ensure a significant reduction in dose. The characteristics of neutron fluxes in long-term storage of spent nuclear fuel are calculated.

KEY WORDS: snf, dry storage, mcnp-simulation, external cask radiation, neutrons, time dependence

X-RAY QUASI-MONOCHROMATIC SOURCE BASED ON ELECTROSTATIC PROTON ACCELERATOR

S.A. Vershynskyi, O.M. Buhay, M.I. Zaharets, V.L. Denysenko, V.E. Storizhko

Full Text :   (1200 kB, Rus.) 

Abstract
The microanalytical facility based on an electrostatic accelerator available at the Institute of Applied Physics, is used to construct a high-intensity quasi-monochromatic X-ray source with ion excitation. The results of ion-optical system modeling for the source are presented. Polycapillary optics is chosen to perform X-ray focusing of radiation, produced by source. K-line yield calculations of characteristic X-rays are performed and compared with experimental data. As preliminary calculations show, 2 MeV proton beams provide the K-line yield similar to that obtained with 30 - 50 keV electron beams but with the bremsstrahlung background reduced by two orders of magnitude. Thus, filters or monochromators are practically unnecessary.

KEY WORDS: X-ray quasi-monochromatic source, electrostatic accelerator, X-ray optics, X-ray yield measurements, ion-optical system

STUDY OF THERMAL PROCESSES IN VACUUM-DIVIDING AND OUTPUT FOILS OF THE ELECTRONIC ACCELERATORS

S.P. Gokov, V.I. Kasilov, L.A. Makhnenko, A.A. Khomich

Full Text :   (750 kB, Rus.) 

Abstract
The mathematical model, based on the principles of thermodynamics, was obtained for a thin metal (titanium) foils used in accelerator technology, on passing through these foils of electron beams with a Gaussian distribution of the current density in the section. The results of calculation using the mathematical package Mathcad 15 the temperature dependences for the foils of various thicknesses and сooling terms are presented.

KEY WORDS: electron beam, titanium foil, ionization losses, the heat balance equation

INFLUENCE OF SUBSTITUTIONAL DISORDER IN MAGNETIC ALLOY Fe_1-xCo_x ON SPIN-DEPENDENT TUNNELING

I.N. Marushchenko, V.M. Karpan, N.A. Azarenkov, P.J. Kelly

Full Text :   (630 kB, Rus.) 

Abstract
A quantitative study of the influence of substitutional disorder on the transport properties of Fe_1-xCo_x magnetic tunnel junctions is presented. From the first principle calculations with taking into account the parameter-free electronic structure it has been found that the substitutional disorder produces a strong effect on the spin-polarized transport in the limit of low concentration of Co in Fe_1-xCo_x alloy, and is negligible when the concentration of cobalt in alloy is larger than 40%. The obtained results are important for understanding the mechanisms responsible for the giant tunneling magnetoresistance.

KEY WORDS: spin-polarized transport, magnetic tunnel junction, surface states, disorder

SIMULATION OF THERMAL EFFECTS OF HIGH-CURRENT RELATIVISTIC ELECTRON BEAM ON THE TITANIUM ALLOY VT1-0

V.V. Lytvynenko, A.G. Ponоmarev, O.A. Startsev, V.T. Uvarov

Full Text :   (950 kB, Ukr.) 

Abstract
Modifying impact of the cannular pulse high current relativistic electron beam on the titanium VT1-0 alloy lamina target is observed. The mathematical model of temperature field of beam-target interaction is constructed and thereafter numerical analysis are carried out. Linkages between microstructure characteristics and exposure factors (temperature field and ablative processes) are ascertained. The process of crater formation is considered. It is describing the influence of condensed process of ablative release on the surface layers structure.

KEY WORDS: ablative processes, electron beam, hydrodynamic sputtering, crater formation

CALCULATION OF A SIMPLE CYLINDRICAL MODERATOR FOR NEUTRON DETECTOR

A.Yu. Buki, S.A. Kalenik

Full Text :   (360 kB, Rus.) 

Abstract
Mathematical modeling of the passage of neutrons through cylindrical polyethylene moderator of neutron detector had been performed. Had been calculated amount of thermal neutrons that fall in located on the axis of the moderator gas discharge tube counters of thermal neutrons. For different diameters of the moderator the energy depending of the detection efficiency of incident neutrons had been obtained. Found the diameter of the moderator, in which the detection efficiency is quite high (10%) and nearly constant for neutrons with energies from thermal to 1 MeV. It is noted that a detector with these characteristics is optimal for the registration of delayed fission neutrons and can be used in installations of activation analysis for the content of fissionable materials.

