Dual Ion Beam Irradiation Research Articles

Study on the mechanism of He effect on dislocation loop formation in three types of dual ion beam irradiations

A comprehensive investigation was conducted to explore the impact of helium on dislocation loops in RAFM steel. This was achieved by employing three types of dual-beam irradiations, which include simultaneous dual-beam irradiation with Ar++He+, sequential dual-beam irradiation with Ar+/He+ and He+/Ar+. In addition, single-beam irradiation with Ar+ and He+ were also performed for reference. The irradiation temperature is 723 ± 5 K. The evolutions of dislocation loop were characterized by transmission electron microscopy (TEM). After He+ irradiated to 0.005 dpa, high-density loops with an average size of 4.3 nm were observed. The main mechanism for the formation of the loops at such a low damage dose should be attributed to the process of the ejection of self-interstitial atoms triggered by He clusters. Significantly, in the RAFM steel exposed to Ar++He+ irradiation, the dislocation loops exhibit a significantly larger average size compared to those resulting from Ar+/He+ and He+/Ar+ irradiation. The loop density produced by He+/Ar+is the largest, and the loop density produced by Ar+/He+ is the smallest. The order of the amount of self-interstitial atoms (loops) caused by three types of dual ion beam irradiation is Ar++He+ > He+/Ar+ > Ar+/He+.

Effect of energy deposition on the disordering kinetics in dual-ion beam irradiated single-crystalline GaAs

The damage induced in GaAs crystals irradiated with dual-ion beam (low-energy I2+ and high-energy Fe9+), producing simultaneous nuclear (Sn) and electronic (Se) energy depositions, was investigated using several characterization techniques. Analysis of the damage buildup shows that Sn alone (single 900 keV ion beam) leads, in a two-step process, to full amorphization of the irradiated layer (at a fluence of 1.5 nm−2) and to the development of a high (2.2%) elastic strain. Conversely, only one step in the disordering process is observed upon dual-ion beam irradiation (i.e., 900 keV I2+ and 27 MeV Fe9+, Sn&Se); hence, amorphization is prevented and the elastic strain remains very weak (below 0.2%). These results provide a strong evidence that, in GaAs, the electronic energy deposition can induce an efficient dynamic annealing of the damage created in collision cascades formed during nuclear energy deposition.

Evolution mechanisms of irradiation-induced helium bubbles, C15 clusters and dislocation loops in ferrite/martensite steels: A cluster dynamics modeling study

• Evolution of helium bubbles , C15 clusters and dislocation loops is studied by a cluster dynamics model. • The model considers the formation of C15 clusters and followed transformation into loops. • Irradiation temperature and dose effects on the microstructural evolution are analyzed. • Helium bubble evolution upon irradiation is governed in sequence by three phases. • Loop growth driven by long-term defect migration follows a power law. Using a cluster dynamics model, we studied the evolution of helium bubbles, C15 clusters and dislocation loops produced by Fe 3+ /He + dual ion beam irradiation in reduced activation ferrite/martensite Eurofer97 steels. The model reasonably reproduced size distributions of experimentally detected helium bubbles and dislocation loops. We show that bubble evolution upon irradiation was governed by three phases in sequence: bubble nucleation dominated phase controlled by irradiation cascade, coupled phase of bubble nucleation and growth, and bubble growth dominated phase. As a first attempt, the model considers the formation of widely reported C15 clusters and develops a scheme for C15 clusters transformation into loops. We show that the loop growth driven by long-term defect migration follows a power law f(n) ~ a/n S . The increase of irradiation temperature from 603 K to 673 K promoted the growth of C15 clusters resulting in pronounced loop evolution. While at 773 K, the high flux of vacancies and low fluxes of single, di- and tri-interstitials suppressed loop nucleation and growth, leading to no loop formation confirmed by experiment. The effectiveness of the model developed in this study demonstrates its potential to be used in similar irradiation cases.

