Search Results (37)

Scintillation fiber-optic detectors (FODs) offer a compact, electrically passive, and versatile solution for real-time proton beam monitoring in clinical radiation therapy. In this work, we systematically investigate and compare FODs based on GAGG:Ce, Al₂O₃:C, and Al₂O₃:C,Mg crystal scintillators under identical proton irradiation conditions. The detectors were evaluated using a 60 MeV clinical proton beam over a dose range of 0.5–15 Gy, with radioluminescence spectra acquired at integration times as short as 70 ms. The GAGG:Ce-based FOD exhibited the highest signal intensity, a fast temporal response, and excellent stability under repeated irradiation cycles, enabling reliable real-time dose monitoring. In contrast, the FODs based on Al₂O₃:C and Al₂O₃:C,Mg demonstrated high sensitivity, reproducible dose–response characteristics, and a low effective atomic number (Z_eff ≈ 11), providing near tissue-equivalent behavior. Mg co-doping modified the luminescence characteristics of Al₂O₃:C by enhancing the contribution of visible emission centers. However, under the present proton irradiation conditions, the overall RL signal remained lower than that of Al₂O₃:C while preserving good signal stability. All detector configurations maintained consistent performance across multiple irradiation cycles, with GAGG:Ce showing the lowest signal variation. Overall, these results demonstrate that scintillation FODs constitute a robust platform for proton beam diagnostics and dosimetry. GAGG:Ce-based detectors are shown to have promising potential for real-time proton beam monitoring, whereas sapphire-based detectors provide advantages for dosimetric applications where tissue equivalence is essential. Full article

The 795 nm wavelength corresponds to the D1 transition of rubidium atoms and is widely used in atomic optical pumping, atomic clocks, magnetometers, and precision spectroscopy. For compact free-space collimation, beam shaping, and efficient fiber coupling, edge-emitting semiconductor lasers with reduced fast-axis (vertical) divergence are highly desirable, yet low-divergence designs at 795 nm remain limited. Here, we propose and demonstrate low-divergence photonic-crystal epitaxy (LD–PC) for 795 nm edge-emitting lasers. By engineering a periodic n-side photonic-crystal stack to place the fundamental vertical mode near the photonic band edge, the vertical mode is expanded while maintaining effective modal discrimination. Narrow-ridge Fabry–Pérot lasers based on GaAsP/AlGaAs single-quantum-well epitaxy were fabricated and characterized. The optimized LD–PC device (3 μm ridge width, 1 mm cavity length) delivers 227 mW at 200 mA with a threshold current of 23 mA, a slope efficiency of 1.28 W/A, and a peak wall-plug efficiency of 55% under continuous-wave operation at 25 °C. The measured far-field divergences (FWHMs) are 7.16° and 18.83° in the lateral and vertical directions, respectively, corresponding to a reduction in the vertical divergence from >40° in the reference structure to <20° with LD–PC. These results validate photonic-crystal epitaxy as an effective route toward compact, high-performance, low-divergence 795 nm semiconductor laser sources for rubidium-based atomic systems. Full article

To increase the wear resistance of a hollow ceramic product, it is necessary to apply wear-resistant coatings to all its surfaces, including the internal surfaces. Before the coating deposition, the surface must be processed with a beam of energetic particles to ensure its adhesion. In this study, a scheme for processing internal surfaces of hollow cylinders with fast argon atoms is proposed and tested. Simultaneous treatment of all surfaces of the rotating ceramic cylinder allowed for deposition of a uniform TiB₂ coating on both sides of the cylinder and a decrease in the abrasion wear by several times. Full article

The removal of defective surface layers can substantially improve the quality of various products. It can be carried out using beams of accelerated ions or fast argon atoms. However, it is difficult to process the inner surface of narrow channels. In the present work, a narrow beam of fast argon atoms is used to sputter and polish the inner surface of drawing dies with 5.7 mm wide working channels. Due to the high angle of incidence to the channel walls, sputtering with fast argon atoms decreased their roughness to Ra ~ 0.004 µm. Full article

Laser nanostructuring via Laser-Induced Periodic Surface Structures (LIPSS), generated using femtosecond laser pulses, has been investigated as a method for precisely modifying titanium surfaces. By adjusting parameters such as the fluence and pulse number of the laser beam, it is feasible to tailor the surface morphology, roughness, and oxidation states of species that can significantly influence the properties and surface bioactivity of the material. In this study, the LIPSS was applied to commercially pure titanium and evaluated for its ability to support calcium phosphate nucleation and growth in Simulated Body Fluid (SBF). Scanning Electron Microscopy (SEM) and Fast Fourier Transform (FFT) analysis confirmed the formation of well-defined periodic structures. Additional characterizations performed by Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS) revealed, after laser treatment of titanium, its increased surface roughness and oxidation levels, respectively. These features, when assessed after immersion in SBF, were associated with an improved potential biological performance of the nanostructured surface of the investigated material. The results demonstrated that LIPSS-treated titanium effectively promoted calcium phosphate growth, indicating its enhanced potential bioactivity. Overall, LIPSS nanostructuring presents a scalable and cost-effective strategy for engineering titanium surfaces with potential bioactive properties, supporting their promising application in advanced biomedical implants. Full article

