Dual-beam Irradiation Research Articles

Effect of simultaneous helium implantation on the microstructure evolution of Inconel X-750 superalloy during dual-beam irradiation

This study focuses on investigation into the effect of helium implantation on microstructure evolution in Inconel X-750 superalloy during dual-beam (Ni+/He+) irradiation. The 1 MeV Ni+ ions with the damage rate of 10−3 dpa/s as well as 15 keV He+ ions using rate of 200 appm/dpa were simultaneously employed to irradiate specimens at 400 °C to different doses. Microstructure characterization has been conducted using high-resolution analytical transmission electron microscopy (TEM). The TEM results show that simultaneous helium injection has significant influence on irradiation-induced microstructural changes. The disordering of γ′ (Ni3 (Al, Ti)) precipitates shows noticeable delay in dose level compared to mono heavy ion irradiation, which is attributed to the effect of helium on promoting the dynamic reordering process. In contrast to previous studies on single-beam ion irradiation, in which no cavities were reported even at high doses, very small (2–5 nm) cavities were detected after irradiation to 5 dpa, which proved that helium plays crucial role in cavity formation. TEM characterization also indicates that the helium implantation affects the development of dislocation loops during irradiation. Large 1/3 〈1 1 1〉 Frank loops in the size of 10–20 nm developed during irradiation at 400 °C, whereas similar big loops detected at higher irradiation temperature (500 °C) during sole ion irradiation. This implies that the effect of helium on trapping the vacancies can help to develop the interstitial Frank loops at lower irradiation temperatures.

Metal-TiO2 Composite Nanofibers for Plasmon-Driven Photocatalytic Hydrogen Generation

We present the preparation of electronspun TiO2 nanofibers co-decorated with Au and Pt nanoparticles. By using these composite nanofibers, we demonstrate the direct evidence of plasmon-enhanced hydrogen generation through through dual-beam irradiation. The Au/Pt/TiO2 nanofibers exhibit certain activity for hydrogen generation under a single irradiation at 420 nm that excites the defect/impurity states of TiO2. Significantly, when a secondary irradiation at 550 nm is introduced to simultaneously excite Au SPR, we observed 2.5 times higher activity for hydrogen generation. Further investigations by finely controlling the irradiation wavelengths reveal that the enhancement factor on hydrogen generation is directly correlated with the plasmon absorption band of the Au nanoparticles in the Au/Pt/TiO2 nanofibers. The control experiments with different sacrificial agents suggest that the hot plasmonic electrons of Au are responsible to the enhanced photocatalytic activity that can be magnified when the semiconductor is simultaneously excited. Our observation and the enhancement principle would have impact to future plasmonic nanocomposite design for efficient solar energy conversion.

Recovery effects due to the interaction between nuclear and electronic energy losses in SiC irradiated with a dual-ion beam

Single and dual-beam ion irradiations of silicon carbide (SiC) were performed to study possible Synergetic effects between Nuclear (Sn) and Electronic (Se) Energy Losses. Results obtained combining Rutherford backscattering in channeling conditions, Raman spectroscopy, and transmission electron microscopy techniques show that dual-beam irradiation of SiC induces a dramatic change in the final sample microstructure with a substantial decrease of radiation damage as compared to single-beam irradiation. Actually, a defective layer containing dislocations is formed upon dual-beam irradiation (Sn&Se), whereas single low-energy irradiation (Sn alone) or even sequential (Sn + Se) irradiations lead to full amorphization. The healing process is ascribed to the electronic excitation arising from the electronic energy loss of swift ions. These results shed new light on the long-standing puzzling problem of the existence of a possible synergy between Sn and Se in ion-irradiation experiments. This work is interesting for both fundamental understanding of the ion-solid interactions and technological applications in the nuclear industry where recovery Sn/Se effects may preserve the integrity of nuclear devices.

Ion irradiation and radiation effect characterization at the JANNUS-Saclay triple beam facility

Abstract

Thermal analysis of film photovoltaic cell subjected to dual laser beam irradiation

The concept of dual laser beam irradiation was firstly demonstrated on the photovoltaic cell, of which the temperature dependent efficiency was investigated for wireless power transmission. Then, an analytical model was established to calculate the multiple reflection–absorption of any monochromatic light in multilayer structure, and the heat generation in photovoltaic cell was interpreted. Finally, the finite element analysis was used to simulate the temperature pattern of the photovoltaic cell subjected to laser irradiation. The spatial-temporal characteristic of the temperature field was obtained for improving the system in future.

