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We report the results of a search for dark photon in-flight decays to μ + μ − pairs at NA62. Dark photons could be produced by dumping protons onto a copper-iron absorber, reach the NA62 decay volume more than 80 m downstream of the dump and decay therein. The measurement is based on data collected in 2021 which correspond to 1.4 × 1017 dumped protons.

The lifetime of tungsten cathodes used in plasma spray torches is limited by processes leading to a loss of cathode material. It was reported in the literature that the mechanism of their erosion is the evaporation. A model of the ionization layer of a cathode is developed to study the diffusive transport of evaporated tungsten atoms and tungsten ions produced due to ionization by electron impact in a background argon plasma. It is shown that the Stefan–Maxwell equations do not reduce to Fick law as one could expect for the transport of diluted species, which is due to significant diffusion velocities of argon ions. The ionization of tungsten atoms occurs in a distance of a few micrometers from the cathode surface and leads to a strong sink, which increases the net flux of tungsten atoms far beyond that obtained in absence of tungsten ions. This shows that the tungsten ions are driven by the electric field towards the cathode resulting in no net diffusive flux and no removal of tungsten species from the ionization layer even if convection is accounted for. A possible mechanism of removal is found by extending the model to comprise an anode. The extended model resolves the inter-electrode region and provides the plasma parameters for a current density corresponding to the value at the center of the cathode under typical arc currents of 600 A and 800 A. The presence of the anode causes a reversal of the electric field on the anode side, which pulls the ions away from the ionization layer of the cathode. The net flux of tungsten ions can be further fortified by convection. This model allows one to evaluate the loss of cathode material under realistic operating conditions in a quantitative agreement with measured values.

Since emerging Metal Halide Perovskites were attracting elevated attention from scientific and industrial communities. Although, we still yet to see commercial products based on perovskite materials a significant body of work has been already done. Here we present our own method of Metal Halide Perovskites integration into possible industrial applications. Our way of Perovskite Quantum Dots encapsulation in polymer fibers provides exceptional water and ambient stability as well as optimal photoluminescence.

Since Complementary metal–oxide–semiconductor technology is the conventional technology for micro- and optoelectronics, integration of emerging materials, such as halide perovskites, into the process is an important branch of perovskite technologies development. In this regard ITO free device research becomes increasingly important. The Perovskite Light-Emitting electrochemical cells are a promising alternative to conventional Perovskite Light Emitting Diodes. In this work we demonstrate green (λEL = 523 nm) CsPbBr3 Perovskite Light-Emitting electrochemical cells with luminescence intensity of 50 kd/m2 integrated with Si++(111) substrate.

Carbon nanotubes are promising materials for use as flexible and transparent electrodes for a wide variety of optoelectronic devices like solar cells and light-emitting diodes. Moreover, the chemical inertness of carbon nanotubes matches with the operation of light-emitting electrochemical cells where ion migration is a main working principle especially based on halide perovskite, in which ions corrode metal electrodes. Here we demonstrate how the removal of synthesis residuals via synthesis enables the use of multiwall carbon nanotubes as a transparent electrode.

This work presents results of a self-consistent modelling analysis on microwave plasma generated in Ar–O2 mixtures at a frequency of 2.45 GHz at atmospheric pressure. The study focuses on how the plasma properties are influenced by the increase of the oxygen fraction in the gas mixture. The oxygen admixture is increased from 1% up to 95% in mass for values of the input microwave power of 1 and 1.5 kW. The results show that for a power of 1 kW and gradually increasing the oxygen admixture from 1% to 25% the electron density drops by a factor of more than four due to the energy lost by the electrons due to dissociation of oxygen molecules and the gas heating. An analysis of the number densities of species produced in the Ar–O2 plasma is presented. Oxygen admixtures of above 50% are considered along with an increase of the input microwave power in order to supply the discharge with electron number density values of the order of 1019 m−3. Gas temperatures above 3700 K are obtained in the plasma core along with a strong production of oxygen atoms with a number density of the order of 1023 m−3.