A new approach to stripping surface layers from ceramics with fast atoms is proposed. The existing beam sources do not allow for a stripping rate of more than a few µm/h to be achieved. Usually, an increase in the etching rate is associated with growing flux density and energy of fast atoms, which can heat the parts of the beam source up to an inadmissible temperature. In the present work, the etching rate was significantly increased at permanent flux density and energy due to an increase in the angle of incidence of fast atoms on the product surface. An increase in the angle of incidence from zero to 80° resulted not only in an increase in the etching rate by several times but also in simultaneous polishing of the surface to a high finishing class. Full article

This study demonstrates that diffusion doping of ZGP single crystals with impurity atoms (Mg, Se, Sn, Pb) leads to a decrease in the specific conductivity of the samples. Consequently, this results in reduced absorption in the terahertz frequency range (150–1000 μm). It has been shown that doping ZGP samples with selenium (Se) and lead (Pb) atoms reduces absorption in the infrared region from 0.3–0.6 cm⁻¹ to 0.06–0.09 cm⁻¹. Doping with tin (Sn) leads to a decrease in absorption only in the wavelength region near 2.1 μm from 0.2 cm⁻¹ to 0.05 cm⁻¹. The proposed mechanism for the decrease in infrared absorption is a reduction in zinc vacancies due to doping with impurity atoms. This research lays the groundwork for a technology that produces ZGP crystals with minimal absorption within the 2–8 μm wavelength range, eliminating the need for fast electron beam irradiation technology. This advancement will facilitate the fabrication of ZGP crystals with arbitrary apertures. Full article

The surfaces of ceramic products are replete with numerous defects, such as those that appear during the diamond grinding of sintered SiAlON ceramics. The defective surface layer is the reason for the low effectiveness of TiZrN coatings under abrasive and fretting wear. An obvious solution is the removal of an up to 4-µm-thick surface layer containing the defects. It was proposed in the present study to etch the layer with fast argon atoms. At the atom energy of 5 keV and a 0.5 mA/cm² current density, the ions were converted into fast atoms and the sputtering rate for the SiAlON samples reached 20 μm/h. No defects were observed in the microstructures of coatings deposited after beam treatment for half an hour. The treatment reduced the volumetric abrasive wear by five times. The fretting wear was reduced by three to four times. Full article

The surface of ceramic products manufactured using diamond grinding is replete with shallow scratches, deep grooves and other defects. The thickness of the defective layer amounts to 3–4 µm and it must be removed to increase wear resistance of the products when exposed to intense thermomechanical loads. In this study, removal of the defective layers from samples made of ZrO₂, Al₂O₃ and Si₃N₄ with a beam of fast argon atoms was carried out with a stripping rate of up to 5 µm/h. To prevent contamination of the source of fast argon atoms by the sputtered dielectric material, the beam was compressed and passed to the sample through a small hole in a wide screen. Due to the removal of the defective layer, abrasive wear decreased by an order of magnitude and the adhesion of coatings deposited on the cleaned ceramic surfaces improved significantly. Full article

Serial crystallography is a rapidly developing method for the determination of the structure of biomolecules at room temperature at near-atomic resolution from an ensemble of small crystals. Numerous advances in detectors, data analysis pipelines, sample delivery methods, and crystallization protocols expand the scope of structural biology to understand the fundamental processes that take place in living cells. Many experimental strategies for serial crystallography are in use, depending on the type and sizes of the crystals or other needs of the experiment. Such strategies should ideally minimize the wastage of samples or beamtime without compromising experimental goals. This paper proposes a way to optimize beamtime utilization in serial crystallography experiments that use fixed-target sample delivery methods, such as chips. The strategy involves two key steps. Firstly, a fast raster scan of the chip is performed to determine the positions of the crystals based on their diffraction. Subsequently, a rotational series is collected at each identified crystal position, covering a narrow range of chip orientations. This approach enables the exclusion of empty positions during data acquisition, resulting in significant savings in beam time utilization and a reduced volume of measured data. Full article

Nickel-based Ni-Cr-Si-B self-fluxing alloys are excellent candidates to replace cobalt-based alloys in aeronautical components. In this work, metal additive manufacturing by directed energy deposition using a laser beam (DED-LB, also known as LMD) and gas-atomized powders as a material feedstock is presented as a potential manufacturing route for the complex processing of these alloys. This research deals with the advanced material characterization of these alloys obtained by LMD and the study and understanding of their solidification paths and strengthening mechanisms. The as-built microstructure, the Vickers hardness at room temperature and at high temperatures, the nanoindentation hardness and elastic modulus of the main phases and precipitates, and the strengthening mechanisms were studied in bulk cylinders manufactured under different chemical composition grades and DED-LB/p process parameter sets (slow, normal, and fast deposition speeds), with the aim of determining the influence of the chemical composition in commercial Ni-Cr-Si-Fe-B alloys. The hardening of Ni-Cr-Si-Fe-B alloys obtained by LMD is a combination of the solid solution hardening of gamma nickel dendrites and eutectics and the contribution of the precipitation hardening of small chromium-rich carbides and hard borides evenly distributed in the as-built microstructure. Full article

