Pb Targets Research Articles

Experimental study of (p, 2p) reactions at 392 MeV on 12C, 16O, 40Ca and 208Pb nuclei leading to low-lying states of residual nuclei

Abstract We have measured the differential cross-sections and analyzing powers for ($p,2p$) reactions at an incident energy of 392 MeV on $^{12}$C, $^{16}$O, $^{40}$Ca, and $^{208}$Pb nuclei, leading to discrete states of the residual nuclei. The data are compared with two kinds of distorted-wave impulse approximation (DWIA) calculations, a standard calculation using a global optical potential and a calculation using wave functions generated in a relativistic Hartree model. The spectroscopic factors deduced from these two calculations agree with those determined in ($e,e'p$) studies mostly within 15% in the case of the lighter three target nuclei. However, those for the $^{208}$Pb target are overestimated compared with the ($e,e'p$) results. In the heavy target case, the DWIA results are very sensitive to the radius parameter of the bound-state potential and thus a careful treatment is required. Regarding the analyzing powers of the present measurement, we confirmed that the $j$-dependence is sufficient for practical spectroscopic use.

Possibility of observation of hidden-bottom pentaquark resonances in bottomonium photoproduction on protons and nuclei near threshold

We study the meson photoproduction on protons and nuclei at near-threshold center-of-mass energies below 11.4 GeV (or at the corresponding photon laboratory energies below 68.8 GeV). We calculate the absolute excitation functions for the nonresonant and resonant photoproduction of mesons off protons at incident photon laboratory energies of 63-68 GeV by considering direct ( ) and two-step ( , , ) production channels within different scenarios for the nonresonant total cross section of the elementary reaction and for branching ratios of the decays , , and . We also calculate an analogous function for the photoproduction of mesons on the 12C and 208Pb target nuclei in the near-threshold center-of-mass beam energy region of 9.0-11.4 GeV by considering the respective incoherent direct ( ) and two-step ( , , and , , ) ) production processes using a nuclear spectral function approach. We demonstrate that a detailed scan of the total photoproduction cross section on proton and nuclear targets in the near-threshold energy region in future high-precision experiments at the proposed high-luminosity electron-ion colliders EIC and EicC in the US and China should provide a definite result for or against the existence of the nonstrange hidden-bottom pentaquark states and ( =1, 2, 3) as well as clarify their decay rates.

Production and study of neutron rich heavy nuclei, GALS setup

A new setup for production and investigation of exotic heavy neutron rich nuclei located in the "north-east" region of nuclear map is under construction at Flerov Laboratory for Nuclear Reactions (FLNR) of JINR, Dubna. The setup will use the available U-400M cyclotron beams for low energy multi-nucleon transfer reactions. Products of 4.5 to 9 MeV per nucleon heavy-ion collisions, such as 136Xe beam on 208Pb target, will be captured in a gas cell, selectively laser-ionized, transported towards mass separator by electrostatic ion guide extraction system and then to detecting system.

Coulomb Excitation of Proton-rich N = 80 Isotones at HIE-ISOLDE

A projectile Coulomb-excitation experiment was performed at the radioactive ion beam facility HIE-ISOLDE at CERN. The radioactive 140Nd and 142Sm ions were post accelerated to the energy of 4.62 MeV/A and impinged on a 1.45 mg/cm2-thin 208Pb target. The γ rays depopulating the Coulomb-excited states were recorded by the HPGe-array MINIBALL. The scattered charged particles were detected by a double-sided silicon strip detector in forward direction. Experimental γ-ray intensities were used for the determination of electromagnetic transition matrix elements. Preliminary results for the reduced transition strength of the of 140Nd and a first estimation for 142Sm have been deduced using the Coulomb-excitation calculation software GOSIA. The states of 140Nd and 142Sm show indications of being the main fragment of the proton-neutron mixed-symmetry state.

Production of Polonium-208, 209 and 210 for use in nuclear battery via particle accelerator

Nuclear reaction processes are used for the production of energetic 208,209,210Po nuclei from Pb and Bi targets with particle accelerators, instead of the production with a nuclear reactor, for use in the nuclear battery and radioisotope thermoelectric generator technologies. The cross-section curves, simulated activity and yields of product of each reaction process were calculated under particular conditions, including 24 h of irradiation with a particle beam current of 1 mA for the energy range Eparticle = 200 → 1 MeV. Based on the calculated and simulated results, to produce 208,209,210Po nuclei, the appropriate target nuclei, nuclear reaction processes, and energy region of reactions were discussed by comparing the obtained results with the experimental data of literature and TENDL database in detail.

