Here you can find JINR preprints and communications in pdf format starting from 1999. File size is given in bytes in round brackets.
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E6-2025-57 (6.053.929)
Izosimov I. N.
Structure of the β-Decay Strength Function
The experimental measurement data on the resonance and fine structure
of the beta-decay strength function Sβ(E) in spherical, transitional, deformed
and halo nuclei are analyzed. Modern nuclear spectroscopy methods allowed
the split of the peaks caused by nuclear deformation to be revealed in Sβ(E)
for transitions of the Gamow–Teller (GT) type. The resonance structure of
Sβ(E) for first-forbidden (FF) transitions in both spherical and deformed
nuclei is experimentally proved. It is shown that at some nuclear excitation
energies, FF transitions can be comparable in intensity with GT transitions.
Analysis of the evolution of the energy differences (EGTR–EIAR) between the GT
resonance (GTR) and the isobar-analog resonance (IAR) with an increase of
the neutron excess in the nuclei was done. The SU (4) Wigner’s spin–isospin
symmetry region was predicted.
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P13-2025-54 (865.277)
Podlesnyy M. M. et al.
Bending of Fuel Assemblies in the IBR-2M Reactor Core and Their Influence on Reactivity
The paper studies the phenomenon of fuel assembly (FA) bending under the
influence of non-uniform temperature distribution in the core of a periodic pulsed
reactor. Numerical calculations of transverse FA deformations are performed for
the IBR-2M reactor, and their impact on reactivity and reactor dynamics is
calculated. It’s shown that the effect introduces positive feedback on reactivity.
Since bending has a negative impact on reactor dynamics, measures must be
taken to reduce this effect in a new neutron source.
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P13-2025-51 (1.327.702)
Pepelyshev Yu. N. et al.
Start-Up of the IBR-2M Reactor after a Long Stop.
Reactor Dynamics
The results of a dynamics study of the IBR-2M reactor obtained during the
first reactor start-up after a long stop are presented. Estimates of the reactor’s
stability are given, and the prospects for reactor operation are presented.
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E13-2025-50 (2.003.258)
Tsyganov Yu. S. et al.
Detection System of DGFRS-2 Setup: Simulation of Heavy Recoil
Spectra and Radiation Limits
The detection system of the DGFRS-2 setup was employed in longterm
experiments using ion beams of 40Ar, 48Ca, 50Ti, and 54Cr generated
by the DC-280 ultraintense cyclotron at the Flerov Laboratory of Nuclear
Reactions (JINR). The registered energy spectra of recoiled superheavy nuclei
were compared to calculated spectra and satisfactory agreement was achieved.
Additionally, radiation effects observed during prolonged irradiation were
investigated. These effects included the growth of leakage current in the DSSD
focal detector as well as limitations on the use of silicon detectors and the
application of ER spectra modeling in long-term heavy-ion beam experiments.
A representative example illustrating the increase in leakage current of a DSSD
detector during the experiment is presented. An attempt to predict the lifetime
of the DSSD detector in heavy-ion-induced nuclear reaction experiments at the
DGFRS-2 setup is proposed, based on simple scaling of radiation damage effects
using the non-ionizing energy loss (NIEL) concept.
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P13-2025-49 (2.342.156)
Pepelyshev Yu.N. et al.
Investigation of Pulse Energy Fluctuations of the IBR-2M Reactor Using the Method of Basic Elements
The dynamics of the spectral structure of the pulse energy noise of the
IBR-2M reactor has been studied with the resonant baseline subtraction from
experimental data using basic elements method. The behavior of the resonant
noise component depending on the reactor power and operating time has shown
good agreement with the results of reactor dynamic modeling studies. The
coincidence of the resonant baseline component with a peak at a frequency of
0.1 Hz and the amplitude-frequency response of the IBR-2M reactor is shown.
This fact once again confirms the completeness and accuracy of the assessment
of the reactor dynamic properties using dynamics model and methods of noise
analysis, as well as the applicability of the dynamics model and basic elements
method for the current state analysis of the reactor and forecast evaluation.
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P13-2025-48 (537.991)
Pepelyshev Yu.N. et al.
Choosing the Optimal Operation Mode of the IBR-2M Reactor
The IBR-2M pulsed reactor has one unpleasant property — low-frequency
oscillatory instability. For ensuring safe operation of the IBR-2M, a pulse energy
noise diagnostic system has been set up using a reactor dynamics model. Taking
into account the rather strong weakening of the power feedback, which causes an
increase in low-frequency resonance in pulse energy fluctuations during energy
release above 1830 MW· day, a conservative estimate of the optimal power
level to ensure reliable and safe operation of the reactor can be chosen equal
to 1.35 MW with a sodium coolant flow rate through the core of 100 m3/h.
