Flerov Laboratory Of Nuclear Reactions Research Articles

Injection System of the DC140 Cyclotron at the Flerov Laboratory of Nuclear Reactions

Injection System of the DC140 Cyclotron at the Flerov Laboratory of Nuclear Reactions

First Tests of the GRAND Gas-Filled Separator at the Superheavy Element Factory (Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research)

First Tests of the GRAND Gas-Filled Separator at the Superheavy Element Factory (Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research)

Study of the 242Pu + 48Ca Reaction at Super Heavy Element Factory

Experiments on the synthesis of isotopes of element 114 in the 242Pu + 48Ca reaction were carried out at a new gas-filled separator DGFRS-2 online to the DC-280 cyclotron of the Superheavy Element Factory at the Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research. The decay properties of 286Fl and 287Fl, as well as their α-decay products, were refined. The possibility of the existence of isomeric states in successive α-decays of 287Fl is discussed. The maximum cross section of \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$10.4_{{ - 2.1}}^{{ + 3.5}}$$\\end{document} pb was measured for the 242Pu(48Ca, 3n)287Fl reaction.

Influence of «FLAT–TOP» of the resonant system of the DC-280 accelerator on the beam of charged particles

Experiments on the synthesis of superheavy elements (SHE) which were done at Flerov Laboratory of Nuclear Reactions (FLNR) measure that the probability of occurrence of one SHE event is ranged from one event per month to one event per week. Nowadays, Z = 118 (Oganesson) is the most used chemical element which is synthesized with 48Ca. The synthesis of new SHEs requires heavier bombarding particles: 50Ti, 54Cr, 58Fe, etc. In the experiments with heavier particles, the SHE isotope production cross section is expected to be lower than in the case of using 48Ca. It follows that it is necessary to increase the intensity of bombarding ion beams in order to collect experimental statistics in a reasonable time. Thus, for the synthesis of superheavy elements in the FLNR at the Joint Institute for Nuclear Research (JINR), the Factory of Superheavy Elements was created. The basic equipment of the SHE Factory is the DC-280 cyclotron complex. The accelerator provides high intensity of ion beams. As the intensity in the beam increases, the energy spread increases. That to minimize this process, the DC-280 cyclotron is equipped with an additional FLAT–TOP accelerating system.

Ion guide simulation for GALS setup

A new setup is under construction at the Flerov Laboratory of Nuclear Reactions (FLNR), JINR, Dubna, to study heavy neutron-rich nuclei along a closed neutron shell N=126. One of the important parts of the setup is the ion guide system. From several ion guide options, a Radio Frequency Quadrupole (RFQ) ion guiding system was chosen. This special ion guiding system was developed and optimized using SIMION simulation software. Also, precise comparison with the alternative Sextupole ion guide (SPIG) system was performed. Along with ion guide simulation, modernization of reference cell was completed and it is ready for offline experiments to find optimal laser ionization scheme.

DGFRS-2—A gas-filled recoil separator for the Dubna Super Heavy Element Factory

The main goal of development of the new Dubna Gas-Filled Recoil Separator (DGFRS-2) is to sufficiently improve the efficiency of studies on heavy and superheavy nuclei at the Super Heavy Element Factory of the Flerov Laboratory of Nuclear Reactions (FLNR) at the Joint Institute for Nuclear Research. The use of beams with the intensity up to 6×1013 s−1 (10 pμA) delivered by the DC280 cyclotron requires an effective setup providing high suppression of background reaction products. The described gas-filled separator is optimized for synthesis and study of heavy isotopes produced in complete fusion reactions of massive nuclei. Basic characteristics of DGFRS-2, as well as the results of the first test experiments, are presented. In comparison to the DGFRS-1, the transmission efficiency was doubled, and the background was reduced by a factor 200.

Изучение механизмов реакций с тяжелыми ионами и получение вторичных радиоактивных пучков с помощью фрагмент-сепаратора КОМБАС.

