The triple-alpha process is a vital reaction in nuclear astrophysics, characterized by two consecutive reactions ($2\alpha\leftrightarrows{^{8}\rm{Be}}(\alpha,\gamma){^{12}\rm{C}}$) that drive carbon formation. The second reaction occurs through the Hoyle state, a 7.65 MeV excited state in ${^{12}\rm{C}}$ with $J^{\pi}=0^{+}$.The rate of the process depends on the radiative width, which can be determined by measuring the branching ratio for electromagnetic decay. Recent measurements by Kib\'edi, \textit{et al.} conflicted with the adopted value and resulted in a significant increase of nearly 50\% in this branching ratio, directly affecting the triple-alpha reaction. This work aims to utilize charged-particle spectroscopy with magnetic selection as a means to accurately measure the total radiative branching ratio ($\Gamma_{\rm{rad}}/\Gamma$) of the Hoyle state in $^{12}{\rm C}$. The Hoyle state in $^{12}{\rm C}$ was populated via $^{12}\rm{C}(\alpha, \alpha')^{12}\rm{C^{*}}$ inelastic scattering. The scattered $\alpha$-particles were detected using a $\Delta$E-E telescope, while the recoiled $^{12}{\rm C}$ ions were identified in a magnetic spectrometer. A radiative branching ratio value of $\Gamma_{\rm{rad}}/\Gamma\times10^{4}=4.0\pm0.3({\rm stat.})\pm0.16({\rm syst.})$ was obtained. The radiative branching ratio for the Hoyle state obtained in this work is in agreement with the original adopted value. Our result suggests that the proton-$\gamma$-$\gamma$ spectroscopy result reported by Kib\'edi \textit{et al.} may be excluded.

A new 3He-driven IGISOL production station and mass separator have been designed to produce neutron-deficient low-mass isotopes at the Cyclotron Institute for the TAMUTRAP facility. The LSTAR design has a mass resolution M/ΔM≥3,000 to reject contaminants with >95% efficiency.

The Texas A&M University Penning Trap (TAMUTRAP) facility aims to test the standard model of the electroweak interaction by measuring the beta-v correlation parameter, alpha(beta v), for beta-delayed proton emitters in the atomic mass range 20 < A < 40. Precision measurements of this correlation parameter and, inextricably, the Fierz interference parameter, are a sensitive probe of physics beyond the standard model. Using off-line ion sources, the TAMUTRAP facility has been commissioned by demonstrating the ability to manipulate the trapped-ion motions as well as to perform precision mass measurements. Our novel cylindrical Penning trap - the world's largest - differs from typical designs in two key aspects: the electrode structure has an 180-mm inner diameter and an overall length of 334.89 mm leading to a uniquely small length/radius ratio l/r = 3.72; and we do not use the long end cap approximation, instead our short endcap electrodes are closed and capable of being placed at an arbitrary potential. This geometry is optimized for observing beta-delayed proton decays, but is also well suited for other in-trap and post-trap precision decay experiments. In addition to presenting an overview of the TAMUTRAP facility, we demonstrate that our unique Penning trap is able to measure masses with a precision similar to typical trap designs. (C) 2021 Elsevier B.V. All rights reserved.

We present the development of a neutron detector array module made with para-terphenyl, a bright, fast, n/gamma discriminating crystalline organic scintillator. The module is comprised of 2 cm x 2 cm x 2 cm p-terphenyl crystals that have been optically coupled together to create a pseudo-bar module. While only relying on two photo detectors, the module is capable of distinguishing interactions between up to eight crystals. Furthermore, the module retains the p-terphenyl's pulse shape discrimination (PSD) capability. Together this makes the pseudo-bar module a promising position-sensitive neutron detector. Here we present characteristics of the pseudo-bar module - its timing resolution as well as its pulse shape and position discrimination capabilities, and briefly discuss future plans for utilizing an array of pseudo-bar modules in a useful neutron detector system.

The current status of fission dynamics studies in heavy-ion collisions around the Coulomb barrier is illustrated with the 34S + 186W reaction. The fission-fragment mass and total kinetic energy were measured at the ALTO facility at IPN Orsay, France, with a dedicated set-up using the (v, E) approach. The measurement reveals the presence of an asymmetric fission component on top of a predominantly symmetric distribution. The asymmetric structure, pointed out for the first time, is discussed along with results of previous experiments studying the same reaction. While these analyses suggested the contribution from either quasi-fission or pre-equilibrium fission, we offer an alternative interpretation, in terms of shell-driven compound-nucleus fission. The present measurement demonstrates the critical influence of resolution when addressing puzzling cases, situated at the crossroads of the various channels opened in a heavy-ion collision. Current status in the field clearly calls for innovative measurements involving manifold correlations and new observables. The outcome of the attempt done in this work in this direction, based on the coincident measurement of prompt \( \gamma\)-rays is reported, and encouraging perspectives are discussed.

