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In this paper, experimental work is supported by multi-scale numerical modeling to investigate nanomechanical response of pristine and ion irradiated with Fe2＋ ions with energy 5 MeV high purity iron specimens by nanoindentation and Electron Backscatter Diffraction. The appearance of a sudden displacement burst that is observed during the loading process in the load–displacement curves is connected with increased shear stress in a small subsurface volume due to dislocation slip activation and mobilization of pre-existing dislocations by irradiation. The molecular dynamics (MD) and 3D-discrete dislocation dynamics (3D-DDD) simulations are applied to model geometrically necessary dislocations (GNDs) nucleation mechanisms at early stages of nanoindentation test; providing an insight to the mechanical response of the material and its plastic instability and are in a qualitative agreement with GNDs density mapping images. Finally, we noted that dislocations and defects nucleated are responsible the material hardness increase, as observed in recorded load–displacement curves and pop-ins analysis. [ABSTRACT FROM AUTHOR]

• The irradiated sample with higher W content shows swelling and melting for all discharges, the CrNbTaVW only shows blisters. • The effect of irradiation was more severe in CrNbTaVW 1.7 when compared to CrNbTaVW. • The deuterium retention was evidenced to be in a deeper depth between 1.3 and 3 μm. • Deuterium retention was higher for CrNbTaVW 1.7 when compared with CrNbTaVW for 3 discharges applied. CrNbTaVW x high-entropy alloys have been developed for plasma facing components to be applied in nuclear fusion reactors. The CrNbTaVW x (x = 1 and 1.7) compositions were prepared by ball milling and consolidated at 1600 °C under 90 MPa. To study the irradiation resistance of these materials, deuterium plasmas were used to irradiate the samples in the PF-1000U facility with 1 and 3 discharges. Structural changes before and after irradiation were analyzed by scanning electron microscopy coupled with energy dispersive X-ray spectroscopy. Nuclear reaction analysis was carried out with 1000 and 2300 keV 3He+ ion beams to evaluate the profile and amount of retained deuterium on the irradiated samples. After irradiation, the sample with higher W content revealed swelling and melting for all discharges, while in the case of CrNbTaVW only blisters were observed. The deuterium retention was higher for CrNbTaVW 1.7 when compared with CrNbTaVW for 3 discharges applied. [ABSTRACT FROM AUTHOR]

Hexagonal boron nitride was irradiated with 140 MeV protons to a fluence of ~6 1020p/cm2 at T irr ~200 °C. Isotropic graphite was also irradiated alongside h-BN under similar conditions and fluence to enable direct comparison of the two similar structures. The effects of proton irradiation on dimensional stability and microstructure were studied using precision dilatometry and energy dispersive Xray diffraction techniques revealing by direct comparison to graphite that h-BN can better resist radiation damage from bombardment when irradiated with protons impinging normal to the crystallographic planes or along the crystallographic c-axis. X-ray diffraction experiments also revealed a preferred orientation of the crystallites in bulk samples near the sample surface, an orientation influenced by irradiation. Thermal studies using differential scanning calorimetry and thermogravimetric analysis to 740 °C, augmented by precision dilatometry, provided evidence of subtle phase transitions attributed to residual w-BN in the matrix. Irradiation appears to induce shifting of such transitions. [ABSTRACT FROM AUTHOR]

During their service in a nuclear power plant, structural materials are subject to high temperature, mechanical stress, corrosive coolant environments, and neutron irradiation. The combination of radiation, corrosion and thermo-mechanical loading represents a unique environment that materials must endure: radiation can significantly alter the material's thermo-mechanical performance and the lifetime of a component. The conditions under which this happens are difficult to study and normally necessitate nuclear reactor experiments followed by post-irradiation examination in hot cells, which renders investigations complex, time consuming and expensive. While few attempts have been made to study the combined effects of radiation and corrosion with lead bismuth eutectic [1] or molten salts [2] none of these experimental set-ups were designed to study the combination of corrosion and irradiation together with mechanical loading. Here the development of a miniature test technique is presented where irradiation, corrosion and strain can synergistically be applied on a material in a controlled way. The experiment is based on scaling down the membrane bulge test [3], using liquid lead as a pressure medium at high temperature. Membrane type specimens are made from the structural material to study, with their back side pressurized thereby inducing corrosion and membrane stretching stress while irradiation damage is generated by proton irradiation at the front surface affecting the entire thickness to the back side of the sample. The paper presents the way how the engineering problems related to the combination of corrosion by liquid metal, stress application and irradiation of the sample have been addressed. [ABSTRACT FROM AUTHOR]

We studied the morphology of the tracks (irradiation damage) of 44, 66, and 84 MeV Au ions in YBa 2 Cu 3 O 7-x (YBCO) thin films using cross-sectional transmission electron microscopy (TEM). The electronic energy loss (S e = 11.6, 16.7, and 20.1 keV/nm) ranged near the onset of ion-track formation previously determined by plan-view TEM and critical-temperature measurements (about 13 keV/nm). The morphology changed from 1D arrays of large spheres of about 5 to 10 nm diameter in 44-MeV irradiation to their elongated variant (spheroid) that were statistically pierced by thin-lines of about 1 to 2 nm and 3 to 5 nm diameter in 66 and 84 MeV, respectively. In the same series of Au-irradiated YBCO films, we observed a sudden increase in critical current density at self-field and 77 K between 44- and 55-MeV irradiation, in agreement with the appearance of the thin-line damage in TEM (between 44- and 66-MeV). [ABSTRACT FROM AUTHOR]

