Yu. S. Tsyganov

Joint Institute for Nuclear Research, Dubna, Moskovskaya, Russia

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Publications (91)217.82 Total impact

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    ABSTRACT: Studies of superheavy nuclei produced in the 249Bk + 48Ca reaction were performed using the Dubna Gas Filled Recoil Separator. The cross section for the production of 293117 and 294117 isotopes was measured at five excitation energies of the 297117 compound nucleus ranging from 30 to 48 MeV and yielding maximum values of 1.1+1.2 −0.6 pb for the 3n and 2.4+3.3 −1.4 pb for the 4n reaction channels. Alpha emission from 281Rg competing with spontaneous fission (α/SF decay probability 1:9) was observed for the first time leading to the identification of the new isotope 277Mt (TSF ≈ 5 ms). The measured decay properties are in good agreement with those expected based on the properties of neighboring even-Z and odd-Z nuclei. The α energies and half-lives of odd-Z isotopes observed in the 293117 and 294117 decay chains together with results obtained for lower-Z superheavy nuclei demonstrate enhanced stability with increasing neutron number toward the predicted new magic number N = 184.
    Physical Review C 05/2013; 87:054621. · 3.72 Impact Factor
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    ABSTRACT: Production and decay of the isotopes of Hs were studied in the 226Ra+48Ca reaction at beam energies Elab=229, 234, and 241 MeV. At the Elab=234 MeV energy, the maximum of the 4n-evaporation channel of the reaction, six identical α-SF decay chains of the nucleus 270Hs were detected corresponding to a cross section of σ4n=16−7+13 pb. At the other 48Ca energies, no Hs isotopes were observed. Nuclei of 270Hs undergo α decay with a Qα=9.15±0.08 MeV and the half-life of the daughter spontaneous fission (SF) isotope 266Sg is 0.28−0.08+0.19 s, in good agreement with the data previously observed in the 248Cm(26Mg,4n)270Hs reaction. The partial α-decay half-life of 270Hs was measured for the first time: Tα=7.6−2.2+4.9 s. For the spontaneous fission, we determined a lower limit TSF⩾10 s. Decay properties of 270Hs corroborate theoretical predictions of its relatively high stability caused by the effect of the deformed shells at Z=108 and N=162.
    Physical Review C 03/2013; 87(3):034605. · 3.72 Impact Factor
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    ABSTRACT: The reaction 243Am + 48Ca has been reinvestigated to provide new evidence for the discovery of elements 113, 115. Twenty eight new 288115 decay chains were detected in this reaction to increase from three to 31 the number of 288115 atoms observed. In addition, four new decay chains were observed for the first time and assigned to the decay of 289115. These new 289115 events have the same properties for their decay chains as those observed for 289115 populated in the alpha decay of 293117 produced in the 249Bk + 48Ca reaction to provide cross-bombardment evidence. These new high statistics data sets and the cross-bombardment agreement provide definitive evidence for the discoveries of the new elements with Z = 113, 115, 117.
    Journal of Physics Conference Series 03/2013; 420(1):2011-.
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    V.B. Zlokazov, V.K. Utyonkov, Yu.S. Tsyganov
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    ABSTRACT: Calibration is the transformation of the output channels of a measuring device into the physical values (energies, times, angles, etc.). If dealt with manually, it is a labor- and time-consuming procedure even if only a few detectors are used. However, the situation changes appreciably if a calibration of multi-detector systems is required, where the number of registering devices extends to hundreds (Tsyganov et al. (2004) [1]). The calibration is aggravated by the fact that needed pivotal channel numbers should be determined from peak-like distributions. But peak distribution is an informal pattern so that a procedure of pattern recognition should be employed to discard the operator interference. The automatic calibration is the determination of the calibration curve parameters on the basis of reference quantity list and the data which partially are characterized by these quantities (energies, angles, etc).The program allows the physicist to perform the calibration of the spectrometric detectors for both the cases: that of one tract and that of many.Program summaryProgram title: VSHECCatalogue identifier: AENN_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AENN_v1_0.htmlProgram obtainable from: CPC Program Library, Queen’s University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 6403No. of bytes in distributed program, including test data, etc.: 325847Distribution format: tar.gzProgramming language: DELPHI-5 and higher.Computer: Any IBM PC compatible.Operating system: Windows XX.Classification: 2.3, 4.9.Nature of problem:Automatic conversion of detector channels into their energy equivalents.Solution method:Automatic decomposition of a spectrum into geometric figures such as peaks and an envelope of peaks from below, estimation of peak centers and search for the maximum peak center subsequence which matches the reference energies in the statistically most plausible way.Running time:On Celeron (R) (CPU 2.66 GHh) it is the time needed for the dialog via the visual interface. Pure computation—less than 1 s for the test run.