Measurements of L-subshell x-ray production cross sections and M-shell x-ray yields of Pb by low-energy electron impact using the thick-target method

The Lα, Lβ, and Lγ x-ray production cross sections and M-shell x-ray yields by 5–29 keV electrons bombarding a thick Pb target were measured. The effects of multiple-scattered electrons, from the bremsstrahlung and other secondary particles within the thick sample were corrected using the Monte Carlo simulations. The experimental results are compared with the DWBA predictions of Bote et al., and also with the experimental data from the literature. The results indicate that the measurements of the production cross sections for the L subshells of the elements with higher atomic numbers using the thick-target method are feasible and reliable.

Rearrangement term in the folding model of the nucleon optical potential

Based on the mean-field determination of the single-particle energy in nuclear matter that contains naturally a rearrangement term (RT) implied by the Hugenholtz–van Hove theorem, the folding model of the nucleon optical potential (OP) is extended to take into account the RT using the effective, density dependent CDM3Yn interaction. With the exchange part of the nucleon folded OP treated exactly in the Hartree–Fock manner, a compact nonlocal version of the folding model is suggested in the present work to determine explicitly the isospin-dependent, nonlocal central term of the nucleon OP. To solve the optical model (OM) equation with a complex nonlocal OP, the calculable R-matrix method is used to analyse the elastic neutron and proton scattering on 40,48Ca, 90Zr, and 208Pb targets at low energies. The inclusion of the RT into the folding model calculation of the nonlocal nucleon OP was shown to be essential for the overall good OM description of elastic nucleon scattering. To validate the nonlocal version of the folding model, the OM results given by the nonlocal folded nucleon OP are also compared with those given by the global parametrization of the nonlocal OP using the analytical nonlocal form factor suggested by Perey and Buck.

The possibility to study in-medium modification of J/ψ mesons from their photoproduction on nuclei near threshold in the case of presence of the LHCb pentaquark states [formula omitted], [formula omitted] and [formula omitted] in this photoproduction

We study the J/ψ photoproduction from nuclei in the near-threshold beam energy region of Eγ=5–11 GeV within the nuclear spectral function approach by considering incoherent direct (γN→J/ψN) and two-step (γp→Pc+(4312), Pc+(4312)→J/ψp; γp→Pc+(4440), Pc+(4440)→J/ψp; γp→Pc+(4457), Pc+(4457)→J/ψp) J/ψ production processes. We calculate the absolute excitation functions for the non-resonant and resonant production of J/ψ mesons off 12C and 208Pb target nuclei within the different scenarios for in-medium modification of the directly photoproduced J/ψ mesons and for branching ratios of the decays Pc+(4312)→J/ψp, Pc+(4440)→J/ψp and Pc+(4457)→J/ψp. We show that the non-resonant subthreshold J/ψ production in γA reactions reveals some sensitivity to employed in-medium modification scenarios for J/ψ mesons, which is not masked by the resonantly produced J/ψ mesons, only if above branching ratios are less than 5%. We also demonstrate that if these branching ratios more than 5% then the presence of the Pc+(4312), Pc+(4440) and Pc+(4457) resonances in J/ψ photoproduction on nuclei produces above threshold additional enhancements in the behavior of the total J/ψ creation cross section on nuclei, which could be also studied in the future JLab experiments at the CEBAF facility to provide both further evidence for their existence and valuable information on their nature.

A novel fluorescence aptamer biosensor for trace Pb(II) based on gold-doped carbon dots and DNAzyme synergetic catalytic amplification

Gold-doped carbon dots (CDAu) and carbon dots (CD) were quickly prepared by microwave irradiation procedure, using glucose as carbon source and HAuCl4 as doped reagent. Both CDAu and DNAzyme of Pb(II)-aptamer (Apt)-heme exhibit catalysis of the new fluorescence indicator reaction of H2O2-3,3′,5,5′-tetramethylbenzidine (TMB) to produce the oxidized TMB (TMBox) with a fluorescent peak at 404 nm. The Apt can be adsorbed on the CDAu surface to form a CDAu-Apt conjugate to inhibit the catalysis to cause the fluorescence intensity decreasing. The target for Pb(II) combined with the Apt to form stable G-quadruplex complex and free CDAu, in which G-quadruplex reacted with heme to form G-quadruplex/heme DNAzyme. Both the free CDAu and DNAzyme catalyzed in synergetic to produce TMBox, and the fluorescence enhanced greatly. Thus, a new and highly sensitive synergetic catalytic fluorescence method for the determination of 0.0005–0.46 μmol/L Pb(II) was established, with a detection limit of 0.25 nmol/L, its sensitivity is several orders of magnitude higher than most previously reported Pb2+ sensors. Compared with the CD, the CDAu has a quantum yield increase of 150%.