• A rate theory model which permits small defect clusters to move is developed. • An algorithm based on modified Fokker-Plank method was used for large clusters. • Mean loop size in Zr-added 310S steel is smaller than that of (Nb, Ta,W)-added one. The evolution of dislocation loops in two types of modified 310S steel under proton irradiation are investigated with rate theory simulations. The growth of dislocation loops is promoted with the increase of irradiation dose and growth rate decreases at high dose, while the number density of the dislocation loops increases first with dose and then tends to be saturated gradually. At the initial stage of irradiation, large number of dislocation loops nucleate and the density increases rapidly. With the development of irradiation, the growth of dislocation loops gradually takes over. Simulation results are in good agreement with the experimental observations of transmission electron microscope. Present study shows that The irradiation resistance of Zr-added steel is slightly better than that of (Nb, Ta, W)-added steel, which may due to the smaller migration energy of interstitials and vacancies in Zr-added steel than that in the (Nb, Ta, W)-added one. [ABSTRACT FROM AUTHOR]

Ion implantation is one of the best methods to manufacture silicon-vacancy (SiV) centers in diamond, which can be used as qubits. In this work, molecular dynamics (MD) simulation was conducted to analyze the damage evolution and distribution during the process of silicon ion implantation into bulk diamond and subsequent annealing. Tersoff-ZBL (Ziegler-Biersack-Littmark) potential was used to describe the atomic interaction. Identify Diamond Structure (IDS) and Wigner-Seitz defect analysis methods were used to calculate damages and vacancies. After 2393 K annealing, about 42.5% of ion induced IDS damages were recovered. During the temperature cooling down from 2393 K to 293 K, the movements of silicon atoms along the implantation direction were sensitive to the temperature variation, while vacancies were almost insensitive. MD simulation is helpful to illustrate the ion implant induced damages' dynamic evolution and Si-V related defects, which can assist a deeper understanding of SiV center's manufacturing. [ABSTRACT FROM AUTHOR]

Highlights • The arc-dpa model is more accurate in comparison with NRT model when predicting N s. • Compared with T , E PKA is more likely to cause damages in Zr. • T has a significant influence on A , while has little effect on B in the power law. • PKA incident direction has little effect on N peak , t peak and N s except for t s. Abstract Atom-scale numerical calculations were performed to investigate the damage behavior in close-packed hexagonal zirconium (HCP-Zr) by primary irradiation through a molecular dynamics (MD) study. The influences of Primary Knock-on Atom (PKA) energy (E PKA), the PKA incident direction and the ambient temperature (T) on the cascade collision were studied comprehensively. The results show that the athermal recombination corrected displacements per atom (arc-dpa) model is more accurate in comparison with the Norgett-Robinson-Torrens (NRT) model when predicting the steady vacancy (N s). It was found that the vacancy peak (N peak), the peak time (t peak), and the steady time (t s) increase as E PKA and T increase. The steady vacancy also increases with the increase of E PKA. It was also found that N s increases and subsequently decreases by increasing T , suggesting that there is a suitable temperature to maximize N s when E PKA is constant. In addition, it was discovered that the PKA incident direction has little effect on vacancy dynamic history. It was proved that E PKA can worsen the irradiation damage in crystal Zr, but T can relieve such damage. In addition, the incident direction was found to have an insignificant effect on the damage. This study highlights that the steady vacancy concentration (C) can characterize the material irradiation damage. [ABSTRACT FROM AUTHOR]

Highlights • Metallic glass Ni 62 Ta 38 maintained amorphous after the irradiation. • No obvious irradiation damage appeared on the surface of metallic glass Ni 62 Ta 38. • Large area of blisters were formed on the surface of metal W at 1.0 × 1018 ions/cm2. • Crystalline size, micro-strain and dislocation line density varied undulately in W. Abstract The protons with an energy of 250 keV were used to irradiate metallic glass Ni 62 Ta 38 and metal W, the changes in structure and surface morphology of both the materials were compared, and their performances against the irradiation were evaluated, in order to provide the reference for the possibility of application of metallic glass Ni 62 Ta 38 in irradiation environment. The results showed that after the proton irradiation, metallic glass Ni 62 Ta 38 still maintained its good amorphousness without obvious irradiation damage on its surface. Meanwhile, stress was generated in metal W, and its crystalline size, micro-strain and dislocation line density varied undulately with the increase of fluence. When the irradiation fluence was 1.0 × 1018 ions/cm2, large area of blisters were formed on the surface of metal W. The surface roughness of metal W increased with the fluence. Compared with metal W, the proton irradiation resistance of metallic glass Ni 62 Ta 38 was better. [ABSTRACT FROM AUTHOR]