The unexplored area of heavy neutron rich nuclei is extremely important for nuclear astrophysics investigations and, in particular, for the understanding of the r-process of astrophysical nucleogenesis. For the production of heavy neutron rich nuclei located along the neutron closed shell N=126 (probably the last waiting point in the r-process of nucleosynthesis) the low-energy multi-nucleon transfer reaction Xe-136+Pb-208 at E-lab=870MeV was explored. Due to the stabilizing effect of the closed neutron shells in both nuclei, N=82 and N=126, and the rather favorable proton transfer from lead to xenon, the light fragments formed in this process are well bound and the Q-value of the reaction is nearly zero.Measurements were performed with the PRISMA spectrometer in coincidence with an additional time-of-flight (ToF) arm on the +20 beam line of the PIAVE-ALPI accelerator in Legnaro, Italy. The PRISMA spectrometer allows identification of the A, Z and velocity of the projectile-like fragments (PLF), while the second arm gives access to the target-like fragments (TLF). Details on the experimental setup and preliminary results are reported.

The level structure of the very neutron rich and unbound 9He nucleus has been the subject of significant experimental and theoretical study. Many recent works have claimed that the two lowest energy 9He states exist with spins Jπ=1/2+ and Jπ=1/2− and widths on the order of 100–200 keV. These findings cannot be reconciled with our contemporary understanding of nuclear structure. The present work is the first high-resolution study with low statistical uncertainty of the relevant excitation energy range in the 8He+n system, performed via a search for the T=5/2 isobaric analog states in 9Li populated through 8He+p elastic scattering. The present data show no indication of any narrow structures. Instead, we find evidence for a broad Jπ=1/2+ state in 9He located approximately 3 MeV above the neutron decay threshold.

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.

Background: In heavy-ion-induced reactions the mechanism leading to the formation of the compound nucleus and the role of quasifission is still not clear.Purpose: Investigation of the quasifission process of superheavy composite systems with $Z=110\text{\ensuremath{-}}116$ and comparison with properties of fusion-fission and quasifission of lighter composite systems.Method: Mass and energy distributions of fissionlike fragments formed in the reactions $^{48}\mathrm{Ca}+^{232}\mathrm{Th}$, ${}^{238}\mathrm{U}$, ${}^{244}\mathrm{Pu}$, and ${}^{248}\mathrm{Cm}$ at energies near the Coulomb barrier have been measured using the double-arm time-of-flight spectrometer CORSET at the U-400 cyclotron of the FLNR JINR.Results: The most probable fragment masses as well as total kinetic energies and their dispersions in dependence on the interaction energies and ion-target combinations have been studied for asymmetric and symmetric fragments formed in the reactions. The capture cross sections were obtained for the reactions $^{48}\mathrm{Ca}+^{244}\mathrm{Pu}$ and ${}^{248}\mathrm{Cm}$. The lower limits for fission barriers of ${}^{283\ensuremath{-}286}\mathrm{Cn}$, ${}^{289\ensuremath{-}292}\mathrm{Fl}$, and ${}^{293\ensuremath{-}296}\mathrm{Lv}$ compound nuclei were estimated.Conclusions: Analysis of the properties of symmetric fragments has shown that a significant part of these fragments may be attributed to fusion-fission process for the reactions ${}^{48}\mathrm{Ca}{+}^{238}\mathrm{U}$, ${}^{244}\mathrm{Pu}$, and ${}^{248}\mathrm{Cm}$.

Received 2 December 2014DOI:https://doi.org/10.1103/PhysRevC.90.069901©2014 American Physical Society

Обсуждается создание экспериментального комплекса на базе светосильного фрагмент-сепаратора КОМБАС и быстродействующего ионного кетчера. Представлены основные характеристики фрагмент-сепаратора КОМБАС и ионного кетчера, определяющие перспективность предлагаемой комбинации. Ожидается, что реализуемый комплекс позволит получать вторичные пучки радиоактивных ядер более высокого качества по сравнению с пучками, получаемыми методом “in-flight” сепарации. Планируется использование комплекса в тандеме с пост-ускорителем для получения моноизотопных и монохроматических интенсивных вторичных пучков радиоактивных ядер в широком диапазоне массовых чисел А и атомных номеров Z. Предлагается перечень перспективных научных задач, для реализации которых требуются высокие интенсивности и качество получаемых вторичных пучков экзотических ядер.

The development of an experimental facility based on the high-luminosity COMBAS fragment separator and a fast ion catcher is discussed. The main characteristics of the COMBAS fragment separator and the ion catcher determining the advantages of the proposed combination are presented. The developed facility is expected to allow production of secondary radioactive beams with a quality higher than the quality of beams obtained using the in-flight separation technique. It is planned that the facility will be used in a tandem with a post-accelerator for producing single-isotope and monochromatic high-intensity secondary radioactive beams in a wide range of mass numbers A and atomic numbers Z. A list of perspective scientific problems requiring high-intensity and high-quality secondary beams of exotic nuclei is proposed.