Structure and Orientation Variations during Growth of Films of Pd–5 at % Pb Solid Solution

This article is devoted to studying morphological, structural, and orientation transformations and variations of elemental composition during growth of films of Pd–Pb solid solution upon magnetron sputtering of Pd–5 at % Pb target in an Ar environment (10–1 Pa); the initial vacuum is 10–3 Pa; growth rate is 4 nm/s; magnetron power during growth of thin films is 630–650 W and of thick films is 750–790 W. It is established that nucleation and growth of films of Pd–Pb solid solution take place according to the Volmer–Weber growth mode and are accompanied by collective recrystallization. The stage of labyrinth morphology is achieved at an average thickness of 10 nm. This stage is characterized by nanocrystalline structure and uniaxial texture 〈 111〉 . Existence of the second component (Pb) suppresses multiple twinning peculiar to Pd island films. The elemental composition in the film bulk is characterized by a decrease in Pb concentration.

Halo Effects in the Low-energy Scattering of \(^{15}\)C with Heavy Targets

The neutron-rich carbon isotope 15C was postulated to be a halo nucleus (Sn = 1215 keV, S2n = 9395 keV) according to different high-energy experiments. If so, it would be the only halo nucleus exhibiting a pure s-wave structure of the ground state. At low collision energies, the effect of this halo structure should manifest as a strong absorption pattern in the angular distribution of the elastic cross section, with a total suppression of the nuclear rainbow due to the large neutron transfer and breakup probabilities, enhanced by the halo configuration. The IS619 experiment, carried out at the HIE-ISOLDE facility at CERN (Switzerland), is the first dynamical study of this nucleus at energies around the Coulomb barrier. It aims to probe the halo structure via the measurement of the elastic cross section on a high-Z 208Pb target. Preliminary results of the elastic cross section are discussed and compared to Optical Model calculations.

Dose Measurements around Spallation Neutron Sources

Neutron dose measurements and calculations around spallation sources are of importance for an appropriate shielding study. Two spallation sources, consisted of Pb target, have been irradiated by high-energy proton beams, delivered by the Nuclotron accelerator (JINR), Dubna. Dose measurements of the neutrons produced by the two spallation sources were performed using Solid State Nuclear Track Detectors (SSNTDs). In addition, the neutron dose after polyethylene and concrete was calculated using phenomenological model based on empirical relations applied in high energy Physics. Analytical and experimental neutron benchmark analysis has been performed using the transmission factor. A comparison of experimental results with calculations is given.

Experimental study of the elastic scattering of 10Be on 208Pb at the energy of around three times the Coulomb barrier * * Supported by the National Natural Science Foundation of China (U1632138, 11575256, 11605253, 11705242, 11875297)

Elastic scattering of 10Be on a 208Pb target was measured at = 127 MeV, which corresponds to three times the Coulomb barrier. The secondary 10Be beam was produced at the Radioactive Ion Beam Line in Lanzhou of the Heavy-Ion Research Facility in Lanzhou. The angular distribution of elastic scattering in the 10Be + 208Pb system shows a typical Fresnel diffraction peak. Optical model analysis of the angular distribution was performed using the Woods-Saxon, double-folding and global potentials. With the global potential, different density distributions were used. The results indicate that different density distributions for the projectile induce distinct effects in the angular distribution.

Computational study of fragmentation cross-sections for 28Si ions in various media using GEANT4

The comparison of simulated data with experimental results is needed for the accuracy and reliability of the transport codes. In this work, we performed a comparative study of simulated results of projectile fragmentation cross-sections (PFXS) for three different models. The obtained results also compared with published experimental data. For simulation purposes, the GEANT4 simulation toolkit based on the Monte Carlo (MC) codes is used. The models in Geant4 employed to compute the PFXS are the Binary Cascade (BIC), the Quantum Molecular Dynamics (QMD), and the Intranuclear cascade (INCL). In the present study we reported the interaction of 28Si ion beam for the energy range 270–1200 A MeV incident on carbon (C), aluminium (Al), copper (Cu), tin (Sn), and lead (Pb) targets. The QMD, the BIC, and the INCL model coupled with the de-excitation models reproduce the results in agreement with experimental fragmentation cross-sections.

