Reaction 32S Research Articles

Theoretical modeling of the above-barrier fusion process for nuclei with [formula omitted] based on the experimental nuclear charge densities

Most of theoretical models of nucleus-nucleus collision are based on the nucleus-nucleus potential. Semi-microscopical double-folding model with the M3Y-Paris NN-forces represents one of the advanced methods for evaluating this potential. Nucleon densities (NDs), being crucial ingredient of this model, must reproduce the experimental nuclear charge densities (NCDs). In theoretical approaches for modeling the fusion process, it is not always so. In the present work, we aim to reach satisfactory description of both the charge nucleon density and the above-barrier fusion cross sections of even-even nuclei with Z=N. We construct an approximation for the ND which is abbreviated as FEV-density (Fermi + Exponential tail with Variable diffuseness). The proton and neutron densities are considered to be identical and having a coordinate-dependent diffuseness. Parameters of the nucleon density are varied to obtain the best fit of the experimental NCD. Then the resulting FEV nucleon densities are used to calculate the nucleus-nucleus potential applying the double-folding model with the density-dependent M3Y-Paris NN-forces. This potential is employed for evaluating the above-barrier fusion cross sections for ten reactions: 32S+12C, 24Mg, 40Ca; 28Si+12C, 16O, 24Mg, 28Si; and 24Mg+12C, 16O, 24Mg where the experimental data are available. The cross sections are calculated using either the barrier penetration model or the trajectory model with surface friction. To find the transmission coefficients for the trajectory model, the Langevin-type equations are solved numerically. For all considered reactions, our trajectory model typically reproduces the above-barrier experimental cross sections within 10–15 % with typical χ2<2. The adjustable parameter of the model, the optimal friction strength KRm, was found to be between 20 and 40 zs·GeV−1 which is in reasonable agreement with two systematics found earlier. We also make predictions for the fusion excitation functions for reactions 32S+16O, 32S+28Si, 24Si+40Ca where we did not manage finding experimental data.

33Cl Spectroscopic Factors via the 32S(3He, d)33Cl One-Proton Transfer Reaction

The structure of light-to-medium mass nuclei is crucial to understand exotic phenomena in nuclear structure, including the appearance of molecular effects in light nuclei and their impact in nuclear astrophysics. In this paper, a new experiment to probe one-proton spectroscopic factors of bound and unbound states in the sd-nucleus 33Cl is discussed. The experiment exploits the reaction 32S(3He, d)33Cl* at 9.68 MeV bombarding energy. This reaction is suitable to probe the single-particle structure of 33Cl states with respect to the population of 1d 3/2, 1f 7/2 and 2p 3/2 shells. Crucial aspects of the investigation are the use of an enriched, high-purity, 32S target and a new generation hodoscope with improved angular resolution, allowing to obtain high-precision angular distribution of the differential cross section in a broad angular range. Results are interpreted by means of finite-range DWBA and coupled-channel calculations.

A theoretical study for the production of 32P radioisotope using neutrons from the 68Zn(p,n)68Ga reaction in a medical cyclotron

In the present study, the theoretical estimation of a combined production of 68Ga and 32P radioisotopes were investigated using a medical cyclotron. Protons are used in the 68Zn(p,n) reaction to produce the medical isotope 68Ga. The neutrons from the 68Zn(p,n)68Ga reaction are used to launch the 32S(n,p) reaction to produce 32P radioisotope. The cross section of these reactions were calculated using TALYS 1.9 code and compared with the available experimental results. SRIM-2013 code was used to calculate the stopping power and range of protons in the 68Zn target and GEANT4 toolkit was used to evaluate the proton and neutron flux within the 68Zn and 32S targets, respectively. The theoretical and simulation production yield of 68Ga and simulation production yield of 32P radioisotopes in each reaction were calculated. The results show that the Monte Carlo method can be used for the design and optimization the targets and calculation of production yield for 68Ga and 32P radioisotopes.

PRODUCTION OF PHOSPHORUS-32 AT A NEUTRON GENERATOR AND IT'S SEDIMENTARY ISOLATION

Phosphorus-32 is a β-emitter with a maximum energy of 1.7 MeV (such radiation is completely absorbed in a layer of water or biological tissue up to 1 cm thick) and a half-life of 14.29 days can find application in medicine to study the circulation of substances. This isotope is best obtained from sulfur by the reaction 32S (n, p) 32P, followed by precipitation using neutron generator.

