Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms最新文献

Nuclear waste storage materials are inevitable in nuclear industry for preventing the release of radioactive waste products. Glassy carbon has been considered being beneficial to be used in the dry cask needed for nuclear waste storage. Thus, we studied the migration of ruthenium implanted in glassy carbon upon annealing. Our investigations show that ruthenium implantation caused defects in the glassy carbon structure, with more defects observed in the room temperature as-implanted samples compared to those implanted at 200 °C. Annealing the as-implanted samples from 500 to 800 °C showed no significant change in the ruthenium depth profiles, indicating the non-diffusivity of ruthenium in glassy carbon at these temperatures. However, annealing at higher temperatures (from 900 and 1300 °C) resulted in an increase in the maximum depth profile peaks, accompanied by a shift towards the surface, and a decrease in the full-width at half-maximum. These changes indicate the aggregation of ruthenium atoms in the near-surface region. Additionally, more ruthenium aggregation was observed in room temperature implanted samples compared to those implanted at 200 °C. This difference is attributed to the higher concentration of defects in room temperature implanted samples, which promotes ruthenium aggregation. Moreover, the migration and aggregation of ruthenium in the near-surface region contributed to an increase in the surface roughness of the glassy carbon.

Zirconium-niobium alloy is widely used in pressurized-water-reactors (PWRs) due to its excellent performance. Herein, the effects of Nb on the formation, migration, and clustering of vacancies/interstitials in Zr-Nb solid solution are studied using first-principles calculations. Nb lowers the formation energy of Zr interstitials and significantly enhances the anisotropy of Zr interstitial migration in the vicinity. Nb shows thermodynamic attraction to vacancies while causes a significant decrease in the vacancy migration barrier, which enhances the mobility of vacancies around Nb. In addition, we find that the vacancy-mediated Nb migration is anisotropic, and these Nb-vacancy interactions play an important role in revealing the mechanism of the precipitation of needle-like Nb phases under high irradiation fluences. Finally, we verified the anisotropic attraction of Nb to vacancies with CI-NEB method. These findings will contribute to a more in-depth comprehension on the mechanism how Nb influences the evolution process of irradiation defects in Zr-Nb alloys.

The characteristics of laser-produced metal hydride plasmas have been investigated in this work. The charge state and velocity of ions were determined by employing a time-of-flight technique in conjunction with an electrostatic deflection method. The ion velocities were found to be supersonic with values in the range of 10⁴ to 10⁵ m/s. The proportion of hydrogen ions was found to be lower than that of titanium ions. The ion emission behavior was studied by using a Faraday cup. When the total integrated space was taken into account, the ns pulsed laser was capable of producing hydrogen ion currents greater than one hundred mA. In order to understand the plasma generation process, we performed a comparative analysis between laser-generated plasma and arc plasma, and also investigated the effect of laser power density on the composition and velocity of the ions, the ablation properties of metal hydrides, and the maintainability of hydrogen ion emission.

The deuteron-boron fusion reaction produces many different charged particles. Data on the reactions cross-sections differ among different authors, so obtaining experimental data is still relevant. Measurements of the reactions cross-section were carried out at the accelerator-based neutron source VITA at Budker Institute of Nuclear Physics (Novosibirsk, Russia) using an α-spectrometer. The ¹⁰B(d,α₀)⁸Be, ¹⁰B(d,α₁)⁸Be*, ¹⁰B(d,p₂)⁹Be*, ¹¹B(d,α₀)⁹Be, and ¹¹B(d,α₂)⁹Be* reactions cross-sections at the deuteron energies up to 2.2 MeV have been measured. The obtained data are presented in tabular form.

