Cross Sections Of Nuclei Research Articles

The 48Ca+181Ta reaction: Cross section studies and investigation of neutron-deficient 86 ≤ Z ≤ 93 isotopes

Fusion-evaporation reactions with the doubly magic projectile 48Ca were used to access neutron-deficient nuclei around neptunium at the velocity filter SHIP, and investigated using the COMPASS decay spectroscopy station. With the use of digital electronics, several isotopes produced via neutron, proton, and α evaporation channels were identified by establishing correlated α-decay chains with short-lived sub-μs members. Data are given on decay chains stemming from 225,226Np, 225U, and 222,223Pa. New information on the isotopes 225,226Np and 222Pa was obtained. Production cross sections of nuclei in the region using a variety of projectiles are discussed. The measured production cross-sections indicate that the usual advantages of using 48Ca as a beam projectile to produce nuclei Z>100 are absent in the production of these slightly lighter nuclei.

Production of exotic neutron-deficient isotopes near N, Z = 50 in multinucleon transfer reactions * * Supported by National Natural Science Foundation of China (11635003, 11025524, 11161130520), the National Basic Research Program of China (2010CB832903) and the European Commissions 7th Framework Programme (FP7-PEOPLE-2010-IRSES) (269131)

The multinucleon transfer reaction in the collisions of 40Ca+ 124Sn at MeV is investigated using the improved quantum molecular dynamics model. The measured angular distributions and isotopic distributions of the products are reproduced reasonably well by the calculations. The multinucleon transfer reactions of 40Ca + 112Sn, 58Ni + 112Sn, 106Cd + 112Sn, and 48Ca + 112Sn are also studied. This demonstrates that the combinations of neutron-deficient projectile and target are advantageous for the production of exotic neutron-deficient nuclei near N, Z = 50. The charged particles' emission plays an important role at small impact parameters in the de-excitation processes of the system. The production cross sections of the exotic neutron-deficient nuclei in multinucleon transfer reactions are much larger than those measured in the fragmentation and fusion-evaporation reactions. Several new neutron-deficient nuclei can be produced in the 106Cd + 112Sn reaction. The corresponding production cross sections for the new neutron-deficient nuclei, 101, 112Sb, 103Te, and 106, 107I, are 2.0 nb, 4.1 nb, 6.5 nb, 0.4 b and 1.0 b, respectively.

Experimental constraints on the Zn73(n,γ)Zn74 reaction rate

Background: The recent observation of a neutron-star merger finally confirmed one astrophysical location of the rapid neutron-capture process (r-process). Evidence of the production of $Al140$ nuclei was seen, but there is still little detailed information about how those lighter elements are produced in such an environment. Many of the questions surrounding the $A\ensuremath{\approx}80$ nuclei are likely to be answered only when the nuclear physics involved in the production of r-process nuclei is well understood. Neutron-capture reactions are an important component of the r-process, and neutron-capture cross sections of r-process nuclei, which are very neutron rich, have large uncertainties.Purpose: Indirectly determine the neutron-capture cross section and reaction rate of $^{73}\mathrm{Zn}(n,\ensuremath{\gamma})^{74}\mathrm{Zn}$.Methods: The nuclear level density (NLD) and $\ensuremath{\gamma}$-ray strength function ($\ensuremath{\gamma}\mathrm{SF}$) of $^{74}\mathrm{Zn}$ were determined following a total absorption spectroscopy (TAS) experiment focused on the $\ensuremath{\beta}$ decay of $^{74}\mathrm{Cu}$ into $^{74}\mathrm{Zn}$ performed at the National Superconducting Cyclotron Laboratory. The NLD and $\ensuremath{\gamma}\mathrm{SF}$ were used as inputs in a Hauser-Feshbach statistical model to calculate the neutron-capture cross section and reaction rate.Results: The NLD and $\ensuremath{\gamma}\mathrm{SF}$ of $^{74}\mathrm{Zn}$ were experimentally constrained for the first time using $\ensuremath{\beta}$-delayed $\ensuremath{\gamma}$ rays measured with TAS and the $\ensuremath{\beta}$-Oslo method. The NLD and $\ensuremath{\gamma}\mathrm{SF}$ were then used to constrain the neutron-capture cross section and reaction rate for the $^{73}\mathrm{Zn}(n,\ensuremath{\gamma})^{74}\mathrm{Zn}$ reaction.Conclusions: The uncertainty in the neutron-capture cross section and reaction rate of $^{73}\mathrm{Zn}(n,\ensuremath{\gamma})^{74}\mathrm{Zn}$ calculated in TALYS was reduced to under a factor of 2 from a factor of 5 in the cross section and a factor of 11 in the reaction rate using the experimentally obtained NLD and $\ensuremath{\gamma}\mathrm{SF}$.