Study of the 33Cl spectroscopic factors via the 32S(3He, d)33Cl one-proton transfer reaction

In this paper we discuss new experimental data on the one-proton transfer reaction 32S(3He, d)33Cl* at 9.68 MeV bombarding energy. An enriched 32S target and a high-granularity hodoscope were used to obtain data for proton transfer reactions to bound and unbound states in 33Cl. Angular distributions were interpreted by means of finite-range DWBA and coupled-channel calculations. The obtained spectroscopic factors have been compared with previous results reported in the literature and with shell model calculations.

Determination of Sulfur and Copper Profile with nuclear reactions

The concentration and depth profile of Cu and S in patinna samples have been determined by using Nuclear Reaction Analysis (NRA) and Rutherford Backscattering Spectroscopy (RBS). For the NRA the differential cross section was mesaured for the 1327 keV 7-ray deexciting the third excited state to the ground state of 6 3Cu through the reaction 63Cu(p,p'7), as well as, for the 2230 keV γ-ray deexciting the first excited state to the ground state through the resonant reaction 32S(p,p'7). The mesaurements of both excitation functions were performed in the energy range 3.0 - 3.7 MeV in 20 keV steps and at an angle of 125°.

Gamma rays as probe of fission and quasi-fission dynamics in the reaction 32S + 197Au near the Coulomb barrier

Compound nucleus fission and quasi-fission are both binary decay channels whose common properties make the experimental separation between them difficult. A way to achieve this separation could be to probe the angular momentum of the binary fragments. This can be done detecting gamma rays in coincidence with the two fragments. As a case study, the reaction 32S + 197Au near the Coulomb barrier has been performed at the Tandem ALTO facility at IPN ORSAY. ORGAM and PARIS, two different gamma detectors arrays, are coupled with the CORSET detector, a two-arm time-of-flight spectrometer. TOF-TOF data were analyzed to reconstruct the mass-energy distribution of the primary fragments coupled with gamma multiplicity and spectroscopic analysis. Preliminary results of will be shown.

Light charged particle multiplicities in fusion and quasifission reactions

The light charged particle evaporation from the compound nucleus and from the complex fragments in the reactions 32S+100Mo, 121Sb+27Al, 40Ar+164Dy, and 40Ar+ nat Ag is studied within the dinuclear system model. The possibility to distinguish the reaction products from different reaction mechanisms is discussed.

Theoretical study of fusion reactions 32S + 94,96Zr and 40Ca + 94,96Zr and quadrupole deformation of 94Zr

The dynamic coupling effects on fusion cross sections for reactions $^{32}$S + $^{94,96}$Zr and $^{40}$Ca + $^{94,96}$Zr are studied with the universal fusion function formalism and an empirical coupled channel (ECC) model. An examination of the reduced fusion functions shows that the total effect of couplings to inelastic excitations and neutron transfer channels on fusion in $^{32}$S + $^{94}$Zr ($^{40}$Ca + $^{94}$Zr) is almost the same as that in $^{32}$S + $^{96}$Zr ($^{40}$Ca + $^{96}$Zr). The enhancements of the fusion cross section at sub-barrier energies due to inelastic channel coupling and neutron transfer channel coupling are evaluated separately by using the ECC model. The results show that effect of couplings to inelastic excitations channels in the reactions with $^{94}$Zr as target should be similar as that in the reactions with $^{96}$Zr as target. This implies that the quadrupole deformation parameters $\beta_2$ of $^{94}$Zr and $^{96}$Zr should be similar to each other. However, $\beta_2$'s predicted from the finite-range droplet model, which are used in the ECC model, are quite different. Experiments on $^{48}$Ca + $^{94}$Zr or $^{36}$S + $^{94}$Zr are suggested to solve the puzzling issue concerning $\beta_2$ for $^{94}$Zr.

Re-evaluation of the EURACOS integral shielding experiment series

The EURACOS experiment series (sodium, iron, and no shielding) has been re-evaluated in the scope of the OECD/NEA SINBAD project to determine how useful these benchmarks can be for the validation of the modern nuclear data evaluations. The measured activation rates of different foils as well as unfolded proton recoil spectra at different depths in sodium and iron have been compared to the Monte Carlo calculated parameters. The results suggest good agreement with the experiment only for the high-threshold 32S(n,p) reaction detectors. The comparison of the lower threshold 103Rh(n,n′) and 115In(n,n′) reactions, and the (n,γ) reaction on 197Au under cadmium cover, reveals large discrepancy between the experimental and calculated spatial distributions for these reaction rates which is expected to be due to the uncertainties in the source and background description rather than due to the cross section uncertainties. On the other hand, the unfolded neutron spectra shapes are in relatively good agreement with the calculated ones. The overall results show that the EURACOS Na and Fe experiments cannot be considered of benchmark quality mainly due to unsatisfactory information on the neutron source. Nevertheless, some activation measurements from the EURACOS sodium and iron experiments such as the high threshold reactions and the spectra measurements are potentially useful for modern nuclear data and computer code benchmarking.

