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Preprints and Communications

Here you can find JINR preprints and communications in pdf format starting from 1999.
File size is given in bytes in round brackets.

Subject Categories for JINR Publications Archive (1999 - 2015)

P15-2016-1 (14221.520)
Didyk A. Yu., Gulbekyan G. G., Myshinskiy G. V.
Anomalies on the Inner Surfaces of the Xenon High-Pressure Chamber XeHPC 250 Bar with the Synthesis of Microparticles of Complex Composition under Irradiation with Bremsstrahlung Threshold Energy of 10 MeV

Natural xenon at an initial pressure of 250 bar in a special chamber (XeHPC) was irradiated for 60 h 16 min (2.17 105 s) by braking γ-rays with a threshold energy of 10 MeV at the electron accelerator MT-25 at an average intensity of the beam of 20–22 µA. With increase in temperature the pressure in the steady state at the beginning of exposure grew up to 270 bar. After opening of the XeHPC both internal chambers with all the structures and particles, but without gas, were measured using a γ-germanium detector. Visual inspection of the inner chambers showed visible dense greenish-yellow coating of significant thickness formed on their surfaces. X-ray microprobe analysis (RMPA) and SEM studies allowed us to determine the composition of the synthesized particles.

P11-2016-4 (255.5)
Amirkhanov I.V. et al.
Investigation of Quasi-Stationary States in the Double-Barrier Open Well

In this paper an investigation of solutions of quasi-stationary states in the framework of the Schroedinger equation with complex energies with piecewise constant potentials for various values of the parameters of the potential is conducted. Quasi-levels are found for the under- and above-barrier cases. For the given potential barrier heights the number of under-barrier quasi-levels for the double-barrier potential is more than for the single-barrier potential. The calculations show that the real part of the energy varies smoothly and the imaginary part of the energy changes irregularly when changing the parameters of the potential.

p9-2016-6 (927.7)
Nozdrin M.A. et al.
Diagnostics at JINR LHEP Photogun Bench

The photoinjector electron beam quality dramatically depends on the laser driver beam quality. For laser beam diagnostics a "virtual cathode" system was realized at the JINR LHEP photogun bench. The system allows one to image laser beam profile at the cathode. The AVINE software complex developed in DESY Zeuthen is being used for imaging. Equipment for emittance measurement using the slit method was installed. The original emittance calculation software EmCa was created and tested with the laser beam.

E17-2016-8 (116.0)
Bogolubov N.N. (Jr.), Soldatov A.V.
Variational Master Equation Approach to Dynamics of Magnetic Moments

Non-equilibrium properties of a model system comprised of a subsystem of magnetic moments strongly coupled to a selected Bose field mode and weakly coupled to a heat bath made of a plurality of Bose field modes were studied on the basis of non-equilibrium master equation approach combined with the approximating Hamiltonian method. A variational master equation derived within this approach is tractable numerically and can be readily used to derive a set of ordinary differential equations for various relevant physical variables belonging to the subsystem of magnetic moments. Upon further analysis of the thus obtained variational master equation, an influence of the macroscopic filling of the selected Bose field mode at low enough temperatures on the relaxation dynamics of magnetic moments was revealed.

P13-2016-10 (405.9)
Pepelyshev Yu.N., Tsogtsaikhan Ts.
Prediction of the Thermal Dynamic Parameters Fluctuation of Coolant System of the IBR-2M Reactor Using Neural Networks

This paper presents an artificial neural network method for long-term prediction of the thermal dynamic parameters of primary coolant circuit of the IBR-2M reactor. The main goal is to predict the temperature and liquid sodium flow rate through the core and thermal power. It is shown that the prediction can reduce three times the effects of slow reactivity fluctuations in power and decrease the requirements for the automatic power stabilization system. Nonlinear autoregressive neural network (NAR) with local feedback connection has been considered. The results of prediction error ~ 5% coincide with the experimental ones.