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.

Study of helium migration in nuclear materials at Jannus–Saclay

The Jannus multi-ion beam facility at Saclay allows performing as well single, dual or triple beam irradiation, ion implantation and ion beam analysis. This versatility is due on one hand to the large range of ion beams available from the three coupled accelerators and on the other hand to the possibility to use several dedicated or multi-purpose vacuum chambers. It is thus possible to investigate the radiation tolerance of inorganic or organic materials and the specific effect of an atomic species of nuclear interest like hydrogen, helium, fission or transmutation products under thermal treatment or ion irradiation. This paper discusses the capabilities offered by the Jannus facility to study helium mobility in advanced nuclear materials.

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.

<i>In Situ</i> TEM Concurrent and Successive Au Self-Ion Irradiation and He Implantation

The development of advanced computational methods used for predicting performance lifetimes of materials exposed to harsh radiation environments are highly dependent on fundamental understanding of solid-radiation interactions that occur within metal components. In this work, we present successive and concurrent in situ TEM dual-beam self-ion irradiation of 2.8MeV Au 4+ and implantation of 10keV He 1+ , utilizing a new facility at Sandia National Laboratories. These experiments, using a model material system, provide direct real-time insight into initial interactions of displacement damage and fission products that simulate damage from neutron exposure. In successive irradiation, extensive dislocation loop and stacking fault tetrahedra damage was formed and could be associated with individual ion strikes, but no evidence of cavity formation was observed. In contrast, concurrent irradiation to the same dose resulted in the onset of cavity formation at the site of a heavy-ion strike. This direct real-time observation provides insight into the complex interplay between the helium and vacancy dynamics. [doi:10.2320/matertrans.MD201316]

Impact of He and Cr on defect accumulation in ion-irradiated ultrahigh-purity Fe(Cr) alloys

The effect of He on the primary damage induced by irradiation in ultrahigh-purity (UHP) Fe and Fe(Cr) alloys was investigated by transmission electron microscopy (TEM). Materials were irradiated at room temperature in situ by TEM in a microscope coupled to two ion accelerators, simultaneously providing 500keV Fe+ and 10keV He+ ions. Single Fe ion and dual Fe and He ion beam experiments were performed up to a dose of 1dpa and to a He content of up to 1000appm. Defects appear in the form of nanometric black dots with sizes between 1 and 5nm. Defocused images reveal a dense population of sub-nanometric cavities after both single-beam and dual-beam irradiation. In Fe(Cr) alloys, the number densities of visible black dot defects still resolved in TEM are significantly higher after single than after dual-beam irradiation. In UHP Fe, conversely, the presence of He strongly increases the defect number density. The presence of He changes a a0〈100〉 dominated defect population to a 1/2a0〈111〉 dominated one in all materials, and the more so in UHP Fe. It appears that Cr increases the number of visible defects relative to UHP Fe. The dependence with increasing Cr content is weak, however, showing only a slight decrease in the number densities. The decrease in the density of visible a0〈100〉 loops and increase in the visible 1/2a0〈111〉 loops in all materials when He is present supports the idea that visible a0〈100〉 loops are formed by the interaction between mobile 1/2a0〈111〉 loops, as the latter would be immobilized by He already at sub-microscopic sizes. It is concluded that the primary loop population is dominated by 1/2a0〈111〉 loops.

Development of dual-beam system using an electrostatic accelerator for in-situ observation of swift heavy ion irradiation effects on materials

We have developed the dual beam system which accelerates two kinds of ion beams simultaneously especially for real-time ion beam analysis. We have also developed the alternating beam system which can efficiently change beam species in a short time in order to realize efficient ion beam analysis in a limited beam time. The acceleration of the dual beam is performed by the 20UR Pelletron™ tandem accelerator in which an ECR ion source is mounted at the high voltage terminal [1,2]. The multi-charged ions of two or more elements can be simultaneously generated from the ECR ion source, so dual-beam irradiation is achieved by accelerating ions with the same charge to mass ratio (for example, 132Xe11+ and 12C+). It enables us to make a real-time beam analysis such as Rutherford Back Scattering (RBS) method, while a target is irradiated with swift heavy ions. For the quick change of the accelerating ion beam, the program of automatic setting of the optical parameter of the accelerator has been developed. The switchover time for changing the ion beam is about 5min. These developments have been applied to the study on the ion beam mixing caused by high-density electronic excitation induced by swift heavy ions.

