Al Reaction Research Articles

Correlated uncertainties in Monte Carlo reaction rate calculations

Context. Monte Carlo methods have enabled nuclear reaction rates from uncertain inputs to be presented in a statistically meaningful manner. However, these uncertainties are currently computed assuming no correlations between the physical quantities that enter those calculations. This is not always an appropriate assumption. Astrophysically important reactions are often dominated by resonances, whose properties are usually normalized to a well-known reference resonance. This insight provides a basis from which to develop a flexible framework for including correlations in Monte Carlo reaction rate calculations. Aims. The aim of this work is to develop and test a method for including correlations in Monte Carlo reaction rate calculations when the input has been normalized to a common reference. Methods. A mathematical framework is developed for including correlations between input parameters in Monte Carlo reaction rate calculations. The magnitude of those correlations is calculated from the uncertainties typically reported in experimental papers, where full correlation information is not available. The method is applied to four illustrative examples: a fictional 3-resonance reaction, $^{27}$Al(p,$\gamma$)$^{28}$Si, $^{23}$Na(p,$\alpha$)$^{20}$Ne, and $^{23}$Na($\alpha$,p)$^{26}$Al. Results. Reaction rates at low temperatures that are dominated by a few isolated resonances are found to minimally impacted by correlation effects. However, reaction rates determined from many overlapping resonances can be significantly affected. Uncertainties in the $^{23}$Na($\alpha$,p)$^{26}$Al reaction, for example, increase by up to a factor of 5. This highlights the need to take correlation effects into account in reaction rate calculations, and provide insight into which cases are expected to be most affected by them. The impact of correlation effects on nucleosynthesis is also investigated.

Thermal and X-ray analyses of aluminum–titanium nanocomposite powder

The present study has investigated the complex mechanisms in the aluminum–titanium system with different percentages of titanium through a combination of thermal and X-ray analyses. Thermogravimetry, derivative thermogravimetric, X-ray diffraction, scanning electron microscope and transition electron microscope were used for characterization of the samples. Initially, different Al–Ti powder mixtures were produced by high-energy ball milling and after 30 h of milling the phases generated at different percentages of Ti were analyzed. The XRD results revealed that the intermetallic Al3Ti powder is obtained after a certain duration of milling. In addition, L12 to D023 phase transformation is possible with increase of the Ti percent. Analyses of the powder annealed at different temperatures yielded interesting results, including the effect of stearic acid as the surface control agent on phase transformations of the aluminum–titanium system and also the formation of unexpected phases such as Al4C3 and TiC. Moreover, ductile to brittle transition during phase transformations of the intermetallic Al3Ti powder was quite conspicuous, which could result in more homogeneity of the powders and the occurrence of more reactions in the system. For example, formation of D023-Al3Ti powder which is more brittle compared to L12 resulted in the exit of Al from among its layers, leading to the increase of the chances for Al reaction with the system impurities.

Structural effects of Na34 in the Na33(n,γ)Na34 radiative capture reaction

The path towards the production of \textit{r}-process seed nuclei follows a course where the neutron-rich light and medium mass nuclei play a crucial role. The neutron capture rates for these exotic nuclei could dominate over their $\alpha$-capture rates, thereby enhancing their abundances at or near the drip line. We calculate the radiative neutron capture cross-section for the $^{33}$Na(n,$\gamma)^{34}$Na reaction via the Coulomb dissociation of $^{34}$Na as it undergoes elastic breakup on $^{208}$Pb when directed at a beam energy of 100 MeV/u using the entirely quantum mechanical theory of finite range distorted wave Born approximation upgraded to incorporate deformation effects. The non-resonant one neutron radiative capture cross-section for $^{33}$Na(n,$\gamma)^{34}$Na is calculated and is found to increase with increasing deformation of $^{34}$Na. An analytic scrutiny of the capture cross-section with neutron separation energy as a parameter is also done at different energy ranges. The calculated reaction rate is compared with the rate of the $^{33}$Na($\alpha$,n)$^{36}$Al reaction (deduced from the Hauser-Feshbach theory), and is found to be significantly higher below a temperature of $T_9 = 2$. Further, at the equilibrium temperature of $T_9 = 0.62$, the rate for the neutron capture had a small but non-negligible dependence on the structural parameters of $^{34}$Na. In addition, this neutron capture rate exceeded that of the $\alpha$-capture reaction by orders of magnitude, indicating that the $\alpha$-process should not break the (n,$\gamma$) \textit{r-}process path at the $^{33}$Na isotope, thus, effectively pushing the abundance of sodium isotopes towards the neutron drip line.