In situ transmission electron microscopy with dual ion beam irradiation and implantation

To study the helium effects and their interactions with displacement damage in irradiated materials, an in situ dual-ion beam irradiation capability with transmission electron microscopy was recently established at the IVEM-Tandem Facility at Argonne National Laboratory. Pure nickel was irradiated in situ individually with 1 MeV Kr ions for displacement damage study, 16 keV He ions for helium implantation, and simultaneously with 1 MeV Kr ions and 16 keV He ions at the rate of 1 at.% He/dpa to study the interaction of helium and displacement damage at 500 °C. Helium bubbles were formed and segregated within dislocation loops during the He implantation experiment and no bubbles were observed outside the loops. The loop size increased with increasing helium concentration. In contrast, helium bubbles were formed uniformly in the matrix when nickel was irradiated simultaneously with 1 MeV Kr ions and 16 keV He ions. It is suggested that the uniformly-distributed defect clusters formed under 1 MeV Kr ion irradiation serve as trapping sites of helium atoms resulting in homogeneous nucleation of helium bubbles under the dual-ion beam irradiation in nickel.

Integrated Modeling of Helium-Vacancy Clustering in Eurofer97 Steel Upon He+/Fe3+ Dual Ion Beam Irradiation

Here, by developing an integrated rate theory model, we studied helium-vacancy (He-V) clustering in ferritic/martensitic steel Eurofer97 under He + /Fe 3+ dual ion beam irradiation condition. Different from the known single peak concentration profile of total atomic He, the ‘solute’ He atom (interstitial He) concentration displays a bimodal distribution during irradiation due to the kick-out mechanism aided by irradiation-induced self-interstitials. We show that the kicked-out interstitial He enhances the He-V clustering rate and leads to the shift of cluster pressurization states. The He-V clustering direction is also governed by the kicked-out interstitial He.

Elucidating He-H assisted cavity evolution in alpha Cr under multiple ion beam irradiation

Dual and triple ion beam irradiations were performed on alpha-Cr using 5 MeV Fe++, 2.9 MeV He++ and/or 270 keV H+ to study the synergy of hydrogen and helium on cavity formation. Results indicate that co-implantation of helium with iron enhances cavity nucleation and co-implantation of hydrogen with iron augments cavity growth. Under triple beam irradiation, hydrogen also accelerates cavity nucleation via stabilizing initial embryos. First-principles calculations reveal that the presence of helium increases the maximum number of hydrogen atoms that can be captured by a vacancy from 6 to 9, providing an atomistic explanation to the triple beam synergy.

An in-situ electron microscopy study of dual ion-beam irradiated xenotime-type ErPO4

Rare-earth phosphates adopting the xenotime (REPO4; RE = Tb − Lu & Y, Sc) structure are proposed as a potential matrix for the confinement of minor actinides. Minor actinides (e.g., Np, Am, Cm) undergo a radioactive decay process in which high-energy recoil atom (70–100 keV) and energetic alpha particles (4.5–5.8 MeV) are produced. In this study, the impact of these energetic decay products on the structure of xenotime-type ErPO4 has been investigated via high energy dual ion-beam irradiation of ErPO4 ceramics. Au2+ (1.5 MeV) and He+ (160 keV) ions were used to simulate the effects of recoil atom and α-particles, respectively. Multiple experiments were carried out in which the Au2+ and He+ ions with varying ion-fluences (ions/cm2) and ion-flux (ions/cm2/s) were implanted sequentially (Au2+ followed by He+ irradiation) and simultaneously (Au2+ + He+ irradiation) into ErPO4 ceramics. Sequential ion-irradiation experiments have shown that the xenotime structure was amorphized by Au2+ ions at a relatively lower ion-fluence (5 × 1013 ions/cm2) in comparison to the monazite structure. Upon irradiation of the amorphous ErPO4 with He+ ions, recrystallization of the amorphous xenotime due to α-particles was not observed. However, simultaneous ion-irradiation experiments on ErPO4 showed that the amorphization of the xenotime structure was prevented upon deposition of higher amounts of electronic energy (Eelectronic) in the lamella. Likewise monazite samples, the α-healing mechanism was also experimentally demonstrated in synthetic xenotime samples.

