Au Reactions Research Articles

151Eu(n,γ)152m1Eu reaction cross-section measurement at the neutron energies of 1.12, 2.12, 3.12 and 4.12 MeV

The 151Eu(n,γ)152m1Eu reaction cross-section at the neutron energies (En) of 1.12, 2.12, 3.12 and 4.12 MeV was determined by using activation and off-line γ-ray spectrometric technique. The mono-energetic neutrons of 1.12–4.12 MeV were generated from the 7Li(p,n) reaction by using the proton beam energies of 3–6 MeV. The 197Au(n,γ)198Au reaction cross-section was used as the neutron flux monitor. The 151Eu(n,γ)152m1Eu reaction cross-section was also calculated by using computer code TALYS 1.6 and compared with the experimental data to check its validity. The Eu(n,γ) reaction cross-section is important for the safety of the fast reactor and conventional fission reactor.

An intensive study on the optical, rheological, and electrokinetic properties of polyvinyl alcohol-capped nanogold

Low-temperature-assisted wet chemical synthesis of nanogold (NG) using gold hydroxide, a new precursor salt in the presence of a macroscopic ligand poly(vinyl alcohol) PVA in water in the form of nanofluid, is reported for the first time in this article. In the absorption spectra, the surface Plasmon resonance absorption band in the range of 520–545 nm signifies the formation of NG via a controlled Au3+ + 3e → Au reaction grafted in small assemblies with polymer. Absorption maximum increases nonlinearly with Au-contents up to 100 µM Au in Au-PVA charge-transfer complex. Marked enhancement in the peak intensity of some of the vibration bands of PVA polymer such as C–H stretching, C=O stretching, CH2 bending, and C–C in-plane bending in the presence of NG reveals an interfacial interaction between NG and oxidized PVA via C=O group. Execution of shear thinning behavior regardless of the Au-content strongly suggests that crosslinking exists between NG and PVA in Au-PVA rheo-optical nanofluids. Hydrodynamic diameter and polydispersity index draw a nonlinear path with the Au doping with 30.0 g/L PVA in water over a wide region of 5–100 μM Au covered in this study. Enhancement in the zetapotential of Au-PVA nanofluid over bare PVA in water is ascribed to buildup of nonbonding electrons of “–C=O” moieties from the oxidized PVA on the NG surface. Displaying of lattice fringes in the microscopic image of core–shell Au-PVA nanostructure confirms that crystalline nature of NG core with inter planar spacing 0.235 nm corresponds to Au (111) plane.

Decomposition of the sensitivity of the symmetry energy observables

To exactly answer which density region that some frequently used symmetry-energy-sensitive observables probe, for the first time, we make a study of decomposition of the sensitivity of some symmetry-energy-sensitive observables. It is found that for the Au+Au reaction at incident beam energies of 200 and 400 MeV/nucleon, frequently used symmetry-energy-sensitive observables mainly probe the density-dependent symmetry energy around 1.25$\rho_{0}$ (for pionic observables) or 1.5$\rho_{0}$ (for nucleonic observables). Effects of the symmetry energy in the low-density region is in general small but observable. The fact that the symmetry-energy-sensitive observables are not sensitive to the symmetry energy in the maximal baryon-density region increases the difficulty of studying nuclear symmetry energy at super-density.

Validation of the MCNP computational model for neutron flux distribution with the neutron activation analysis measurement

The objective of this work is to demonstrate the method for validating the predication of the calculation methods for neutron flux distribution in the irradiation tubes of TRIGA research reactor (TRR-1/M1) using the MCNP computer code model. The reaction rate using in the experiment includes 27Al(n, α)24Na and 197Au(n, γ)198Au reactions. Aluminium (99.9 wt%) and gold (0.1 wt%) foils and the gold foils covered with cadmium were irradiated in 9 locations in the core referred to as CT, C8, C12, F3, F12, F22, F29, G5, and G33. The experimental results were compared to the calculations performed using MCNP which consisted of the detailed geometrical model of the reactor core. The results from the experimental and calculated normalized reaction rates in the reactor core are in good agreement for both reactions showing that the material and geometrical properties of the reactor core are modelled very well. The results indicated that the difference between the experimental measurements and the calculation of the reactor core using the MCNP geometrical model was below 10%. In conclusion the MCNP computational model which was used to calculate the neutron flux and reaction rate distribution in the reactor core can be used for others reactor core parameters including neutron spectra calculation, dose rate calculation, power peaking factors calculation and optimization of research reactor utilization in the future with the confidence in the accuracy and reliability of the calculation.

