Nuclear Reaction Analysis Techniques Research Articles

Effect of Microstructure on Oxidation and Micro-mechanical Behavior of Arc Consolidated Mo-Ti-Si-(B) Alloys

AbstractThe present study deals with the development and characterization of Mo-35Ti-10Si and Mo-35Ti-10Si-2B (wt.%) alloy for ultra-high temperature applications beyond the temperature limit of existing super alloys. The microstructural characterization using scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), electron back scattered diffraction (EBSD), x-ray diffraction (XRD) revealed that the Mo-35Ti-10Si-2B alloy was consisted of three phases, namely, (Mo, Ti)ss, (Mo, Ti)5SiB2 and (Ti, Mo)5Si3; whereas, Mo-35Ti-10Si alloy was found to be consisting of (Mo, Ti)ss, and (Mo,Ti)3Si phases. Since quantification of boron is difficult by EDS, Particle Induced Gamma-ray Emission (PIGE), a nuclear reaction analysis technique was used for chemical composition analysis of boron. The oxidation behavior of the Mo-35Ti-10Si-2B alloy in the temperature regime of 825-1250 °C was studied in detail and compared with boron-free Mo-35Ti-10Si alloy. Mo-35Ti-10Si-2B alloy exhibited superior oxidation behavior at intermediate temperatures of 825 °C, and excellent oxidation resistance at higher temperatures between 1000 and 1250 °C due to the formation of the protective borosilica and double oxide layers (TiO2 and duplex borosilica-TiO2), respectively. High-temperature oxidation mechanisms were discussed using detailed microstructural cross section analysis of the oxidized alloy samples. The micro-mechanical behavior of constitutive phases of the Mo-35Ti-10Si-2B alloy were studied by microhardness, nano-indentation and micropillar compression testing. The micropillar compression of (Mo, Ti)ss phase showed fairly ductile behavior with the evidence of activation of dislocation in the form of slip lines revealed through the post-deformation fractography. Deformation studies of (Mo, Ti)5SiB2 and (Ti, Mo)5Si3 phases were also carried out which showed large strain bursts indicating possibility of activation of dislocation activities even at room temperatures imparting low level of ductility.

Correlated characterization of 20Ne-implanted targets using nuclear reaction analysis, Rutherford backscattering spectrometry, and ion transport modeling

We present the preparation and characterization of a large sample of implanted noble gas targets for use in precision nuclear astrophysics measurements with intense proton beams. Tantalum and titanium backings were prepared using wet-acid etching, outgassed via resistive heating, and implanted with 20Ne+ beams from differing ion sources. These experimental targets were investigated using both nuclear reaction analysis techniques on the 1169-keV resonance in 20Ne(p, γ)21Na and Rutherford backscattering spectrometry analysis with 2-MeV α-particle beams. Results from these analyses reveal small target-to-target variations in stoichiometry, while exhibiting excellent agreement independent of ion-beam analysis method. We also present a self-consistent validation of the nuclear reaction analysis results using ion transport simulations in TRIM-2013 that rely on input parameters from SIMNRA scattering-yield fits to Rutherford backscattering spectra. In addition to a complete description of the implantation profile, this analysis method provides an alternate solution for characterizing a large sample of implanted targets when no suitable resonances are available for nuclear reaction analysis.

Deuterium retention in tungsten, tungsten carbide and tungsten-ditungsten carbide composites

The selection of the most suitable material for the EU DEMO divertor is still underway. Current research focuses on the development of tungsten-based materials for plasma-facing applications. In addition to other requirements, the candidate material must also exhibit low intrinsic hydrogen isotope retention. To verify the suitability of the tungsten carbide-containing materials, we examined the effect of carbon in the form of carbide or free carbon on deuterium (D) retention.The samples were consolidated by Field Assisted Sintering (FAST) and examined in terms of phase composition and microstructure before the d-retention studies. The Nuclear Reaction Analysis (NRA) technique was used to determine the depth distribution of D after the exposure to D plasma (fluence of 1.3 × 1024 D/m2 and 1.3 × 1025 D/m2 and an exposure temperature of 370 K and 523 K, respectively). Thermal Desorption Spectroscopy (TDS) was used to measure the D desorption spectra. The surfaces of samples exposed to D plasma were also examined in terms of microstructure by scanning electron microscopy. The study has shown that apart from the d-fluence and exposure temperature, the materials’ composition plays a vital role in d-retention, accompanied by blisters and pillar formation. The lowest d-retention was observed for tungsten and the highest in the W-W2C composite. The blisters and pillars were formed in these two materials but not in the WC, which also contains free carbon. At higher D fluence, approximately 15 to 20-times more blisters and pillars were formed in the W-W2C composite than in the tungsten prepared by the same method. The results suggest that the number of defects causing higher d-retention is the highest in W-W2C. On the other hand, the absence of surface irregularities in the WC-C sample after D retention studies indicates that the cause for higher D retention does not lie in the carbides, but, presumably, the microstructural and crystal lattice defects govern the D retention in tungsten-tungsten carbide systems.