Emulation of fast reactor irradiated T91 using dual ion beam irradiation

Dual ion irradiations using 5 MeV defocused Fe2+ ions and co-injected He2+ ions were conducted on a ferritic-martensitic steel alloy, T91, in the temperature range of 406 °C–570 °C over a damage range of 14.6–35 dpa followed by characterization of the microstructure using transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM). Dislocation loops were observed to increase in diameter and decrease in density with temperature until only network dislocations were observed at the highest temperatures of 520 °C and 570 °C. Swelling exhibited the expected bell-shaped trend with temperature following the number density of cavities, peaking at 460 °C and with a bimodal size distribution except at 520 °C and 570 °C. Nickel- and silicon-rich clusters formed under dual ion irradiations near the surface at all but the highest temperatures of 520 °C and 570 °C. Very little Cr and Si segregation was observed at lath boundaries while Ni enriched at all temperatures examined. Segregation of Cr and Ni appeared to saturate by 17 dpa, while Si enriched up to 35 dpa. The dislocation and cavity microstructures of dual ion irradiated T91 and T91 irradiated in the BOR-60 fast reactor matched extremely well using a temperature shift of +60–70 °C. However, segregation to grain boundaries and formation of nickel-silicon rich clusters were minimal in the dual ion irradiated T91 and less than that in T91 irradiated in the BOR-60 fast reactor.

Damage effects of Au&He dual ion irradiated silicon carbide

Synergistic effects of Au and He dual ion beam irradiations were investigated by comparing the damage accumulated in single crystalline silicon carbide (SiC). By implanting Au ions at 600 K and He ions at room temperature into 6H-SiC, the resulting damage was characterized using several advanced techniques, including Raman spectroscopy, Rutherford backscattering spectrometry in channeling mode (RBS/C), nano-indentation and high-resolution x-ray diffraction (HRXRD). Here, we report the complex effects induced by dual ion beam irradiations and we also investigate the isothermal annealing effects on dual ion irradiation damage. Synergy effects of Au and He dual irradiations have been observed. Irradiation damage produced by Au&He ions is larger than single ion irradiation. The displacement damage induced by heavy recoil atoms and helium atoms interact with each other, causing more serious damage. Interestingly, Au + He successive irradiation induced a larger damage level than He + Au successive irradiation, probably due to thermal annealing effect during Au irradiation. Finally, the hardness and Young’s modulus of irradiated SiC were found to be highly related with single or dual ion irradiations, implantation sequences and the corresponding fluences.

Investigation of microstructure defects in EUROFER97 under He+/Fe3+ dual ion beam irradiation

Fusion like conditions for reduced activation ferritic/martensitic steels in the first wall are simulated with single Fe3+ and He+/Fe3+ dual ion beam irradiation of EUROFER97 at the Jannus laboratory, CEA Saclay, introducing a damage of 16 dpa and a helium content up to 260 appm. The samples are irradiated at temperatures of 330 °C, 400 °C and 500 °C. The quantitative determination of size distribution and density of dislocation loops is obtained using weak-beam dark-field imaging mode. Burgers vectors of a02〈111〉 are observed for the majority of dislocation loops at irradiation temperatures of 330 °C and 400 °C. At 500 °C no dislocation loops are found. The impact of single and dual ion beam irradiation on mechanical properties is determined by means of nanoindentation. An increase in nano-hardness of up to 35% due to irradiation was measured at samples irradiated at 400 °C. A kinetic rate model is applied for the description of nucleation and evolution of helium bubbles and compared with the experimental results. Evaluating the rate model with help of TEM-results for size and density of bubbles indicates the nucleation scheme as the main source for quantitative disagreement between the model and irradiation.

3p-C-2 NiSi、CuAu合金の照射誘起析出における2重イオンビーム照射効果(*)

3p-C-2 NiSi、CuAu合金の照射誘起析出における2重イオンビーム照射効果(*)

Effects of in situ dual ion beam (He+ and D+) irradiation with simultaneous pulsed heat loading on surface morphology evolution of tungsten–tantalum alloys

The strong thermal and mechanical properties of tungsten (W) are well suited for the harsh fusion environment. However, increasing interest in using tungsten as plasma-facing components (PFCs) has revealed several key issues. These potential roadblocks necessitate more investigation of W and other alternative W based materials exposed to realistic fusion conditions. In this work, W and tungsten–tantalum (W–Ta) alloys were exposed to single (He+) and dual (He+ + D+) ion irradiations with simultaneous pulsed heat loading to elucidate PFCs response under more realistic conditions. Laser only exposer revealed significantly more damage in W–Ta samples as compared to pure W samples. This was due to the difference in the mechanical properties of the two different materials. Further erosion studies were conducted to evaluate the material degradation due to transient heat loading in both the presence and absence of He+ and/or D+ ions. We concluded that erosion of PFC materials was significantly enhanced due to the presence of ion irradiation. This is important as it demonstrates that there are key synergistic effects resulting from more realistic fusion loading conditions that need to be considered when evaluating the response of plasma facing materials.