Time-dependent quantum models of the dynamics of neutron transfer reactions near the barrier

Time-dependent valence neutron wave functions were calculated for nucleus-nucleus collisions 6He + 197Au, 18O + 58Ni, 48Ca + 18O, 40,48Ca + 238U. Probabilities of the neutron transfer and near-barrier population of two-center levels were calculated. The energy dependence of the neutron transfer cross section in the 6He + 197Au reaction has been explained.

Charged-particle flow measured with the KRATTA detector in the ASY-EOS experiment

The flow of light charged particles from the Au+Au reaction at 400 AMeV measured with the KRATTA detector is presented. The results are compared with the FOPI data. The KRATTA detector (Krakow Triple Telescope Array) [1] has been used to measure the energy, emission angles and isotopic composition of light charged reaction products in the ASY-EOS experiment at GSI laboratory [2]. This versatile, low threshold, broad energy range system consists of 38 independent modules which can be arranged in an arbitrary configuration Fig. 1 presents the used 7×5 array. A single module, covering actively about 4.5 msr of the solid angle at the optimal distance of 40 cm from the target, consists of three identical, 500 μm thick, large area photodiodes, used also for direct detection, and of two CsI(1500 ppm Tl) crystals of 2.5 and 12.5 cm length, respectively. The presented results come from the analysis of the experimental data for Au+Au at 400 MeV/nucleon incident energy. Signals from the KRATTA modules have been stored for the off-line analysis using the 100 MHz V1724 CAEN digitizers. The pulse shape analysis allowed to decompose the complex signals from the middle photodiode (Single Chip Telescope [3] segment, SCT) into the ionization and scintil

Neutron Induced Reactions with the 17 Mev Facility at the Athens Tandem Accelerator NCSR ‘Demokritos’

In the 5.5 MV tandem T11/25 Accelerator Laboratory of NCSR “Demokritos” monoenergetic neutron beams have been produced in the energy range∼ 15-20 MeV using anew Ti-tritiated target of 373 GBq activity, by means of the 3H(d,n)4He reaction. The corresponding deuteron beam energies obtained from the accelerator, were in the 1.5-4.5MeV range.The maximum flux has been determined to be of the order of 106 n/cm2 s, implementing reference reactions. The 17.1MeV neutron beam has been used for the measurement of 197Au(n,2n) reaction cross section. Theoretical calculations have been performed via the statistical model code EMPIRE and compared to the experimental data of the present work and data from literature.

A new technique to determine fusion barrier heights using proximity potentials

We develop a new technique to calculate fusion barrier heights of any fixed target reaction series. We calculate the barrier heights for the fusion reactions of 119 Sn and 197 Au targets using this technique. This technique is simple and very useful for estimating the fusion barrier heights for those reactions for which empirical values are not available. A formula is derived by performing theoretical calculations using different versions of proximity potential. Using this formula, we can predict the barrier height for the fusion reaction of any projectile with 119 Sn or 197 Au target using the empirical barrier height for the fusion reaction of same projectile with 62 Ni target. In order to check the accuracy of this technique, the fusion parameters calculated by this new technique are compared with the fusion parameters calculated by using parameterized formulae presented in a systematic study conducted by using double folding model. the colliding nuclei. The separation between the two col- liding nuclei is related to the internuclear distance between the centers of the colliding nuclei through their nuclear radii. So we need accurate knowledge of nuclear radii. In the present study, we propose a new technique, which can be used to calculate the fusion barrier heights of any fixed target reaction series. For this study, we first compute barrier heights for X + 62 Ni, X + 119 Sn and X + 197 Au reaction series using different versions of proximity potential. Here, X projectile varies from 1 Ht o 59 Co. This study is carried out using proximity potentials PROX 77, PROX 88, PROX 2000, PROX 2000DP, PROX 2010 and MOD-PROX 88.