An effective method to improve the irradiation resistance of austenitic stainless steels is adding oversized solutes into steels. In this work, the irradiation resistances of two type of modified 310S steels, in one of which Zr was added and in another Nb, Ta, and W were added, were investigated by proton irradiations at 563 K. Irradiation induced vacancy-type defects was characterized with positron annihilation spectroscopy (PAS), while dislocation loops and bubbles whose size are greater than 1 nm are characterized with transmission electron microscopy (TEM). It is found that the relative S parameter ΔS/S extracted from PAS is more effective than S parameter in evaluating the quantity of vacancy-type defects. It was revealed from ΔS/S that more vacancy-type defects produced in (Nb, Ta, W)-added steels than that in Zr-added steels, and this trend became more obvious with the dose increasing. S-W curves reveal that proton irradiation induced two kinds of vacancy-type defects, i.e. vacancy clusters and proton-vacancy clusters. TEM observation shows that the density of small bubbles induced by proton in (Nb, Ta, W)-added steels is much higher than that in Zr-added steels. Both 1 3 〈1 1 1〉 and 1 2 〈1 1 0〉 dislocation loops were observed with TEM in all of the specimens. The mean size and number density of dislocation loops in (Nb, Ta, W)-added steels are slightly larger than that in Zr-added steels, and increased with increasing irradiation dose. Both PAS and TEM observations shows that irradiation damage in Zr-added steels is less serious than that (Nb, Ta, W)-added steels, and the possible mechanisms are discussed through the enhancement of point defect recombination by oversized solute atoms. [ABSTRACT FROM AUTHOR]

W–2%Y 2 O 3 composites were prepared by wet chemical and powder metallurgy. Commercial roll tungsten was selected as a comparative sample in the He + irradiation experiment. The experiment was conducted under He + beam energy of 50 eV, irradiation dose of approximately 9.9 × 10 24  ions/m 2 , and temperature of 1503–1553 K. The samples were annealed at 1173, 1373, and 1573 K for 1 h. The irradiation surface was observed in situ. The W–2%Y 2 O 3 composites and pure tungsten displayed different grain orientation damage morphologies. In addition, the fuzzy structure was more likely to converge densely at the phase interface. Annealing repairs material surface irradiation damage, whereas the phase interface acts as a He + migration channel. [ABSTRACT FROM AUTHOR]

Metallic glasses are considered to possess good resistant against irradiation due to their inherent structural long-range disorder and a lack of grain boundaries. The He 2+ with an energy of 300 keV was used to irradiate Ni 62 Ta 38 binary metallic glass to investigate its resistance against the irradiation, and the irradiated behaviour of the metallic glass was compared with that of W metal. The irradiation fluence range over 2.0 × 10 17 ions/cm 2 –1.6 × 10 18 ions/cm 2 . The TEM results show that nanocrystals of μ-NiTa phase and Ni 2 Ta phase appeared in Ni 62 Ta 38 metallic glass under the irradiation fluence of 1.6 × 10 18 ions/cm 2 . The SEM results show that the surfaces of Ni 62 Ta 38 metallic glasses maintained flat and smooth, whereas a large area of blisters with peeling formed on the surface of W metal at the irradiation fluence of 1.0 × 10 18 ions/cm 2 . It indicates that the critical irradiation fluence of surface breakage of the Ni 62 Ta 38 metallic glass is higher than that of W metal. After the irradiation, stress was generated in the surface layer of W metal, leading to the increase of the hardness of W metal. [ABSTRACT FROM AUTHOR]

The anti-thermal radiation performance of tungsten was investigated by high intensity pulsed ion beam technology. The ion beam was mainly composed of C n+ (70%) and H + (30%) at an acceleration voltage of 250 kV under different energy densities for different number of pulses. GIXRD analysis showed that no obvious phase structural changes occurred on the tungsten, and microstress generated. SEM analysis exhibited that there was no apparent irradiation damage on the surface of tungsten at the low irradiation frequency (3 times and 10 times) and at the low energy density (0.25 J/cm 2 and 0.7 J/cm 2 ). Cracks appeared on the surface of tungsten after 100-time and 300-time irradiation. Shedding phenomenon even appeared on the surface of tungsten at the energy densities of 1.4 J/cm 2 and 2.0 J/cm 2 . The surface nano-hardness of tungsten decreased with the increase of the pulse times and the energy density. The tungsten has good anti-thermal radiation properties under certain heat load environment. [ABSTRACT FROM AUTHOR]

Silicon carbide fiber-reinforced silicon carbide matrix composites have been investigated for their use as structural materials for advanced nuclear reactor. Although quite a number of researches have been devoted to probe the effects of irradiation on various properties of the composites, there is little known about the atomistic mechanism for irradiation resistance. In this study, a two-temperature model has been used to investigate the irradiation damage of SiC/Gra/SiC composites, which includes three parts and two SiC/C interfaces, two single crystal cubic silicon carbide on two sides and a few graphene sheets in the middle part. By simulating 100 keV displacement cascades, we find that the number of defects in the reinforcement is larger than that in the matrix, which indicates the damage in the reinforcement is more serious than that in the matrix. Moreover, we explicitly investigate the damage behavior of the interphase graphene layers and find that some atoms in one graphene sheet form many new chemical bonds with atoms in another one, which leads to the transition from sp 2 to sp 3 hybridization. The newly formed chemical bonds link the different graphene layers and make graphene-like electronic structure more “diamond-like”, enhancing the irradiation resistance of the matrix. [ABSTRACT FROM AUTHOR]