Damage production in silicon carbide by dual ion beams irradiation

Lattice damage and evolution in single crystalline 6H-SiC under Si + He successively dual ion beams irradiation is studied by using Raman spectroscopy, high resolution X-ray diffraction (HRXRD) and nano-indentation tests. Single Si and He ion irradiations are also performed for the comparison. The results of Raman spectra reveal that the damage level increases with the fluence. A normal strain profile along the ion path is generated due to ion irradiation induced dilation of lattices, contributing mainly by interstitial related defects. Moreover, Si and He ion implantation produced different types of defects. The damage and chemical bonding states are significantly changed after He atoms implanted in Si pre-irradiated samples. Si + He dual ion irradiations increase the damage level further, resulting in changes of the damage states because of complex defects interactions. The nano-hardness of irradiated SiC is combined results of hardening effects of some kinds of defects and the breakdown of covalent-bonds. The mechanical properties present significant differences between single Si, He and Si + He successively dual ion beam irradiations, due to defects evolution during the irradiation process.

Irradiation effect of yttria-stabilized zirconia by high dose dual ion beam irradiation

Yttria-stabilized zirconia (YSZ) is irradiated with 2.0-MeV Au2+ ions and 30-keV He+ ions. Three types of He, Au, Au + He (successively) ion irradiation are performed. The maximum damage level of a sequential dual ion beam implanted sample is smaller than single Au ion implanted sample. A comparable volume swelling is found in a sequential dual ion beam irradiated sample and it is also found in a single Au ion implanted sample. Both effects can be explained by the partial reorganization of the dislocation network into weakly damaged regions in the dual ion beam implanted YSZ. A vacancy-assisted helium trapping/diffusion mechanism in the dual ion beam irradiated condition is discussed. No phase transformation or amorphization behavior happens in all types of ion irradiated YSZ.

A dual ion irradiation study of helium–dpa interactions on cavity evolution in tempered martensitic steels and nanostructured ferritic alloys

Cavity evolutions in a normalized and tempered martensitic steel (TMS) and two nanostructured ferritic alloys (NFA) under Fe3+ and He+ dual ion beam irradiations (DII) at 500°C and 650°C were characterized. The irradiation conditions encompass a wide range of displacement per atom damage (dpa), He and He/dpa. The 500°C DII produced damage and He levels of ≈10–47dpa and ≈400–2000appm, respectively. Transmission electron microscopy (TEM) showed that DII of a 8Cr TMS, at 500°C to up to 60dpa and 2100appm He, produced a moderate density of non-uniformly distributed cavities with bimodal sizes ranging from ≈1nm He bubbles to ≈20nm faceted voids, and swelling ≈0.44%. In contrast, the same irradiation conditions produced only small ≈1.3nm diameter bubbles and swelling of ≈0.05% in the NFA MA957. Similar bubble distributions were observed in MA957 and a developmental NFA DII at 650°C up to ≈80dpa and ≈3900appm He. These results demonstrate the outstanding He management capability of the oxide nano-features in the NFA. The various data trends are shown as a function of dpa, He, He/dpa and He*dpa.

Nanoindentation hardness and its extrapolation to bulk-equivalent hardness of F82H steels after single- and dual-ion beam irradiation

The irradiation hardening behavior of reduced-activation ferritic steels after single Fe-ion beam irradiation and dual-ion (Fe ion and He ion) beam irradiation experiments was investigated with nanoindentation tests. The ion-irradiation experiments were conducted at 563K with 6.4MeV Fe3+ ions up to 3dpa at a 600nm depth from the irradiated surface. Furthermore, these experiments were conducted with and without simultaneous energy-degraded 1MeV He+ ions up to 300appm. The materials used were F82H, F82H+1Ni, and F82H+2Ni to investigate the effect of Ni addition on the irradiation hardening behavior. The measured nanoindentation hardness was converted to the bulk-equivalent hardness based on a combination of the Nix–Gao model to explain the indentation size effect and the composite hardness model to explain the softer substrate effect of the nonirradiated region beyond the irradiated depth range. It is clearly shown that the Ni addition enhances the irradiation hardening of F82H. The bulk-equivalent hardness is compared with the experimentally obtained Vickers hardness of F82H steels after neutron irradiation. The effect of simultaneously implanted helium on the irradiation hardening is negligible in the investigated irradiation conditions.