At this power, the total calendar operating time of the reactor is 3 years. The
optimal power value can be increased by further optimizing the sodium flow
through the core.
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P13-2025-47 (1.465.033)
Verkhoglyadov A. E., Verkhoglyadova V.N.
On Methods for Eliminating Positive Feedback in Periodic Pulse Reactors
The paper investigates the phenomenon of transverse bending of rod fuel
elements of the active zone under the influence of temperature, which plays an important role in the dynamics of a periodic pulse reactor. Analytical calculation
of thermoelastic deformation showed that positive feedback is directly related to the method of fixing the fuel elements. The possibility of fixing, eliminating the positive effect of reactivity, is demonstrated, and ways of technical solution of
the problem are proposed.
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P4-2025-46 (270.510)
Usmanov P.N. et al.
Analysis of the Probabilities of E2 Transitions and Energies
for States of Positive Parity of 182, 184W Isotopes
The probabilities of E2 gamma transitions and energies for states of positive
nuclear parity are investigated. The energy spectrum, the structure of the states
of the main, β- and γ-vibrational bands, the probabilities of in-band and interband
E2 transitions, as well as the ratios of the probabilities of E2 transitions from
the levels of the γ-vibrational band are calculated. The possibility of studying
mixing effects using the same inertial parameters for all mixing adiabatic bands
is demonstrated, which cannot be done without taking into account the Coriolis
interaction. The analysis showed that the nonadiabatic behaviour manifested in
the energy spectrum and electromagnetic characteristics is associated with a
strong mixing of β- and γ-bands levels due to the closeness of their head levels.
The calculated values of energy, E2 transition probabilities, and their ratios are
in good agreement with experimental data.
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P10-2025-45 (1.868.232)
Truntova L. A., Kirilov A. S.
A New Version of SpectraViewer for Data Visualizsation
at thå IBR-2 Reactor Instruments
The SpectraViewer program is an important component of the Sonix+ software
package designed for data visualization at the IBR-2 reactor instruments.
Its development history goes back more than 20 years, during which it was
changed several times, which required the code correction. The paper discusses
the features of the new version of the program, in which the so-called refactoring
was performed, i. e., complete code reprocessing while maintaining its
functionality. Like the previous version, the program is implemented in the
Python language using the PyQt framework, the matplotlib library and the
numpy package. After this the code size was reduced by four times. Besides,
the program can be used both as a 32- and 64-bit application, which practically
does not limit the size of the spectra. This year the program was installed and
successfully used at a number of the IBR-2 instruments.
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P13-2025-44 (6.415)
Petukhova T. B., Papushkin I.V.
The Loading Machine Control on the FSD Diffractometer
of the IBR-2 Reactor in the Sonix+ Software Package
The work is devoted to the integration of loading machine LM-20 control into
the Sonix+ Software Package. The loading machine is installed on channel 11 of
the IBR-2 reactor (neutron Fourier stress diffractometer FSD) to study samples
under external load (±20 kN) and at high temperatures (up to 800°C) in the
in situ mode in a neutron beam.
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E2-2025-43 (122.799)
Pestov I.
Essence of Dark Matter
The right-hand side of the Einstein equation is purely phenomenological.
We note that in the Lorentz theory of electrons the right-hand side of the
Maxwell equations is purely phenomenological as well. But with the discovery
of field, or quantum, electrodynamics, based on the Maxwell–Schrödinger and
Maxwell–Dirac equations, the details of the right-hand side of the Maxwell
equations were clarified on the fundamental field-theoretical level. In this paper,
we formulate a field theory of the gravitodynamics. The main notions and
equations of the field, or quantum, gravitodynamics are established and, hence,
the essence of the so-called dark matter is disclosed.
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P3-2025-37 (2.419.280)
Sumnikov S.V. et al.
High-Resolution Neutron Fourier Diffractometer with Wide-Aperture Detector
The high-resolution neutron Fourier diffractometer (HRFD), which
implements the correlation method of diffraction data acquisition, has been
successfully operated at the IBR-2 pulsed reactor at the Frank Laboratory
of Neutron Physics (JINR) for more than 30 years. This paper summarizes
the results of the modernization of a number of the HRFD main units. The
Fourier chopper, neutron guide, and data acquisition electronics were replaced
with new, state-of-the-art devices, and the initial results from commissioning
a new wide-aperture scintillation detector with a total sensitive element area
of about 13 m2 and a total solid angle of about 2.0 sr are presented. The
newly emerged capabilities for investigating atomic and magnetic structures of
crystalline materials and analyzing various types of transient processes in them
in real time mode are discussed.
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P3-2025-36 (2.078.772)
Podlesnyy M. M., Shabalin E. P., Hassan A. A.