Experiments in that Be and Ta targets have been bombarded by heavy ions in series 12C, 15N, 18O, 22Ne and 40Ar are discussed. Ions was accelerated at energy 35-45 MeV/nucleon on the U-400M cyclotron at Flerov Laboratory of Nuclear Reactions, JINK. The targets were placed at the entrance focus of the COMB AS separator. Reaction products near zero-angle degrees were collected and then analyzed. The telescope formed from silicon detectors was placed at the exit achromatic focus of separator. One from pair of parallel plate avalanche counters (PPAC) has been placed at the dispersive focal plane and the other before the silicon detectors. Reaction products was identified on the mass number A and atomic number Z by the (ДЕ. K) telescope and by the (AE. T) method using lime of flight between PPAC. The measurements of the yields of isotopes were carried out by scanning the range of magnetic rigidities covering the velocity distributions of the studied isotopes. The results of the experiments was analyzed and compared with different theoretical models. The generation of radioactive beam of 11Li with maximum intensity and its purity was the objective of this experiment. Achieved maximum intensity is 104 nuclei at second.

Fission properties of Rf253 and the stability of neutron-deficient Rf isotopes

An analysis of recent experimental data [J. Khuyagbaatar et al., Phys. Rev. C 104, L031303 (2021)] has established the existence of two fissioning states in $^{253}$Rf: the ground state and a low-lying isomeric state, most likely involving the same neutron single-particle configurations as in the lighter isotone $^{251}$No. The ratio of fission half-lives measured in $^{253}$Rf was used to predict the fission properties of the 1/2$^{+}$ isomeric state in $^{251}$No and draw conclusions as to the stability against fission of even lighter Rf systems. This paper focusses again on the fission properties of $^{253}$Rf and their impact on the stability of other neutron deficient isotopes, using new and improved data collected from two experiments performed at the Flerov Laboratory of Nuclear Reactions in Dubna, Russia. Two fission activities with half-lives of 52.8(4.4)$~\mu$s and 9.9(1.2) ms were measured in the case of $^{253}$Rf, confirming the results of J. Kkuyagbaatar et al. A third state, at much higher excitation energy, was also observed through the detection of its electromagnetic decay to the 52.8$~\mu$s state. This observation leads to the opposite quantum-configuration assignments for the fissioning states as compared to the ones established by J. Khuyagbaatar et al., namely that the higher-spin state has the shortest fission half-life. This inversion of the ratio of fission hindrances between the low and high-spin states is corroborated in the isotone $^{251}$No by the non observation of any substantial fission branch from the low-spin isomer.

Magnetic System of the New DC140 Isochronous Cyclotron Based on the DC72 Electromagnet

The creation of a new multipurpose isochronous cyclotron DC140 is being carried out at the Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research. The DC140 cyclotron is intended for microchip testing on radiation resistance, the production of track pore membranes, and applied physics. The cyclotron will accelerate heavy ions with mass-to-charge ratio A/Z ranging from 5 to 8 up to fixed energies of 2.1 and 4.8 MeV per nucleon. The new cyclotron DC140 will be created as a deep reconstruction of the DC72 cyclotron. In particular, it is supposed to adapt the DC72 electromagnet for obtaining new acceleration regimes. In this paper, the main parameters of the DC72 and DC140 magnetic systems, the results of calculations and measurements of the magnetic field, and estimations of the possibility of formation of new acceleration regimes with minimal changes in the DC72 magnetic system are presented.

Spectroscopy of the Isotopes of Transfermium Elements in Dubna: Current Status and Prospects

A great many experimental studies devoted to exploring in detail the properties of radioactive decay of the isotopes of transfermium elements by means of alpha, beta, and gamma spectroscopy have been performed over the past fifteen years at the Flerov Laboratory of Nuclear Reactions (Joint Institute for Nuclear Research, Dubna). High-intensity accelerated heavy-ion beams of $${}^{22}$$ Ne, $${}^{48}$$ Ca, $${}^{50}$$ Ti, and $${}^{54}$$ Cr from the U-400 cyclotron were used in experiments with the SHELS kinematic separator. An upgrade of the separator and detector system is planned in the future with the aim of improving the transportation efficiency for the nuclei under study and the detection efficiency for gamma rays.

Study of 10Li Low Energy Spectrum in the 2H(9Li, p) Reaction

The one-neutron transfer 2H(9Li, p)10Li reaction has been investigated at 29 A MeV incident energy at the ACCULINNA-2 facility (Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research). The setup has been used in order to detect the recoil protons at backward angles in coincidences with the outgoing 9Li and neutrons from the 10Li decay at forward angles. This setup allows to study the 10Li emitted in the crucial region at forward angles in the center of mass. The preliminary results in the part of the analysis of double proton–9Li coincidence are reported.