Nanocavity formation and hardness increase by dual ion beam irradiation of oxide dispersion strengthened FeCrAl alloy

Open volume defects generated by ion implantation into oxide dispersion strengthened (ODS) alloy and the related hardness were investigated by positron annihilation spectroscopy and nanoindentation measurements, respectively. Synchronized dual beam implantation of Fe and He ions was performed at room temperature and at moderately enhanced temperature of 300°C. For room temperature implantation a significant hardness increase after irradiation is observed which is more distinctive in heat treated than in as-received ODS alloy. There is also a difference between the simultaneous and sequential implantation mode as the hardening effect for the simultaneously implanted ODS alloy is stronger than for sequential implantation.The comparison of hardness profiles and of the corresponding open volume profiles shows a qualitative agreement between the open volume defects generated on the nanoscopic scale and the macroscopic hardness characteristics.Open volume defects are drastically reduced for performing the simultaneous dual beam irradiation at 300°C which is a more realistic temperature under application aspects. Few remaining defects are clusters of 3–4 vacancies in connection with Y oxide nanoparticles. These defects completely disappear in a shallow layer at the surface. The results are in agreement with hardness measurements showing little hardness increase after irradiation at 300°C.Suitable characteristics of ODS alloy for nuclear applications and the close correlation between He-related open volume defects and the hardness characteristics are verified.

Dual ion beam irradiation of polymeric materials for the modification of optical properties with improved adhesion

Metallic (chromium) coating has often been applied on the surface of polymeric components, mainly to improve their appearance with a metallic luster and to protect from degradation under UV and visible light. However, the toxic nature of hexavalent chromium and delamination problems are an increasing concern in the plating industry. A similar metallic luster and the UV–visible light protection can be achieved by treating the surface of polymers by ion beams. However, a degradation by weathering including cracks, loss of glossiness, blistering, and eventual delamination have been problematic for ion beam processed polymers, particularly with a single ion beam irradiation. The main cause of adhesion failure is the abrupt change in material properties at the interface between coating and polymer or ion beam treated surface and the underlying untreated bulk polymer. In this work, therefore, a method is developed that improves adhesion by producing a graded interface by employing a dual ion beam processing. For demonstration purposes in this work, polycarbonate/acrylonitrile butadiene styrene blends were irradiated first with nitrogen ions followed by helium ions, achieving the desired metallic luster with improved adhesion. The experimental findings are explained in light of the stopping range of ions in materials and their interaction mechanisms with polymeric materials.

Void swelling in reduced activation ferritic/martensitic steels under ion-beam irradiation to high fluences

Swelling behavior of a 9Cr–2.0W–V,Ta reduced activation ferritic/martensitic steel (JLF-1) and a tungsten-enriched 9Cr–2.5W–V,Ta steel (JLS-1) under ion-beam irradiation was studied. A technique of dual-beam ion irradiation utilizing a pair of electrostatic accelerators was employed to achieve high fluence levels and a helium production rate that are relevant to fusion power reactor blanket environments. Under single ion-beam irradiation at 743 K, a cavity structure was formed only in regions of more than 40 dpa. Cavities were in the martensite lath structure. Cavities did not form at the displacement peak about 1400 nm. Under dual ion-beam irradiation at 743 K, a cavity structure was formed at dual ion-beam irradiated regions. A bi-modal size distribution of faceted voids and spherical helium bubbles of diameter up to 2 nm were observed.

Damage evolution in TiC crystals during hydrogen and helium dual-ion beam irradiation

The effect of He + ion irradiation after H + 2 ion pre-injection and of simultaneous 25 keV H + 2 and 20 keV He + ion irradiation at RT to 1423 K on the formation of bubbles in TiC crystals were examined. No amorphization occurred under these irradiation conditions. The formation and growth of bubbles produced by He + ion irradiation is not enhanced by pre-injection of hydrogen atoms at RT. Bubbles are formed but do not grow appreciably by He + ion, H + 2 pre-injection and H + 2+He + dual-ion irradiation at room temperature. Remarkable growth and coalescence occurred during irradiation at high temperature of 1423 K.