Effect of the Al/O ratio on the Al reaction of aluminized RDX-based explosives

Aluminum (Al) powders are used in composite explosives as a typical reducing agent for improving explosion performance. To understand energy release of aluminum in aluminized RDX-based explosives, a series of thermal measurements and underwater explosion (UNDEX) experiments were conducted. Lithium fluoride (LiF) was added in RDX-based explosives, as a replacement of aluminum, and used in constant temperature calorimeter experiments and UNDEXs. The influence of aluminum powder on explosion heat () was measured. A rich supply of data about aluminum energy release rate was gained. There are other oxides (CO, CO, and HO) in detonation products besides alumina when the content of RDX is maintained at the same levels. Aluminum cannot fully combine with oxygen in the detonation products. To study the relationship between the explosive formulation and energy release, pressure and impulse signals in underwater experiments were recorded and analyzed after charges were initiated underwater. The shock wave energy (), bubble energy (), and total energy () monotony increase with the Al/O ratio, while the growth rates of the shock wave energy, bubble energy, and total energy become slow.

Accurate accelerator energy calibration using selected resonances in proton elastic scattering and in (p,γ) and (p,p′γ) reactions

The present work aims at contributing to the field of Ion Beam Analysis by providing a set of standard, high-accuracy nuclear resonance reaction data points to be used for accelerator energy calibration up to 4.6MeV, more specifically with the use of the 27Al(p,γ), 13C(p,γ), 12C(p,p0) and 32S(p,p′γ) resonant reactions, as a result of a comprehensive investigation in two different laboratories. The use of resonances at higher energies, namely up to 6MeV, is also discussed. The measurements have been performed at two different electrostatic accelerators, namely at the 5.5MV HV TN-11 of NCSR “Demokritos”, Greece, and at the 5MV 15SDH-2 Pelletron Tandem accelerator at Uppsala University in Uppsala, Sweden. Common points were used to normalize and validate the data. The possible use of the 16O(p,p0) resonance at 3.47MeV is also discussed and analyzed.

Study of [formula omitted] and [formula omitted] reactions with a Multi-Sampling Ionization Chamber

A large number of (α,p) and (α,n) reactions are known to play a fundamental role in nuclear astrophysics. This work presents a novel technique to study these reactions with the active target system MUSIC whose segmented anode allows the investigation of a large energy range of the excitation function with a single beam energy. In order to verify the method, we performed direct measurements of the previously measured reactions 17O (α,n)20Ne, 23Na (α,p)26Mg, and 23Na (α,n)26Al. These reactions were investigated in inverse kinematics using 4He gas in the detector to study the excitation functions in the energy range of about 2–6MeV in the center of mass. We found good agreement between the cross sections of the 17O (α,n)20Ne reaction measured in this work and previous measurements. Furthermore we have successfully performed a simultaneous measurement of the 23Na (α,p)26Mg and 23Na (α,n)26Al reactions.

Determination of neutron capture cross sections of 232Th at 14.1 MeV and 14.8 MeV using the neutron activation method**Supported by Chinese TMSR Strategic Pioneer Science and Technology Project-The Th-U Fuel Physics Term (XDA02010100) and National Natural Science Foundation of China (11205076, 21327801)

The 232Th(n, γ)233Th neutron capture reaction cross sections were measured at average neutron energies of 14.1 MeV and 14.8 MeV using the activation method. The neutron flux was determined using the monitor reaction 27Al(n,α)24Na. The induced gamma-ray activities were measured using a low background gamma ray spectrometer equipped with a high resolution HPGe detector. The experimentally determined cross sections were compared with the data in the literature, and the evaluated data of ENDF/B-VII.1, JENDL-4.0u+, and CENDL-3.1. The excitation functions of the 232Th(n,γ)233Th reaction were also calculated theoretically using the TALYS1.6 computer code.