Dynamic Bending of Fuel Rods in Pulsed Reactors
The work demonstrates and evaluates the dynamic bending effect which is typical for pulsed reactors due to the presence
of periodic power pulses and non-uniform neutron flux in the reactor core. A model of heat transfer in a single fuel element is developed,
and the non-stationary heat conductivity equation is considered in the isotropic approximation. The obtained function of the temperature
distribution over time of fuel pellets and cladding, which is specified as an input parameter with a coefficient corresponding to the energy release
gradient, is used in the mathematical model of the fuel element to calculate the dynamic bending of the cladding.
The results of the assessment of the dynamic bending of fuel elements of the designed NEPTUNE reactor are discussed.
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P13-2025-30 (1.068.272)
Verhoglyadov A. E.
Measurements of Mechanical Properties of Fuel Elements
of a Pulsed Reactor on a Vibration Diagnostics Stand
In order to verify the parameters of the mathematical model of a periodic
pulsed reactor and to develop the design of the active zone of a new neutron
source, a vibration diagnostics stand for model fuel elements was manufactured.
The work describes the structure of the stand and the tasks that are planned
to be solved on it. The results of the first measurements are compared with
numerical simulations. Prospects for further experiments and development of the
stand’s instrumentation are discussed.
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P7-2025-29 (3.040.235)
Fomichev A. S. et al.
Research of Neutron-Rich Nuclei in Reactions
with Radioactive Beams and a Cryogenic Tritium Target
The work is devoted to the research in the field of fundamental nuclear
physics on the study of the structure of light neutron-rich nuclei in experiments
with radioactive beams (E ∾ 20–50 MeV/nucleon) and a cryogenic tritium
target (gas or liquid) at the ACCULINNA-2@U-400M complex. The main
emphasis in the article is on the uniqueness of the new complex and its
advantages in relation to the ACCULINNA-1 equipment, the prospects of using
direct nuclear reactions (t, α) and (t, p) at these energies for the purpose of
studying such isotopes as 7H, 10Íå, 13Li, 16Âå, etc., and also on the first day
experiments.
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P13-2025-19 (8.433.416)
Verhoglyadov A. E., Kushnir I. V.
Numerical Calculations of Fuel Assemblies Bending in the IBR-2 Reactors
The work is dedicated to study of bending of fuel assemblies (FA) under the
non-uniform temperature distribution in the core of a periodic pulsed reactor.
Numerical calculations of the transverse deformation of the IBR-2 fuel assembly
in full geometry were carried out taking into account the coolant flow. The
shape of the bend, the displacement of fuel pellets and the time dependence of
deformation after pulsed energy release were found. Since the bending of the
FA changes the reactivity and has a negative effect on the reactor dynamics, a
possible method for reducing the bending value is proposed using coolant flow
profiling. The results can be used in the design of a new neutron source.
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P9-2025-16 (8.433.416)
Sumbaev A. P. et al.
Accelerator LUE-200.
Status, Capabilities and Development Problems
The article reports on the status of the accelerator facility of the Laboratory of Neutron Physics (LNP) of the Joint Institute for Nuclear Research (JINR, Dubna) — the
driver of an intense pulsed source of resonant neutrons. The general scheme of the linear electron accelerator and the features of its basic systems are presented.
LUE-200 consists of two accelerating sections on a traveling wave with an operating frequency of 2856 MHz with SLEDtype microwave power compression systems.
The pulsed beam current at the accelerator output reaches 2 A with a pulse duration of 80–120 ns. With an average beam particle energy of 90–110 MeV
and an acceleration cycle frequency of 50 Hz, the average beam power reaches 0.95–1.0 kW. The integral neutron flux (in the thermal and resonance energy range)
from a non-multiplying W-target reaches values of ∼ 1.06 · 1012 s-1. The possibilities of further development of the accelerator are discussed.
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P13-2025-15 (289.266)
Verkhoglyadov A. E., Shabalin E. P.
Model of the Dynamics of the IBR-2 Reactor Based on Two-Component Power Feedback
In the course of the work on studying the dynamics of the IBR-2 reactor, two main effects of reactivity feedback were indicated: the elongation of the column
of fuel pellets and the transverse bending of the fuel assemblies. A model of the dynamics of the IBR-2 reactor is described that takes these effects into account.
It is assumed that the instability of the dynamics occurs due to a change in
the amplitude of one of the effects, which depends on fuel burnout. It is shown
that at a certain value of the burnout parameter the reactor dynamics becomes
unstable.
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E4-2025-14 (628.141)
Efimov A.D., Koval I.V., Izosimov I.N.