Compound nucleus evaporative decay as a probe for the isospin dependence of the level density

The evaporative decay of the compound nucleus 139Eu produced by the 180MeV 32S + 107Ag reaction was studied with the aim to test the empirical isospin expressions of the level density, recently appeared in the literature. We measured light charged particle spectra and angular correlations in coincidence with the evaporation residues and the invariant velocity distribution of the evaporation residues. In addition, an independent experiment was performed on the reaction 32S + 109Ag at the same incident energy. Evaporation residue angular distribution was measured and the fusion-evaporation cross-section was determined. All the measured quantities are compared with the predictions of different level density prescriptions: a) isospin independence, b) a dependence from N - Z and c) a dependence from Z-Z0 as proposed by Al-Quraishi et al. Results show that the predictions of the Z-Z0 dependence are far off the experimental data for all the measured observables. Regarding the isospin independent prescription and the N - Z dependence, although no great differences appear between their predictions the N - Z prescription seems to better describe the experimental data.

Measurement of differential cross-sections and widths of resonances in 32S(p,p′γ) 32S reaction in the 3.0–4.0 MeV region

The paper reports the widths and differential cross-sections of resonances at 3.089, 3.379 and 3.717 MeV in the 32S(p,p′γ) 32S nuclear reaction. The cross-sections are computed at 0° and 90° angles (relative to the beam direction) from thick target excitation curves constructed by measuring 2230 keV γ-rays, characteristic of the reaction. The differential cross-sections of resonances are about 18, 64 and 70 mb/sr respectively at 0° angle and decrease by about half around an angle of 90°. The first resonance, the sharpest among the three, exhibits a width of about 400 eV while those at 3.379 and 3.717 MeV are in 1.0–1.5 keV range. The widths of the resonances are extracted from the respective thick target excitation curves by an interquartile separation method and also by simulating their leading edges. A study of thick target yields in the 3.0–4.0 MeV proton energy region for several sulphide forming elements shows the absence of any significant interference. These resonances, as a result, can be effectively utilised for sensitive and high resolution depth profile measurements of sulphur in films and materials surfaces.

An electrostatic deflector for a fusion reaction

An electrostatic deflector for separating the fusion evaporation residues from the beam-like products in heavy ion reactions was installed. The evaporation residue separation and identification with the electrostatic deflector setup was tested with the reaction 32S+96Zr at several energies. The fusion evaporation residues and the beam-like particles were well separated after the electrical separation and the experimental fusion cross section obtained from the angular distribution is in good agreement with the calculated value well above the Coulomb barrier. This confirms the reliability of the setup.

Nuclear Data Sheets for A = 30

Evaluated spectroscopic data and level schemes from radioactive decay and nuclear reaction studies are presented for 30F, 30Ne, 30Na, 30Mg, 30Al, 30Si, 30P, 30S, and 30Cl. This evaluation for A=30 supersedes the previous evaluation 1998En04. However, some additional information for these nuclides can be found in earlier evaluations 1990En08 and 1978En02. Highlights of this publication are the following: The latest studies (2010StZZ, 2010De26) by fusion evaporation reaction of 14C and 18O using GAMMASPHERE array, consisted of 101 Compton-suppressed HPGe detectors, provided new data for 30Al, 30Si, and 30Mg nuclides and extended the level scheme to higher spin states. 2010Se07 reported a new level at 4814(3) keV for 30S nuclide studied by the 32S(p,t) reaction. It did not observe the 5168(6) keV level that was reported earlier as a possible doublet by 2007Ba69. In the absence of further experiment, 2010Se07 considers the level as one of the doublets.

Particle– γ coincidences and coplanarity in the 32S + 24Mg binary reaction

The reaction 32S (165.4 MeV) + 24Mg is studied using the binary reaction spectrometer (BRS) coupled to the Euroball Ge-detector array. Particle–particle– γ and particle– γ– γ coincidences have been examined together with γ– γ-only coincidences for the fusion-evaporation residues. Recent reports of evidence for hyper-deformation from angular correlations in similar data are investigated. Analogous out-of-plane angular correlations are observed but attributed to reactions with the target contaminants 16O and 12C. This is consistent with the contamination observed in the γ– γ-only data.