Ion bombardment technique induced alterations in the surface chemical composition and shielding parameters of polymeric material

At present, ion beam technology is one powerful technique to improve the physico-chemical properties of polymeric material. In this work, ultra high molecular weight polyethylene samples were bombarded with 1 MeV He-ion beam at fluences ranging from 1×1013 to 5×1014 ions/cm2. The changes in the chemical composition of the treated layer caused by the ion beam were investigated. The hydrogen escapes due to the ion beam irradiations were measured by the nuclear reaction analysis (NRA) technique using the 1H(15N, αγ)12C reaction. The oxygen uptake has been studied by the Rutherford backscattering spectrometry (RBS) and Fourier transform infrared spectrometer (FTIR) techniques. The partial and total mass attenuation coefficients of photons at energies 81, 356, 511 and 1332 keV were estimated using the XCOM program (version 3.1). The obtained results showed that the hydrogen release was increasing with an increase in ion fluence. Moreover, important oxygen uptake of bombarded samples was also observed. These effects led to significant improvements in the surface characteristics of the treated materials such as changes in the shielding parameters. The changes in the mass attenuation coefficients (μ/ρ) were calculated relying on the incoming photon energies and the atomic concentrations of the elements that are present in the target material. The total atomic cross-sections and effective atomic numbers were calculated by using the data of the total mass attenuation coefficients. A decrease in both the total atomic cross-section and effective atomic numbers was noticed with an increase in the ion beam fluence.

Differential cross section measurements of the 9Be(3He,p)11B reaction for NRA applications

The differential cross sections of the 9Be(3He,pi)11B reactions for i = 0–6 were determined within the laboratory energy range 1.24–2.87 MeV and for backward angles from 107° to 164° with 2° steps using two double sided silicon strip detectors. The obtained cross sections covered the angle and energy ranges typically used for the analysis of beryllium targets with the nuclear reaction analysis technique. The experiments were carried out at the Ruđer Bošković Institute and the determined cross sections were benchmarked with the measurement of thick target reaction yields from a pure beryllium target at two beam energies, 1.8 and 2.7 MeV. The results are presented in graphical form and for 134° and 164° are also given as tables in the Appendix. The correctness of the data, verified through the comparison of thick target spectra as well as the observed discrepancies with previous data are discussed and analyzed.

Lithium-enriched graphite anode surfaces investigated using nuclear reaction analysis.

Non-destructive Li nuclear reaction analysis techniques were used to profile the Li distribution at the surface of graphitic Li-ion battery anodes. These techniques show that Li concentrations are elevated within 300 nm of the anode surface, even in fully delithiated states. The surface region, which includes the solid electrolyte interphase, contains at least 60% of the total Li irreversibly lost during formation and cycling.

Application of Nuclear Techniques to the Investigation of the Oxidation Behavior of Ion-Implanted Steels

The oxidation behavior of ion-implanted steel samples in air, using Nuclear Reaction Analysis (NRA) and Rutherford Backscattering Spectroscopy (RBS) techniques. Austenitic stainless steel AISI 321 (Fe/Crl8/Ni8/Mn2/Ti) samples implanted with magnesium-, aluminum- and zirconium-ions (implantation energy 40 keV, dose: 1-1017 to 2-1017 ions/cm2) were oxidized in air in the temperature region 450-650 °C for several periods of time. The above implants were selected on the basis of the affinity to oxygen, as well as their ability to form protective oxides as MgO, AI2O3, Zr02 in order to improve the oxidation resistance of steel. The determination of the oxygen concentration and depth-profiles was performed by means of the 160(d, p)170 nuclear reaction. Rutherford Backscattering Spectroscopy was applied to investigate the near-surface layers and to determine the depth profiles of the implanted ions. The determination of the aluminum concentration and the depth distribution of the Al-ions was performed using the resonance at 992 keV of the 27Al(p, 7)28Si nuclear reaction whereas the concentration and the depth distribution of the Mg-ions by the means of the 24Mg(o;, p)27Al reaction. The excitation function of the 24Mg(a:, p)27Al nuclear reaction was studied in the energy region 4600-5000 keV and absolute cross section data allowing the determination of the Mg-profile were determined for this purpose.