Single- and multi-foils 27Al(p,3pn)24Na activation technique for monitoring the intensity of high-energy beams

This paper discusses an experimental study of the spallation reaction 27Al(p,3pn)24Na in Al foils exposed to 24GeVc−1 protons, in the context of monitoring the intensity of multi-GeV proton beams through foil activation techniques. Since this reaction is sensitive to secondary neutrons and other energetic secondary hadrons, it is important to evaluate the impact of the foil thickness on the calculation of the beam intensity. This effect is determined experimentally using a stack of Al foils of varying thickness. The experimental results are then compared to Monte Carlo simulations.

Growth of Dual-Layer Nanorods and Nanowalls Using Al Reaction Layer For Cholesterol Biosensor

In this paper, a single-step chemical bath deposition method was developed for the growth of novel aluminium (Al)-doped zinc oxide nanostructures (NSs) comprising a dual-layer of nanorods/nanowalls. This particular mesoporous structure can accommodate a larger number of ChOx molecules than is possible in a traditional nanorod array. The formation of this dual-layer of NSs depends largely on the content of Al ions and reaction time. A cholesterol biosensor was constructed using these NSs as supporting materials for cholesterol oxidase loading. The device achieved sensitivity of $93.82\mu \text{A}/\text{mMcm}^2$ within a linear-range of 1.3–13 mM.

(n, p) Reaction Cross Sections Calculations of Some Stellar Iron Group Fusion Materials

The excitation functions for (n, p) reactions from reaction threshold to 24 MeV on some important iron (Fe) group target elements (20 ≤ Z ≤ 28) for astrophysical (n, p) reactions such as Si, Ca, Sc, Ti, Cr, Fe, Co and Ni were calculated using TALYS-1.0 nuclear model code. The new calculations on the excitation functions of 28Si(n, p)28Al, 29Si(n, p)29Al, 42Ca(n, p)42K, 45Sc(n, p)45Ca, 46Ti(n, p)46Sc, 53Cr(n, p)53V, 54Fe(n, p)54Mn, 57Fe(n, p)57Mn, 59Co(n, p)59Fe, 58Ni(n, p)58Co and 60Ni(n, p)60Co reactions have been carried out up to 24 MeV incident neutron energy. In these calculations, the compound nucleus and pre-equilibrium reaction mechanism studied extensively. According to these calculations, we assume that these model calculations can be applied to some heavy elements, ejected into interstellar medium by dramatic supernova events.

Study of (n,2n) reaction on 191,193Ir isotopes and isomeric cross section ratios

The cross section of 191 Ir(n,2n) 190 Ir g+m1 and 191 Ir(n,2n) 190 Ir m2 reactions has been measured at 17.1 and 20.9 MeV neutron energies at the 5.5 MV tandem T11/25 Accelerator Laboratory of NCSR “Demokritos”, using the activation method. The neutron beams were produced by means of the 3 H(d,n) 4 He reaction at a flux of the order of 2 × 10 5 n/cm 2 s. The neutron flux has been deduced implementing the 27 Al(n,α) reaction, while the flux variation of the neutron beam was monitored by using a BF3 detector. The 193 Ir(n,2n) 192 Ir reaction cross section has also been determined, taking into account the contribution from the contaminant 191 Ir(n,γ) 192 Ir reaction. The correction method is based on the existing data in ENDF for the contaminant reaction, convoluted with the neutron spectra which have been extensively studied by means of simulations using the NeusDesc and MCNP codes. Statistical model calculations using the code EMPIRE 3.2.2 and taking into account pre-equilibrium emission, have been performed on the data measured in this work as well as on data reported in literature.