Further development of GALS setup at JINR

The aim of this paper is to report on the present status of the GAs cell based Laser ionization and separation Setup (GALS project) that is under construction at the Flerov Laboratory of Nuclear Reactions (FLNR) of JINR, Dubna. This project is directed on production of neutron-rich isotopes in the region of the magic N = 126 neutron number using multi-nucleon transfer reactions. The laser laboratory extension based on new TiSa lasers was performed, options of using a straight sextupole (SPIG) or an S-shaped quadrupole ion guides in the setup were compared based on the computer simulations, and the work on the rest of the GALS subsystems is being continued.

150th Anniversary of the Periodic Table of the Chemical Elements

The year 2019 was proclaimed by the UN and UNESCO as the International Year of the Periodic Table of the Chemical Elements; by its beginning, the seventh period of the Table was already filled with new, very heavy elements. According to theoretical predictions, isotopes of superheavy elements with increased stability form a large zone in the form of an island with a vertex located near the “magic” numbers of protons Z = 114 and neutrons N = 184 on the nuclide map. New elements with atomic numbers from 114 to 118 were synthesized in the Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research (JINR, Dubna), in 2000–2012 by fusion reactions of target nuclei (heavy actinide isotopes (Z = 94–98)) with bombarding 48Ca ions. The experimental results suggest that there may exist nuclei or elements with atomic numbers greater than 118 and mass greater than 300 amu. A new experimental complex, the Factory of Superheavy Elements (SHEF), was created in Dubna to study the nuclear and electronic structures of new elements and their chemical properties and to synthesize elements from the beginning of the eighth period of the Periodic Table. A new DC-280 accelerator has already been launched in the SHEF, and experiments are planned to begin. The introductory and final parts of my speech at the scientific session of the General Meeting of the Members of the Russian Academy of Sciences are related to the discovery of the Periodic Law published by D.I. Mendeleev 150 years ago. The action of this law in the properties of the heaviest elements represents today one of the most urgent and interesting problems of the natural sciences.

Study of neutron-rich isotopes near N=152 shell closure using Timepix type detectors integrated into the mass separator MASHA

The MASHA facility [1–3] was developed as a high precision mass-spectrometer for heavy and super heavy elements with masses up to 450 a.m.u. It uses ISOL (Isotope Separation On-Line) method. Its unique properties opens great prospective for the investigation of neutron-rich nuclei produced in multinucleon transfer reactions. Mainly nuclei near the neutron N = 126 and N = 152 shell closures are of great interest. This region of nuclei is not so far thoroughly enough investigated while its research has direct relation to the synthesis of super heavy elements. As is known the island of stability close to super heavy elements (Z = 112–118) exists due to the shell effects in nuclei. More detailed investigation of these shell effects can greatly help in the synthesis of next super heavy elements. Heavy neutron rich radon isotopes were produced in the multinucleon transfer reaction 40Ar + 232Th at Flerov Laboratory of Nuclear Reactions, Dubna. Radon isotopes with given masses were detected using two types of detectors: a multi-strip well-type detector (made in Canberra) and a position-sensitive quantum counting hybrid pixel detector of the Timepix type [1]. The latter detector has an array of 256×256 square pixels each with a pitch size of 55 μm for the full sensitive area 14×14 mm2. Radon isotopes implanted into the detector emit then alpha and beta particles until they reach the stable or long-lived isotopes at the end of their decay chains. The positions of radon isotopes, the tracks, times and energies of the beta particles were measured and analyzed. New software for the particle recognition and data analysis of the results obtained from the experiment was developed and used. It has been proven that MASHA + Timepix setup is a powerful instrument for investigation of neutron-rich isotopes far from stability limits.

Prompt Neutrons from Spontaneous 254Rf Fission

The neutron yield from the spontaneous fission of the short-lived neutron-deficient 254Rf nucleus produced in the complete fusion reaction with the beam of multiply charged ions from the U400 accelerator at the Flerov Laboratory of Nuclear Reactions (FLNR), Joint Institute for Nuclear Research (JINR), is measured using the combined detection system of the SHELS velocity filter. The half-life and the branching ratio of 254Rf are also measured. The data on the multiplicity of prompt neutrons from spontaneous fission of 256Rf ($$\bar {\nu }$$ = 3.87 ± 0.34) are presented for the first time.