P11-2016-14 (1.859.0)
Batgerel B., Nikonov E.G., Puzynin I.V.
A Procedure for Constructing Symplectic Numerical Schemes for Solving Hamiltonian Systems of Equations

A new procedure for constructing symplectic numerical schemes for solving the Hamiltonian systems of equations is proposed. A method for symmetrization of the obtained symplectic numerical schemes is suggested. The numerical schemes constructed by the above procedure conserve the energy of a system on the large interval of numerical integration for relatively large integration step in comparison with the Verlet method which is usually used for solving equations of motion in molecular dynamics. Results of numerical experiments are given. These results show the main advantages of the obtained symmetric symplectic numerical schemes of the third order of accuracy for the integration step for the Hamiltonian systems of equations in comparison with numerical schemes of the Verlet method of the second order of accuracy.

P13-2016-17 (156.5)
Pepelyshev Yu.N., Popov �.�., Sumkhuu D.
Estimation of Power Feedback Parameters of the IBR-2M Reactor by Square Wave Reactivity

Parameters of the IBR-2M reactor power feedback (PFB) are estimated based on the analysis of power transients caused by deliberate square wave reactivity when the pulsed reactor operates in the self-regulation mode. The PFB of the IBR-2M is described by three linear first-order differential equations. Two components of the PFB are responsible for the negative feedback and one, for the positive. The overall feedback is negative, i.e., it has a stabilizing effect for the operation of the reactor. The slowest negative component of the PFB is probably caused by heating of the fuel. Periodically repeated in the process of exploitation, estimation of the PFB parameters is one of the methods to ensure safety operation of the reactor.

P13-2016-20 (1.004.3)
Pepelyshev Yu.N. et al.
Application of the Properties of Toeplitz Matrices of the Noise Correlation Characteristics to the Diagnostics of the IBR-2M Pulsed Reactor

The safeguarding of a nuclear reactor during the operation process is one of the most significant tasks. The difficulty is in the necessity to use nondestructive methods. One of such perspective methods is the neutron noise diagnostics of a nuclear reactor. Possibility of the noise diagnostics by the new method of norms of positive definite Toeplitz correlation matrices is studied. The advantage of this method is its purely mathematical nature; no model of the process is employed. The neutron noise analysis of the IBR-2M pulse energy has been carried out by the represented method. Both the static state and dynamic state of the reactor have been studied. Frequency analysis of unstable components of the reactor noise has been carried out. The main unstable components of the neutron noise are frequencies of 0.8 and 1.6 Hz, which are conditional on the vibration of the movable reflector blades of the reactivity modulator. The results of this diagnostics have been compared with the results of the classical spectral analysis.

E7-2016-21 (292.6)
Volkov V.V., Cherepanov E.A., Kalandarov Sh.A.
Interpretation of the Mechanism of Spontaneous Fission of Heavy Nuclei in the Framework of Dinuclear System Conception

A new approach to the interpretation of the process of spontaneous fission of heavy nuclei is suggested. It is based on nuclear physics data which are obtained in heavy ion collisions. The process of spontaneous fission consists of three sequential stages: clusterization of the valent nucleons of a heavy nucleus into a light nucleus-cluster, which leads to the formation of a dinuclear system; evolution of the dinuclear system which proceeds by nucleon transfer from the heavy to light nucleus; and decay of the dinuclear system from the equilibrium configuration into two fragments.

P13-2016-23 (543.803)
Tsulaia M. I. et al.
Upgraded Experimental Setup KOLHIDA Designed to Study Interactions of Polarized Neutrons with Polarized Nuclei

We study the adsorption of anionic surfactant, sodium dodecyl diphenyloxide disulfonate (SDDD) on three types of polyethylene terephthalate (PET) substrates from aqueous solutions of SDDD of different concentrations. Neutral electrolyte (KCl) was added to the solutions to vary the ionic strength. Three types of substrates were used: 1) original PET film; 2) etched nonporous film, obtained from pristine film by chemical etching and bearing negative charge on the surface; 3) etched porous membranes, fabricated from pristine film by ion irradiation and subsequent chemical etching. The membranes have negative charge on the flat surface and on the inner pore walls. The comparison shows that the negative charge on the flat surface has weak effect on adsorption of the anionic surfactant, and the SDDD adsorption on the inner walls of pores is much weaker than on flat surface, even if the pore radius is significantly larger than the Debye length. This exclusion effect strongly depends on ionic strength of solution.

