Al Reaction Research Articles

Excitation functions for 7Be, 22,24Na production in Mg and Al by deuteron irradiations up to 50 MeV

New experimental data for production of 7Be and 22,24Na in deuteron irradiation of natMg and Al up to 50MeV are presented. The induced activity, measured with HPGe spectroscopy, allows us to determine excitation functions of natMg(d,x) and 27Al(d,x) reactions involved in the activation process with reference to natTi(d,x)48V monitor cross sections. A comparison with experimental literature values and results from updated theoretical codes is discussed.Thick target yields were derived from fits to our cross-sections and integrated personnel dose was calculated for different irradiation cycles and exposure scenarios around high power deuteron accelerator facilities.

Particle size and gas environment effects on blast and overpressure enhancement in aluminized explosives

Aluminized RDX-based explosives were detonated under controlled conditions while varying particle size and atmosphere in an effort to quantify the contribution of aerobic and anaerobic Al reaction to blast and overpressure. Early time reaction of aluminum acts to enhance the primary explosive blast, and this reaction is approximately half aerobic and half anaerobic (i.e. oxidation by detonation products and/or nitridation), suggesting that very rapid early-time mixing occurs in explosive fireballs. Particle size effects are surprisingly negligible over the range of 3–40μm, which implies that conventional scaling laws for aluminum combustion provide less insight than previously assumed. Quasi-static pressures obtained in the time period from 5 to 10microns after detonation suggest that oxidation of aluminum is complete in the presence of 20% oxygen. However, for nitrogen environments, oxidation only proceeds to half its theoretical maximum, except for the smallest (3μm particles) for which oxidation was nearly complete. These results demonstrate that oxidation of aluminum in aluminized explosives is robust in anaerobic environments, and that simulation efforts cannot neglect anaerobic channels, even though aerobic oxidation provides the greatest energy release.

Measurement of radiative capture resonance energies with an extended gas target

The DRAGON facility for the study of radiative capture reactions has an extended gas target, surrounded by an array of BGO detectors. The distribution of detected gamma rays amongst the segmented array permits an estimate of the reaction position and consequently of the resonance energy. We report a study of the technique, using the 24Mg(p, γ)25Al reaction. Energy determination to better than 0.5% has been demonstrated.

Exclusive giant dipole resonance measurement on the Jacobi transition in the19F+27Al system

Evaporation-residue-gated high-energy gamma-ray spectra were measured in the ${}^{19}$F+${}^{27}$Al reaction at two beam energies of $\ensuremath{\sim}$75 and 125 MeV. The compound nuclear angular momenta populated at the higher energy should extend beyond the critical value for the Jacobi shape transition, while those at the lower energy should be mostly restricted below the critical value. A sharp low-energy (at $\ensuremath{\sim}$10 MeV) component has been observed in the gamma-ray strength function superimposed on a broad distribution. At the higher beam energy, the component becomes more prominent at higher angular momentum, whereas an opposite behavior is witnessed at the lower beam energy. The implication of these observations in connection with the occurrence of the Jacobi shape transition is discussed.

Cross-sections for (n,2n), and (n,α) reactions on 55Mn isotope around neutron energy of 14 MeV

Cross sections for (n,2n) and (n,α) reactions on the Manganese isotope have been measured at the neutron energies of 14.1 and 14.7MeV using activation method with the monitor reaction 27Al(n, α)24Na. This measurement was carried out by γ-detection using a coaxial HPGe detector. High-purity natural Manganese powder (99.9%) was used to produce the samples. The fast neutrons were produced by T(d, n)4He reaction. The results obtained are compared with the previous data.

