Ultra-intense MeV photon and neutron beams are indispensable tools in many research fields such as nuclear, atomic and material science as well as in medical and biophysical applications. For ...applications in laboratory nuclear astrophysics, neutron fluxes in excess of 10
n/(cm
s) are required. Such ultra-high fluxes are unattainable with existing conventional reactor- and accelerator-based facilities. Currently discussed concepts for generating high-flux neutron beams are based on ultra-high power multi-petawatt lasers operating around 10
W/cm
intensities. Here, we present an efficient concept for generating γ and neutron beams based on enhanced production of direct laser-accelerated electrons in relativistic laser interactions with a long-scale near critical density plasma at 10
W/cm
intensity. Experimental insights in the laser-driven generation of ultra-intense, well-directed multi-MeV beams of photons more than 10
ph/sr and an ultra-high intense neutron source with greater than 6 × 10
neutrons per shot are presented. More than 1.4% laser-to-gamma conversion efficiency above 10 MeV and 0.05% laser-to-neutron conversion efficiency were recorded, already at moderate relativistic laser intensities and ps pulse duration. This approach promises a strong boost of the diagnostic potential of existing kJ PW laser systems used for Inertial Confinement Fusion (ICF) research.
Experiments were performed to study electron acceleration by intense sub-picosecond laser pulses propagating in sub-mm long plasmas of near critical electron density (NCD). Low density foam layers of ...300-500 m thickness were used as targets. In foams, the NCD-plasma was produced by a mechanism of super-sonic ionization when a well-defined separate ns-pulse was sent onto the foam-target forerunning the relativistic main pulse. The application of sub-mm thick low density foam layers provided a substantial increase of the electron acceleration path in a NCD-plasma compared to the case of freely expanding plasmas created in the interaction of the ns-laser pulse with solid foils. The performed experiments on the electron heating by a 100 J, 750 fs short laser pulse of 2-5 × 1019 W cm−2 intensity demonstrated that the effective temperature of supra-thermal electrons increased from 1.5-2 MeV in the case of the relativistic laser interaction with a metallic foil at high laser contrast up to 13 MeV for the laser shots onto the pre-ionized foam. The observed tendency towards a strong increase of the mean electron energy and the number of ultra-relativistic laser-accelerated electrons is reinforced by the results of gamma-yield measurements that showed a 1000-fold increase of the measured doses. The experiment was supported by 3D-PIC and FLUKA simulations, which considered the laser parameters and the geometry of the experimental set-up. Both, measurements and simulations showed a high directionality of the acceleration process, since the strongest increase in the electron energy, charge and corresponding gamma-yield was observed close to the direction of the laser pulse propagation. The charge of super-ponderomotive electrons with energy above 30 MeV reached a very high value of 78 nC.
We report on enhanced laser driven electron beam generation in the multi MeV energy range that promises a tremendous increase of the diagnostic potential of high energy sub-PW and PW-class laser ...systems. In the experiment, an intense sub-picosecond laser pulse of ∼1019 Wcm−2 intensity propagates through a plasma of near critical electron density (NCD) and drives the direct laser acceleration (DLA) of plasma electrons. Low-density polymer foams were used for the production of hydrodynamically stable long-scale NCD-plasmas. Measurements show that relativistic electrons generated in the DLA-process propagate within a half angle of 12 ± 1° to the laser axis. Inside this divergence cone, an effective electron temperature of 10-13 MeV and a maximum of the electron energy of 100 MeV were reached. The high laser energy conversion efficiency into electrons with energies above 2 MeV achieved 23% with a total charge approaching 1 μC. For application purposes, we used the nuclear activation method to characterize the MeV bremsstrahlung spectrum produced in the interaction of the high-current relativistic electrons with high-Z samples and measured top yields of gamma-driven nuclear reactions. The optimization of the high-Z target geometry predicts an ultra-high MeV photon number of ∼1012 per shot at moderate relativistic laser intensity of 1019 Wcm−2. A good agreement between the experimental data and the results of the 3D-PIC and GEANT4-simulations was demonstrated.
