MeV 4He Ions Research Articles

Irradiation effects on copper oxide superconductors including high-entropy REBCO(HE-REBCO)

Polycrystalline specimens of copper oxide superconductors YBa2Cu3O7-δ(YBCO), Y0.39Sm0.30Eu0.31Ba2Cu3O7-δ(ME-REBCO), Y0.18La0.24Nd0.14Sm0.14Eu0.15Gd0.15Ba2Cu3O7-δ (HE-REBCO) were irradiated with 1 MeV-He ions at room temperature. Magnetization measurement using superconducting quantum interference device (SQUID) and microstructure observation using transmission electron microscope (TEM) were conducted before and after irradiation. The improvement of properties in HE-REBCO and degradations in YBCO, ME-REBCO were suggested by SQUID measurement. HE-REBCO had smaller irradiation defects and volume fractions although disappearance of twin boundaries due to tetragonal transition occurred in peak-damage area as well as YBCO. These defects work as optimal flux pinning centers leading to improve properties in HEREBCO.

Helium irradiation induced microstructural damages and mechanical response of Al2O3-ZrO2-SiC composites

Ceramic composites are promising candidates as structural materials for future fission and fusion reactors. In present work, Al2O3-ZrO2-SiC ternary ceramic composites were irradiated with 2.0 MeV He-ions at 300 and 800 ℃. Grazing incidence X-ray diffraction results confirmed that there was irradiation induced shift and broadening of diffraction peaks, but no amorphization of Al2O3-ZrO2-SiC composite were observed up to fluence of 1.72 × 1018 ions/cm2. Transmission electron microscopy observations showed that throughout the entire irradiation region, nano-sized helium bubbles are mostly distributed in Al2O3 grains and partly in ZrO2 grains, while no detectable bubbles are observed in SiC grains. No obvious agglomeration of bubbles was found at grain/phase boundaries. By using nanoindentation technique, slight hardening or softening was confirmed for the samples irradiated at 300 and 800 ℃ respectively. The absence of amorphization and surface exfoliation indicating the Al2O3-ZrO2-SiC composite exhibits remarkable resistance to He-ions irradiation.

Scattering processes of helium nuclides on nuclei 28Si

Experimental data on elastic and inelastic scattering of 50.5 MeV α-particles and 60 MeV 3He ions by 28Si nuclei were analyzed within the framework of the standard optical model of the nucleus, in which the effect of inelastic channels is taken into account by the phenomenological introduction of an imaginary absorbing part into the interaction potential between colliding nuclei. The optimal values of the internuclear interaction potential obtained as a result of the theoretical analysis were used to study the cross sections for inelastic scattering of helium ions with the excitation of the 1.78 and 4.61 MeV states of the nucleus under study. From the analysis by the channel coupling method, where the calculation was performed taking into account both elastic and inelastic channels, the value of the quadrupole deformation parameter for α-particles β2 = 0.37 and for 3He ions β2 = 0.49 was determined. Optimal agreement between the calculated values and experimental data was achieved by varying the parameters V, W, and β2. The found parameters agree with the previously obtained values from the scattering of protons, deuterons and α-particles. Taking into account only the quadrupole deformation extracted from the 0+ – 2+ bond, a good description of all three experimental data on elastic and inelastic scattering of the cross sections was achieved.

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

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

Excitation of elliptical and toroidal Alfvén eigenmodes by 3He-ions of the MeV-energy range in hydrogen-rich JET plasmas

Elliptical (EAE) and toroidal Alfvén eigenmode (TAE) instabilities have been observed in hydrogen-rich JET discharges of the D-(3He)-H ion cyclotron resonance heating (ICRH) scenario, which is characterized by strong absorption of radio frequency waves at very low concentrations of the resonant 3He-ions. In the experiments, core localized TAEs with a frequency fTAE ≈ 280 kHz with mode numbers n= 3, 4, 5 and 6 were detected. Following the phase with TAE excitation, EAE modes at higher frequencies fEAE ≈ 550–580 kHz with mode numbers n = 1, 3, 5 were seen. These high frequency modes indicate that a MeV range population of trapped energetic ions was present in the plasma. The experimental evidence of existence of the MeV-energy 3He-ions able to excite the AEs is provided by neutron and gamma-ray diagnostics as well as fast ion loss measurements. The ICRH modelling code calculations confirm the acceleration of 3He-ions to MeV energies. The magnetohydrodynamic (MHD) analysis results are consistent with the experimental data showing that the MeV 3He ions satisfy to resonant conditions interacting with TAE and EAE modes. This experiment demonstrates the efficient plasma heating mimicking the conditions representative for the ITER plasmas and contribute to the understanding of fast-ion interaction with MHD wave modes.