Addition of Aluminum and Gallium Species to Aromatic and Alkyl-Substituted 1,4-Diaza-1,3-butadiene Ligands

In this report, we investigate the interactions of Me(x)MCl(3-x) (x = 0-3, M = Al, Ga) with various aromatic and alkyl-substituted 1,4-diaza-1,3-butadiene (R)DAB ligands (or α-diimine ligands) to give a variety of structures in solution and in the solid state. In combination with other previously reported structures, certain general trends of reactivity of these species can be deduced, although there are still some unexplained modes of reactivity. The methylated Al species react with aromatic-substituted (R)DAB ligands to provide final products that result from C═N insertion into the Al-CH(3) group followed by rearrangement reactions. The addition of methyl groups onto the backbone of the (R)DAB ligand is insufficient to stop the insertion and rearrangement processes from occurring. In the case of MeAlCl(2) with the bulky (DiPP)DAB ligand, the reaction could be followed spectroscopically from the monoadduct through the inserted/rearranged final product. Methylated Ga species, however, are much less predictable in their behavior with aromatic-substituted (R)DAB ligands. Depending on the exact species and ratios used, coordinated adducts can be formed and identified, or inserted/rearranged products similar to the aluminum reactions can be obtained. Quite interestingly, cation/anion pairs can also be formed in which GaCl(3) or MeGaCl(2) act as a chloride acceptors. This behavior was unique and substantially different from the analogous Al reactions which formed either a dicoordinated adduct or an inserted/rearranged complex. When the stronger-donating alkyl-substituted (R)DAB ligands were used with Me(2)GaCl, only cation/anion pairs were obtained. Surprisingly, when the same reactions were performed using Me(2)AlCl as a reagent, irreproducible results were obtained.

The role of chemical activation on the combustion and phase formation laws in the Ni–Al-promoter system

In this work we first time investigate the reaction mechanism and possibility of synthesizing NiAl intermetallic compound under the activated combustion mode. A halogen containing organic polymer, namely, polytetrafluoroethylene – PTFE is used as promoter. It is shown that the single-phase target product is obtained when amount of the promoter is 0.1%. Differential thermal (DTA), thermogravimetric (TG) and XRD analyses testify that reaction proceeds stepwise. It is shown that in first stage decomposition products of PTFE remove the oxide film from Al particles; then follows reaction between Ni and pure Al. This reaction undergoes two different modes. First the solid-state reaction takes place, then Al melts and reaction continues between solid Ni and molten Al. It is established that the increase in the promoter amount higher than 1% shifts kinetic activation mode to thermal-kinetic mode. The latter leads to misbalance of green mixture and formation of undesired by-products. The optimal conditions of chemically activated synthesis for NiAl intermetallic are established.

Measurement of Prompt Fission γ-ray Spectra in Fast Neutron-induced Fission

Knowledge of prompt fission γ-ray emission has been of major interest in reactor physics for a few years. Since very few experimental spectra were ever published until now, new measurements would be also valuable to improve our understanding of the fission process. An experimental method is currently being developed to measure the prompt fission γ-ray spectrum from some tens keV up to 10 MeV at least. The mean multiplicity and total energy could be deduced. In this method, the γ-rays are measured with a bismuth germanate (BGO) detector which has the advantage to present a high P/T ratio and a high efficiency compared to other γ-ray detectors. The prompt fission neutrons are rejected by the time of flight technique between the BGO detector and a fission trigger given by a fission chamber or a scintillating active target. Energy and efficiency calibration of the BGO detector were carried out up to 10.76 MeV by means of the 27Al(p,γ) reaction. First prompt fission γ-ray spectrum measurements performed for the spontaneous fission of 252Cf and for 1.7 and 15.6 MeV neutron-induced fission of 238U at the CEA, DAM, DIF Van de Graaff accelerator, will be presented.