Background: In heavy-ion-induced reactions the mechanism leading to the formation of the compound nucleus and the role of quasifission is still not clear.Purpose: Investigation of the quasifission process of superheavy composite systems with Z = 110-116 and comparison with properties of fusion-fission and quasifission of lighter composite systems.Method: Mass and energy distributions of fissionlike fragments formed in the reactions Ca-48 + Th-232, U-238, Pu-244, and Cm-248 at energies near the Coulomb barrier have been measured using the double-arm time-of-flight spectrometer CORSET at the U-400 cyclotron of the FLNR JINR.Results: The most probable fragment masses as well as total kinetic energies and their dispersions in dependence on the interaction energies and ion-target combinations have been studied for asymmetric and symmetric fragments formed in the reactions. The capture cross sections were obtained for the reactions Ca-48 + (244) Pu and Cm-248. The lower limits for fission barriers of (283-286)Cn, (289-292)Fl, and (293-296)Lv compound nuclei were estimated.Conclusions: Analysis of the properties of symmetric fragments has shown that a significant part of these fragments may be attributed to fusion-fission process for the reactions Ca-48+U-238, Pu-244, and Cm-248.

A Viewpoint on: Production cross sections from 82 Se fragmentation as indications of shell effects in neutron-rich isotopes close to the drip-line O. B. Tarasov, M. Portillo, D. J. Morrissey, A. M. Amthor, L. Bandura, T. Baumann, D. Bazin, J. S. Berryman, B. A. Brown, G. Chubarian, N. Fukuda, A. Gade, T. N. Ginter, M. Hausmann, N. Inabe, T. Kubo, J. Pereira, B. M. Sherrill, A. Stolz, C. Sumithrarachichi, M. Thoennessen, and D. Weisshaar Phys. Rev. C 87, 054612 (2013) – Published May 20, 2013

The Cyclotron Institute at Texas A&M is currently configuring a scheme for the production of radioactive-ion beams that incorporates a light-ion guide and a heavy-ion guide coupled with an electron-cyclotron-resonance ion source constructed for charge-breeding. This scheme is part of an upgrade to the facility and is intended to produce radioactive beams suitable for injection into the K500 superconducting cyclotron. The current status of the project and details on the ion sources used in the project is presented.

The cross sections and velocity distributions of projectile-like fragments from the reaction of 25 MeV/nucleon 86Kr + 64Ni have been measured using the MARS recoil separator at Texas A&M, with special emphasis on the neutron rich isotopes. Proton-removal and neutron pick-up isotopes have been observed with large cross sections. A model of deep-inelastic transfer (DIT) for the primary interaction stage and the statistical evaporation code GEMINI for the deexcitation stage have been used to describe the properties of the product distributions. The results have also been compared with the EPAX parametrization of high-energy fragmentation yields. The experimental data show an enhancement in the production of neutron-rich isotopes close to the projectile, relative to the predictions of DIT/GEMINI and the expectations of EPAX. We attribute this enhancement mainly to the effect of the extended neutron distribution (neutron "skin") of the 64Ni target in peripheral interactions of 86Kr with 64Ni. The large cross sections of such reactions near the Fermi energy, involving peripheral nucleon exchange, suggest that, not only the N/Z of the projectile and the target, but also the N/Z distribution at the nuclear surface may properly be exploited in the production of neutron-rich rare isotopes. This synthesis approach may offer a fruitful pathway to extremely neutron-rich nuclei, towards the neutron-drip line.

Production cross sections for neutron-rich nuclei from the fragmentation of a 82Se beam at 139 MeV/u were measured. The longitudinal momentum distributions of 126 neutron-rich isotopes of elements 11 <= Z <= 32 were scanned using an experimental approach of varying the target thickness. Production cross sections with beryllium and tungsten targets were determined for a large number of nuclei including several isotopes first observed in this work. These are the most neutron-rich nuclides of the elements 22 <= Z <= 25 (64Ti, 67V, 69Cr, 72Mn). One event was registered consistent with 70Cr, and another one with 75Fe. The production cross sections are correlated with Qg systematics to reveal trends in the data. The results presented here confirm our previous result from a similar measurement using a 76Ge beam, and can be explained with a shell model that predicts a subshell closure at N = 34 around Z = 20. This is demonstrated by systematic trends and calculations with the Abrasion-Ablation model that are sensitive to separation energies.

Production cross sections for neutron-rich nuclei from the fragmentation of a 82Se beam at 139 MeV/u were measured. The longitudinal momentum distributions of 122 neutron-rich isotopes of elements 11 ≤ Z ≤ 32 were determined by varying the target thickness. Production cross sections with beryllium and tungsten targets were determined for a large number of nuclei including several isotopes first observed in this work. These are the most neutron-rich nuclides of the elements 22 ≤ Z ≤ 25 (64Ti, 67V, 69Cr, 72Mn). One event was registered consistent with 70Cr, and another one with 75Fe. A one-body Qg systematics is used to describe the production cross sections based on thermal evaporation from excited prefragments. The current results confirm those of our previous experiment with a 76Ge beam: enhanced production cross sections for neutron-rich fragments near Z = 20.