Quantum Diffusion of Deuterium in Sodium.

The online nuclear reaction analysis technique has been applied to study the temperature dependence of deuterium diffusion coefficients for deuterium in sodium at temperatures ranging between 110 and 240 K, and at cryogenic temperatures, below 160 K, tunneling of deuterium atoms in the metal lattice has been observed. Above 160 K, diffusion occurs by the classical mechanism of overbarrier atomic jumps. Results of quantum diffusion of deuterium in a metal have been obtained for the first time; they used to be known only for the lightest hydrogen isotope, protium, in niobium and tantalum. The analysis has shown that the necessary condition for carrying out the quantum mechanism of deuterium migration is low Debye temperature of a metal, below 200 K. Experimental data on diffusion of hydrogen isotope in an alkali metal have also been obtained for the first time in this paper.

Depth profiling of titanium nitride thin films deposited on stainless steel utilizing combined EBS and NRA techniques

Abstract Composition and depth profiling of titanium nitride thin films deposited on stainless steel using vacuum arc discharge device have been determined. A combination of two ion beam analysis techniques has been applied to allow accurate quantification of nitrogen in the prepared titanium nitride thin films. These include elastic backscattering (EBS) spectrometry together with nuclear reaction analysis (NRA) technique utilizing 14N(α,p0)17O nuclear reaction, both performed at resonance energy for incident alpha beam of 4500 keV. They were applied simultaneously, using two independent charged particle detectors, one is dedicated for combined EBS/NRA measurements and the other for pure NRA one. Experimental conditions have been carefully optimized to avoid overlapping of peaks of the two spectra correspond to each reaction. Novel Multi-SIMNRA software has been utilized to enable simultaneous elemental depth profile determination of both data sets. Experimental setup of the in-vacuum system has been carefully characterized. Independent complement measurements utilizing scanning electron microscopy (SEM) equipped with energy dispersive X-ray analysis (EDX) were also applied to verify the experimental findings obtained by combined EBS and NRA techniques. The results have revealed N/Ti ratio of around 1 for the prepared films, with low levels of contamination elements. Finally, X-ray diffraction (XRD) measurements have demonstrated TiN structure with low oxygen contamination.

Influence of Nitrogen on Hydrogenated Amorphous Carbon Thin Films Deposited by Plasma Focus Device

To carry out our research, a plasma focus device is used to deposit thin films of nitrogen doped hydrogenated amorphous carbon (a-C:H:N) onto the stainless steel-AISI-304 substrates at room temperature. Thin films are deposited with the same numbers of focus shots, at the same distance from the anode tip and with different partial pressures of nitrogen in the mixtures of acetylene/nitrogen as working gas. The nitrogen contents of deposited films are studied using nuclear reaction analysis (NRA) techniques. The results prove that nitrogen contents of the samples do not increase significantly by increasing partial pressure of nitrogen of the working gas for both sets of the samples. Moreover, NRA results exhibit the limitation of nitrogen incorporated into the samples, when this experimental setup is used. G-peak position and peak intensity ratio of the D-band to G-band (ID/IG) are used to investigate the diamond characters. Also, they show that sp2 clustering is highly dependent on the nitrogen atomic contents and angular position of the samples. Scanning electron microscopy (SEM) shows the granular surface morphology of the films. Furthermore, it shows that angular position of the samples with respect to the anode axis plays an important role in the grain size of the surface of the samples. The thickness of the films decreases significantly by increasing angular position of the samples, while it decreases slightly by increasing partial pressure of nitrogen of the working gas. The Vickers surface hardness of the thin films exhibits significant dependency on the sp2 clustering.

Studies on synthesis of plasma fusion relevant tungsten dust particles and measurement of their hydrogen absorption properties

In this communication, we identify some thermal-plasma assisted synthesis techniques for the alternative production of fusion relevant tungsten dust particles in bulk amounts, to allow for the statistically meaningful study of their hydrogen absorption properties. Fast, single step synthesis of fine particles in the α-tungsten phase was demonstrated, using a high heat flux device for sizes in the micrometer region and an experimental nanoparticle reactor for dust with nanometer sizes. Production of both equilibrium polyhedral and nonequilibrium spherulitic crystal shapes was demonstrated, dust morphologies similar to which were identified before in existing tokamaks and divertor simulator systems. Their hydrogen retention characteristics were measured by the Nuclear Resonance Reaction Analysis technique, which was found to be orders of magnitude higher compared to the same metal in the bulk form. The mesoporous crystals generated during high power, high pressure synthesis conditions were assumed to be responsible for the unusually high gas retention of the nanoparticle sample. It was concluded that non-equilibrium tungsten dust morphologies would be dominant in the high power fusion machines in the future, which may aggravate the hydrogen isotope retention issues further.