BULK NANOSTRUCTURED MATERIALS OBTAINED BY SHOCK WAVES COMPACTION OF ULTRAFINE TITANIUM AND ALUMINUM

Theoretical and experimental Investigations of shock wave consolidation processes of Ti - Al nano sized and ultra-disperse powder compositions are discussed. For theoretical calculations of the shock wave loaded materials were used the hydrodynamic theory and experimental adiabatic of Ti and Al . The normal and tangential stresses in the cylindrical steel tube (containers of Ti - Al reaction mixtures) were estimated using the partial solutions of elasticity theory. The mixtures of ultra-disperse Ti and nano sized (≤ 50nm) Al powder compositions were consolidated to full or near-full density by explosive-compaction technology. The ammonium nitride based industrial explosives were used for generation of shock waves. To form ultra-fine grained bulk TiAl intermetallics with different compositions, ultra-disperse Ti particles were mixed with nano-crystalline Al . Each reaction mixture was placed in a sealed container and explosively compacted using a normal and cylindrical detonation set-up. Explosive compaction experiments were performed in range of pressure impulse (5-20) GPa. X-ray diffraction (XRD), structural investigations (SEM) and micro-hardness measurements were used to characterize the intermetallics phase composition and mechanical properties. The results of analysis revealing the effects of the compacting conditions and precursor particles sizes, affecting the consolidation and the properties of this new ultra high performance alloys are discussed.

Comparison of experimental data with predictions of various models for silicon and aluminum fragmentation under the effect of high-energy cosmic rays

The accuracy attained in theoretically estimating the yields of isotopes and isobars and their energy, charge, and mass distributions in silicon fragmentation that occurs in spacecraft electronics under the effect of cosmic-ray protons is an important factor in forecasting the probability for single-event upsets in the electronics and the reliability of spacecraft operation in general. In previous studies of our group, it was shown that the results of the calculations are highly sensitive to the choice of parameters for opticalmodel potentials. In addition to cross sections for elastic and inelastic proton scattering and charge, mass, and energy distributions of heavy nuclear-reaction products, the results of our calculations for doubledifferential spectra of protons originating from the interaction of highly energetic (30–400 MeV) protons with aluminum and double-differential spectra of other particles (neutrons and alpha particles) arising in competing channels of the p + 27Al reaction are also described in the present article. The calculations in question were performed on the basis of the EMPIRE-II-19 code by using various optical-model potentials, including the Becchetti-Greenlees potential for the (p, n) channel, the Wilmore-Hodgson potential for the (p, n) channel, the Madland potential for the (p, p) channel, the Koning-Delaroche potential for the (p, p) channel, and the McFadden-Satchler potential for the (p, α) channel. A comparative analysis of the double-differential spectra obtained for outgoing protons, neutrons, and alpha particles experimentally and in the calculations of various authors was performed.

Cross sections from 5 to 35 MeV for the reactions natMg(3He,x)26Al, 27Al(3He,x)26Al, natCa(3He,x)41Ca, and natCa(3He,x)36Cl: Implications for early irradiation in the solar system

Abstract– Cross sections were measured for the nuclear reactions natMg(3He,x)26Al, 27Al(3He,x)26Al, natCa(3He,x)41Ca, and natCa(3He,x)36Cl in the energy region from approximately 5–35 MeV. The rates of these reactions are important for studies of early solar system irradiation scenarios. The 26Al, 36Cl, and 41Ca were separated chemically, and the numbers of atoms produced in each reaction channel were measured using accelerator mass spectrometry (AMS). From these results, 26 cross sections were determined and compared with predictions of the TALYS code. Agreement is within 40% for most cross sections. Our measurements were used to model the production of 7Be, 10Be, 26Al, and 41Ca in the early solar system. For projectiles 1H, 3He, and 4He, we assumed energy spectra of the general form E−α. For a wide range of parameterizations, the modeled ratios of 7Be/Be and 10Be/Be on the one hand and of 26Al/27Al and 41Ca/Ca on the other are coupled because the excitation functions for the relevant nuclear reactions have similar shapes. Modeling of a closed system with the constraint that 10Be/9Be = 0.001 fails to reproduce simultaneously the range of 7Be/9Be, 26Al/27Al, and 41Ca/Ca ratios inferred for the early solar system from studies of meteorites.