    Computer Physics Communications 02/2013; 184(2):428–431. · 2.41 Impact Factor
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    ABSTRACT: Results from the production and decay properties of element 115 nuclei observed using the reaction 243Am + 48Ca at various beam energies between November 1, 2010, and February 26, 2012, at the Dubna Gas Filled Recoil Separator are presented. This long-running experiment with a total beam dose of 3.3 × 1019 and carried out in the excitation energy range E ∗ = 31–47 MeV of the 291115 compound nucleus resulted in observation of three isotopes of element 115 with masses 287, 288, and 289. The 28 detected decay chains of 288115 show that this isotope is produced with the maximum probability at E ∗ = 34.0–38.3 MeV with a corresponding cross section of σ3n = 8.5+6.4 −3.7 pb. The four events attributed to the isotope 289115 that decays via a short α → α → SF chain could be detected only at the lowest excitation energy E ∗ = 31–36 MeV, in accordance with what could be expected for the 2n-evaporation channel of the reaction. The decay characteristics of this nuclide were established earlier (2010) and more recently (2012) in the reaction 249Bk(48Ca,4n)293117 and following α decay to 289115. At the energy E ∗ = 44.8 ± 2.3 MeV we observed only a single long chain of the isotope 287115. The decay properties of nuclei starting at 288115 and 287115 isotopes obtained in the present work reproduce in full the results of the first experiment of 2003 that reported the discovery of elements 115 and 113. The excitation functions of the production of the isotopes of element 115 and observation of the isotope 289115 in cross-bombardment reactions with the targets of 243Am and 249Bk provide additional evidence of the identification of the nuclei of elements 115 and 113. The experiments were carried out using the 48Ca beam of the U400 cyclotron of the Flerov Laboratory of Nuclear Reactions, JINR.
    Physical Review C 01/2013; 87:014302. · 3.72 Impact Factor
  • Yu. S. Tsyganov
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    ABSTRACT: As far as the detection system is concerned, experimens on synthesis and study of the properties of superheavy nuclei is one of the most difficult tasks. In fact, these experiments can be considered extreme in many senses: —extremely low (fractions of a picobarn-picobarns) formation cross sections of the products under investigation —extremely high heavy ion beam intensities for example, ∼1.1–1.5 pμA1 48Ca —high radioactivity of actinide targets, which are used in the experiments aimed at the synthesis of super-heavy nuclei —very long duration of the experiment (as long as a year) —extremely low yield of the products under investigation (sometimes less than 1 per month) —very high sensitivity of the detection system —radical suppression of the background products (method of “active correlations”). The two last points are the subject of the present paper, as well as the subject of two of my reviews published before. It is evident that without knowledge of the nature of the internal processes in semiconductor detectors it is virtually impossible to provide clear detection of ultra rare signals. In the present paper, the author reports on the investigation of near-surface phenomena in silicon radiation detectors, first of all bearing in mind the theoretical-methodological aspect of these phenomena. Non-equilibrium electron-hole recombination, pulse height defect formation, charge multiplication, and formation of “hot” electron system, are considered. With just these phenomena one can observe nonlinearity of energy-charge-amplitude conversion for heavy ion (recoil nucleus) registered by a silicon detector. Practical applications are also considered. One of them is a deeply modified method of “active correlations”. Projection of applying the method in the experiments with the modernized cyclotron (DC-280 FLNR project) is projected as well as possible applications in the heavy-ion-induced complete fusion nuclear reactions.
    Physics of Particles and Nuclei 01/2013; 44(1). · 0.67 Impact Factor
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    ABSTRACT: Two years after the discovery of element 117, we undertook a second campaign using the ^{249}Bk+^{48}Ca reaction for further investigations of the production and decay properties of the isotopes of element 117 on a larger number of events. The experiments were started in the end of April 2012 and are still under way. This Letter presents the results obtained in 1200 hours of an experimental run with the beam dose of ^{48}Ca of about 1.5×10^{19} particles. The ^{249}Bk target was irradiated at two energies of ^{48}Ca that correspond to the maximum probability of the reaction channels with evaporation of three and four neutrons from the excited ^{297}117. In this experiment, two decay chains of ^{294}117 (3n) and five decay chains of ^{293}117 (4n) were detected. In the course of the long-term work, ^{249}Cf-the product of decay of ^{249}Bk (330 d)-is being accumulated in the target. Consequently, in the present experiment, we also detected a single decay of the known isotope ^{294}118 that was produced during 2002-2005 in the reaction ^{249}Cf(^{48}Ca,3n)^{294}118. The obtained results are compared with the data from previous experiments. The experiments are carried out in the Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, using the heavy-ion cyclotron U400.