Comparison of neutron attenuation properties of ferro boron slabs containing 5% natural boron with other high density materials

Modeling and designing cost-effective neutron attenuation along with shield volume reduction is a challenging task in fast reactors. It involves reducing the neutron energy and absorbing them with suitable materials. A series of experiments were conducted in the South beam end of Kalpakkam Mini reactor with powders of ferro boron (FeB), ferrotungsten (FeW), boron carbide, slabs of FeB, and mild steel plates to study their neutron attenuation characteristics. In one of the experiments, FeB slab cast with 5% natural boron was used, and neutron attenuation measurements were carried out. The attenuation factors were found over a thickness of 28 cm for the measured reaction rates of 195 Pt (n, n') 195m Pt, 111 Cd (n, n') 111m Cd, 103 Rh (n, n') 103m Rh, 115 In (n, n') 115m In, 180 Hf (n, n') 180m Hf, 63 Cu (n,g) 64 Cu, 23 Na (n,g) 24 Na, 55 Mn (n,g) 56 Mn, and 197 Au (n,g) 198 Au reactions representative of fast, epithermal, and thermal neutron fluxes. A comparative analysis of the neutron attenuation behavior measured with various materials is presented. In case of attenuation of both thermal and fast fluxes, FeB is better than other high density materials such as mild steel and FeW. The outcome of the experimental study is that FeB slab cast with 5% natural boron can be utilized as cost-effective neutron shield in streaming paths in nuclear reactors.

Establishment of a trimodality analytical platform for tracing, imaging and quantification of gold nanoparticles in animals by radiotracer techniques.

This study aims to establish a (198)Au-radiotracer technique for in vivo tracing, rapid quantification, and ex vivo visualization of PEGylated gold nanoparticles (GNPs) in animals, organs and tissue dissections. The advantages of GNPs lie in its superior optical property, biocompatibility and versatile conjugation chemistry, which are promising to develop diagnostic probes and drug delivery systems. (198)Au is used as a radiotracer because it simultaneously emits beta and gamma radiations with proper energy and half-life; therefore, (198)Au can be used for bioanalytical purposes. The (198)Au-tagged radioactive gold nanoparticles ((198)Au-GNPs) were prepared simply by irradiating the GNPs in a nuclear reactor through the (197)Au(n,γ)(198)Au reaction and subsequently the (198)Au-GNPs were subjected to surface modification with polyethylene glycol to form PEGylated (198)Au-GNPs. The (198)Au-GNPs retained physicochemical properties that were the same as those of GNP before neutron irradiation. Pharmacokinetic and biodisposition studies were performed by intravenously injecting three types of (198)Au-GNPs with or without PEGylation into mice; the γ radiation in blood specimens and dissected organs was then measured. The (198)Au-radiotracer technique enables rapid quantification freed from tedious sample preparation and shows more than 95% recovery of injected GNPs. Clinical gamma scintigraphy was proved feasible to explore spatial- and temporal-resolved biodisposition of (198)Au-GNPs in living animals. Moreover, autoradiography, which recorded beta particles from (198)Au, enabled visualizing the heterogeneous biodisposition of (198)Au-GNPs in different microenvironments and tissues. In this study, the (198)Au-radiotracer technique facilitated creating a trimodality analytical platform for tracing, quantifying and imaging GNPs in animals.

Chlorine leaching of Au from copper anode slimes using the response surface method in an agitated reactor

The response surface methodology (RSM) was employed to study the interactions among different factors (i.e. temperature, liquid to solid ratio, HCl concentration and chlorine gas flowrate) involved in the leaching of Au from copper anode slimes. The interactions such as liquid to solid ratio, chlorine gas flowrate×temperature and HCl concentration×temperature were found to be statistically significant. Under the optimum operational conditions of Cl2 = 1·99 L min−1, 10 000/T = 28·7 K−1, L/S = 12·57 L kg−1, HCl = 2·74 mol L−1 in a semi-pilot 3-L agitated reactor, the maximum recovery achieved for Au was around 93% using the second polynomial equation. This led to a selectivity factor (i.e. the ratio of ‘Au reaction fraction’ to the sum of ‘Se and Cu reaction fractions’) of 86. Process optimisation was carried out based on the maximum selectivity factor achieved. This resulted in the following optimum conditions: Cl2 = 1·26 L min−1, 10 000/T = 30·83 K−1, L/S = 5 L kg−1 and HCl = 2·66 mol L−1, with a separation factor of 112.