Wear-resistant coatings improve the machining capability of cutting tools and extend their useful life. However, when a tool needs to be reused, it is mandatory to remove the existing coating to facilitate resharpening and recoating. The existing technique uses electrochemical stripping, which is hazardous to the environment. The environmentally friendly pulsed laser stripping causes the melting and mixing of tools and coating materials, which makes it difficult to separate and remove the coating. This paper presents the results of coating stripping via a beam of fast argon atoms. Due to the twentyfold compression of the beam, a 3 µm thick AlTiN coating was removed from a rotating solid carbide end mill within 25 min. A subsequent one-hour-long irradiation of the cleaned tool with the same beam led to a decrease in the radius of the tool’s cutting edges from 10.5 to 3.5 µm. This allowed us to redeposit a 3.5 µm thick AlTiN coating and obtain a coated end mill with a cutting-edge radius of 7 µm. Full article

Li-Nb-O-based insertion layers between electrodes and electrolytes of Li-ion batteries (LIBs) are known to protect the electrodes and electrolytes from unwanted reactions and to enhance Li transport across interfaces. An improved operation of LIBs, including all-solid-state LIBs, is reached with Li-Nb-O-based insertion layers. This work reviews the suitability of polymorphic Li-Nb-O-based compounds (e.g., crystalline, amorphous, and mesoporous bulk materials and films produced by various methodologies) for LIB operation. The literature survey on the benefits of niobium-oxide-based materials for LIBs, and additional experimental results obtained from neutron scattering and electrochemical experiments on amorphous LiNbO₃ films are the focus of the present work. Neutron reflectometry reveals a higher porosity in ion-beam sputtered amorphous LiNbO₃ films (22% free volume) than in other metal oxide films such as amorphous LiAlO₂ (8% free volume). The higher porosity explains the higher Li diffusivity reported in the literature for amorphous LiNbO₃ films compared to other similar Li-metal oxides. The higher porosity is interpreted to be the reason for the better suitability of LiNbO₃ compared to other metal oxides for improved LIB operation. New results are presented on gravimetric and volumetric capacity, potential-resolved Li⁺ uptake and release, pseudo-capacitive fractions, and Li diffusivities determined electrochemically during long-term cycling of LiNbO₃ film electrodes with thicknesses between 14 and 150 nm. The films allow long-term cycling even for fast cycling with rates of 240C possessing reversible capacities as high as 600 mAhg⁻¹. Electrochemical impedance spectroscopy (EIS) shows that the film atomic network is stable during cycling. The Li diffusivity estimated from the rate capability experiments is considerably lower than that obtained by EIS but coincides with that from secondary ion mass spectrometry. The mostly pseudo-capacitive behavior of the LiNbO₃ films explains their ability of fast cycling. The results anticipate that amorphous LiNbO₃ layers also contribute to the capacity of positive (LiNi_xMn_yCo_zO₂, NMC) and negative LIB electrode materials such as carbon and silicon. As an outlook, in addition to surface-engineering, the bulk-engineering of LIB electrodes may be possible with amorphous and porous LiNbO₃ for fast cycling with high reversible capacity. Full article

The optical radiation in a gaseous medium upon the irradiation of a lithium layer with a fast electron beam of a 5 ns duration has been studied. The irradiation chamber was filled with argon, krypton, or xenon at a pressure of 10 kPa up to 60 kPa. The lines of lithium atoms appear in the emission spectrum at a lithium layer temperature of 650–680 K, and the intensity of these lines sharply increases with the increasing temperature of the lithium layer. The optical radiation arises from both the transitions of noble gas atoms and the transition of the lithium atom in a time of about 20–30 ns. The duration of the radiation pulses at half maximum at temperatures above 800 K was 60–100 ns at a wavelength of 610.4 nm and 140–220 ns at 670.8 nm in krypton and argon. The various mechanisms for the population of lithium levels during the radiation pulse are discussed. Full article

In order to significantly reduce the computing time while, at the same time, keeping the accuracy and precision when determining the local values of the density and effective atomic number necessary for identifying various organic material, including explosives and narcotics, a specialized multi-stage procedure based on a multi-energy computed tomography investigation within the 20–160 keV domain was elaborated. It consisted of a compensation for beam hardening and other non-linear effects that affect the energy dependency of the linear attenuation coefficient (LAC) in the chosen energy domain, followed by a 3D fast reconstruction algorithm capable of reconstructing the local LAC values for 64 energy values from 19.8 to 158.4 keV, and, finally, the creation of a set of algorithms permitting the simultaneous determination of the density and effective atomic number of the investigated materials. This enabled determining both the density and effective atomic number of complex objects in approximately 24 s, with an accuracy and precision of less than 3%, which is a significantly better performance with respect to the reported literature values. Full article