•Films with transition metal oxides produce exotic physical phenomena.•Spin-orbit coupling energy in 5d Ir oxide comparable with other energies of crystals.•This fact allows you to create a variety ...of magnetic states in films with Ir oxides.•The new magnetic state of the SrIrO3 film in bilayer with manganite is demonstrated.
In this paper, we demonstrate for the first time an experimental observation of ferromagnetic ordering at temperatures below 60 K in SrIrO3 film which was the upper layer in SrIrO3/La0.7Sr0.3MnO3 bilayers. Epitaxial bilayers were deposited on (1 1 0) NdGaO3 substrates, after which the temperature dependences of the electron spin resonance spectra of the fabricated heterostructures were investigated. The analysis of these spectra showed that under certain conditions, the magnetization of the SrIrO3 layer reached a value of ~1 μB/Ir, comparable to the magnetization of the La0.7Sr0.3MnO3 layer that transfers into a ferromagnetic state at temperatures of 320–350 K.
Electron microscopy is used to study the evolution of microstructure of copper–aluminum composites, which takes place as the degree of reduction upon rotary swaging increases, and their conductivity ...is measured. The effect of reinforcing the copper–aluminum composites with steel fibers on the conductivity is studied.
•As-cast Al-8%Ca eutectic aluminum alloy was processed by laser irradiation.•Laser irradiation leads to a 4-fold increase in the microhardness of the alloy.•The hardened state has increased thermal ...stability.•A supersaturated solid solution of calcium in aluminum is formed.•Numerous dislocation loops are formed.
The relationship between the change in the structure and the hardening effect of an Al-8%Ca eutectic aluminum alloy under laser irradiation was studied. Laser surface processing of the as-cast alloy was carried out at a laser power of 370 W and a beam velocity of 750 mm/s. It is shown that laser irradiation leads to a 4-fold increase in the microhardness of the alloy (up to 3.6 GPa) due to the creation of a supersaturated solid solution of calcium in aluminum and a multiple increase in the dislocation density.
The high prevalence of Helicobacter pylori and the variety of gastroduodenal diseases caused by this pathogen necessitate the use of only accurate methods both for the primary diagnosis and for ...monitoring the eradication effectiveness. There is a broad spectrum of diagnostic methods available for detecting H. pylori. All methods can be classified as invasive or non-invasive. The need for upper endoscopy, different clinical circumstances, sensitivity and specificity, and accessibility defines the method chosen. This article reviews the advantages and disadvantages of the current options and novel developments in diagnostic tests for H. pylori detection. The progress in endoscopic modalities has made it possible not only to diagnose precancerous lesions and early gastric cancer but also to predict H. pylori infection in real time. The contribution of novel endoscopic evaluation technologies in the diagnosis of H. pylori such as visual endoscopy using blue laser imaging (BLI), linked color imaging (LCI), and magnifying endoscopy is discussed. Recent studies have demonstrated the capability of artificial intelligence to predict H. pylori status based on endoscopic images. Non-invasive diagnostic tests such as the urea breathing test and stool antigen test are recommended for primary diagnosis of H. pylori infection. Serology can be used for initial screening and epidemiological studies. The histology showed its value in detecting H. pylori and provided more information about the degree of gastric mucosa inflammation and precancerous lesions. Molecular methods are mainly used in detecting antibiotic resistance of H. pylori. Cultures from gastric biopsies are the gold standard and recommended for antibiotic susceptibility tests.
This paper studies the form of the instantaneous impact cost function in a financial market with transaction costs via an axiomatic approach. We show that several kinds of convexity of the cost ...function are equivalent to the corresponding properties of the price impact functions. The results clarify the implicit assumptions made when selecting a particular form of the cost function and can be used when choosing the correct portfolio optimization framework.
Abstract
The article presents the results of a study of low-temperature exposure on animal biological tissue using the novel prototype of a liquid nitrogen cryoapplicator. The data obtained are ...compared with the cryoapplicator characteristics cooled by nitrogen dioxide that are currently used for the atrial fibrillation treatment. Data analysis confirmed the liquid nitrogen cryoapplicators effectiveness and made it possible to highlight their advantages.
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