The irradiation behaviors and corrosion properties of a modified N36 zirconium alloy with the composition of Zr-0.8Sn-1Nb-0.3Fe, developed by Nuclear Power Institute of China, were investigated by transmission electron microscopy and focused ion beam. The polished samples were irradiated by 400 keV Kr + ions up to 25 dpa at 360 °C using a NEC 400 kV ion implanter. The as-received and irradiated samples were corroded for 14 days at the water-vapor environment with 10.3 MPa and 400 °C. The krypton gas bubbles were formed in zirconium matrix and their size was increased with increasing ion dose. Meanwhile, a model that related with gas bubble size and displacement damage had been established. After the corrosion, a layer composed of zircona with different stoichiometric composition was formed on the sample surface. The higher the displacement damage was, the thicker the corrosion layer would be. An empirical equation between oxide thickness and displacement damage was provided. From sample surface to matrix inner, the oxygen content was decreased with increasing corrosion depth. Correspondingly, the zircona was changed from ZrO 2 with monoclinic structure on the sample surface to the mixtures of ZrO 2 with tetragonal structure and ZrO 2 with monoclinic structure in the middle of corrosion layer, and then to ZrO 2 with tetragonal structure near alloy matrix. [ABSTRACT FROM AUTHOR]

Boron carbide is widely used either as armor-plate or neutron absorber. In both cases, a good structural stability is required. However, a few studies have shown amorphisation may occur in severe conditions. Hard impacts lead to the formation of amorphous bands. Some irradiations in electronic regime with H or He ions have also shown amorphisation of the material. Most authors however consider the structure is not drastically affected by irradiations in the ballistic regime. Here, we have irradiated at room temperature dense boron carbide pellets with Au 4 MeV ions, for which most of the damage is in the ballistic regime. This study is part of a program devoted to the behavior of boron carbide under irradiation. Raman observations have been performed after the irradiations together with transmission electron microscopy (TEM). Raman observations show a strong structural damage at moderate fluences (10 14 /cm 2 , about 0.1 dpa), in agreement with previous studies. On the other hand, TEM shows the structure remains crystalline up to 10 15 /cm 2 then partially amorphises. The amorphisation is heterogeneous, with the formation of nanometric amorphous zones with increasing density. It then appears short range and long range disorder occurs at quite different damage levels. Further experiments are in progress aiming at studying the structural stability of boron carbide and isostructural materials (α-B, B 6 Si,…). [ABSTRACT FROM AUTHOR]

In this article, a large scale multi-particle molecular dynamics (MD) simulation model was developed to study the dynamic structural changes in single crystal diamond under 5 keV Ga + irradiation in conjunction with a transmission electron microscopy (TEM) experiment. The results show that the thickness of ion-induced damaged layer (∼9.0 nm) obtained from experiments and simulations has good accordance, which demonstrates the high accuracy achieved by the developed MD model. Using this model, the evolution of atomic defects, the spatial distributions of implanted Ga particles and the thermal spike at the very core collision area were analysed. The local thermal recrystallizations observed during each single ion collision process and the increase of the density of the non-diamond phase (mostly sp 2 bonded) at irradiation area are fund to be the underling mechanisms responsible for ion fluence dependent amorphization of diamond observed in previous experiments. [ABSTRACT FROM AUTHOR]

The effect of neutron irradiation on recovery (annealing) of irradiation damage has been investigated for self-ion implanted Si. A damage layer was introduced by 200keV Si+ implantation to a fluence of 5x1014Si/cm² at room temperature. The damaged samples were neutron-irradiated to 3.8x1019n/cm² (fast neutron), without intentional heating, in the core of the Kyoto University Reactor. During neutron irradiation, the samples were heated only by nuclear reactions, and the irradiation temperature was estimated to be less than 90°C. The damage levels of the samples were characterized by Rutherford backscattering with channeling. Reduction of damage peaks as a result of neutron irradiation was clearly observed in the samples. The annealing efficiency was calculated to be 0.44 defects/displacement. [ABSTRACT FROM AUTHOR]

Abstract: Magnesium oxide (MgO) has been of interest for several decades as a promising tunable broadband laser due to its vacancy defects (color centers). In this work we introduced color centers into MgO nanocube by electron irradiation in a transmission electron microscope (TEM). Square nano-holes were formed from the electron-exit face using 100 and 300keV electrons, and a broad O-vacancy (color-center) absorption peak around 4.1–6.6eV was observed by valence-electron energy-loss spectroscopy (VEELS). We investigated the mechanism of MgO damage by high-energy electron beams. The hole formation is believed to involve a mixed removal of diatomic MgO molecules as well as Mg and O species in stoichiometric proportion. Observations using high-resolution transmission electron microscopy (HRTEM) and VEELS suggest that bulk O-vacancies are generated near the electron-exit face, due to the forward momentum transferred from fast-electron collisions and the Coulomb attraction of negative O-ions by the positively charged MgO surface. [Copyright &y& Elsevier]

Highlights: [•] Metallic glasses and W were irradiated with 500keV He2+ at different fluences. [•] Metallic glasses could maintain amorphous state at different irradiation fluences. [•] The resistance to He2+ irradiation of metallic glasses was superior to the one in W metal. [•] Cu- and Zr-based metallic glasses had better resistance to He2+ irradiation. [ABSTRACT FROM AUTHOR]