Measurement of Thermal Neutron Capture Cross Section and Resonance Integral for the \(^{45}\)Sc\((n,\gamma)^{46}\)Sc Reaction with Pulsed Neutrons

Thermal neutron capture cross section and resonance integral for the $^{45}$Sc(n,$\gamma )^{46}$Sc reaction were measured by the activation method using the $^{197}$Au(n,$\gamma )^{198}$Au reaction as a single comparator. The high-purity scandium and gold samples with and without Cd cover with the thickness of 0.5 mm were irradiated in a pulsed neutron field of the 100 MeV electron linac of the Pohang Accelerator Laboratory (PAL). The induced activities in the activated foils were measured with a well calibrated HPGe detector. In order to improve the accuracy of the experimental results the effect of the non-ideal epithermal spectrum was taken in to account by determining the neutron spectrum shape factor ($\alpha )$, and the corrections for the thermal (G$_{th})$ and the resonance (G$_{epi})$ neutron self-shielding effects, the $\gamma $-ray attenuation (F$_{g})$ and the $\gamma $-ray coincidence summing effect were made. The thermal neutron cross-section for the $^{45}$Sc(n,$\gamma )^{46}$Sc reaction has been determined to be $\sigma _{o}$ = 27.6 $\pm $ 0.8 barn. By assuming the cadmium cut-off energy of 0.55 eV, the resonance integral for the $^{45}$Sc(n,$\gamma )^{46}$Sc reaction has been determined to be I$_{o}$ = 12.7 $\pm $ 0.7 bar. The present results are compared with the reference data and discussed.

Experimental cross section of the 71Ga(n,γ)72Ga reaction at 0.0334 eV energy

The cross section of the 71Ga(n,γ)72Ga reaction at 0.0334eV was measured for the first time using monochromatic neutrons from powder diffractometer at TRIGA Mark II nuclear reactor. The 197Au(n,γ)198Au reaction was used to monitor the neutron beam intensity. The HPGe γ-ray spectrometry was used to determine the radioactivity of the product radionuclides. The obtained cross section value amounted 3.42±0.27b is about 95% consistent with JENDL-4, but about 17% and 14% lower than that of the ENDF/B-VII and TENDL-2012 data libraries, respectively. The measured value at 0.0334eV and the previous measured value at 0.0536eV would be useful to confirm the reliability of the data evaluated by 1/v relation in the above libraries.

Thermal neutron capture cross section and resonance integral of the 139La(n,γ)140La reaction

The thermal neutron capture cross section (σ0) and resonance integral cross section (I0) of the 139La(n,γ)140La reaction have been measured relative to that of the 197Au(n,γ)198Au reaction by means of the activation method. High-purity natural lanthanum and gold foils were exposed to pulsed neutrons at the Pohang neutron facility. One set of foils was irradiated directly and a second set of foils was shielded with a cadmium cover of 0.5mm thickness. The induced activities in the activated foils were measured by a γ-ray spectrometer based on a calibrated high purity germanium (HPGe) detector. In order to improve the accuracy of the experimental results the epithermal neutron spectrum shape factor (α) was determined, and the corrections for the thermal neutron self-shielding (Gth), the resonance neutron self-shielding (Gepi), the γ-ray attenuation (Fg) and the γ-ray coincidence summing effects were made. The thermal neutron cross-section for the 139La(n,γ)140La reaction has been determined to be 9.16±0.36 barn, relative to the reference value of 98.65±0.09 barn for the 197Au(n,γ)198Au reaction. By assuming the cadmium cut-off energy of 0.55eV, the resonance integral cross section for the 139La(n,γ)140La reaction is 11.64±0.69 barn, which is determined relative to the reference value of 1550±28 barn for the 197Au(n,γ)198Au reaction. The measured results are compared with literature values and discussed.