Investigation the optical band gap of self-assembled monolayer of tin selenide synthesized by chemical solution deposition

In this study, the fabrication and characterization of the thin layer of SnSe self-assembled were investigated by control of the preparation parameters. SnSe binary nanoparticles semiconductor were prepared using chemical solution deposition technique. The deposition time and temperature and the solution concentration that govern the evolution of the configuration films and optical band gap in chemical deposition processes was explored. We benefited from Rutherford Backscattering Spectrometry with 2 MeV 4He ions to determine the depth profile of the elements in tin selenide. UV–visible spectroscopy was used for energy band gap determination. Also, the nanostructured and the morphologies of the thin films were analyzed by scanning electron microscopy. We were able to achieve a broad optical band gap ranging from 5.82 to 3.06 eV of SnSe thin films appropriate for solar cell and photovoltaic applications.

4He irradiation of zircon, ZrSiO4, using a micro-patterned, Si-based energy filter

The quantitative evaluation of alpha-particle damage in the mineral zircon, ZrSiO4, using 4He irradiation experiments is difficult because the vast majority of atomic knock-ons in the target are concentrated in a narrow depth range near the ends of the He-ion trajectories. Here we present a new concept to overcome this problem, namely, tailoring the depth profile of damage by means of a micromechanically fabricated “energy filter”. Lamellae of 1.5 μm thickness, prepared from ZrSiO4 using the focused-ion-beam technique, were subjected to irradiation with 8.8 MeV 4He ions. Five irradiations with ion fluences in the range 2.5 × 1015–1 × 1017 cm−2 have resulted in mild to severe damage, as monitored by the broadening and downshift of SiO4-stretching Raman bands. Our results may provide a means for quantifying the contribution of alpha particles to the total self-irradiation damage in zircon.

ToF-SIMS and ERDA study of hydrogen and deuterium in nickel-base alloys oxidized in water

The depth profiling of hydrogen and deuterium in polycrystalline and monocrystalline Nickel-base alloys (Ni-16Cr-8Fe, wt%) was performed by Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and Elastic Recoil Detection Analysis (ERDA) after oxidation in simulated primary medium conditions containing 9 at.% D2O. The use of deuterium isotopic tracer in ToF-SIMS has demonstrated the presence of deuterium in the oxide layer for oxidation times of 300 min and 100 h. The quantities of deuterium were determined by ERDA using a 2 MeV 4He ion beam. Finally, the penetration coefficient α was calculated, and ranged from 0.01 to 0.04.

Formation of dislocations in LiF irradiated with 3He and 4He ions

Influence of the irradiation with 13.5 MeV 3He and 5 MeV 4He ions on the micro-structure and mechanical properties of LiF single crystals was studied. The depth profiles of nanoindentation, dislocation mobility, selective chemical etching and photoluminescence served for the characterization of damage. Strong ion-induced increase of hardness and decrease in dislocation mobility at the stage of track overlapping due to accumulation of dislocations and other extended defects was observed. At high fluences (1015 ions/cm2) the hardness saturates at about 3.5 GPa (twofold increase in comparison to a virgin crystal) thus confirming high efficiency of light projectiles in modifications of structure and properties. The effects of ion-induced increase of hardness and decrease of dislocation mobility are observed also beyond the ion range and possible mechanisms of such damage are discussed.

Erosion and deposition in the JET divertor during the second ITER-like wall campaign

Erosion of plasma-facing materials and successive transport and redeposition of eroded material are crucial processes determining the lifetime of plasma-facing components and the trapped tritium inventory in redeposited material layers. Erosion and deposition in the JET divertor were studied during the second JET ITER-like wall campaign ILW-2 in 2013–2014 by using a poloidal row of specially prepared divertor marker tiles including the tungsten bulk tile 5. The marker tiles were analyzed using elastic backscattering with 3–4.5 MeV incident protons and nuclear reaction analysis using 0.8–4.5 MeV 3He ions before and after the campaign. The erosion/deposition pattern observed during ILW-2 is qualitatively comparable to the first campaign ILW-1 in 2011–2012: deposits consist mainly of beryllium with 5–20 at.% of carbon and oxygen and small amounts of Ni and W. The highest deposition with deposited layer thicknesses up to 30 μm per campaign is still observed on the upper and horizontal parts of the inner divertor. Outer divertor tiles 5, 6, 7 and 8 are net W erosion areas. The observed D inventory is roughly comparable to the inventory observed during ILW-1. The results obtained during ILW-2 therefore confirm the positive results observed in ILW-1 with respect to reduced material deposition and hydrogen isotopes retention in the divertor.