Combined effects of nuclear and electronic energy losses in solids irradiated with a dual-ion beam

Single and dual-beam irradiations of oxide (c-ZrO2, MgO, Gd2Ti2O7) and carbide (SiC) single crystals were performed to study combined effects of nuclear (Sn) and electronic (Se) energy losses. Rutherford backscattering experiments in channeling conditions show that the Sn/Se cooperation induces a strong decrease of the irradiation-induced damage in SiC and MgO and almost no effects in c-ZrO2 and Gd2Ti2O7. The healing process is ascribed to electronic excitations arising from the electronic energy loss of swift ions. These results present a strong interest for both fundamental understanding of the ion-solid interactions and technological applications in the nuclear industry where expected cooperative Sn/Se effects may lead to the preservation of the integrity of nuclear devices.

Dislocation loop formation under various irradiations of laser and/or electron beams

A high-voltage electron microscope (HVEM) equipped with a laser head (laser-HVEM) was developed at Hokkaido University and is used to investigate the surface modification of semiconductors and the behaviour of lattice point defects in metals under various irradiations of laser (photon) and/or electron beams. In the present study, the annealing effect of pulsed laser irradiation on a face-centred-cubic metal was experimentally investigated and theoretically calculated. The systematic assessment of dislocation loop evolution under laser-electron sequential irradiation and laser-electron dual-beam irradiation was performed. Our results show that the rapid heating and quenching that occurred during pulsed laser irradiation caused vacancies to be introduced at the surface of the specimen and to diffuse to the interior, which led to the formation and growth of vacancy-type (V-type) dislocation loops. These loops gradually shrank and finally disappeared during the subsequent electron irradiation of the sample. During laser-electron simultaneous dual-beam irradiation, the type of loop formed, interstitial-type (I-type) or V-type loops, is determined by the relative intensities of the laser beam and electron beam, which indicates that the loop type can be controlled by changing the relative intensities of the beams. Accordingly, models of dislocation loop formation during various irradiations were proposed. The newly developed laser-HVEM instrument is expected to be employed in the exploration of mechanisms in material science, as well as in other scientific fields.

The Irradiation Effect of a Simultaneous Laser and Electron Dual-beam on Void Formation

Randomly distributed lattice point defects such as supersaturated vacancies (SVs) and Frenkel-pairs (FPs, an interstitial and a vacancy) can be simultaneously introduced into the crystal by energetic beam irradiation in outer space and/or nuclear reactors, but their behavior has not been fully understood. Using a high-voltage electron microscope equipped with a laser (laser-HVEM), we show the striking effects of simultaneous laser-electron (photon-electron) dual-beam irradiation on void formation. Our results reveal that during laser-electron sequential irradiation, pre-laser irradiation enhanced void nucleation and subsequent electron irradiation enhanced void growth. However, the laser-electron dual-beam irradiation was analyzed to depress void swelling remarkably because the recombination of SVs and interstitials was enhanced. The results provide insight into the mechanism underlying the dual-beam radiation-induced depression of void swelling in solids.

Radiation effects in nuclear materials: Role of nuclear and electronic energy losses and their synergy

Ceramic oxides and carbides are promising matrices for the immobilization and/or transmutation of nuclear wastes, cladding materials for gas-cooled fission reactors and structural components for fusion reactors. For these applications there is a need of fundamental data concerning the behavior of nuclear ceramics upon irradiation. This article is focused on the presentation of a few remarkable examples regarding ion-beam modifications of nuclear ceramics with an emphasis on the mechanisms leading to damage creation and phase transformations. Results obtained by combining advanced techniques (Rutherford backscattering spectrometry and channeling, X-ray diffraction, transmission electron microscopy, Raman spectroscopy) concern irradiations in a broad energy range (from keV to GeV) with the aim of exploring both nuclear collision (Sn) and electronic excitation (Se) regimes. Finally, the daunting challenge of the demonstration of the existence of synergistic effects between Sn and Se is tackled by discussing the healing due to intense electronic energy deposition (SHIBIEC) and by reporting results recently obtained in dual-beam irradiation (DBI) experiments.