Abstract: The mechanical properties of copper nanowires irradiated with energetic ions have been investigated by using molecular dynamics simulations. The Cu ions with energies ranging from 0.2 to 8.0keV are used in our simulation, and both the elastic properties and yields under tension and compression are analyzed. The results show that two kinds of defects, namely point defects and stacking faults, appear in the irradiated nanowires depending on the incident ion energy. The Young modulus is significantly reduced by the ion irradiation, and the reduction magnitude depends on the vacancy number, which is determined by the ion energy. Moreover, the irradiated nanowires yield at a smaller strain, compared with the unirradiated nanowire. The mechanism for these changes are also discussed. [Copyright &y& Elsevier]

In order to compare the resistance to He2+ ion induced irradiation between metallic glass and polycrystal W metal, this paper used different fluences of He2+ ion-irradiated metallic glass (Cu47Zr45Al8)98.5Y1.5 and polycrystal W with an energy of 500keV. The SRIM simulation calculation results showed that the range (1.19μm) of He2+ in metallic glass was greater than the one (0.76μm) in polycrystal W. The SEM analysis showed that there was no significant irradiation damage phenomenon on the surface of metallic glass, and there was only a damage layer 1.45μm away from the surface when the fluence reached 2×1018 ions/cm2. For W, there were surface peeling, flaking and other surface damages at a fluence of 1×1018 ions/cm2; when the fluence increased to 2×1018 ions/cm2, multilayer detachment phenomenon appeared. The surface root mean square roughness of metallic glass (Cu47Zr45Al8)98.5Y1.5 first increased and then decreased with the increase of fluence. The surface reflectivity of (Cu47Zr45Al8)98.5Y1.5 decreased with the increase of fluence. Through detection by XRD, it was found that (Cu47Zr45Al8)98.5Y1.5 always maintained amorphous phase after different fluences of radiation. The resistance to He2+ irradiation of metallic glass (Cu47Zr45Al8)98.5Y1.5 was superior to the one in polycrystal W. [ABSTRACT FROM AUTHOR]

Abstract: Formation kinetics of defect clusters in pure iron during irradiation has been numerically investigated by reaction rate theory, with focusing on nucleation process of vacancy clusters (voids) and self-interstitial-atoms (SIA) clusters under a wide range of atomic displacement damage rate (dpa rate) and temperature conditions. In the rate theory model, the size dependence of thermal stability of a defect cluster is treated for a wide range of cluster size. The numerical analysis shows that the nucleation processes of voids and SIA-clusters are quite different from each other. As to the voids, the nucleation rate of voids depends much on temperature and dpa rate, and has the individual peak temperature for each dpa rate, during which the peak temperature increases with increasing dpa rate. This tendency for void nucleation is similar to that for void swelling observed in experiments. As to the SIA-clusters, the nucleation rate of SIA-clusters does not depend much on temperature and has no peak temperatures because of the relatively high thermal stability of an SIA-cluster, indicating that the conventional model (di-interstitial model) is applicable to describe the nucleation of SIA-clusters in a wide range of temperature. [Copyright &y& Elsevier]

Abstract: The results from mass spectrometry of clusters sputtered from Cs+ irradiated single-walled carbon nanotubes (SWCNTs) as a function of energy and dose identify the nature of the resulting damage in the form of multiple vacancy generation. For pristine SWCNTs at all Cs+ energies, C2 is the most dominant species, followed by C3, C4 and C1. The experiments were performed in three stages: in the first stage, Cs+ energy E(Cs+) was varied. During the second stage, the nanotubes were irradiated continuously at E(Cs+)=5keV for 1,800s. Afterwards, the entire sequence of irradiation energies was repeated to differentiate between the fragmentation patterns of the pristine and of heavily irradiated SWCNTs. The sputtering and normalized yields identify the quantitative and relative extent of the ion-induced damage by creating double, triple and quadruple vacancies; the single vacancies are least favored. Sputtering from the heavily irradiated SWCNTs occurs not only from the damaged and fragmented nanotubes, but also from the inter-nanotube structures that are grown due to the accumulation of the sputtered clusters. Similar irradiation experiments were performed with the multi-walled carbon nanotubes; the results confirmed the dominant C2 followed by C3, C4 and C1. [Copyright &y& Elsevier]

Abstract: Single crystalline samples of highly ionic Ca2La8(SiO4)6O2 and covalent 6H–SiC have been irradiated with different ions/energies to study the effects of dose, temperature, damage-energy density, and in-cascade ionization rate on the dynamics of irradiation-induced amorphization. Above temperatures of 100–150K, the dose for complete amorphization, D, increases with temperature in a single stage and exhibits a strong dependence on the ratio of in-cascade recovery to displacement cross sections, σ r/σ d. A fit of a dynamic model for amorphization to these data indicates that irradiation-induced dynamic recovery occurs with an activation energy of 0.15±0.02 and 0.12±0.01eV for Ca2La8(SiO4)6O2 and 6H–SiC, respectively. Analysis of these data reveals that ionization processes are the dominant contributor to in-cascade recovery in Ca2La8(SiO4)6O2; while in 6H–SiC, ionization processes are less dominant. [Copyright &y& Elsevier]

