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Povzetek: A high-precision 5-axis goniometer has been installed and commissioned at the INSIBA end station of the 2 MV Tandetron accelerator at the Jožef Stefan Institute. The system provides three translational and two rotational degrees of freedom with an angular resolution of 0.01°, enabling precise sample alignment for Rutherford Backscattering Spectrometry (RBS-C) and Nuclear Reaction Analysis (NRA-C), both in channeling mode. The goniometer is equipped with a versatile sample stage allowing continuous heating up to 1470 K, liquid-nitrogen cooling, and biasing up to 500 V. A load-lock system ensures vacuum integrity during sample exchange. The system supports simultaneous data acquisition from up to five detectors. Commissioning was performed using pristine and W-ion irradiated W(111) single crystals by 10.8 MeV W ions inducing damage of 0.02 and 0.2 dpa at RT, as well as D-plasma-exposed W(100) crystals containing deuterium-decorated defects. Simultaneous RBS-C and NRA-C measurements demonstrated consistent results with benchmark data, confirming the system’s precision and stability. The setup also enables in-situ RBS-C during thermal annealing, facilitating real-time studies of defect recovery and hydrogen behaviour. This system represents a major enhancement in ion beam analysis capabilities for investigating defect dynamics and light element trapping and transport in materials.
Ključne besede: Tandetron, channeling
Objavljeno v DiRROS: 27.03.2026; Ogledov: 430; Prenosov: 372
Celotno besedilo (12,46 MB)
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Povzetek: The influence of grain boundaries (GBs) on the deuterium (D) transport and the creation of defects in nanocrystalline tungsten (W) films deposited on a W substrate was studied. Samples with three different grain sizes were produced for this purpose: a sample with a film having nanometer-size grains, a sample with hundred nanometer-grained film and a sample with micrometer-grained film. Samples were irradiated by 20 MeV W ions at 300 K to create displacement damage and exposed to 300 eV D ions at 450 K to populate the created and any pre-existing defects. The D transport and retention was assessed by measuring D depth profiles after certain exposure times by nuclear reaction analysis (NRA) using a 3He ion beam. From the final D concentration in the damaged area we could determine the concentration of defects that trap hydrogen, showing that the sample with the smallest grain size had the highest D concentration and it decreases with the increase of the grain size. Therefore, in nanocrystalline tungsten irradiated at 300 K, GBs do not improve radiation resistance, which would lead to fewer defects. For the first time, we show experimentally, that D transport is faster inside the nanometer-grained sample as compared to the micrometer-grained sample, meaning that D atoms have enhanced bulk diffusion along GBs. Accidentally, the film thickness was so thin that the W irradiation reached the interface between the W film and substrate, where NRA showed enhanced retention of oxygen. At that depth, two times higher D concentration was observed compared to D concentration in the damaged area in the middle of the film indicating on defect stabilization due to the presence of oxygen.
Ključne besede: grain boundaries, deuterium, tungsten, transport, displacement damage
Objavljeno v DiRROS: 12.12.2025; Ogledov: 753; Prenosov: 472
Celotno besedilo (4,49 MB)
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Povzetek: Radiation-induced defect production in tungsten was studied by a combination of experimental and simulation methods. The analysis of structural defects was performed using multi-energy Rutherford backscattering spectroscopy in channeling configuration (multi-energy C-RBS). To create different microstructures, (111) tungsten (W) single crystals were irradiated with W ions at two different doses (0.02 and 0.2 dpa) at 290 K. Detailed transmission electron microscopy (TEM) analysis of the samples revealed the presence of dislocation lines and loops of different sizes. The RBSADEC code was used to simulate the measured C-RBS spectra, recorded with four different He beam energies along the <111> direction. For the first time for tungsten, molecular dynamics (MD) simulations of overlapping cascades were used as input. The well-known method of randomly displaced atoms (RDA) was applied for comparison. RDA does not provide a satisfactory understanding of the nature of the induced defect structure. With MD, a very good agreement between the simulated and experimental spectra was obtained for the sample prepared at a lower dose, despite the fact that the absolute defect densities are two orders of magnitude higher than those found with TEM. A discrepancy is observed for the high-dose-irradiated sample, which is ascribed to the presence of extended defects such as dislocation lines, which are clearly observed by TEM, but cannot be formed in finite size MD cells. RBSADEC with MD cells as input can describe correctly the response of the RBS signal with analysing beam energy while RDA as input gives the wrong trend.