Harris Model and IBM for Pu, Cm, Fm, No
For heavy even nuclei Pu, Cm, Fm and No, the description of the energies
of yrast bands in the Harris phenomenological model of the variable moment of inertia and in the interacting boson model (IBM), including IBM phenomenology, is considered. For two nuclei,
244Pu and 248Cm, the results of calculations in the extended IBM version are also presented. Comparison of these results made it possible to identify different characteristics
of the behavior of the moment of inertia as a function of the square of the rotational frequency and obtain corresponding interpretations of their features. In particular, a version
is proposed that explains the weakening of the growth of the moment of inertia for spins of states greater than 24+ in a number of nuclei.
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P9-2025-9 (3.758.571)
Amoskov V. M. et al.
Achieving the Desired Field Gradient in PM-Based Quads through Computerized Sort-Out of PM Units with Measured Parameters
The study is focused on the optimized design and fabrication of a PM-based quadrupole for beam transportation and focusing in the DC140 cyclotron. The quad has
a modular configuration with a set of geometrically similar PM bricks in every module. Prior to assembly, geometrical and magnetic parameters were measured over the whole set of PMs.
The measured data were used to adjust positions and orientations of PM bricks. A generalized procedure is proposed in a form of a program module to retrieve, sort out,
and group specifications of individual PMs from the measurement database. This procedure can be applied to compare and select parameters for various magnets based on PM assemblies
without limitation on the PM nomenclature.
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P9-2025-8 (1.532.364)
Amoskov V. M. et al.
Inspection of Geometric and Magnetic Parameters of PM-Based Quads in Precision Transport System for Accelerator Application
The study is focused on performance of permanent magnet–based quadrupoles (PMQ) used for beam transportation and focusing in the DC140 cyclotron.
An inspection procedure is examined, which combines 3D field simulation and measurement for geometric and magnetic parameters of PM units. The results are used to
guide practical measurement technique and instrumentation decisions. A set of supplied PM units has been measured and an optimum intramagnet PMQ
configuration has been determined. As a result, the prototype, reference, and test magnets have been assembled.
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P3-2025-7 (1.235.980)
Verhoglyadov A. E. et al.
Calculation of the Reactivity of a Pulsating Reactor Taking into Account the Thermoelastic Deformation of the Fuel
The paper studies the change of the reactivity of the pulsed reactor IBR-2 due to the thermal expansion of the fuel caused by a single power pulse.
In the accepted model, the temperature is found by solving a system of two-dimensional nonstationary heat equations.
The deformation of fuel pellets is calculated in 3D geometry using the finite element method. Critical calculations were performed using the Monte Carlo method
in the full geometry of the reactor. It is shown that the reactivity of the reactor has a complex dependence on time. The obtained results will be used for accurate calculations
of the dynamics of a pulsed reactor.
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E4-2025-4 (537.889)
Efimov A.D., Koval I.V., Izosimov I.N.
Comparison of the Description of Yrast Bands in the Harris and IBM Models for Even Nuclei Th and U
For even Th and U nuclei, the description of the energies of yrast bands in the Harris variable moment of inertia model is studied in its phenomenological
application. For some of these nuclei, the results obtained in the IBM microscopic
version are presented, in which high-spin excitation modes are also considered.
For other nuclei, in cases where high-spin orbits are not so significant in
describing the properties of yrast bands, in addition to the Harris model, IBM
with a full standard Hamiltonian constructed only from s, d bosons is utilized.
Since the Harris model is considered with no more than four parameters, it can
be used for both heavy and superheavy nuclei to approximate the energies of
high-spin states. The study of the properties of nuclei in various models will
reveal the possibilities of describing different behavior of the moments of inertia
in IBM and outline additional criteria for the implementation of band crossing.
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P13-2025-2 (2.515.072)
Mitrofanov S.V. et al.
Beam Profile Measurement at the Entrance of the Gas-Filled Solenoid GASSOL
A beam profilometer has been developed and tested for use at the entrance
of the gas-filled solenoid GASSOL during its commissioning and adjustment.
The profilometer is constructed as a mosaic of cathodes, each measuring current
generated by secondary emission during bombardment by accelerated ions being
measured from each cathode. A corresponding number of current amplifier
channels is used to measure the currents from the cathodes. A software program
has been developed for visualizing the beam profile. During an experiment with
a 40Ar+4 ion beam at an energy of 4 MeV per nucleon, the lower sensitivity limit
of the profilometer was found to be less than 0.001 pnA. The upper sensitivity
limit, determined through thermal calculations, is 100 pnA. A critical factor is
the risk of signal cable contact failures due to heating. The accuracy of beam
centre determination, ∓1 mm, falls within the specified tolerance for radial
displacement of the beam axis relative to the magnetic axis of the solenoid.
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