Asymmetric and symmetric fission of excited nuclei of 180,190Hg and 184,192,202Pb formed in the reactions with 36Ar and 40,48Ca ions

Background: Observation of asymmetric fission of 180Hg has led to intensive theoretical and experimental studies of fission of neutron-deficient nuclei in the lead region. Purpose: The study of asymmetric and symmetric fission modes of 180,190Hg and 184,192,202Pb nuclei. Methods: Mass-energy distributions of fission fragments of 180,190Hg and 184Pb formed in the 36Ar+144,154Sm and 40Ca+144Sm reactions, respectively, at energies near the Coulomb barrier have been measured using the double-arm time-of-flight spectrometer CORSET and compared with previously measured 192,202Pb isotopes produced in the 48Ca+144,154Sm reactions. The mass distributions for 180,190Hg and 184,192,202Pb together with old data for 187Ir, 195Au, 198Hg, 201Tl, 205,207Bi, 210Po, and 213At [J. Nucl. Phys. 53, 1225 (1991)] have been decomposed into symmetric and asymmetric fission modes. The total kinetic-energy distributions for different fission fragment mass regions have been analyzed for 180,190Hg and 184Pb. Results: The stabilization role of proton numbers at Z≈36, 38, Z≈45, 46, and Z=28/50 in asymmetric fission of excited preactinide nuclei has been observed. The high (≈145−MeV) and the low (≈128−MeV) energy components have been found in the total kinetic-energy distributions of 180,190Hg fission fragments corresponding to the fragments with proton numbers near Z≈46 and Z≈36, respectively. In the case of fission of 184Pb only the low-energy component (≈135MeV) for the fragments with masses corresponding to the proton numbers Z≈36 and 46 has been found. Conclusions: The studied properties of asymmetric fission of 180,190Hg and 184,192,202Pb nuclei point out the existence of well deformed proton shell at Z≈36 and less deformed proton shell at Z≈46.peerReviewe

Fission of 180,182,183Hg and 178Pt nuclei at intermediate excitation energies

Purpose: The study of asymmetric and symmetric fission of 180,182,183Hg and 178Pt nuclei as a function of their excitation energy and isospin. Methods: Mass-energy distributions of fission fragments of 180Hg, 178Pt (two protons less than 180Hg), and 182Hg (two neutrons more than 180Hg) formed in the 36Ar+144Sm,142Nd, and 40Ca+142Nd reactions were measured at energies near and above the Coulomb barrier. Fission of 183Hg obtained in the reaction of 40Ca with 143Nd was also investigated to see if one extra neutron could lead to dramatic changes in the fission process due to the shape-staggering effect in radii, known in 183Hg. The measurements were performed with the double-arm time-of-flight spectrometer CORSET. Results: The observed peculiarities in the fission fragment mass-energy distributions for all studied nuclei may be explained by the presence of a symmetric fission mode and three asymmetric fission modes, manifested by the different total kinetic energies and fragment mass splits. The yield of symmetric mode grows with increasing excitation energy of compound nucleus. Conclusions: The investigated properties of asymmetric fission of 180,182,183Hg and 178Pt nuclei point out the existence of well-deformed proton shell at Z≈36 and a less deformed proton shell at Z ≈ 46.peerReviewe

Magnetic flux in stacks of superconducting tapes of different architecture

Stacks of superconducting tapes nowadays have multiple applications and many new modifications are currently considered to enhance their beneficial properties. We have studied the field trapping in stacks of commercial superconducting tapes with different configurations. Experimental and numerical analyses were performed. The superconducting stacks were magnetized to act as powerful permanent magnets using pulsed field magnetization and field cooling at 77 K. The configurations include a basic stack made of layered tapes, a stack interlayered with ferromagnetic material, a sectioned stack made of thin tapes and a shielded basic stack. The present study shows that, in terms of total trapped flux, the basic stack performs best, closely followed by the shielded stack. No significant positive effect due to the presence of ferromagnetic layers was found in the studied configuration. The sectioned stack is the worst according to every analysed criterion. The possibility of application of the analysed modification is discussed

Inverse quasifission in the reactions Gd 156,160 + W 186

Background: Low-energy multinucleon transfer reactions may be used for production of new neutron-enriched heavy nuclei. Purpose: Our aim is to investigate the influence of proton (Z=82) and neutron (N=82, 126) shells as well as orientation effects on the formation of reaction products in the inverse quasifission process in the reactions 156,160Gd + 186W. Methods: Mass, energy, and angular distributions of primary binary fragments formed in the reactions 156Gd+186W at an energy of 878 MeV, and 160Gd+186W at 860 and 935 MeV, have been measured using the double-arm time-of-flight spectrometer CORSET at the U400 cyclotron of the Flerov Laboratory of Nuclear Reactions (FLNR) at the Joint Institute for Nuclear Research (JINR), Dubna. Results: Enhancement in the yield of products with masses 200–215 u has been found for both reactions. The cross sections of the formation of trans-target fragments with masses around 208 u are found to be about 10μb at the Coulomb barrier energy and reach the level of 0.5 mb at the energy above the barrier for side-to-side collision. Conclusions: The enhanced yield of products with masses heavier than the target mass confirms the important role of the closed shells at Z=82 and N=82, 126 in the inverse quasifission process in low-energy damped collisions. The orientation effect caused by the strong deformation of colliding nuclei can result in a gain in the yield of heavy target-like fragments