E14-2016-24 (664.7)
Nyamdavaa E. et al.
Preparation and Characterization of La1-xCexCoO3 Perovskite Oxides for Energy Materials

Cerium-doped lanthanum cobaltite perovskites (La1-xCexCoO3 with x = 0, 0.2, 0.4) were prepared by the sol-gel method (calcined for 5 h at 750ºC) and characterized by X-ray diffraction (XRD), X-ray absorption (XAS), energy-dispersive X-ray spectroscopy (EDS), and BET surface area analysis. The results showed that the cerium doping promoted the structural transformation of LaCoO3 from rhombohedral into the cubic structure. High specific surface area and small crystallite size are achieved at x = 0.2. The XAS results confirmed the formation of compound La1-xCexCoO3.

P14-2016-26 (691.931)
Artoshina O. V. et al.
Structure and Phase Composition of the Titanium Dioxide Thin Films Deposited on the Surface of the Metallized Track Membranes from Polyethyleneterephthalate by Reactive Magnetron Sputtering

Thin films of TiO2, Ag, Ag-TiO2, Cu-TiO2 deposited on the surface of polyethyleneterephthalate track membranes (TM) were investigated. Metals and oxide deposition was carried out by the method of vacuum reactive sputtering with application of a planar magnetron. The microstructure of samples was studied by the scanning and transmission electron microscopy (TEM) techniques. The elemental composition of coatings was investigated using energy-dispersive spectroscopy. For the identification of phase structure, X-ray diffraction phase analysis was used at various temperatures, and the XRD crystal structure patterns of the samples were obtained by the selected area electron diffraction (SAED) in TEM analysis. It was found that titanium dioxide on the TM surface can be present in three forms: nanocrystals of tetragonal anatase with impurity of rhombic brookite and the so-called X-ray amorphous TiO2. Cubical Cu2O was identified in TM metallized by copper. Optical properties of composite membranes and films were investigated by the method of absorption spectroscopy. Calculation of energies of the direct and indirect allowed optical transitions was carried out based on the analysis of absorption spectra of the studied composite membranes.

P6-2016-29 (231.164)
Gustova M. V., Maslov O. D., Sabelnikov A. V.
Application of TEVA Resin for the Separation of the Products of Photonuclear Reaction 237Np(γ, n) 236mNp → (β)236Pu

The paper reports on the possibility of using TEVA resin (TRISKEM company), made on the basis of the Aliquat-336 extractant (a quaternary ammonium salt), for the isolation and concentration of 236Pu. The 236Pu isotope was produced as a result of the photonuclear reaction 237Np(γ, n) 236mNp → (β)236Pu using the linebreak MT-25 microtron at FLNR, JINR. Plutonium-236 was separated on the TEVA resin from 237Np target. Products of (γ, f) photonuclear reactions, daughter products of 236Pu and 237Np, fragments of 237Np(γ, n) (237Np, 232U, 228Th, 233Pa, 137Cs, etc.) induced fission were also separated. The content of the actinide elements in 236Pu was less than 10-6 Bq/Bq.

P13-2016-33 (500.863)
Azorskii N. I. et al.
New Type of Drift Tubes for Gas-Discharge Detectors Operating in Vacuum: Production Technology and Quality Control

A device for fabricating thin-wall (straw) drift tubes using polyethylene terephthalate film 36 µm thick by ultrasonic welding is described together with the technique for controlling their quality. The joint width amounts to 0.4–1.0 mm. The joint breaking strength is 31.9 kg/mm2 The argon leakage from a tube of volume 188.6 cm3 under a pressure gradient of 1.0 atm does not exceed 0.3 10-3cm3min, which is mainly related to the absence of metallization in the joint vicinity. The high strength, the low tensile creep due to the absence of glued layers, and the small value of gas leakage make the new tubes capable of reliable and long-term operation in vacuum, which is confirmed by the operation of 7168 straw tubes for two years in the NA62 experiment.