Ion-Irradiation Hardening of Brazed Joints of Tungsten and Oxide Dispersion Strengthened (ODS) Ferritic Steel

Irradiation hardening and microstructural change of the brazed-joint of W and oxide dispersion strengthened ferritic steel (ODS-FS) was investigated by nano-indentation hardness test and transmission electron microscopy after ion irradiation with 6.4MeV Fe 3+ ions at 500°C up to 10dpa. Dual-beam irradiation of Fe 3+ ions and energy-degraded 1MeV He + ion was also carried out. A considerable irradiation hardening occurred in the W base metal where dislocation loops and nano-scaled voids or He-bubbles were observed. Dual-beam irradiation enhanced the hardening. No significant hardening was observed in ODS-FS. The hardness of insert material was reduced after irradiation, which is due to the recovery of dislocations generated during joining process. [doi:10.2320/matertrans.MG201212] (Received October 19, 2012; Accepted December 17, 2012; Published February 16, 2013)

A Dual-Beam Irradiation Facility for a Novel Hybrid Cancer Therapy

In this paper we present the main ideas and discuss both the feasibility and the conceptual design of a novel hybrid technique and equipment for an experimental cancer therapy based on the simultaneous and/or sequential application of two beams, namely a beam of neutrons and a CW (continuous wave) or intermittent sub-terahertz wave beam produced by a gyrotron for treatment of cancerous tumors. The main simulation tools for the development of the computer aided design (CAD) of the prospective experimental facility for clinical trials and study of such new medical technology are briefly reviewed. Some tasks for a further continuation of this feasibility analysis are formulated as well.

Modifications of optical properties of PC/ABS by dual ions beam irradiation

Polycarbonate (PC)/acrylonitrile butadien styrene (ABS) blends used in the inner parts of automobiles require a glossy and metallic colored optical property. Such a surface can be produced by ion beam irradiation, but the surface treated by a single ion species irradiation tends to be degraded upon a long term exposure under UV and visible lights, which includes the loss of glossiness and the delamination of the irradiated layer. Such degradations can be prevented or greatly reduced by a combined irradiation of heavy and light ions such as N and He ions. This may be attributable to a graded interface between the irradiation affected layer and the base materials by overlapping penetration depths of the heavy and light ions. This work is motivated by an effort to substitute the conventional Cr plating process with the ion beam process in the automobile industry.

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.

Effect of H and He irradiation on cavity formation and blistering in ceramics

Single- or poly-crystalline specimens of SiC, Si3N4, MgO, Al2O3 and MgAl2O4 were implanted with 0.4–1MeV H+ or He+ ion beams at room temperature and 650°C up to fluences of ∼1×1022/m2. This produced peak implanted gas and displacement damage levels as high as ∼50at.% and 34 displacements per atom (dpa). The specimens were subsequently examined optically, and in cross-section using transmission electron microscopy. Subsurface blistering occurred for specimens irradiated to H or He fluences greater than about 3×1021/m2 (∼15at.% peak implanted gas concentration), and surface exfoliation occurred for fluences above ∼1×1022/m2 (∼40at.% implanted gas). Both helium and hydrogen had comparable effectiveness for inducing blistering and exfoliation on an atomic basis. The threshold blistering and exfoliation fluences for both ions were weakly dependent on temperature between 25 and 650°C. Both H and He were found to be very effective in inducing matrix cavity formation, due to their low solubility in these ceramics. The implanted gas concentrations that resulted in visible cavity formation generally ranged from 1 to 5at.%. Visible cavity formation was readily induced during room temperature irradiation despite the limited vacancy mobility in these ceramics at room temperature. Three general types of cavity morphologies were observed: isolated cavities, clusters of small cavities (typically associated with dislocation loops), and two-dimensional platelets. Cavity formation was observed to initiate at the periphery of dislocation loops in some cases. During elevated temperature irradiation, cavity formation was often observed to be preferentially associated with certain low-index habit planes, particularly if the habit plane was oriented nearly parallel to the irradiated surface: (0001) and {11¯00} for Al2O3, (0001) for α–SiC, {001} and {110} for MgO, and {110} and {111} for MgAl2O4. The bubble formation and blistering behavior of the ceramics was similar to that observed in other studies of metals irradiated at comparable homologous temperatures. Ionization-induced diffusion effects associated with dual-beam light ion irradiation appeared to exert only a weak effect on cavity and dislocation loop growth compared to the single ion irradiation conditions.