Density distributions, form factors and reaction cross sections for exotic 11Be and 15C nuclei

The ground state proton, neutron and matter densities of exotic 11Be and 15C nuclei are studied by means of the TFSM and BCM. In TFSM, the calculations are based on using different model spaces for the core and the valence (halo) neutron. Besides single particle harmonic oscillator wave functions are employed with two different size parameters Bc and Bv. In BCM, the halo nucleus is considered as a composite projectile consisting of core and valence clusters bounded in a state of relative motion. The internal densities of the clusters are described by single particle Gaussian wave functions.
 Elastic electron scattering proton form factors for these exotic nuclei are analyzed via the plane wave born approximation (PWBA). As the calculations in the BCM do not distinguish between protons and neutrons, the calculations of the proton form factors are restricted only by the TFSM.
 The reaction cross sections for these exotic nuclei are studied by means of the Glauber model with an optical limit approximation using the ground state densities of the projectile and target, where these densities are described by single Gaussian functions. The calculated reaction cross sections at high energy are in agreement with the experimental data.

Advantages of the multinucleon transfer reactions based on 238U target for producing neutron-rich isotopes around N = 126

The mechanism of multinucleon transfer (MNT) reactions for producing neutron-rich heavy nuclei around N=126 is investigated within two different theoretical frameworks: dinuclear system (DNS) model and isospin-dependent quantum molecular dynamics (IQMD) model. The effects of mass asymmetry relaxation, N/Z equilibration, and shell closures on production cross sections of neutron-rich heavy nuclei are investigated. For the first time, the advantages for producing neutron-rich heavy nuclei around N=126 are found in MNT reactions based on 238U target. We propose the MNT reactions with 238U target for producing unknown neutron-rich heavy nuclei around N=126 in the future.

Towards Neutron Capture on Exotic Nuclei: Demonstrating (d,pγ) as a Surrogate Reaction for (n,γ).

The neutron-capture reaction plays a critical role in the synthesis of the elements in stars and is important for societal applications including nuclear power generation and stockpile-stewardship science. However, it is difficult-if not impossible-to directly measure neutron capture cross sections for the exotic, short-lived nuclei that participate in these processes. In this Letter we demonstrate a new technique which can be used to indirectly determine neutron-capture cross sections for exotic systems. This technique makes use of the (d,p) transfer reaction, which has long been used as a tool to study the structure of nuclei. Recent advances in reaction theory, together with data collected using this reaction, enable the determination of neutron-capture cross sections for short-lived nuclei. A benchmark study of the ^{95}Mo(d,p) reaction is presented, which illustrates the approach and provides guidance for future applications of the method with short-lived isotopes produced at rare isotope accelerators.

EAS longitudinal development distribution parameters for different extrapolations of the nuclei intaraction cross section to the very high energy domain

Determination of the primary particle mass using air fluorescence or a Cherenkov detector array is one of the most difficult task of experimental cosmic ray studies. The information about the primary particle mass is a compound of the produced particle multiplicity, inelasticity, interaction cross-section and many other parameters, thus it is necessary to compare registered showers with sophisticated Monte-Carlo simulation results. In this work we present results of the studies of at least three possible ways of extrapolating proton- Nucleus and Nucleus-Nucleus cross sections to cosmic ray energies based on the Glauber theory. They are compared with experimental accelerator and cosmic ray data for the proton-air cross section. We also present results of the EAS development with the most popular high-energy interaction models adopted in the CORSIKA program with our cross section extrapolations. The average position of the shower maximum and the width of its distribution are compared with experimental data and some discussion is given.

Numerical Study of Fusion Cross Sections for 12C+12C and 16O+16O Reactions by Using Wong Formula

The height of the barrier between the interacting nuclei is one of the interesting topics in nuclear reaction, especially in charged-particle nuclear reactions. Wong formula is one method that can be used to perform such study, especially about fusion cross section. Therefore, a study about fusion cross sections of some light nuclei with Wong formula becomes very interesting to be performed. In this study, the fusion cross sections of 12C+12C and 16O+16O reactions have been calculated by using Wong formula at 12<=E<=32 MeV of energies. The potential of the interacting nuclei was approached by using Woods-Saxon potential. The calculations performed numerically by using both finite different and Nelder-Mead methods. The obtained results of this study have achieved a good agreement with the experimental results and the calculation results of the other researchers. Those results were indicated that Wong formula has good capability in explaining the experimental results concerning fusion cross section of light nuclei.