    Physical Review Letters 10/2012; 109(16):162501. · 7.73 Impact Factor
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    ABSTRACT: Results of a new series of experiments on the study of production cross sections and decay properties of the isotopes of element 115 in the reaction (243)Am+(48)Ca are presented. Twenty-one new decay chains originating from (288)115 were established as the product of the 3n-evaporation channel by measuring the excitation function at three excitation energies of the compound nucleus (291)115. The decay properties of all newly observed nuclei are in full agreement with those we measured in 2003. At the lowest excitation energy E*=33 MeV, for the first time we registered the product of the 2n-evaporation channel, (289)115, which was also observed previously in the reaction (249)Bk+(48)Ca as the daughter nucleus of the decay of (293)117. The maximum cross section for the production of (288)115 is found to be 8.5 pb at E*≈36 MeV.
    Physical Review Letters 01/2012; 108(2):022502. · 7.73 Impact Factor
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    ABSTRACT: No abstract prepared.
    Physical Review. 12/2011;
  • Yu. S. Tsyganov
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    ABSTRACT: Experiments carried out on the gas-filled separator of recoil nuclei at the Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, in the past several years have proved the hypothesis of the existence of a stability island of superheavy nuclei. The accelerator, beam diagnostics, and detector technologies underlay the success. It is the highly sensitive detecting system of the separator combined with the method of “active correlations” that allowed rare events of the decay of superheavy nuclei to be reliably detected under almost background-free conditions. In turn, to a large extent, this has been made possible owing to special algorithms and software developed for long-term experiments in the beam of 48Ca ions.
    Physics of Particles and Nuclei 09/2011; 42(5):812-845. · 0.67 Impact Factor
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    Yu. S. Tsyganov
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    ABSTRACT: Basic approaches by K.-H. Schmidt and V.B. Zlokazov to estimate the probability of registered multichain event to be explained by random coincidences are considered. A specific feature of the long-term experiments aimed at the synthesis of superheavy nuclei with the Dubna Gas-Filled Recoil Separator is usage of a real-time mode for radical suppression of background products. In fact, this assumes that the first correlation group, namely, recoil-alpha correlation, stops target irradiation for a short time and the forthcoming signals are detected in more favorable background conditions. Due to the application of this detection mode the first recoil-alpha chain can be considered as a “starter” for the detection of the forthcoming alpha-particle signals with high background suppression. This fact is taken into account in the given PIPS detector statistical model.
    Physics of Particles and Nuclei Letters 07/2011; 8(4):374-378.
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    Yu. Tsyganov
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    ABSTRACT: A complex analysis has been performed on the energy amplitude signals corresponding to events of Z = 117 element measured in the 249Bk + 48Ca complete fusion nuclear reaction. These signals were detected with PIPS position sensitive detector. The significant values of pulse height defect both for recoils (ER) and for fission fragments2 were measured. Comparison with the computer simulations and empirical formulae has been performed both for ER and FF signals.
    Physics of Particles and Nuclei Letters 01/2011; 8(1):37-39.
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    ABSTRACT: The heaviest isotopes of elements Z=117 to Z=105, 294117, 293117, 290115, 289115, 286113, 285113, Rg282, Rg281, Mt278, Bh274, and Db270, were identified by means of the Dubna gas-filled recoil separator among the products of the Bk249 + Ca48 reaction. The details of the observed six decay chains, indicating the production and decay of isotopes 293117 and 294117, are presented and discussed. The decay energies and resulting half-lives of these new nuclei show a strong rise of stability with increasing neutron number, validating the concept of the island of enhanced stability for superheavy nuclei [Oganessian , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.104.142502 104, 142502 (2010)].
    Physical Review C 01/2011; 83(5). · 3.72 Impact Factor
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    ABSTRACT: The heaviest isotopes of elements Z = 117 to Z = 105, 294117, 293117, 290115, 289115, 286113, 285113, 282Rg, 281Rg, 278Mt, 274Bh, and 270Db, were identified by means of the Dubna gas-filled recoil separator among the products of the 249Bk + 48Ca reaction. The details of the observed six decay chains, indicating the production and decay of isotopes 293117 and 294117, are presented and discussed. The decay energies and resulting half-lives of these new nuclei show a strong rise of stability with increasing neutron number, validating the concept of the island of enhanced stability for superheavy nuclei.
    Physical Review Letters 01/2011; 83(5). · 7.73 Impact Factor
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    ABSTRACT: During the recent years, at the FLNR (JINR) a successful cycle of experiments has been accomplished on the synthesis of the superheavy elements with Z=112-118 with <sup>48</sup>Ca beam. From the viewpoint of the detection of rare decays and background suppression, this success was achieved due to the application of a new radical technique-the method of active correlations. The method employs search in a real-time mode for a pointer to a probable correlation like recoil-alpha for switching the beam off. In the case of detection in the same detector strip an additional alpha-decay event, of “beam OFF” time interval is prolonged automatically. Reasonable scenarios of developing the method are considered. PC based data acquisition system as well as the monitoring and control system of the Dubna Gas Filled Recoil Separator is considered in brief too.