Ključne besede: tungsten, defects, Rutherford backscattering spectroscopy in channeling configuration, displacement damage, molecular dynamic simulations, transmission electron microscopy
Objavljeno v DiRROS: 12.12.2025; Ogledov: 877; Prenosov: 537
Celotno besedilo (8,29 MB)
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Povzetek: We investigated the microstructural evolution of W(111) single crystals under high-energy self-ion irradiation at 290 K and 800 K, using complementary characterization techniques, including Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Rutherford backscattering spectrometry in channelling regime (RBS-C), Positron annihilation spectroscopy (PAS), and Nuclear reaction analysis (NRA). Irradiation with MeV W ions allowed for controlled defect formation, with dose and temperature significantly affecting defect type and distribution. At 290 K, interstitial defects evolved from dislocation loops at low doses (0.02 dpa) to dislocation networks at higher doses (0.2 dpa). In contrast, at 800 K, lower dislocation densities were observed, with nm-sized dots and isolated lines forming at 0.02 dpa and developing into longer dislocation lines (~30 nm) at 0.2 dpa. RBS-C spectra support these findings, showing a trend of increasing dislocation density with dose but decreasing with temperature. PAS analyses revealed mono-vacancies and small vacancy clusters (V2–V4) at 290 K, coalescing into larger clusters (V25–V50) at 800 K. NRA measurements indicated greater deuterium retention at 290 K than at 800 K, consistent with lower vacancy mobility at the lower temperature. Combined TEM, RBS-C, PAS, and NRA observations highlight increased vacancy mobility and defect recombination with temperature, forming larger vacancy clusters at 800 K. This comprehensive study provides quantitative insights into defect formation and evolution in W single crystals, presenting a comparative analysis of defect distributions across multiple techniques and revealing temperature-dependent mechanisms of microstructural change.
Ključne besede: heavy-ion irradiation, structural defects
Objavljeno v DiRROS: 11.12.2025; Ogledov: 822; Prenosov: 484
Celotno besedilo (9,96 MB)
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Povzetek: Correlative imaging is a powerful tool for revealing information on cell-type structures and their biochemistry, with the potential to inform healthier food choices and improved dietary recommendations. Determination of plant structures and their structural biochemistry advances our understanding of specific structures designed to store different biomolecules within cells and tissues. Compared to the classical biochemical separation techniques, the key advantage of sequential correlative imaging techniques is in relating spatial plant (micro)structures to their biochemistry in a nondestructive manner. Sequential imaging reported here comprises six methodologies on a single sample, a cross-section of a Tartary buckwheat (Fagopyrum tataricum) grain, namely, bright-field and autofluorescence microscopy, fluorescence microspectroscopy, MeV-secondary ion mass spectrometry, micro-particle-induced X-ray emission, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, and laser ablation-inductively coupled plasma-mass spectrometry. Results confirm that the stepwise addition of the desired information across several classes of biomolecules and several spatial scales informs the quality and safety of plant-based produce across scales. Therefore, a viable workflow is proposed, enabling sequential spatial analysis of grain and highlighting plant structures' in situ specificity. The advantages and disadvantages of the selected methodologies were critically evaluated.
Ključne besede: autofluorescence, correlative molecular imaging, element distribution, grain tissues
Objavljeno v DiRROS: 07.11.2025; Ogledov: 641; Prenosov: 512
Celotno besedilo (1,71 MB)
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