Role of breakup processes in deuteron-induced spallation reactions at 100–200 MeV/nucleon

Use of deuteron-induced spallation reactions at intermediate energies has recently been proposed for transmutation of several long-lived fission products (LLFPs). In the design study of a transmutation system using a deuteron primary beam, accurate cross section data of deuteron-induced reactions on the LLFPs are indispensable. Reliable model predictions play an important role in completing the necessary cross section data since currently available experimental data are very limited. Under the circumstances, we have been developing a code system dedicated for deuteron-induced reactions, which is called DEURACS. Aiming to predict the production cross sections of residual nuclei, the purpose of the present work is to clarify a role of deuteron breakup processes in deuteron-induced spallation reactions at intermediate energies. Isotopic production cross sections of residual nuclei in the deuteron-induced reactions on 93Zr and 107Pd at 100-200 MeV/nucleon are analyzed using DEURACS, in which the breakup processes are explicitly taken into account. The calculated cross sections are decomposed into individual components corresponding to the absorption of either neutron or proton in the incident deuteron, or the deuteron itself. The calculated cross sections reproduced the experimental data well over a wide mass number range of residual nuclei. From a component-by-component analysis, it was found that the components of nucleon absorption have the significant contributions to the production of residual nuclei. Consideration of the breakup processes is essential to predict the production cross sections of residual nuclei in deuteron-induced reactions. The framework of DEURACS is applicable to deuteron-induced spallation reactions at intermediate energies.

Phenomenological approach affecting of (n, p) reaction cross sections via 14.5-MeV neutrons

A new systematic formula is suggested to evaluate the (n, p) reaction cross sections at neutron energy of 14.5 MeV based upon the reaction’s Q-value dependence, explicit symmetry breaking, and shell effects. The measured data for the (n, p) reaction cross sections have been gathered from the available literature, and then, it was analyzed for isotopes having 3 ≤ Z ≤ 83. It has been noted that the plot of σ(n,p) against $$\left( {{Z \mathord{\left/ {\vphantom {Z {A^{{{ 3\mathord{\left/ {\vphantom { 32}} \right. \kern-0pt} 2}}} }}} \right. \kern-0pt} {A^{{{ 3\mathord{\left/ {\vphantom { 32}} \right. \kern-0pt} 2}}} }}} \right)$$ , $$\left( {{{\left( {N - Z + 1} \right)} \mathord{\left/ {\vphantom {{\left( {N - Z + 1} \right)} {A^{{{ 4\mathord{\left/ {\vphantom { 43}} \right. \kern-0pt} 3}}} }}} \right. \kern-0pt} {A^{{{ 4\mathord{\left/ {\vphantom { 43}} \right. \kern-0pt} 3}}} }}} \right)$$ and $$\left( {N/Z \cdot A^{{{ 2\mathord{\left/ {\vphantom { 23}} \right. \kern-0pt} 3}}} } \right)$$ is more efficient in determining the (n, p) reaction cross sections, as the reaction Q-value is related to values of σ(n,p) too, which has been adequately represented and compared to other terms such as Sp, Sn, and Sα separation energies. The odd–even effects investigated in the cross sections of odd-mass nuclei are higher than those of their neighboring even–even nuclei close to magic numbers. The estimates of the current formula are compared with the experimental data gathered from the literature, and they are found to be in good agreement.

Production cross sections for exotic nuclei with multinucleon transfer reactions

The main progresses in the multinucleon transfer reactions at energies close to the Coulomb barrier are reviewed. After a short presentation of the experimental progress and theoretical progress,the predicted production cross sections for unknown neutron-rich heavy nuclei and the trans-uranium nuclei are presented.