Photon induced positron annihilation spectroscopy: A nondestructive method for assay of defects in large engineering materials

This paper describes a new methodology for volumetric assay of defects in large engineering materials nondestructively. It utilizes high energy photons produced by nuclear reaction to create positrons in situ whose fate is followed using conventional positron spectroscopic techniques. The photon induced positron annihilation (PIPA) spectroscopy system has been set-up using a Folded Tandem Ion Accelerator (FOTIA). Possibility of using prompt γ-rays produced in nuclear reactions 27Al( 1H,γ) 28Si and 19F( 1H,αγ) 16O has been examined. The reaction 19F( 1H,αγ) 16O is seen to provide higher photon flux (and positron yield) and measurements have been carried out in large samples of metals and polymers. We could establish good sensitivity of the technique as well as reproducibility in a number of measurements. This technique has been used to carry out defect studies in cold worked zircaloy-2 plates. The measured S-parameter, indicative of defect concentration, was seen to correlate well with the measured residual stress using X-ray technique. The results were validated by γ-induced positron annihilation lifetime measurements at ELBE LINAC based GiPS facility.

Light ion induced nuclear reactions close to the Coulomb barrier

The aim of our study is to determine excitation functions for the formation of different reaction products with light ions near the Coulomb barrier and to compare the results with computations according to different reaction mechanisms (compound reactions, direct reactions). In the present study results from experiments with a beam of 9Be on a thin Aluminum target below and around the Coulomb barrier are presented. The formation of several reaction products was determined by the characteristic gamma emissions from these nuclei. Excitation functions of the reactions 27Al(9Be,8Be?2a)28Al, 27Al(9Be,2n)34Cl, 27Al(9Be,pn)34S and 27Al(9Be,a2n)30P with lab energies between 5 and 14 MeV have been determined.

Self-Aligned Top-Gate Oxide Thin-Film Transistor Formed by Aluminum Reaction Method

We developed a novel highly reliable self-aligned top-gate oxide semiconductor thin-film transistor (TFT) formed by the aluminum (Al) reaction method. In this method, Al diffusion into the oxide semiconductor was observed. The low sheet resistivity of the source/drain regions was attributed to Al working as a donor in the oxide semiconductor. The TFTs with 4 µm channel length exhibited a field-effect mobility of 9.8 cm2 V-1 s-1, a threshold voltage of -1.5 V, and a subthreshold swing of 0.22 V/decade. Highly reliable TFTs were obtained after 300 °C annealing without increasing the sheet resistivity of source/drain regions.

High-precision28Si(p,t)26Si reaction to determine22Mg(α,p)25Al reaction rates

The rise time of stellar x-ray bursts is a signature of thermonuclear runaway processes in the atmosphere of neutron stars and is highly sensitive to a series of ($\ensuremath{\alpha}$,$p$) reactions via high-lying resonances in $sd$-shell nuclei. Lacking data for the relevant resonance levels, the stellar reaction rates have been calculated using statistical, Hauser-Feshbach models, assuming a high-level density. This assumption may not be correct in view of the selectivity of the ($\ensuremath{\alpha}$,$p$) reaction to natural parity states. We measured the ${}^{28}$Si($p$,$t$)${}^{26}$Si reaction with a high-resolution spectrometer to identify resonance levels in ${}^{26}$Si above the $\ensuremath{\alpha}$-emission threshold at 9.164 MeV excitation energy. These resonance levels are used to calculate the stellar reaction rate of the ${}^{22}$Mg($\ensuremath{\alpha}$,$p$)${}^{25}$Al reaction and to test the validity of the statistical assumption.

Validation of nuclear reaction models of 180 MeV proton-induced fragmentation of 27Al

Kinetic energy, angular distribution, and isobaric cross section data for A = 7–25 fragments formed in p + 27Al reaction at bombarding energy of 180 MeV are compared with the calculations of the Binary Cascade Model (BIC), the Cascade Exciton Model (CEM), JQMD/PHITS, as well as the Statistical Model with Final State Interaction (SMFSI). For completeness, the kinetic energy spectra of light particles (n, p, α) formed in p + 27Al reaction at bombarding energy of 156 MeV are also presented. A general agreement between the data and predictions of these models is found. However, disagreement with the data for the yields of light-mass fragments as well as near-target fragments is also found and discussed. The importance of this comparative study to simulation and analysis of radiation effects on microscopic electrical components operating in space is also discussed.