Abstract: Hydrogen trapping and its interaction with defects in Li2TiO3 and Li2ZrO3 that were irradiated with hydrogen isotopes and exposed to air were investigated using ion beam techniques and photo-stimulated luminescence (PSL) measurements. During irradiation with 10keV H2 +, the incident hydrogen was trapped in Li2TiO3 at the end of its trajectory until the local concentration reached 12.5at.%, whereas an increase in the hydrogen retained in Li2ZrO3 was observed at a considerably greater depth as compared to the projected range. A broad PSL emission with two peaks at around 2.8 and 3.1eV was observed under irradiation of Li2ZrO3 with 5.17eV light. The PSL intensity of the band at 2.8eV showed a remarkable decrease as compared to the peak at 3.1eV upon irradiation with 10keV D2 +. The results of isochronal annealing subsequent to irradiation showed that the recovery of the luminescence intensity in the 2.8eV luminescent centers and release of hydrogen occurred in the same temperature range of 350–450K. In addition, the formation of a Li2CO3 layer at the surface of Li2TiO3 and Li2ZrO3 following exposure to air was subject to the humidity conditions and was considered to play an important role in the dissociation of water vapor and hydrogen trapping beneath the reaction layer in Li2TiO3 and Li2ZrO3. [Copyright &y& Elsevier]

Abstract: In order to clarify formation kinetics of self-interstitial atoms (SIA) clusters in cubic silicon carbide (β-SiC) during irradiation, the nucleation and growth process of SIA-clusters have been investigated by a kinetic Monte-Carlo (KMC) simulation technique. It has been found from the KMC simulations that the formation kinetics of SIA-clusters in β-SiC during irradiation is classified into the following two types, depending on temperature. At relatively high temperatures, the thermal stability of an SIA-cluster is crucial for the nucleation and growth of the cluster, in which the composition of the cluster is almost stoichiometric. In contrast, at relatively low temperatures where the cluster thermal stability is no longer crucial, even an SIA-cluster far from stoichiometric composition is formed. [Copyright &y& Elsevier]

Abstract: Irradiation damage in nickel alloy C-276 irradiated by 115keV argon ions at room temperature with irradiation doses from 0.28 to 82.5dpa has been investigated by transmission electron microscopy. Nano-scale black spot damage appeared at a dose higher than 0.83dpa. Large interstitial-type dislocation loops were observed at the dose of 8.25dpa. Both the density of dislocation loops and the density of network dislocations grew significantly with the increase of irradiation dose. However, the density of network dislocations declined at the dose of 27.5dpa. But the total of dislocation density (density of dislocation lines plus density of dislocation loops) kept increasing and no signs of saturation were seen in the dose range explored. The results showed that the nickel alloy C-276 had good performance in delaying the development of black spots, dislocations and dislocation loops. However, original grains have formed into subgrains at the dose of 82.5dpa, meaning that the grains in C-276 lost its structural integrity at doses higher than 82.5dpa. [Copyright &y& Elsevier]

Abstract: To elucidate the underlying physics of ion beam assisted deposition (IBAD), irradiation damage effects in magnesia (MgO) and yttria-stabilized zirconia (YSZ) were investigated. Ion irradiations were performed on MgO and YSZ single crystals of three low-index crystallographic orientations using 100 and 150keV Ar+ ions over a fluence range from 1×1014 to 5×1016 Ar/cm2. Damage accumulation was analyzed using Rutherford backscattering spectrometry combined with ion channeling. Damage evolution with increasing ion fluence proceeded via several characteristic stages and the total damage exhibited a strong dependence on crystallographic orientation. For both MgO and YSZ, damage anisotropy was maximal at a stage when the damage saturated, with the (110) crystallographic orientation being the most radiation damage resistant. The Ion/Atom ratio deposition parameter reported for IBAD of MgO and YSZ films was found to correlate with the damage plateau stage described above. Finally, the role of the Ion/Atom ratio is discussed in terms of radiation damage anisotropy mechanism. [Copyright &y& Elsevier]

Abstract: Energetics of point defects in β-SiC have been investigated using atomistic calculations with the empirical interatomic potential, where a simple static relaxation method and a dynamic relaxation method are separately employed. In addition to formation energy of isolated silicon interstitials, migration energies for interstitials and vacancies obtained from the dynamic relaxation method are much lower than those obtained from the simple static relaxation method. It indicates that the dynamic relaxation method possibly can provide more relaxed defect configuration than the simple static relaxation method. [Copyright &y& Elsevier]

Abstract: Genesis, a member of NASAs Discovery Mission program, is the world’s first sample return mission since the Apollo program to bring home solar matter in ultra-pure materials. Outside the protection of Earth’s magnetosphere at the Earth–Sun Lagrange 1 point, the deployed sample collectors were directly exposed to solar wind irradiation. The natural process of solar wind ion implantation into a highly pure silicon (Si) bulk composition array collector has been measured by spectroscopic ellipsometry and scanning transmission electron microscopy (STEM). Ellipsometry results show that bulk solar wind ions composed of approximately 95% H+, 4% He+ and <1% other elements physically altered the first 59–63nm of crystalline silicon substrate during 852.8days of solar exposure. STEM analysis confirms that the solar accelerated ions caused significant strain and visible structural defects to the silicon structure forming a 60–75nm thick irradiation damage region directly below the surface SiO2 native oxide layer. Monte Carlo simulations of solar wind H, He, C, O, Ne, Mg, Si and Fe ion collisions in the Si collector with fluences calculated from the Genesis and ACE spacecrafts were used to estimate the energy deposited and Si vacancies produced by nuclear stopping in a flight-like Si bulk array collector. The coupled deposited energy model with the flown Genesis Si in situ measurements provides new insight into the basic principles of solar wind diffusion and space weathering of materials outside Earth’s magnetosphere. [Copyright &y& Elsevier]