A new neutron detector designed for (n,2n) and (n,3n) reaction cross section measurements

A large 4π liquid scintillator was commonly used as the neutron detector to measure nucleus (n,2n) and (n,3n) reaction cross sections in the past direct neutron counting method. However, this type of detector was often criticized for its high γ-rays background. Hence we constructed a new 4π3He array detector to substitute the large liquid scintillation detector, which can effectively suppress the γ-rays. This work mainly studies the detection efficiency and moderation time of this new detector through experimental and simulational methods. Due to its spherical configuration, a relatively stable and weak angular dependence detection efficiency is obtained for the secondary neutrons from (n,2n) and (n,3n) reactions. In addition, the character that the moderation time is nearly independent of neutron energy guarantees gate width has a same influence on the detection efficiency of the secondary neutrons from different samples. These features make it a good candidate detector for (n,2n) and (n,3n) reaction cross section measurements. At last, the preliminary experiment plan and the corresponding calculation method are briefly described.

Production mechanism of neutron-rich nuclei around N = 126 in the multi-nucleon transfer reaction 132Sn + 208Pb**Supported by National Natural Science Foundation of China (11705118, 11475115, 11647026) and Natural Science Foundation of SZU (2016017)

The time-dependent Hartree-Fock approach in three dimensions is employed to study the multi-nucleon transfer reaction 132Sn + 208Pb at various incident energies above the Coulomb barrier. Probabilities for different transfer channels are calculated by using the particle-number projection method. The results indicate that neutron stripping (transfer from the projectile to the target) and proton pick-up (transfer from the target to the projectile) are favored. De-excitation of the primary fragments is treated by using the state-of-art statistical code GEMINI++. Primary and final production cross sections of the target-like fragments (with Z=77 to Z=87) are investigated. The results reveal that fission decay of heavy nuclei plays an important role in the de-excitation process of nuclei with Z > 82. It is also found that the final production cross sections of neutron-rich nuclei depend only slightly on the incident energy, while those of neutron-deficient nuclei depend strongly on the incident energy.

Constraining Neutron Capture Cross Sections for Unstable Nuclei with Surrogate Reaction Data and Theory.

Obtaining reliable data for nuclear reactions on unstable isotopes remains an extremely important task and a formidable challenge. Neutron capture cross sections-crucial ingredients for models of astrophysical processes, national security applications, and simulations of nuclear energy generation-are particularly elusive, as both projectile and target in the reaction are unstable. We demonstrate a new method for determining cross sections for neutron capture on unstable isotopes, using ^{87}Y(n,γ) as a prototype. To validate the method, a benchmark experiment is carried out to obtain the known ^{90}Zr(n,γ) cross section analogously. Our approach, which employs an indirect ("surrogate") measurement combined with theory, can be generalized to a larger class of nuclear reactions. It can be used both with traditional stable-beam experiments and in inverse kinematics at rare-isotope facilities.

First measurement of the Ti(e,e′)X cross section at Jefferson Lab

To probe CP violation in the leptonic sector using GeV energy neutrino beams in current and future experiments using argon detectors, precise models of the complex underlying neutrino and antineutrino interactions are needed. The E12-14-012 experiment at Jefferson Lab Hall A was designed to perform a combined analysis of inclusive and exclusive electron scatterings on both argon ($N = 22$) and titanium ($Z = 22$) nuclei using GeV energy electron beams. The measurement on titanium nucleus provides essential information to understand the neutrino scattering on argon, large contribution to which comes from scattering off neutrons. Here we report the first experimental study of electron-titanium scattering as double differential cross section at beam energy $E=2.222$ GeV and electron scattering angle $\theta = 15.541$ deg, measured over a broad range of energy transfer, spanning the kinematical regions in which quasielastic scattering and delta production are the dominant reaction mechanisms. The data provide valuable new information needed to develop accurate theoretical models of the electromagnetic and weak cross sections of these complex nuclei in the kinematic regime of interest to neutrino experiments.

Production of neutron-rich Pt209–212 isotopes based on a dinuclear system model

The production cross sections of new neutron-rich nuclei $^{209\text{--}212}\mathrm{Pt}$ are investigated with multinucleon transfer reactions by the dinuclear system model. It is found that the $^{133}\mathrm{Sn}+^{204}\mathrm{Hg}$ and $^{145}\mathrm{Xe}+^{208}\mathrm{Pb}$ systems are advantageous to produce the neutron-rich nuclei, in which the production cross sections are much higher than those produced in projectile fragmentation reactions. The optimal incident energies for these two systems are about 1.18 and 1.40 times the Coulomb barrier, respectively. The highest cross sections of unknown isotopes $^{209\text{--}212}\mathrm{Pt}$ in the $^{145}\mathrm{Xe}+^{208}\mathrm{Pb}$ reaction are 2.7 nb, 0.4 nb, 8.2 pb, and 2.7 pb, respectively, and those for the $^{133}\mathrm{Sn}+^{204}\mathrm{Hg}$ reaction are 1.7 nb, 0.4 nb, 23.3 pb, and 4.8 pb, respectively.