35.3: Distinguished Paper: A Novel Self‐Aligned Top‐Gate Oxide TFT for AM‐OLED Displays

AbstractWe developed a novel self‐aligned top‐gate oxide TFT for AM‐OLED displays. Our developed Al reaction method to obtain source/drain regions is effective to fabricate a short channel and highly reliable TFT. A 9.9‐inch diagonal qHD AM‐OLED display was demonstrated to provide applicable solution for a large‐sized and ultra‐high definition OLED mass production.

Investigation of cross sections of reactions used in neutron activation analysis

Abstract In this study, neutron incident reaction cross sections for some target nuclei such as 24Mg, 27Al, 28Si, 56Fe, and 63Cu used in neutron activation analysis have been investigated. The new calculations on the excitation functions of 24Mg(n, p)24Na, 27Al(n, p)27Mg, 27Al(n, α)24Na, 28Si(n, p)28Al, 56Fe(n, p)56Mn, and 63Cu(n, 2n)62Cu reactions have been carried out for incident neutron energies up to 20 MeV. In these calculations, the pre-equilibrium and equilibrium effects have been investigated. The pre-equilibrium calculations involve the new geometry dependent hybrid model and the full exciton model. Equilibrium effects are calculated according to the Weisskopf–Ewing model. In the present work, reaction cross-sections have been calculated by using empirical formulas developed for energies of 14–15 MeV. The calculated results are discussed and compared with the experimental data taken from the EXFOR database.

Associated gamma radiation in interaction of 14.9 MeV neutrons with natural silicon

The associated gamma radiation in the interaction of 14.9MeV neutrons and a natural silicon sample is investigated with the total gamma radiation measurement technique (TGRM). According to the systematic knowledge of 14.9MeV neutron-induced 28,29,30Si(n,xγ) reactions, 50 prompt gamma lines from (n,n′γ), (n,2nγ), (n,npγ), (n,dγ), (n,pγ), (n,αγ), and (n,nαγ) reactions of 28Si, 29Si, and 30Si and one delayed gamma line from 28Si(n,p)28Al(β−)28Si⁎(γ) (f1/2=2.24m) process, and nine final nuclei were determined, and 54 possible transitions are designated. Differential elemental production cross-sections of 40 gamma lines at 40°, 55°, 90°, 125°, and 140° are determined. Using relative differential production cross-sections, accurate integral isotopic cross-sections of the 28Si(n,p)28Al reaction were determined, and partial integral isotopic cross-sections of some reaction channels were also estimated. The present results are in good agreement with some recent experimental and evaluated results. Comparison between present experimental results and the model calculations shows that effect of isospin conservation is maybe important for associated gamma radiation in alpha and proton emission processes.

Cross sections for monitor reactions 27Al((p, x)24Na, 27Al(p, x)22Na, and 27Al(p, x)7Be at proton energies in the range 0.04–2.6 GeV

The cross sections for the monitor reactions 27Al(p, x)24Na, 27Al(p, x)22Na, and 27Al(p, x)7Be at 12 proton energies, 2605, 1598, 1199, 799, 600, 400, 249, 147.6, 97.2, 66.0, 44.6, and 40.8 MeV, have been determined with 72 × 72-mm square and 10.5-mm-diameter round aluminum foils. The rates of the reactions of the production of 24Na, 22Na, and 7Be in the foils in each irradiation run have been determined by γ spectrometry, whereas the number of protons transmitted through these foils has been determined using calibrated fast current transformers. The cross sections have been determined as the ratios of the corresponding reaction to the average proton fluence.