Abstract: In order to study the mechanism of the nucleotide directly damaged by energetic heavy ions, the residual ratio of uridine molecules after irradiation was measured by means of High Performance Liquid Chromatography (HPLC). The experimental results show that the irradiation damage probability depends on the electronic energy loss rate (Se ) of incident ions: first it increases quickly with Se , then becomes stable when Se reaches 800eV/nm. The contribution of the nuclear collisions can be neglected compared with that of the electronic process. This is not only because that the nuclear energy loss rate (Sn ) is much smaller than Se for MeV heavy ions, but also because the energy deposition through the electronic process is more efficient in damaging molecules than through the nuclear process. [Copyright &y& Elsevier]

Abstract: The irradiation damage caused on polyethylene terephtalate (Mylar, PET) samples by 1.6MeV deuteron ions has been measured using simultaneously the nuclear reaction analysis (NRA) and the transmission energy loss (TEL) techniques. The irradiation was carried out at normal incidence relative to the target surface with the irradiation beam being used as the analysis beam. The evolution of the overall damage during irradiation was evaluated by measuring the variation of the energy loss of the deuteron beam passing through the target. For this purpose, a solid state Si detector placed at a forward angle of 30° relative to the incident beam direction was used. The NRA spectra recorded by a second Si detector located backward at 150° allowed the evaluation of the carbon and the oxygen depletion. The beam spot size was circular in shape and 1mm in diameter and the beam current was set at 5nA. The ion fluence was increased up to the value of 2.5×1016 deuterons/cm2. It was observed that the target energy loss decreased steadily as the fluence increased and levelled off at high fluence. The 16O(d,p0)17O, 16O(d,p1)17O∗ and 12C(d,p0)13C reactions were used for monitoring the evolution of the oxygen and carbon content as a function of the deuteron fluence. A monotonic decrease of the oxygen content with the increase of ion fluence was observed. At the highest fluence the oxygen depletion reached a value of about 75%. For carbon, a weak depletion was observed at fluence ranging from 2.5×1015 d/cm2 to 1.0×1016 d/cm2 followed by a levelling-off with a total loss around 20%. [Copyright &y& Elsevier]

Abstract: The surface structures of Si (100) wafers subjected to gas cluster ion beam (GCIB) irradiation have been analyzed by cross-sectional transmission electron microscopy (XTEM) and atomic force microscopy (AFM). GCIB irradiation is a promising technique for both precise surface etching and planarization of Si wafers. However, it is very important to understand the crystalline structure of Si wafers after GCIB irradiation. An Ar-GCIB used for the physically sputtering of Si atoms and a SF6-GCIB used for the chemical etching of the Si surface are also analyzed. The GCIB irradiation increases the surface roughness of the wafers, and amorphous Si layers are formed on the wafer surface. However, when the Si wafers are annealed in hydrogen at a high temperature after the GCIB irradiation, the surface roughness decreases to the same level as that before the irradiation. Moreover, the amorphous Si layers disappear completely. [Copyright &y& Elsevier]

Abstract: Classical molecular dynamics simulation of a high energy collision cascade initiated at 50keV is used to study the primary damage state in a stoichiometric mono crystalline ZrC matrix. Analysis of the dynamics and the morphology of the displacement cascade reveals three distinct, well-defined time frames: collision phase, thermal spike and relaxation phase. On average, most of the atoms migrate over short distances, typically less than 11Å, leading to numerous collision sequences in each sublattice. No amorphisation is observed, only a few point defects are created at the end of the collision cascades. All the Zr interstitials form a dumbbell structure oriented in the 〈111〉 direction and C interstitials are either isolated or form a 〈111〉 dumbbell structure. However, unlike metals, few antisites are created. Clusters of two interstitials of different species have a tendency to form small interstitial dislocation loops in the (111) plane. [Copyright &y& Elsevier]

Abstract: The objective of the present paper is to put in evidence the influence of damages due to the collision cascades which take place at the end of the heavy ion micrometer range, on the zirconium surface oxidation. A comparison between two zirconium oxidation experiments under heavy ion irradiation performed in the same temperature and pressure conditions is presented. In the first experiment, a 6μm thick zirconium foil is irradiated with a 50MeV 129Xe beam which stops in the Zr foil. In the second one, a 2μm thick zirconium foil is crossed by the whole fission fragment distribution emitted in the 235U fission. In order to explain the unexpected increase of the oxidation rate observed in the first case, MeV argon irradiation experiments have been performed at IPNL. Results show that collision cascades created in the Zr foil, far from the surface, increase significantly the Zr oxidation. [Copyright &y& Elsevier]