KEY WORDS: neutron detector, neutron counter, neutrons, neutron fields, simulation

DIFFUSION IN THE SURFACE LAYERS OF OXIDE INCLUSIONS IN DISPERSE STRENGTHENING α-FE

V.G. Kirichenko, O.V. Kovalenko, M.G. Kompaniiets, V.N. Leonov

Full Text :   (1400 kB, Rus.) 

Abstract
The results of the concentration dependence analyzing of the inclusions elemental composition and the matrix to determine the comparative values of diffusion coefficients in disperse strengthening α-iron. Numerical simulation of two-dimensional data is allowed to obtain the three-dimensional forms of oxide inclusions. The values for D_Al, D_Y in the iron, involving published data on the diffusion of iron in different temperature ranges. According to our data, the diffusion coefficients of the elements included (Y, Al, Ti) in the case of the model system is higher than the self-diffusion coefficient of iron.

KEY WORDS: iron, nanoparticles, oxide, yttrium, structure, phase composition, diffusion

THE STRUCTURE OF NANOMETRIC FERRITE’S FILMS AFTER ION IMPLANTATION

V.G. Kirichenko, O.V. Kovalenko

Full Text :   (410 kB, Eng.) 

Abstract
The results of study of hexaferrite Ва and Bi-Gd garnet films on gadolinium gallium garnet substrates are presented. In the result of ion-beam induced deposition the amorphous paramagnetic films of Ва-hexaferrite and Bismuth gadolinium garnet film are formed on substrate surface and then under the thermal annealing they transform their state into magnetically ordered one. For the easy magnetization axis to turn into the film plane the most efficient makes is ion beam implantation of Не+ ions.

KEY WORDS: thin films, element and phase composition, hexaferrite Ва, Bi-Gd garnet, spectroscopy

AN EFFECT OF WATER ON THE URANIUM SUPERCRITICAL CO2 EXTRACTION EFFECTIVENESS FROM NATURAL MINERALS

B.V. Borts, Y.G.Kazarinov, S.A. Sirenko, S.F. Skoromnaya, V.I. Tkachenko

Full Text :   (800 kB, Rus.) 

Abstract
Experimental data on investigation of water effect on efficiency of supercritical fluid extraction by carbon dioxide (SFE-CO₂) of uranium complexes from nature minerals at carbon dioxide pressure to 20.0 MPa and temperature to 45°C are presented. It is shown that dependence of extraction efficiency on water quantity has the peak pattern, that is, under specific pressure and temperature the efficiency of extraction is maximal. Conditions under which the maximal efficiency of SFE-CO₂ complexes of uranium is attained are determined. Two level model for description of SFE-CO₂ extraction of water is proposed. The proposed model corresponds well with experimental data. Double two level model for description of SFE-CO₂ extraction of uranium complex in the presence of water is proposed. The experimentally observed decrease of uranium complex extraction efficiency with the increase of free water quantity is described analytically by the use of double model. It is confirmed in the frame of double model that the maximum efficiency of extraction is attained for water quantity completely bounded by uranium complex and corresponding to its limit of solubility in supercritical CO₂. The proposed models allowed evaluate the values of probability of induced transitions in two-level systems.

KEY WORDS: supercritical carbon dioxide, supercritical extraction, uranium, water, tributyl phosphate, two-level system

MODIFIED ABSORPTION METHOD OF DIFFUSION PARAMETERS DETERMINATION

O.S. Posukhov, V.Y. Semenenko, M.G. Styervoyedov, T.O. Kovalenko

Full Text :   (520 kB, Rus.) 

Abstract
Both the modified method for the study of diffusion in metals and alloys and the structure of instrumental measuring complex has been presented. The new method for the determination of activation energy Е and preexponential factor D_o for one cycle of the diffusion annealing has been developed. The results obtained for the diffusion parameters are in good agreement with published data.

KEY WORDS: diffusion, modified absorption method, temperature gradient

USING THE ACCOMPANYING WINDOW IN BOR-FDTD METHOD FOR THE CALCULATION OF CONDUCT PRECURSOR IN THE DIELECTRIC WAVEGUIDE

A. Butrym, L. Kolomietc, M. Legenkiy

Full Text :   (340 kB, Rus.) 

Abstract
The paper deals with numerical solution of Maxwell equations by the method of finite differences in the time domain for bodies of revolution (BOR-FDTD) in an open domain using moving frame. The latter made possible to calculate long time propagation of a pulse precursor in a dielectric waveguide.

KEY WORDS: method of finite differences in the time domain for bodies of revolution, BOR-FDTD, precursor, dielectric waveguide