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

Understanding nuclear reactions between light-charged nuclei in the sub-Coulomb energy region is crucial for several astrophysical processes. Accurate determination of the reaction cross-section within the astrophysically important Gamow range is challenging due to electron screening. Various methods, including polynomial fits, R-Matrix, and the indirect Trojan Horse Method (THM), have estimated electron screening energies that exceed the adiabatic limit. This study aims to derive the bare astrophysical S-factor for the reaction ${}^6\text{Li}{(\text{p},\alpha )}^3\text{He}$ and to extract electron screening energies using Multi-Layer Perceptron-based Artificial Neural Network (ANN) analysis. Experimental S-factors for ${}^6\text{Li}{(\text{p},\alpha )}^3\text{He}$, obtained from the literature, are reanalyzed with the ANN algorithm to determine the energy-dependent S-factor. The bare astrophysical S-factor is calculated from data above 60 keV, where electron screening is negligible. The electron screening potential is then derived by comparing the shielded S-factor with the bare S-factor. The ANN-based analysis yields an electron screening potential of 220 eV, suggesting that ANN could be a viable tool for estimating electron screening potentials in light nuclei reactions.

The betavoltaic effect is characterized by multiple random scatterings and high energy density exchange. The conversion of beta-particles’ energy to electric current is a sophisticated process. A GEANT4-based code is used to model the energy-loss mechanisms of emitted electrons from ⁶³Ni radioisotope, considering the physics behind these losses (such as Coulomb scattering, nuclear stopping, and Bethe-Bloch theory) while taking into account self-absorption and backscattering factors. The study indicates the existence of a significant non-ionizing energy-loss of penetrating beta-particles that may stimulate remarkable local heating in the absorbing structure, which results in a degradation in the performance of betavoltaic batteries using ⁶³Ni as nuclear fuel.

The micro-trench method is a new technique to measure polar and azimuthal incident ion angles, material erosion, and impurity deposition at plasma-facing surfaces, and has been applied in the DIII-D divertor. This article gives a tutorial of the micro-trench technique consisting of six steps: (1) micro-trench fabrication, (2) pre-exposure measurement of the fabricated micro-trench geometry, (3) tracer material deposition, (4) plasma exposure, (5) post-exposure observation of the tracer material, and (6) post-exposure measurement of the micro-trench geometry. Two criteria need to be satisfied to apply the micro-trench method successfully: (i) uniform impurity deposition on the micro-trench floor, and (ii) erosion dominated by the physical sputtering induced by the impinging ions. When those two criteria are satisfied, post-exposure analysis of the impurity deposition patterns on the micro-trench floor may be used to determine the polar and azimuthal incident ion directions (mean values of the ion angle directions), erosion rate, and impurity deposition rate during plasma exposure without computational interpretation.

In the present work, the differential cross sections of the ¹²C(³He,p_0-2)¹⁴N and ¹²C(³He,α₀)¹¹C nuclear reactions, as well as, the ¹²C(³He,³He₀)¹²C elastic scattering were determined at 5 detection angles (θ = 120°, 140°, 150°, 160°, 170°) covering the E_lab = 2000–6000 keV energy range, with a 25 to 100 keV energy step. Benchmarking measurements were also performed using two different thick glassy carbon targets to validate the cross-section values obtained for the reactions. All measurements were carried out at the 4 MV Tandem Dynamitron Accelerator facility of the Central Unit for Ion Beams and Radionuclides of the Ruhr University Bochum in Bochum, Germany. The experimental, data analysis and benchmarking procedures are presented in detail.

Ningyo-toge is a uranium (U) mine that was operative in Japan. Currently, the mining area retains a dump of mill tailings. Groundwater is contaminated with U ore, and mill tailings might contain radioactive elements, such as U and radium (Ra), which can negatively impact the human body. This study determined the soil composition at the tailings dumping site using particle-induced X-ray emission, scanning electron microscopy, and X-ray diffraction and observed the adsorption structure of barium (Ba), an analog of Ra, using X-ray absorption fine structure analysis. The results revealed the existence of silicate minerals, such as quartz and mica, and metal oxides, such as Fe and Mn, in the soil. Ningyo-toge soil is similar to montmorillonite and bentonite. In particular, it was proposed that the adsorption of Ba on Mn oxide is an inner-sphere complex that immobilizes Ba. These findings will provide valuable information for estimating the behavior of Ra in the environment. The results of this study will be helpful for safety assessment and evaluating the impacts on the surrounding environment.