Measurements of the (n,2n) Reaction Cross Section of 181Ta from 8 to 15 MeV

The cross section for the reaction 181Ta(n,2n)180Tag was measured from 8 to 15 MeV in small energy steps to resolve inconsistencies in the existing databases. The activation technique was used, and the 93.4 keV γ-ray from the decay of the 180Tag ground state was recorded with a HPGe detector. In addition, the γ-rays from the monitor reactions 27Al(n,α)24Na and 197Au(n,2n)196Au were measured for neutron fluence determination. As a cross check, a calibrated neutron detector was also used. The ENDF/B-VII.1 and TENDL-2011 evaluations are in considerable disagreement with the present data, which in turn agree very well with the majority of the existing data in the 14 MeV energy region.

Experimental cross section for the 152Sm(n, γ)153Sm reaction at 0.0334 eV

Abstract The neutron capture cross section for the 152Sm(n, γ)153Sm reaction at an energy of 0.0334 eV was measured for the first time using monochromatic neutrons of a powder diffractometer at the TRIGA Mark II nuclear reactor at Dhaka, Bangladesh. The 197Au(n, γ)198Au reaction was used to monitor the neutron beam intensity. The radioactivity of the products was determined via high resolution γ-ray spectrometry. The obtained cross section value is 184 ± 22 b, which is consistent with both the ENDF/B-VII and TENDL-2012 data libraries. The measured value at 0.0334 eV and the previous data at 0.0536 eV confirm the reliability of the data in the above libraries.

Cluster Emission for the Pre-equilibrium Exciton Model with Spin Variables

We address the angular momentum effects within the state density approach to the Iwamoto-Harada-(Bisplinghoff) model of the pre-equilibrium cluster emission. Using this way, the cluster emission is independent of the cluster formation probability, which — using a rough approximation — contains also all angular momenta couplings related to the creation of a cluster in nuclear reaction. Consequently, the angular-momentum part of the cluster emission rate is formally the same as it is in the nucleon emission case (but energy parts are substantially different). The 197Au(p,α) reaction at 62 MeV serves as an illustration of the suggested model. Inclusion of spin variables causes the enhancement of the α channel (and a weakening of the sum of nucleon channels due to particle emission competition) compared to the spin-independent case.

Forward scintillation hodoscope for nuclear fragment detection at the high acceptance dielectron spectrometer (HADES) setup

The main characteristics of the forward scintillation hodoscope and readout electronics of the high acceptance dielectron spectrometer (HADES) at GSI (Darmstadt, Germany) are presented. Methods for adjustment and amplitude-time calibration of hodoscope detectors using cosmic rays and results of measurements of the Au + Au reaction at a beam energy of 1.24 GeV/nucleon are described. The use of the forward hodoscope for tagging the n + p reaction by means of the deuteron beam incident on a liquid hydrogen target is discussed. A procedure for determining the reaction plane angle in event-by-event analysis of the Au + Au reaction data (at 1.24 GeV/nucleon) is presented.

Musett: A segmented Si array for Recoil-Decay-Tagging studies at VAMOS

A new segmented silicon-array called MUSETT has been built for the study of heavy elements using the Recoil-Decay-Tagging technique. MUSETT is located at the focal plane of the VAMOS spectrometer at GANIL and is used in conjunction with a γ-ray array at the target position. This paper describes the device, which consists of four 10×10cm2 Si detectors and its associated front-end electronics based on highly integrated ASICs electronics. The triggerless readout electronics, the data acquisition and the analysis tools developed for its characterization are presented. This device was commissioned at GANIL with the EXOGAM γ-ray spectrometer using the fusion–evaporation reaction 197Au(22Ne,5n)214Ac. Additionally, the performance of the VAMOS Wien filter used during the in-beam commissioning is also reported.

Measurement of Fragment Production Cross Sections in the $^{12}$C+$^{12}$C and $^{12}$C+$^{197}$Au Reactions at 62 $A$ MeV for Hadrontherapy and Space Radiation Protection

Measurement of Fragment Production Cross Sections in the $^{12}$C+$^{12}$C and $^{12}$C+$^{197}$Au Reactions at 62 $A$ MeV for Hadrontherapy and Space Radiation Protection