Behavior of liquid Li-Sn alloy as plasma facing material on ISTTOK

The high power loads impinging on the first wall and particularly the divertor of fusion reactors is a decisive factor to the success of nuclear fusion. An alternative to solid plasma facing components is the use of liquid metals such as lithium or tin due to the regenerative properties of the liquid surface. Another suitable candidate is the eutectic lithium tin alloy (30at.% Li) which is suggested to display beneficial properties of both its constituent elements. The application of these materials as liquid metal plasma facing components depends on several factors such as their affinity to retain hydrogenic isotopes and the discharge performance degradation induced by the enhanced impurity contamination, among others. An experimental setup has been developed to produce and expose samples to ISTTOK plasmas on both liquid and solid states. Samples of Li-Sn alloy were exposed at ISTTOK to deuterium plasmas. Post-mortem analysis of the samples was performed by means of ion beam diagnostics. To quantify the fuel retention on the samples the nuclear reaction analysis (NRA) technique was applied. Complementary, Rutherford backscattering spectrometry (RBS) was used for determination material composition, particularly of impurities, on the samples. Regardless of the high sensitivity of these techniques no deuterium was detected in the samples. Emission of the Li-I 670.7nm line indicates that there was interaction of the plasma with the samples. Alternative reasons for the low retention of this material are discussed. Lithium segregation to the surface of the sample was observed.

Deuterium retention in tin (Sn) and lithium–tin (Li–Sn) samples exposed to ISTTOK plasmas

The use of lithium (Li) or tin (Sn) as a liquid metal plasma facing component is proposed as a solution to the high power load issue on the divertor region of nuclear fusion reactors. The possibility to use these materials depends on their compatibility with hydrogen plasmas. With the purpose of realizing deuterium retention studies, specimens of pure Sn (99.999% Sn) and Li–Sn alloy (30 at.% Li) were exposed in the ISTTOK edge plasma. Ex situ analysis of the samples was performed by means of ion beam diagnostics. Nuclear reaction analysis (NRA) technique was applied using the D(3He,p)4He reaction to quantify the fuel retention on the samples.In this work the deuterium retention is compared between pure Sn and Li–Sn alloy samples in both liquid and solid states. All the samples were found to have retention ratios smaller than 0.1 at.%. This low retention ratio is expected for pure tin given its high mass and the instability of tin hydrides. However the retention was unexpectedly low for the case of Li–Sn which was thought to be dominated by the lithium fraction in the alloy. These results suggest that tin has a role in the retention mechanism in this material.

Effect of high flux plasma exposure on the micro-structural and -mechanical properties of ITER specification tungsten

We have performed a combined study using transmission electron microscopy (TEM), nuclear reaction analysis (NRA) and nano-indentation (NI) techniques to reveal the impact of high flux plasma exposure on the properties of a sub-surface region of the commercially available pure tungsten fabricated following the ITER specification. TEM examination revealed the formation of a dense dislocation network and dislocation tangles, resulting in a strong increase in the dislocation density by at least one order of magnitude as compared to the bulk density. The plasma-induced dislocation microstructure vanishes within a depth of about 10–15μm from the top of the exposed surface. Surface hardness after the plasma exposure was characterized by NI and was found to increase significantly in the sub-surface region of 1.5–3μm. That was attributed to the resistance of the plasma-induced dislocation networks and deuterium-induced defects, whose presence within a depth of ∼1μm was unambiguously detected by the NRA measurements as well.

The influence of the annealing temperature on deuterium retention in self-damaged tungsten

The influence of the annealing temperature on deuterium retention was studied for self-ion damaged tungsten in the range from 600–1200 K. Samples were damaged by 20 MeV W ions at room temperature to the peak damage level of 0.5 dpa. Samples were then annealed at the desired temperature for 1 h and exposed to deuterium atom beam with the flux of for 144 h to populate the remaining defects. An unannealed sample was also used as a reference. Nuclear reaction analysis technique was used for deuterium depth profile analysis and thermal desorption was performed on the same samples to measure the amount of total retained D. Scanning transmission electron microscopy was used for the calculation of dislocation densities in the samples. After annealing at 1200 K approximately 66% of those initial defects which retain deuterium were annealed.

