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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)

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.

P13-2016-17 (156.5)
Pepelyshev Yu.N., Popov А.К., 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.

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.