P13-2016-37 (653.4)
Babkin V. A. et al.
Setup for Testing of Detectors at the Nuclotron MPD Test Beam

A new specialized setup MPD test beam was created at the extracted beam of the Nuclotron to carry out methodical research and testing detectors for the MPD experiment at the NICA collider. The setup is described in detail. Results of the test of fast detectors for the MPD TOF system are presented as an example of the setup operation.

P3-2016-39 (514.3)
iselev . ., Zemlyanaya . V.
Dehydration of the Intermembrane Space in the Multilamellar Membranes of Dipalmitoylphosphatidylcholine under the Influence of Dimethyl Sulfoxide. Neutron and Synchrotron Study

On the basis of the separated form factors method (SFF), the analysis of data on the small-angle neutron scattering (SANS) on polydispersed population of unilamellar vesicles of dipalmitoylphosphatidylcholine (DPPC) in heavy water with dimethyl sulfoxide (DMSO) is carried out. It is shown that the growth of DMSO molar fraction in water from 0 to 15% leads to increase of thickness of the bilayer to values of the repeat distance of multilamellar membranes of DPPC, which means a dehydration of the intermembrane space and steric contact of the neighbor bilayers of DPPC at a DMSO molar fraction of 15%.

E3-2016-43 (1.532.519)
Vu D. C. et al.
Representation of the Radiative Strength Functions in the Practical Model of Cascade Gamma Decay

The developed in Dubna practical model of the cascade gamma decay of neutron resonance allows one, from the fitted intensities of the two-step cascades, to obtain parameters both of level density and of partial widths of emission of nuclear reaction products. In the presented variant of the model a part of phenomenological representations is minimized. Analysis of new results confirms the previous finding that dynamics of interaction between Fermi- and Bose-nuclear states depends on the form of the nucleus. It also follows from the ratios of densities of vibrational and quasi-particle levels that this interaction exists at least up to the binding neutron energy and probably differs for nuclei with varied parities of nucleons.

E3-2016-43 (1.532.519)
Omelyanenko M. M. et al.
Low-Noise Pulse-Mode Current Power Supply for Magnetic Field Measurements of Magnets for Accelerators

The described pulse-mode current power supply has been designed and fabricated for the magnetic field measurement system of superconducting magnets for accelerators. The power supply is based on a current regulator with pass transistor bank in linear mode. The output current pulses (0100 A) are produced by using the energy of preliminary charged capacitor bank (540 V), which is charged additionally after each pulse. There is no AC-line frequency and harmonics ripple in the output current, the relative noise level is less than 100 dB (or 10-5 of RMS value (it is defined as the ratio of output RMS noise current to the maximal output current 100 A within the operating bandwidth, expressed in dB).

P15-2016-44 (219.4)
Kabdrakhimova G. D. et al.
Investigation of the Total Cross Sections in the Interactions of 6He and 4He Nuclei with Si Nuclei at 550 MeV/A

The analysis of the experimental excitation functions of the total cross sections of nuclear reactions 6He+Si and 4He+Si in the energy range 550 MeV/A and a brief overview of the techniques by which experimental data were obtained have been presented. Detailed attention is given to the description of experiments conducted with beams of radioactive nuclei of the accelerators of FLNR JINR. Analysis of experimental data was performed using the semi-microscopic optical model.

P4-2016-50 (251.6)
Pupyshev V. V.
The Amplitude Functions Method in the Theory of Two-Dimensional Scattering

In the present work, we formulate and give the mathematical foundation of the amplitude functions method. This method is adopted for solving the radial problem of two-dimensional scattering of a quantum particle by the sum of the Coulomb potential and a central short- or long-range potential.