Development of a versatile user-friendly IBA experimental chamber

Reliable performance of the Ion Beam Analysis (IBA) techniques is based on the accurate geometry of the experimental setup, employment of the reliable nuclear data and implementation of dedicated analysis software for each of the IBA techniques. It has already been shown that geometrical imperfections lead to significant uncertainties in quantifications of IBA measurements. To minimize these uncertainties, a user-friendly experimental chamber with a heuristic sample positioning system for IBA analysis was recently developed in the Van de Graaff laboratory in Tehran. This system enhances IBA capabilities and in particular Nuclear Reaction Analysis (NRA) and Elastic Recoil Detection Analysis (ERDA) techniques. The newly developed sample manipulator provides the possibility of both controlling the tilt angle of the sample and analyzing samples with different thicknesses. Moreover, a reasonable number of samples can be loaded in the sample wheel. A comparison of the measured cross section data of the 16O(d,p1)17O reaction with the data reported in the literature confirms the performance and capability of the newly developed experimental chamber.

ChemInform Abstract: Hydrogen Detection Near Surfaces and Shallow Interfaces with Resonant Nuclear Reaction Analysis

AbstractReview: 783 refs.

Application of PIGE, BS and NRA techniques to oxygen profiling in steel joints using deuteron beam

In order to study the oxygen content and to characterize the oxygen depth profile on the surface of welded steel joints in the function of the applied shielding gases, particle induced gamma-ray emission (PIGE), backscattering spectrometry (BS) and nuclear reaction analysis (NRA) methods were used. The measurements were carried out at 1.0, 1.4 and 1.8MeV deuteron energies. From the PIGE oxygen and carbon elemental maps (1000×1000μm2) taken with a beam of 2×2μm2 beam size, oxygen rich regions were chosen for the depth profile analysis. The investigated depth was ∼6μm using particle detection (BS, NRA), which was extended to ∼11μm with the application of the differential-PIGE method, using the numerical integration of experimental cross-section data. The oxygen depth profiles show systematic discrepancy in the oxide layer thickness and composition between the two different kind of shielding gases.

Nuclear reaction analysis as a tool for the 3He thermal evolution in Li2TiO3 ceramics

Li2TiO3 ceramic is one of the promising solid breeding candidates for fuel generation in deuterium–tritium Fusion reactors. The Tritium (T) release characteristics consist of a complex combination of gas diffusion stages inside the solid. Considering that this ceramic will produce high concentration of gaseous transmutation products (3H and 4He) when exposed to high-energy neutrons, there are considerable interests in studying 3He thermal evolution for the fundamental understanding of the light ion behavior in breeder blanket materials under reactor conditions. 3He atoms used to simulate the 4He incorporation were implanted by a 600keV ion beam at a fluence of 1017 at/cm2 and the 3He(d,α)1H nuclear reaction analysis (NRA) technique was subsequently used to study depth profiles evolution after different thermal annealing treatments. The release experiments showed that 3He outgassing is not effective at room temperature, remaining quite negligible till 300°C. After this temperature, the 3He content in the sample reduces steadily with increasing the annealing temperature, and less than 5% of the initial 3He concentration was found at 900°C after an isochronal annealing, without significant depth-profile broadening. Scanning and transmission electron microscopies characterization highlight the microstructural changes of the implanted and annealed ceramic within the nuclear cascades zone. The correlation of results obtained by electron microscopy and NRA technique leads to the conclusion that the helium release is governed by a transport mechanism that involves rapid migration/diffusion through interconnected gas cavities and resulting microcracks before reaching grain boundaries and opened pores.

Structure, electrical conductivity, critical superconducting temperature and mechanical properties of TiNxOy thin films

For thermal applications, one needs to manufacture titanium nitride based films with as high as possible critical superconductivity temperature while minimizing the mechanical constraints. We investigated the structural and mechanical properties of titanium oxynitride thin films TiNxOy with 0.385≤x ([N]/[Ti])≤1.13 and y ([O]/[Ti])≤0.3 deposited in a temperature range of 320–400K, at 800W, by reactive DC magnetron sputtering deposition from a Ti target in Ar+N2 plasma discharge. The working pressure was fixed at 0.2–0.25Pa and the nitrogen concentration, x, modified by increasing the N2 flow from 4.2 to 15sccm. The Ar flow was set at 60sccm. We thus tried different physical conditions during realization and characterized the films obtained. We also studied the influence of the substrate onto these film properties. The chemical analysis was performed with the Rutherford backscattering and nuclear reaction analysis techniques. The structural properties of the films were characterized by X-ray diffraction and the mass density by X-ray reflectivity. The electrical resistivity and the critical superconducting temperature were measured by the four-point probe method. Acoustic and elastic properties were determined by the picosecond ultrasonic and the Brillouin light scattering techniques as a function of the nitrogen concentration.