The fusion-fission process in the reaction 34S+186W near the interaction barrier

The reaction S-34 + W-186 at E-lab=160 MeV was investigated with the aim of diving into the features of the fusion-fission process. Gamma rays in coincidence with binary reaction fragments were measured using the high efficiency gamma-ray spectrometer ORGAM at the TANDEM Accelerator facility of I.P.N., Orsay, and the time-of-flight spectrometer for fission fragments (FF) registration CORSET of the Flerov Laboratory of Nuclear Reactions (FLNR), Dubna. The coupling of the ORGAM and CORSET setups offers the unique opportunity of extracting details for characterizing the fusion-fission process and gives information regarding production of neutron-rich heavy nuclei. The FF-gamma coincidence method is of better use then the gamma - gamma coincidence method when dealing with low statistic measurements and also offers the opportunity to precisely correct the Dopler shift for in-flight emitted gamma rays. Evidence of symmetric and asymmetric fission modes were observed in the mass and TKE distributions, occurring due to shell effects in the fragments. Coincident measurements allow for discrimination between the gamma rays by accepting a specific range within the mass distribution of the reaction products. Details regarding the experimental setup, methods of processing the acquisitioned data and preliminary results are presented

Investigating Mass–Energy Distributions of Fragments Produced in the 32S + 232Th → 264Sg Reaction at Energies Below and Near the Coulomb Barrier

Abstract: The mass-energy distributions of fragments of the reaction 32S + 232Th leading to the formation of 264Sg (Z = 106) at energies of incident ions 32S of 165, 181 and 200 MeV are measured. The contribution from the quasifission process is found at energies below and above the Coulomb barrier in the region of symmetric masses (АCN/2 ± 20). A high-energy symmetric fission mode is found at an energy of 165 MeV, which corresponds to the excitation energy of the compound 264Sg nucleus 45 MeV

The fusion-fission process in the reaction 34^{34}S + 186^{186}W near the interaction barrier

International audienceThe reaction 34S + 186W at Elab=160 MeV was investigated with the aim of diving into the features of thefusion-fission process. Gamma rays in coincidence with binary reaction fragments were measured using the high efficiencygamma-ray spectrometer ORGAM at the TANDEM Accelerator facility of I.P.N., Orsay, and the time-of-flight spectrometerfor fission fragments (FF) registration CORSET of the Flerov Laboratory of Nuclear Reactions (FLNR), Dubna. The couplingof the ORGAM and CORSET setups offers the unique opportunity of extracting details for characterizing the fusion-fissionprocess and gives information regarding production of neutron-rich heavy nuclei. The FF-$\gamma$ coincidence method is of betteruse then the $\gamma$ - $\gamma$ coincidence method when dealing with low statistic measurements and also offers the opportunity toprecisely correct the Dopler shift for in-flight emitted gamma rays.Evidence of symmetric and asymmetric fission modes were observed in the mass and TKE distributions, occurring due toshell effects in the fragments. Coincident measurements allow for discrimination between the gamma rays by accepting aspecific range within the mass distribution of the reaction products. Details regarding the experimental setup, methods ofprocessing the acquisitioned data and preliminary results are presented

Investigation on Competing Fission Modes in 178Pt* Produced by 36Ar + 142Nd Reaction up to High Excitation Energies

Abstract: The mass–energy distributions of binary fission fragments (FFs) of excited exotic nucleus 178Pt* were measured via the fusion reaction 36Ar + 142Nd at different beam energies within 158–222 MeV range using the double arm time-of-flight spectrometer CORSET. The analysis of mass–energy matrices reveals the presence of both asymmetric and symmetric modes corresponding to respective lower and higher total kinetic energy (TKE) of the fragments within 42–64 MeV excitation energy. The agreement of measured mass width with theoretical systematics and dominance of the associated symmetric TKE component at 93 MeV excitation energy indicates the significant predominance/suppression of symmetric/asymmetric mode, respectively. The most probable light and heavy mass peaks of asymmetric fission mode of 178Pt are spotted at 79 and 99 u, respectively. As inferred from the theory, the mass–TKE events observed at the highest measured excitation energy (93 MeV) endorse the presence of the fast-fission process in 178Pt* at high angular momentum

Investigation of Shell Effects in the Fusion-Fission Process in the Reaction 34^{34}S + 186^{186}W Near the Interaction Barrier

International audienceThe reaction 34S + 186W at Elab = 160 MeV was investigated with the aim of diving into the features of the fusion-fission process. Gamma rays coincident with binary reaction fragments were measured using the high efficiency gamma-ray spectrometer ORGAM at the TANDEM Accelerator facility of I.P.N., Orsay, and the time-of-flight spectrometer for fission fragments registration CORSET of the Flerov Laboratory of Nuclear Reactions (FLNR), Dubna. Evidence of symmetric and asymmetric fission modes were observed in the mass and TKE distributions, occurring due to shell effects in the fragments. The coupling of the ORGAM and CORSET setups enables the FF-γ coincident measurement which offers the opportunity to extract the isotopic distribution of the fragments of different masses formed in the aforementioned reaction and to find the exact neutron multiplicity, the average spin and average angular momenta. Details regarding the experimental setup, methods of processing the acquisitioned data and preliminary results are presented