Abstract: With the implementation of time-of-flight elastic recoil detection (ToF-ERD) for the analysis of thin films with high depth resolution using a standard ‘low-energy’ accelerator, routine application of ERD in semiconductor technology becomes possible. In case of irradiation-sensitive materials, like organosilicate low-k films, the energetic incident beam damages the sample during the measurement, resulting in loss of the lighter elements and, as a consequence, altering the sample composition. The ion beam induced damage is investigated for 19F, 35Cl, 63Cu, 79Br and 127I beams at energies of 6–16MeV and typical fluences for ERD analysis. By means of Fourier transform infrared (FTIR) spectroscopy a direct correlation between elemental losses and molecular broken bonds is obtained. The H losses can be described by the bulk molecular release model, with the associated release cross section for H linearly dependent on the energy deposited by the primary beam in the film. [Copyright &y& Elsevier]

Abstract: Irradiation damage in the several thickness polyimide films induced by 2.0MeV He ions has been evaluated by Rutherford backscattering (RBS) and elastic recoil detection (ERDA) methods. For the samples without annealing, gradual decrease of hydrogen content has been observed with the increase of ion dose. After 5min annealing at 100°C, a large amount of hydrogen atoms disappeared suddenly. Then small and continuous depletion of hydrogen content was also observed after ion beam irradiation. After 5min annealing at 300°C, hydrogen concentration has recovered for the 100°C annealed film in the case of no ion beam irradiation. Initial depletion rate of hydrogen for annealing and change of hydrogen content for the successive ion beam irradiation was found to be dependent on the film thickness. [Copyright &y& Elsevier]

Abstract: The formation of irradiation damage for Si(001) surfaces by Ar cluster ion beams at different acceleration voltages was investigated by utilizing the Rutherford backscattering spectrometry (RBS) measurement. For the peak size of 10000 atoms per cluster, the Si surfaces had no damage by the irradiation of the cluster ions, when the acceleration voltages were less than 5kV. Furthermore, for the acceleration voltages larger than 5kV, the amount of displacement atoms increased with an increase of the acceleration voltage. On the other hand, when the cluster size decreased, the threshold voltage for the damage formation decreased, and it was 2kV for the peak size of 3000 atoms per cluster. To be compared with the experimental results, molecular dynamic (MD) simulation was used, and it showed that the irradiation of Ar cluster ions with large size and low incident energy did not produce any damage on the Si surfaces. In addition, the Si surfaces, which were previously damaged at a dose of 1×1015 ions/cm2 by the irradiation of high energy cluster ion beams such as 5keV ion beams, were re-irradiated at a dose of 1×1016 ions/cm2 by low energy cluster ion beams such as 2keV ion beams. The RBS channeling showed that the number of displacement atoms on the damaged surface decreased. The deposited energy on the Si surface was used to improve the crystalline state of the damaged surface, which suggests that the cluster ion irradiation has the ability to anneal the solid surfaces by adjusting the acceleration voltage and the cluster size. [Copyright &y& Elsevier]

Proton irradiations were performed on four kinds of optocouplers and the changes in current transfer ratio were studied. Its degradation was recognized as the proton fluence increased. The degradation’s dependence on the energy of incident protons, the kind of optocouplers and the drive current of the light emitting diode was demonstrated. [Copyright &y& Elsevier]

The dependence of desorption yield for the natural botanic sample bombarded with heavy ion on the electronic stopping power (Se) and dose has been measured by weighing sample mass before and after irradiation. Primary ions including 50 keV N+, 1.5 MeV F+, 3.0 MeV F2+, 4.0 MeV F2+ and 3.0 MeV Si2+ were used in the experiment. Three megaelectron volts of F2+ with doses ranging from 4×1015 to 4×1016 ions/cm2 were used in order to investigate the influence of ion dose. A mass spectrum from the sample bombarded with 3 MeV Si2+ was also taken for a better understanding of the desorption process. Results show that the natural botanic sample is very easily to be desorpted. The yield of MeV heavy ions can be as high as thousands CH2O/ion, and significantly depends on both the Se and dose. The measured yields increase quickly with Se, but drop down with increasing ion dose. These results fit roughly with the prediction of the pressure pulse model. [Copyright &y& Elsevier]

Elastic proton proton scattering is a sensitive and fast method for hydrogen analysis. Utilising a nuclear microprobe it is actually the only technique for the absolute quantification of hydrogen distributions with micrometer or even better lateral resolution. High proton energies, e.g. 20 MeV, allow a wide field of applications since even materials, some 100 μm thick, can be analysed. Irradiation damage is reduced to a minimum compared to all other known ion beam analysis techniques, because a large solid angle of detection of some stradian can be used and the nuclear scattering cross section for protons at these energies is enhanced nearly three orders of magnitudes compared to Coulomb scattering. As a consequence, a sensitivity in the ppm range for hydrogen microscopy is possible. However, the large solid angle of detection induces geometrical effects in the energy analysis which are kept within a physical limit by an angular resolution of 10 mrad e.g. by utilising an annular silicon strip detector of 2.3 sr solid angle of detection. Therefore, the third dimension is provided with a depth resolution better 10 μm using the energy information of the scattered protons. [Copyright &y& Elsevier]

Abstract: The dynamical response of helium bubbles to irradiation with high-energy self-ions in pure gold has been studied by in situ electron microscopy. It is found that sporadic movement of small helium bubbles is induced in random directions within a few nm or less under the irradiation with 400keV Au+ ions at room temperature, where bubbles are thermally immobile. Computer simulation indicates that these facts are consistent with the bubble movement interacting with the collision sub-cascades. [Copyright &y& Elsevier]