Studying the ejection of light charged particles induced by 50 MeV 3He ions upon interacting with a 112Sn nucleus

Experimental double-differential and integral spectra of (3He, xp), (3He, xd), (3He, xt), (3He, x3He) and (3He, xα) reactions on 112Sn nuclei induced by 50 MeV 3He ions are presented. Theoretical calculations of the experimental inclusive spectra of the reactions are performed using the exciton model of preequilibrium decay. The corresponding mechanisms of reactions are determined. The experimental results can be used to develop new approaches in the theory of nuclear reactions, and to design safe and wasteless hybrid nuclear power plants.

Track-average LET of secondary electrons generated in LiF:Mg,Ti and liquid water by 20–300 kV x-ray, 137Cs and 60Co beams

Electrons generated in matter by photons could be a fundamental basis for an adequate analysis of radiation effects and damage. We have studied separately the ‘primary electrons’ generated directly by photons from the ‘secondary electrons’ (SE) produced by electron–electron interactions. In this work, track-average linear energy transfer, , of SE in LiF:Mg,Ti and liquid water produced by twelve photon energy beams from 20 kV x-ray to 60Co gamma rays have been investigated using the EGSnrc Monte Carlo Code. The exposure of LiF:Mg,Ti in different phantom materials has been considered. Depending on the photon energy, SE represent 40%–90% of the total electron fluence (TEF) between 1 keV and 10 keV, being higher when the photon energy increases. Independent of the medium, versus mean photon energy displays a local minimum at around 40 keV, followed by a local maximum at ~80 keV–100 keV. The of SE generated by the x-ray beams are of order of 11 keV µm−1 to 19 keV µm−1 in LiF:Mg,Ti and 5 keV µm−1 to 9 keV µm−1 in liquid water which represent 3–5 times those produced by 60Co gamma rays in both media. These values were considerably greater than those of TEF, by factors of 3–8. Furthermore, of SE generated in liquid water by 20 kV–200 kV x-rays are similar to those of 76 MeV–120 MeV 3He ions. Contrary to the TEF, where were independent of the phantom material, at low photon energies of SE was found to be sensitive to the surrounding medium showing higher values within the phantom than in air. This result, which agrees with published experimental results, implies the importance of the SE ionization density for an understanding of dosimeter response induced by photon beams.

Charged particle spectra upon interaction between 50.5 MeV 3He ions and 27Al nuclei

The inclusive spectra of light charged particles formed upon interaction between 50.5 MeV 3Не ions and 27Al nuclei are studied. The experimental results are analyzed using the exciton model of nucleus decay, with the PRECO-2006 code describing the transition of an excited system to equilibrium state. The contributions from composite, pre-equilibrium, and direct processes of integral cross section formation are calculated. Determination of these mechanisms is of interest to both fundamental nuclear physics and different areas of application, particularly the nuclear transmutation of long-lived radioactive contamination.

XRD and RBS studies of quasi-amorphous zinc oxide layers produced by Atomic Layer Deposition

Although zinc oxide has been widely investigated for many important applications such as laser diodes, photovoltaics, and sensors, some basic properties of this material have not been established up to now. One of these are stopping power values which are crucial for the Rutherford Backscattering Spectrometry analysis. For this kind of measurements, amorphous materials should be used.In this paper we show the results of stopping power measurements for ZnO films grown by Atomic Layer Deposition. The films were grown on a silicon (100) substrate and parameters of the growth were chosen in a way that prevents crystallization of ZnO films. A series of ZnO films with thickness between 20 and 160nm have been investigated. Extended film characterization has proven that the obtained nanopolycrystalline ZnO films can be considered as truly amorphous with respect to ion beam applications.ZnO films have been used for precise stopping power measurement of MeV He-ions in the energy range from 200 to 5000keV. These results provide indispensable data for ion beam modification and analysis of ZnO.

Radiolytic hydrogen generation at silicon carbide–water interfaces

While many of the proposed uses of SiC in the nuclear industry involve systems that are assumed to be dry, almost all materials have dissociated chemisorbed water associated with their surface, which can undergo chemistry in radiation fields. Silicon carbide α-phase and β-phase nanoparticles with water were irradiated with γ-rays and 5 MeV 4He ions followed by the determination of the production of molecular hydrogen, H2, and characterization of changes in the particle surface. The yields of H2 from SiC–water slurries were always greater than expected from a simple mixture rule indicating that the presence of SiC was influencing the production of H2 from water, probably through an energy transfer from the solid to liquid phase. Although the increase in H2 yields was modest, a decrease in the water mass percentage led to an increase in H2 yields, especially for very low amounts of water. Surface analysis techniques included diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), nitrogen absorption with the Brunauer – Emmett – Teller (BET) methodology for surface area determination, X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Little change in the SiC surface was observed following radiolysis except for some conversion of β-phase SiC to the α-phase and the formation of SiO2 with He ion radiolysis.