Differential cross section measurements of the 32S(d,p)33S reaction for nuclear reaction analysis purposes

Differential cross sections of the 32S(d,p0,1,2,3,4–6,7) reactions were determined for deuteron energies Elab=1975–2600keV (in steps of 25keV) and for detector angles between 140–170° in steps of 10°. A comparison of the experimental data with the existing ones and possible applications to nuclear reaction analysis (NRA) studies are discussed.

Industrial production and purification of 32P by sulfur irradiation with partially moderated neutron fluxes and target melting

Target purification of Sα is carried out by distillation at 444±2 °C under N atmosphere and diluting the vapors in CS2. The solution is filtered through fiberglass, Teflon and cellulose to obtain Sα by CS2 evaporation. Once 30 g of this target are irradiated with fast neutron fluxes from 4.5 to 7.4·1012 n·cm−2s−1 from 6 to 12 hours, the nuclear reaction 32S(n,p)32P takes place. So, the irradiated Sα sample is placed in a Pyrex container situated inside a furnace as the most important piece of equipment in one aluminum and Lucite glove box. The distillation of irradiated sulfur takes place at 444±2 °C under N atmosphere during 1–2 hours. The vapors are connected to a sulfur diluter containing 20% CS2 aqueous solution, followed by an activated carbon filter and the two similar additional sulfur diluters. Once cooled, the distillation chamber keeps the radioactive, carrier-free 32P stuck to the wall. Then 25–50 ml of 0.1N HCl acid was injected by suction and heated again at 110±2 °C during 1 hour. The corresponding chemical reaction takes place and the labeled H332PO4 solution is produced. In such a way, industrial production of 32P labeled molecules has started in Mexico, with an initial production of 3700–5550 MBq per week.

Investigation of copper patinas using ion beam analysis and scanning electron microscopy

AbstractIon beam analysis (IBA) techniques were applied successfully to the investigation of non‐corroded and artificially corroded patina layers grown on copper substrates in order to explore their potential use in the study of degradation phenomena of copper and copper alloys subjected to chemical treatment and exposed to selected environmental conditions. Rutherford backscattering spectroscopy (RBS) with deuterons as projectiles and the nuclear reactions 16O(d,p)17O and 32S(p,p′γ)32S were applied to the investigation of the depth distribution of oxygen and sulphur in near‐surface layers of synthetic patina consisting of mineral phases corresponding to chalcanthite as well as to cuprite + chalcanthite and antlerite + brochantite + chalcanthite. Electrochemical techniques (potentiodynamic polarization and cyclic voltammetry in 0.5 M Na2SO4) were used for artificial acceleration and study of the corrosion processes, and scanning electron microscopy (SEM/EDS) was used for examination of the surface morphology of the samples. A patinated roof sample from the Vienna Hofburg also was investigated using the same techniques. The measurement showed that IBA can provide valuable information for the study of patina near‐surface layers of thickness up to a few micrometres and indicated that cuprite was the mineral phase primarily formed on the copper substrates and the main component of the interface between the patina layer and the metallic substrate. The investigated copper patinas looked rather heterogeneous and were characterized by high porosity. Mixed patinas exhibited considerable stability to further corrosive attack. Copyright © 2005 John Wiley &amp; Sons, Ltd.

Effective Charges in thefpShell

Following the heavy-ion fusion-evaporation reaction 32S+24Mg at 95 MeV beam energy the lifetimes of analogue states in the T(z)=+/-1/2 A=51 mirror nuclei 51Fe and 51Mn have been measured using the Cologne plunger device coupled to the GASP gamma-ray spectrometer. The deduced B(E2;27/2(-)-->23/2(-)) values afford a unique opportunity to probe isoscalar and isovector polarization charges and to derive effective proton and neutron charges, epsilon(p) and epsilon(n), in the fp shell. A comparison between the experimental results and several different large-scale shell-model calculations yields epsilon(p) approximately 1.15e and epsilon(n) approximately 0.80e.

Reactions of Massive Nuclei for the Synthesis of Heavy and Superheavy Nuclei

We study the effect of the entrance channel and the shell structure of reacting massive nuclei on the fusion mechanism and the formation of evaporation residues of heavy and superheavy nuclei. In the framework of the combined dinuclear system concept and advanced statistical model, we analyze the reactions 32S+182W, 48Ti+166Er and 60Ni+154Sm leading to 214Th*, and the reactions 48Ca+248Cm and the 48Ca+249Cf leading to the 296116 and 297118 compound nuclei, respectively.