    Real Time Conference (RT), 2010 17th IEEE-NPSS; 06/2010
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    ABSTRACT: The discovery of a new chemical element with atomic number Z=117 is reported. The isotopes (293)117 and (294)117 were produced in fusion reactions between (48)Ca and (249)Bk. Decay chains involving 11 new nuclei were identified by means of the Dubna gas-filled recoil separator. The measured decay properties show a strong rise of stability for heavier isotopes with Z > or = 111, validating the concept of the long sought island of enhanced stability for superheavy nuclei.
    Physical Review Letters 04/2010; 104(14):142502. · 7.73 Impact Factor
  • A. M. Sukhov, A. N. Polyakov, Yu. S. Tsyganov
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    ABSTRACT: A modified integrated parameter-monitoring and control system for experiments on the synthesis of superheavy nuclei at the U-400 cyclotron of the Flerov Laboratory of Nuclear Reactions is considered. Experiments on the irradiation of heavy actinide targets were performed at the Dubna Gas-Filled Recoil Separator (DGFRS) [1]. This system consists of three components, namely, the detection module parameter control subsystem, the beam parameter monitoring subsystem, and the separator technical parameter control subsystem. The system is designed in CAMAC standard, the software is written under Windows XP using RAD Borland C++ Builder 6.0 and Kk009Pci interface (LNR) [2, 3].
    Physics of Particles and Nuclei Letters 01/2010; 7(5):370-377.
  • Y.S. Tsyganov, A.N. Polyakov, A.M. Sukhov
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    ABSTRACT: PC-based one-crate monitoring and control system of the Dubna Gas Filled Recoil Separator (DGFRS) is considered. It is developed for the long-term experiments at the U400 FLNR cyclotron and is aimed at the synthesis of super heavy nuclei in heavy ion induced complete fusion reactions. Parameters related to: a) beam and cyclotron; b) separator by itself, c) detection system, d) target and entrance window are measured and stored in the protocol file of the experiment. Special attention is paid to generating the “alarm” signals and implementing further the appropriate procedures.
    Real Time Conference (RT), 2010 17th IEEE-NPSS; 01/2010
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    ABSTRACT: Currently, gas phase chemistry experiments with heaviest elements are usually performed with the gas-jet technique with the disadvantage that all reaction products are collected in a gas-filled thermalisation chamber adjacent to the target. The incorporation of a physical preseparation device between target and collection chamber opens up the perspective to perform new chemical studies. But this approach requires detailed knowledge of the stopping force (STF) of the heaviest elements in various materials. Measurements of the energy loss of mercury (Hg), radon (Rn), and nobelium (No) in Mylar and argon (Ar) were performed at low kinetic energies of around (40–270) keV per nucleon. The experimentally obtained values were compared with STF calculations of the commonly used program for calculating stopping and ranges of ions in matter (SRIM). Using the obtained data points an extrapolation of the STF up to element 114, eka-lead, in the same stopping media was carried out. These estimations were applied to design and to perform a first chemical experiment with a superheavy element behind a physical preseparator using the nuclear fusion reaction 244Pu(48Ca; 3n)289114. One decay chain assigned to an atom of 285112, the α-decay product of 289114, was observed.
    Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 01/2010; · 1.19 Impact Factor
  • V. B. Zlokazov, Yu. S. Tsyganov
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    ABSTRACT: An algorithm has been proposed to build an estimate of the half-life of a “daughter” nucleus in case, when it is unknown, which nucleus is its “mother” (“indefinite start time”). For a decay of the “mother” at an instant t we can determine P—a probability of such a decay, if we assume that each “mother”, which has been decayed before t has equal chances to be “mother” of this “daughter”: $$ \sum\limits_{i = 1}^{n_t } {exp\left( { - \frac{{t - t_i }} {\tau }} \right)} , $$ where τ is the life-time of the “daughter” and n t is their total number; t i ist the instant of the “mother” decay, such that t i ⩽ t. We can consider this formula as function of the “mother-daughter” relation for our case, and, in principle, build an estimator of the τ quantity: $$ \hat \tau = \sum\limits_{i = 1}^{n_t } {w_i \frac{{t - t_i }} {{n_t }}} , w_i = exp\left( { - \frac{{t - t_i }} {\tau }} \right), i = 1,...,n_t , $$ where the weights w i i have been normalized by their sum for each t. The averaged sum of such estimates over all the “daughter” decays will give us the final estimate of the τ parameter.
    Physics of Particles and Nuclei Letters 01/2010; 7(6):401-405.