Gamma and He Ion Radiolysis of Copper Oxides

Two copper oxides, cuprous and cupric oxide, were characterized using a variety of surface techniques including scanning electron microscopy, temperature-programmed desorption, diffuse reflectance infrared Fourier transform spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction to analyze changes in the oxide surface following irradiation with γ-rays and 5 MeV 4He ions. The radiation chemical yield for molecular hydrogen was also measured for copper oxide powders with adsorbed water as well as with slurries containing various amounts of water. The yield of hydrogen was found to be slightly greater than the yield expected for bulk water radiolysis, indicating some small radiation chemical effect of the oxide surface on water. X-ray photoelectron spectroscopy indicated that the amount of OH groups present on the cuprous oxide surface decreased as a result of the irradiation while the cupric oxide surface had an increase in OH groups on the surface. This result suggests that the mechanism for the formation of H2 differs based on the surface composition and structure of the oxide.

Study of Proton and 3He Induced Reactions on 235U at Low Energies

Highly enriched 235U targets were irradiated with 6.5−16.1 MeV protons and 20.4−42.0 MeV 3He ions. The irradiated targets were measured with γ and α spectrometric methods to identify and quantify the produced reaction products. After primary activity measurements the targets were dissolved, and interesting Pu and Np reaction products were chemically separated from the target material, and measured for activity again. From the activity results it was possible to calculate the reaction cross sections for differently produced nuclides. The data obtained from the experiment resulted in earlier unknown excitation functions on proton and 3He induced nuclear reactions on 235U.

Vacancy type defect formation in irradiated α-iron investigated by positron beam Doppler broadening technique

Vacancy type defects formations have been investigated in virgin and irradiated a-iron samples using slow positron beam Doppler broadening technique. Mono-vacancies and vacancy clusters are observed in 1.5 MeV 4He ions irradiated Fe samples at varying fluences from 1×1013 to 1×1017 cm−2. In the 1.2 MeV Yttrium ions implantation at low fluence 1×1014 cm−2 vacancy clusters with higher concentration and larger size are formed. In this sample, vacancy defects are detected deeper than predicted by SRIM calculation due to channelling.

Charge Collection in n-SOI Planar Microdosimeters

An n-SOI microdosimeter which has been proposed as a device for predicting the occurrence of single event effects in semiconductor electronics in the high-energy, mixed heavy ion space radiation environment has been investigated to better understand the charge collection geometry and charge collection mechanisms. Ion beam induced charge collection studies using 20 MeV 12C ions, 5.5 MeV 4He ions, and 2 MeV H ions were carried out, and the effects of different bias conditions, angles of ion incidence, and coincidence analysis were observed to understand the sensitive volume geometry. The energy response of the n-SOI microdosimeter has been observed to exhibit an over-response of 56%, 113%, and 23% for the above ions compared to expected energy depositions calculated using SRIM 2008. No relationship between particle LET AU: Please provide spelling for “LET” and the enhance energy response was apparent. A comparison of experimentally measured and simulated spectra suggest a cylindrical charge collection geometry despite the physical rectangular parallelepiped geometry of the p-i-n diode. This was supported by observing the response of the microdosimeter to ions at oblique ion incidence. A simplified model of diffusion charge collection found that diffusion charge collection contributes to the low-energy tail observed in experimental spectra, but does not account for the observed enhanced energy response. This supports the current theory that the enhanced energy response is a result of a displacement current produced when charge carriers in the substrate induce charge in the SOI layer due to the parasitic capacitance of the buried SiO2 insulating layer.

Hydrogen trapping in 3He-irradiated Fe

The characteristics of irradiation-induced hydrogen (deuterium) traps in pure Fe were investigated for quantitative evaluation of tritium retention in fusion reactor components. The deuterium depth profiles of an Fe disk sample exposed to deuterium plasma were observed by means of nuclear reaction analysis (NRA) before and after irradiation with 0.8MeV or 1.3MeV 3He ions. Irradiation generated a number of traps, and deuterium retention was drastically increased subsequent to irradiation. Steady-state deuterium concentration in the trap and the solution sites were obtained by continuously charging the sample with deuterium during the NRA. Based on these values, the trapping energy, which is the enthalpy difference between the two sites, was estimated to be 0.38eV. The number ratio of the trap to atomic displacement was 0.013. Some of the traps were annihilated around 523K. The annihilation temperature, the trapping energy, and the equilibrium constant suggest that the trap is a dislocation loop introduced by the irradiation. It is deduced that the tritium inventory in the Fe components of a reactor should be drastically increased by neutron irradiation due to the formation of traps, but may be significantly reduced by high temperature operation of the components.