Energy loss measurements for heavy ions (²⁸Ni,²⁴Cr and ²²Ti) crossing thin polymeric foil such as PVC and Mylar in the energy range 0.1–0.3 MeV/n have been carried out utilizing the 6MV Tandem accelerator facility at iThemba-labs in Johannesburg (South Africa). These measurements deduced experimental stopping force data have been compared with those calculated using Lindhard, Scharff and Schiott formulation (LSS) and SRIM-2013 predictions. A large significant deviation has been observed between experimental values and those calculated by LSS formula. Based on physical postulate, we have developed a reasonably simple semi-empirical formula that takes in to account a mean residual projectile charge $\overline{Z1}$ and suitable ${\xi }_e$ factor which depend on Z1 and Z2. This new modified LSS formula has been tested and the calculated stopping force values generated by this formula are in close agreement with the measured ones.

Due to their some beneficial properties, molybdenum-based alloys, such as Mo-Re alloys, are recognized as potential structural materials for nuclear power reactors. Irradiation induced precipitation of rhenium (Re) atoms causes hardening and embrittlement of Mo-Re alloys, restricting their application. The interaction of rhenium (Re) atoms with point defects (PDs), as well as the diffusion behavior of Re atoms in BCC-Mo (Body Center Cubic-molybdenum), were investigated using first-principles methods. The results revealed that Re atoms exhibited high binding energies with both vacancy (Vac) and interstitial dumbbells. Furthermore, the binding energies increased with the number of Re atoms. The binding energies of Re with self-interstitial dumbbell (SIA, ie., Mo-Mo) and mixed interstitial dumbbell (Mo-Re) were quite close to. Due to the high exchange barrier between Vac and Re, the diffusion of rhenium through the vacancy-drag mechanism was difficult. Due to the low migration and rotation barrier of Mo-Re mixed interstitial dumbbell, the diffusion of Re atoms in Mo was dominated by the interstitial-mediated mechanism. From the perspective of diffusion dynamics, only interstitial dumbbells can promote the aggregation of Re atoms. By comparing the binding energy of interstitial dumbbell with interstitial dumbbell and interstitial dumbbell with Re atoms, pairs of Mo-Re interstitial dumbbell was suggested to be the nucleation sites to attract more interstitial dumbbells, thereby promoting the precipitation of Re clusters. It was because they had high binding energy and were difficult to decompose once combined.

Multimodal microscopic imaging based on ion beam irradiation is a useful approach for conducting biological research due to its: accurate positional correlation between different types of images and potential for super resolution beyond the diffraction limit of light. We are currently developing such an imaging system that can simultaneously acquire elemental maps by particle-induced X-ray emission (PIXE) and ion beam-induced fluorescence (IBIF) microscopic imaging employing a sub-micron diameter focused beam. To apply the system to experiments, an inorganic ultraviolet (UV) phosphor, YPO4:Gd³⁺, was synthesized and Gd³⁺ dopant concentration was optimized for use as a fluorescent probe for IBIF imaging. Furthermore, other irradiation with X-ray beam was attempted for application to synchrotron radiation. As a result, fluorescence was observed in the experiment.

For the first time at the SOLEIL synchrotron facility’s MARS beamline, UO₂ single-crystal-like samples underwent characterization, and strain depth profiles were established. Single crystals oriented along (1 1 0) and (1 1 1) were submitted to ion irradiation in the nuclear energy-loss regime (S_n) using 900 keV I²⁺ ions, and also with concomitant electronic energy deposition (S_e) using 27 MeV Fe⁹⁺ ions. X-ray diffraction measurements were conducted at the MARS beamline, specialized for radioactive material analysis. High-angular-resolution reciprocal space maps around asymmetrical reflections and conventional symmetrical θ/2θ scans were recorded. Analysis with the RaDMaX software allowed retrieving the strain depth profiles. Results reveal that the S_n-irradiated surface layer exhibits tensile strain along its normal with no in-plane strain, that this normal strain is partially relaxed by S_e. Both crystal orientations display similar behavior, but not with the same magnitude. Comparison with polycrystals indicates a more pronounced strain relaxation in the latter case.