Hot fusion reactions with deformed nuclei for synthesis of superheavy nuclei: An extension of the fusion-by-diffusion model

The fusion-by-diffusion model proposed by Swiatecki {\it et al.} [Phys. Rev. C71, 014602 (2005)] has provided a simple and convenient tool to estimate evaporation residue cross sections for superheavy nuclei. I extend this model by taking into account deformation of the target nucleus, and discuss the role of orientation of deformed target in hot fusion reactions at energies around the Coulomb barrier. To this end, I introduce an injection point for the diffusion process over an inner barrier which depends on the orientation angle. I apply this model to the $^{48}$Ca+$^{248}$Cm reaction and show that the maximum of evaporation residue cross section appears at an energy slightly above the height of the capture barrier for the side collision, for which the effective inner barrier is considerably lower than that for the tip collision, thus enhancing the diffusion probability. I also discuss the energy dependence of the injection point, and show that a large part of the energy dependence found in the previous analyses can be attributed to the deformation effect of a target nucleus.

مطالعه سنتز برخی از ایزوتوپهای هسته فلروویوم Fl، واقع در جزیره پایداری و مقایسه پارامترهای سد همجوشی آنها

In the present research, we want to study synthesis of some isotopes of Flerovium ، ، and were produced in the nuclear fusion of 48Ca ions with 239Pu, 240Pu, 241Pu, and 242Pu nuclei. We obtain the parameters of the fusion barriers between48Ca ions with Pu isotopes and compare these parameters with each other. Furthermore, we investigate influence of the direction of target nuclei on the parameters of the fusion barriers. we show that the minimum energies for synthesis of 287Fl, 288Fl, 289Fl and 290Fl nuclei are 184.16 MeV, 183.95 MeV, 183.75 MeV and 183.56 MeV. Finally in the framework of the statistical model, we estimate the evaporation residue cross section for 286Fl, 287Fl nuclei after emission of three and four neutrons from 290Fl nuclei and we will show that the results of calculations for 286Fl nuclei are in good agreement with the experimental data. Although, the results of the calculations of the evaporation residue cross section for 287Fl nuclei lie somewhat below the results of the experimental data.

The Possibility of Reconstructing the Low-Energy Part of the Neutron Spectrum of a Photoneutron Source via Neutron Activation Analysis

Ways of reconstructing the form of the energy spectrum of the W–Be photoneutron source at the Russian Academy of Sciences’ Institute for Nuclear Research are considered, along with contributions to the spectrum of thermal and epithermal neutrons. A comparative analysis of neutron capture cross sections for various nuclei is performed, accompanied by convolutions of these cross sections with different energy regions of the model neutron spectrum. A number of elements are selected as samples for irradiation by source neutrons and subsequent neutron activation analysis. Only thermal and epithermal neutrons or combinations of them make an appreciable contribution to the measured activities of these elements. The samples are irradiated and the activation spectra are measured using a low-background gamma spectrometer. The shape of the source neutron spectrum in the low-energy part of the spectrum is reconstructed. The values of the neutron flux density for these regions of the spectrum are estimated.

Measurement of activation cross sections of the target and the proton beam window materials at J-PARC

To improve the accuracy of the nuclear design for spallation neutron sources and transmutation systems, nuclear reaction cross sections are required. Considering decommissioning of the accelerator facilities, accurate cross sections are mandatory. The activation cross sections have been measured in several facilities. However, they have low accuracy and precision. Especially, since there is almost no data for 3 GeV protons which are used for the spallation neutron source (MLF) in J-PARC, the experimental data is required for in order to improve the target materials. For the sake of the forthcoming full-time measurement of the activation cross sections for various nuclei, we measured the cross sections of aluminium with 0.4 GeV, 1.3 GeV, 2.2 GeV, and 3.0 GeV protons as a test case. It was found that more accurate data than current ones would be measured by using precise beam controls and highly accurate beam monitoring. We compared the experimental data, the evaluated data (JENDLHE/2007), and the calculations with several intranuclear cascade models using the PHITS code. Although the experimental data agreed with JENDL-HE/2007, the calculations underestimated by about 40%. This arises from the evaporation model (GEM) being included in PHITS code. We found that the calculations could be made to agree with the experimental data by upgrading the PHITS code.