A Flexible Real-Time Algorithm for the RedStorm#2 Software Package

A new real-time algorithm for the C++ RedStorm#2 software package to radically suppress the background at the total fusion reactions on the new DC-280 cyclotron (Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research) is reviewed. This algorithm assumes some flexibility with the execution of the data set program in contrast to earlier algorithms applied at the Dubna gas-filled recoil separator. Namely, the experimenter sets the allowable value of the relative real-time loss of target irradiation, but not a fixed time interval between the implantation of a nuclide into a silicon detector and its α-decay. The block diagram of the algorithm execution is presented and possible branches of the algorithm are considered. The edge effects and their role in collecting a nonequilibrium charge from the p–n junction of the DSSSD detector (double-sided silicon strip detector) of the focal plane of recoil separator are also considered.

Start-Up of the DC-280 Cyclotron, the Basic Facility of the Factory of Superheavy Elements of the Laboratory of Nuclear Reactions at the Joint Institute for Nuclear Research

The basic facility of the Factory of Superheavy Elements (SHE), the DC-280 cyclotron, in the Flerov Laboratory of Nuclear Reactions at the Joint Institute for Nuclear Research has been completed. Both new and experimentally tested engineering solutions of the laboratory underlie the project. Planned beam intensities of up to 10 pμA of ions with average masses (A ~ 50) are one order of magnitude higher than those produced at the U-400 cyclotron up to now. From 2016 to 2018, the DC-280 cyclotron equipment was installation and set up. The first 84Kr14+ ion beam was accelerated in the DC-280 on December 26, 2018, and extracted to the accelerated ion transportation channel on January 17, 2019. In March 2019, beams of accelerated 84Kr+14 ions with an intensity of 1.36 pμA and 12С+2 ions with an intensity of 10 pμA were extracted from the DC-280 to the beam transportation channel with an energy of about 5.8 MeV/nucleon. The main task of the new accelerator is to implement a long-term research program at the SHE Factory aimed at the synthesis of new elements (Z ≥ 119) and a detailed study of nuclear–physical and chemical properties of previously discovered elements nos. 112–118.

Scientific program of DERICA—prospective accelerator and storage ring facility for radioactive ion beam research

Studies of radioactive ions (RIs) are the most thriving field of low-energy nuclear physics. In this paper, the concept and the scientific agenda of the prospective accelerator and storage ring facility for RI beam (RIB) research are proposed for a large-scale international project based at the Flerov Laboratory of Nuclear Reactions of the Joint Institute for Nuclear Research. The motivation for the new facility is discussed and its characteristics are briefly presented and shown to be comparable to those of advanced world centers, the so-called “RIB factories”. In the project, the emphasis is made on studies with short-lived RIBs in storage rings. A unique feature of the project is the possibility of studying electron–RI interactions in a collider experiment to determine the fundamental properties of nuclear matter, in particular, electromagnetic form factors of exotic nuclei.

Low-Background Techniques in Nuclear Physics

Methods for detecting rare α-decays of heavy nuclei lately implemented at JINR’s Flerov Laboratory of Nuclear Reactions (FLNR) are reviewed. Particular attention is paid to developing the active-correlation technique and various algorithms for real-time searches for correlated subprocesses in the nucleosynthesis of superheavy elements. These are required for suppressing the background events generated by the JINR heavy-ion cyclotron. A novel flexible approach to the search for correlated events based on a probabilistic algorithm is proposed. A simple criterion for optimizing the procedure of radical background suppression in full-fusion reactions is formulated. The implementation of the approaches proposed in this paper is motivated by the ever-increasing intensities of heavy-ion beams.

REDSTORM2 С++ Program Package for the New Gas-Filled Recoil Separator at the FLNR JINR

The С++ program package for the new gas-filled recoil nuclei separator of the Flerov Laboratory of Nuclear Reactions of the Joint Institute for Nuclear Research is presented. This version of software is a total redesign of the REal-time Detection and STORage of Multichain events (REDSTORM) package and intended for operation with the focal double-side silicon strip detector (DSSSD) of the separator and with the gas time-of-flight low-pressure module in experiments for searching for rare α-decays of superheavy nuclei. The spectrometry data-acquisition program operates using the method of active correlations. The programs are considered separately, which simulate a course of experiment and a number of tests with the application of both fixed-amplitude generator and external α-particle sources.