Reaction production + AMS: An alternative method to study low energy reactions.26Al as a test case

Considering the importance of the 26 Al nuclei in Astrophysics, in this work, preliminary results regarding a campaign of measurements related with this radioisotope production, are presented. We have taken advantage of two different facilities: first, the radio-nucleus is produced by means of irradiation of targets selected in correlation with particular reactions; once the enrichment with 26 Al was made, the targets are analyzed in an AMS machine to obtain the concentration of 26 Al produced during the irradiation. With this off-line method, it is possible to measure acceptable small cross sections of a selected low energy reaction. In this work, our preliminary results for three different energies of 28 Si(d,α) 26 Al reaction cross sections are shown, as well as our first considerations to commence with measurements of 25 Mg(p,γ) 26 Al reaction cross sections below 1 MeV.

Extended methods using thick-targets for nuclear reaction data of radioactive isotopes

The nuclear transmutation is a technology to dispose of radioactive wastes. However, we do not have enough basic data for its developments, such as thick-target yields (TTY) and the interaction cross sections for radioactive material. We suggest two methods to estimate the TTY using inverse kinematics and to obtain the excitation function of the interaction cross sections which is named the thick-target transmission (T3) method. We deduce the energy-dependent conversion relation between the TTYs of the original system and its inverse kinematics, which can be replaced to a constant coefficient in the high energy region. Furthermore we show the usefulness of the T3 method to investigate the excitation function of the 12 C + 27 Al reaction in the simulation.

Thick target yields of proton induced gamma-ray emission from Al, Si and P

Thick target excitation yield curves of gamma-rays from the reactions 27Al(p,p′γ)27Al (Eγ=844 and 1014keV), 27Al(p,αγ)27Al (Eγ=1369keV), 28Si(p,p′γ)28Si (Eγ=1779keV), 29Si(p,p′γ)29Si (Eγ=1273keV) and 31P(p,p′γ)31P (Eγ=1266keV) were measured by bombarding pure-element targets with protons at energies below 3MeV. Gamma-rays were detected with a High Purity Ge detector placed at an angle of 90° with respect to the beam direction. The obtained thick target gamma-ray yields were compared with the previously published data. The overall systematic uncertainty of the thick target yield values was estimated to be better than ±9%.

Experimental study of the astrophysically important Na23(α,p)Mg26 and Na23(α,n)Al26 reactions

The $^{23}$Na$(\alpha,p)^{26}$Mg and $^{23}$Na$(\alpha,n)^{26}$Al reactions are important for our understanding of the $^{26}$Al abundance in massive stars. The aim of this work is to report on a direct and simultaneous measurement of these astrophysically important reactions using an active target system. The reactions were investigated in inverse kinematics using $^{4}$He as the active target gas in the detector. We measured the excitation functions in the energy range of about 2 to 6 MeV in the center of mass. We have found that the cross sections of the $^{23}$Na$(\alpha,p)^{26}$Mg and the $^{23}$Na$(\alpha,n)^{26}$Al reactions are in good agreement with previous experiments, and with statistical model calculations.

Influence of Sintering Temperature on the Microstructure and Mechanical Properties of In Situ Reinforced Titanium Composites by Inductive Hot Pressing.

This research is focused on the influence of processing temperature on titanium matrix composites reinforced through Ti, Al, and B4C reactions. In order to investigate the effect of Ti-Al based intermetallic compounds on the properties of the composites, aluminum powder was incorporated into the starting materials. In this way, in situ TixAly were expected to form as well as TiB and TiC. The specimens were fabricated by the powder metallurgy technique known as inductive hot pressing (iHP), using a temperature range between 900 °C and 1400 °C, at 40 MPa for 5 min. Raising the inductive hot pressing temperature may affect the microstructure and properties of the composites. Consequently, the variations of the reinforcing phases were investigated. X-ray diffraction, microstructural analysis, and mechanical properties (Young’s modulus and hardness) of the specimens were carried out to evaluate and determine the significant influence of the processing temperature on the behavior of the composites.