The European Spallation Source, ESS, is a neutron research facility under construction in Lund, Southern Sweden. The Facility will produce neutrons by spallation, using a powerful linear accelerator to deliver protons to a tungsten target. In addition to the desired neutron production, a long list of radionuclides will be created as by-products of the nuclear reaction inside the target. The Swedish Radiation Safety Authority has established a list of the most relevant radionuclides, in terms of contribution to the effective dose to ESS workers and the general public, should an accidental release of irradiated target material occur. This list includes radionuclides that are not produced by the nuclear energy industry, in particular ^178mHf, ¹⁸²Ta, ¹⁸⁷W, ¹⁴⁸Gd and ¹⁷³Lu. Ongoing research efforts aim to determine the best analytical methods to assess these exotic and often difficult-to-measure radionuclides in environmental samples. This work investigates the potential of X-ray fluorescence and time-of-flight elastic Recoil detection analysis for the assessment of soil samples, and the potential of particle induced X-ray emission for the assessment of crop samples. These techniques require only simple sample preparation steps and no chemical extraction, unlike the conventional environmental monitoring methods such as inductively-coupled plasma mass spectrometry, and show promise as complimentary methods enabling fast sample throughput. This study focuses on the analysis of uncontaminated soil and crops, to provide baseline data, whilst simultaneously assessing the available measurement capabilities. For the X-ray fluorescence system used in this study, the method detection limit for W in soil was determined to be 0.147 ppth, and Zr which can be correlated with the migration of Hf was clearly measurable.

This study investigates the effectiveness of novel nanocomposite shielding materials in reducing out-of-field radiation doses during radiation therapy, employing Geant4 Monte Carlo (MC) simulations alongside an anthropomorphic female phantom. The research focuses on two radiation modalities: 6 MV beams with and without flattening filters. Utilizing the Geant4 MC code, detailed simulations of a Varian Clinac 2100C/D linear accelerator and an ICRP-145 mesh-type human phantom were conducted to estimate the doses to out-of-field organs from unintended secondary radiation. This involved simulating a comprehensive linac model, including all relevant beam-line components, and assessing the shielding effects of three different nanocomposites doped with metal nanoparticles at various thicknesses. The nanocomposites, comprising Polytetrafluoroethylene (PTFE), with PtO₂, IrO₂, and Bi₂O₃ nanoparticles, were evaluated for their potential to reduce patient organ doses from stray photon doses. The results showed that these materials could significantly lower radiation exposure to non-target tissues.

A design study for the $\gamma$-ray detector array of the gSPEC project, which aims at measuring nuclear moments at GSI/FAIR, is presented. Foreseen setups, involving DEGAS and the new gDEGAS triple cluster detectors for $\gamma$-ray spectroscopy are simulated using the Geant4 framework. The main characteristics associated to these detector assemblies with the envisaged configurations, namely the photo-peak efficiency and the angular resolution, are discussed. A new correction procedure for a better reconstruction of the time-perturbed angular distribution is proposed.

In this study, X-ray absorption near edge structure (XANES) spectral analysis and column experiments were used to verify the selectivity of rare earth (RE) ions by alkyl diamide amine (ADAAM) adsorbent. In addition, the interactions between the N atoms of ADAAM and RE ions were evaluated to determine whether any of the RE ions are a valid simulant for developing a mutual separation process for minor actinides (MAs) in highly radioactive liquid waste. It was confirmed that La and Ce interacted with the amine N atom of ADAAM and they showed a peak shift of the N-K edge XANES spectrum; this finding suggested that a soft interaction is an essential factor influencing ion selectivity. Therefore, the selection factor of RE ions by ADAAM adsorbent was similar to that of MAs. It was concluded that RE ions are reasonable species to simulate MAs.