Populating high spin states of a compound nucleus with the incomplete fusion mechanism: the effectiveness of heavy projectiles

Using a classical dynamical reaction model, angular momentum (L) values of a compound nucleus due to incomplete fusion (ICF) at energies near and above the Coulomb barrier are studied. In this model, a projectile consisting of two cluster nuclei is fired at a stationary target nucleus. After breakup of the projectile due to Coulombic and nuclear forces, an α-cluster fuses with a 208Pb target, forming an excited 212Po compound nucleus. Results show that all ICF reactions produced higher angular momentum in the compound nucleus compared to a direct beam of α particles at the same incident energy. The highest angular momentum values produced in 212Po for near and above Coulomb barrier energies were obtained using a 20Ne projectile at and , respectively. This produced 25% and 50% L values above the next highest-Z projectile used, 8Be, respectively.

Spallation reactions induced by 4.4 GeV deuterons on lead isotopes

Independent and cumulative production cross sections for radioactive nuclear fragments from the deuteron-irradiation of isotopically enriched lead (204Pb, 206Pb, 207Pb, and 208Pb) targets were obtained for the first time. The experiment has been performed with a 4.4 GeV deuteron beam from the Nuclotron of the Laboratory of High Energy Physics (LHE), Joint Institute for Nuclear Research (JINR) at Dubna. The production cross sections of target fragments were determined by off-line γ-ray spectroscopy. Charge dispersion and mass-yield distributions were deduced from these data. The results are discussed in terms of the relative importance of different reaction mechanisms (evaporation–spallation, fission and multifragmentation). Comparison of our results with the data from the reaction induced by protons of about the same kinetic energy per nucleon, has been performed. The coexistence of the different decay modes in the formation of the reaction residues, such as spallation, fission and multifragmentation is suggested.

A Comprehensive Description of 19F Elastic Scattering by 12C, 16O, 66Zn, 159Tb, and 208Pb Target Nuclei

In this study, we analyze the elastic scattering angular distributions of 19F projectiles on 12C, 16O, 66Zn, 159Tb, and 208Pb target nuclei at different incident energies. In this context, our work is carried out in three stages. First of all, different and alternative density distributions of the 19F nucleus are proposed. Then, the real potentials of the optical model are obtained by using the density distributions obtained for the 19F nucleus within the double-folding model. The imaginary potential is assumed to have a Woods-Saxon form. It is observed that the theoretical results are in good agreement with the experimental data. Finally, new and global imaginary potential equations which will be evaluated in the analysis of the interactions of 19F projectiles on different targets are achieved for each density distribution.

Microscopic description of proton-induced spallation reactions with the constrained molecular dynamics (CoMD) model

We studied the complete dynamics of the proton-induced spallation process with the microscopic framework of the constrained molecular dynamics (CoMD) model. We performed calculations of proton-induced spallation reactions on 181Ta, 208Pb, and 238U targets with the CoMD model and compared the results with a standard two-step approach based on an intranuclear cascade model followed by a statistical deexcitation model. The calculations were also compared with recent experimental data from the literature. Our calculations showed agreement with some aspects of the experimental data and suggest further improvements in the models. We point out that this CoMD study represents the first complete dynamical description of spallation reactions with a microscopic N-body approach and may lead to advancements in the physics-based modeling of the spallation process.

Investigations of laser produced x-rays effect on the structural, morphological and electrical properties of Pb and Cu

X-rays produced by LASER have many applications in research and electronic industries. Current work is based on effects of x-rays on the structural, morphological and electrical properties of lead (Pb) and copper (Cu). In vacuum, KrF Excimer laser is irradiated on Cu and Pb targets. After that, Cu and Pb targets are exposed by these x-rays which are obtained from laser induced plasma. XRD showed that grain size of exposed samples is decreased as compared to unexposed samples. SEM analysis showed that the lead surface is more damaged as compared to Cu. Electrical conductivity of metals is decreased after exposure of x-rays, according to four-point probe technique. The present study will facilitate the effect of x-rays of Cu and Pb on different properties of material. The results thus obtained will be applicable in many industries including optoelectronics, biomedical etc.

Systematic study of proton-induced spallation reactions with the Constrained Molecular Dynamics (CoMD) model

Proton – induced spallation reactions on 238U, 208Pb, 181Ta and 197Au targets at high energies were studied and investigated using the microscopic Contrained Molecular Dynamics (CoMD) model. Total fission cross sections, the ratio fission cross section to residue cross section, mean kinetic energy of fission fragments, mass yield curves and the number of nucleons emitted, before and after scission, as well as the total nucleon multiplicity were calculated using the CoMD model and compared with experimental data from the literature. Some of our calculations showed satisfactory agreement with available experimental data.The calculations of cross sections and the ratio fission cross section to residue cross section as a function of the proton energy gave us the opportunity to estimate observables for unmeasured nuclides.