Comprehensive reuse of drinking water treatment residuals in coagulation and adsorption processes

While drinking water treatment residuals (DWTRs) inevitably lead to serious problems due to their huge amount of generation and limitation of landfill sites, their unique properties of containing Al or Fe contents make it possible to reuse them as a beneficial material for coagulant recovery and adsorbent. Hence, in the present study, to comprehensively handle and recycle DWTRs, coagulant recovery from DWTRs and reuse of coagulant recovered residuals (CRs) were investigated. In the first step, coagulant recovery from DWTRs was conducted using response surface methodology (RSM) for statistical optimization of independent variables (pH, solid content, and reaction time) on response variable (Al recovery). As a result, a highly acceptable Al recovery of 97.5 ± 0.4% was recorded, which corresponds to 99.5% of the predicted Al recovery. Comparison study of recovered and commercial coagulant from textile wastewater treatment indicated that recovered coagulant has reasonable potential for use in wastewater treatment, in which the performance efficiencies were 68.5 ± 2.1% COD, 97.2 ± 1.9% turbidity, and 64.3 ± 1.0% color removals at 50 mg Al/L. Subsequently, in a similar manner, RSM was also applied to optimize coagulation conditions (Al dosage, initial pH, and reaction time) for the maximization of real cotton textile wastewater treatment in terms of COD, turbidity, and color removal. Overall performance revealed that the initial pH had a remarkable effect on the removal performance compared to the effects of other independent variables. This is mainly due to the transformation of metal species form with increasing or decreasing pH conditions. Finally, a feasibility test of CRs as adsorbent for phosphate adsorption from aqueous solution was conducted. Adsorption equilibrium of phosphate at different temperatures (10–30 °C) and initial levels of pH (3–11) indicated that the main mechanisms of phosphate adsorption onto CRs are endothermic and chemical precipitation; the surfaces are energetically heterogeneous for adsorbing phosphate.

High-Performance Top-Gate and Self-Aligned In–Ga–Zn-O Thin-Film Transistor Using Coatable Organic Insulators Fabricated at 150 °C

We fabricated top-gate and self-aligned indium–gallium–zinc-oxide thin-film transistors (IGZO TFTs) at a maximum process temperature of 150 °C using a coatable organic gate insulator (OGI). By forming a damage and contamination-free interface between the IGZO channel and OGI, and forming low-resistive source/drain regions by Al reaction method, we achieved good TFT properties, such as field effect mobility of 9.8 cm $^{{\mathrm {2}}}$ /Vs, subthreshold swing of 0.21 V/decade, and hysteresis of 0.3 V, with minimizing a parasitic capacitance. Although the TFT showed an abnormal degradation behavior under positive gate bias stress testing in an ambient air, it was suppressed by forming an additional organic passivation layer.

Synthesis, microstructure and mechanical properties of (Mo,Ti)Si2/Al2O3 composites prepared by thermite-reaction-assisted combustion synthesis

(Mo0.95Ti0.05)Si2/3.3mol%Al2O3 composites were synthesized by self-propagating high-temperature synthesis using Mo, Si, Al and TiO2 powders. The addition of alloying element Ti to MoSi2 and the synthesis of reinforcing particulate Al2O3 phase were achieved through the thermite reaction, Al + TiO2→Ti + Al2O3. The results showed that the combustion synthesis reaction mode in the Mo, Si, Al and TiO2 reaction mixture was spiral and self-propagating, and the reaction product was composed of MoSi2, (Mo,Ti)Si2 and Al2O3. The combustion products were consolidated by vacuum hot-pressing at 1773 K and 27.5 MPa for 90 min to consolidate composites with relative densities above 95% of theoretical. The hot-pressed (Mo0.95Ti0.05)Si2/3.3mol%Al2O3 composite with relative density of 97.5% exhibited finer microstructure and superior mechanical properties compared to MoSi2 monolithic material; Vicker’s hardness of 12.9 GPa, bending strength of 320 MPa and fracture toughness of 3.37 MPa m1/2.

A precise method to determine the activity of a weak neutron source using a germanium detector

A standard high purity germanium (HPGe) detector was used to determine the previously unknown neutron activity of a weak americium-beryllium (AmBe) neutron source. γ rays were created through 27Al(n,n′), 27Al(n,γ) and 1H(n,γ) reactions induced by the neutrons on aluminum and acrylic disks, respectively. These γ rays were measured using the HPGe detector. Given the unorthodox experimental arrangement, a Monte Carlo simulation was developed to model the efficiency of the detector system to determine the neutron activity from the measured γ rays. The activity of our neutron source was determined to be 307.4±5.0n/s and is consistent for the different neutron-induced γ rays.