Edible coatings can play a leading role in food storage. In baked goods, attention is focused on inhibiting the processes of mold development and moisture loss. Adding functional ingredients to coatings can slow the spoilage process thus increasing shelf-life. The purpose of this study was to prepare edible coatings with polysaccharides and coconut oil enriched with an ethanol extract of Malva sylvestris L. flowers (mallow) and to characterize its physico-chemical and antibacterial properties. A computerized method for analysis of the digital dispersions images was used to further describe the enriched coatings. The rheological characteristics of the coatings were determined by structural mechanical analysis. All developed model emulsion coatings demonstrated a polydisperse character-the diameter of the globules in the studied volume ranged from 1.5 μm to 12 μm. All enriched coatings with mallow extract had better dispersion characteristics. The results showed that the presence of a mallow extract had a positive effect on the antibacterial activity of the xanthan food coating by increasing the zone of inhibition against Escherichia coli ATCC 8739. The pectin coating with mallow extract exhibited antibacterial activity against Salmonella NCTC 6017, while a suppressive effect on tests pathogen did not characterize the control sample.

An analysis of weak quantum fluctuations of a spatial soliton in a laser with fast saturable absorption in the possible presence of weak holding radiation is carried out. In the c-number representation with adiabatic elimination of atomic variables, the master Heisenberg–Langevin equation is linearized in the vicinity of a stable classical (in the absence of fluctuations) laser soliton. The linearized equation’s solution is constructed on the basis of the spectral expansion in eigenfunctions of the evolution operator unperturbed by fluctuations. The discrete spectrum of this operator is found and used to determine the mean values of the squared fluctuations of the coordinates of the soliton center and its momentum. A comparison is made with similar fluctuations in driven interferometers with Kerr non-linearity of the medium.

Here we report on the development of NbN/SiNx:H/SiO2-membrane structures for investigation of the thermal transport at low temperatures. Thin NbN films are known to be in the regime of a strong electron-phonon coupling, and one can assume that the phononic and electronic baths in the NbN are in local equilibrium. In such case, the cooling of the NbN-based devices strongly depends on acoustic matching to the substrate and substrate thermal characteristics. For the insulating membrane much thicker than the NbN film, our preliminary results demonstrate that the membrane serves as an additional channel for the thermal relaxation of the NbN sample. That implies a negligible role of thermal boundary resistance of the NbN-SiNx:H interface in comparison with the internal thermal resistance of the insulating membrane.

In this work, we present for the first time a unified model of a low-current short-length arc between copper electrodes. The model employs one-dimensional fluid description of the plasma in argon and copper vapour at atmospheric pressure and the heat transfer in the electrodes made of copper. The solution of the particle and energy conservation of electrons and heavy particles is coupled with the solution of the Poisson equation, from which the self-consistent electric field is obtained. The operation of the non-refractory cathode is based on thermo-field emission. Heat fluxes from the plasma to the electrodes are considered so that a phase change and evaporation from the cathode and a release of copper atoms into the plasma are taken into account. The influence of the copper atoms and ions on the plasma properties is analysed and discussed. The model’s predictions are compared with experimental data and a qualitative agreement is obtained besides the restrictions of the one-dimensional fluid model.

The article discusses the problem of increasing the energy efficiency of the 3 kV DC traction power supply system on the railways of the Russian Federation. As one of the ways to amplify it, the authors consider a system of contactless automatic voltage regulation under load of converting units of traction substations, where reactor controlled devices serve as the regulatory body. As one of the directions for improving the system, the use of thyristors in the design of a controlled device is proposed. The article presents the functional diagrams of contactless automatic voltage control systems with thyristor-reactor and thyristor controlled devices, shows the external characteristics of the converter unit with these systems. To calculate the economic efficiency when introducing contactless automatic voltage control systems with reactor, thyristor-reactor and thyristor controlled devices, a methodology has been developed based on calculating the savings in reduced costs, as well as the payback period when replacing a contactless automatic voltage control system under load with a reactor controlled device by a system with thyristor-reactor and system with thyristor.

As part of this work, a simulation model was constructed to evaluate the print quality of three-dimensional objects using a 3D printer. A study was conducted using non-contact scanning of a 3D model and varying the parameters affecting print quality, followed by an assessment of the degree to which the printed 3D model corresponded to its standard using software. The result of this study is the obtained values of the optimal printing parameters of the 3D model, which allow to obtain a high estimate of the degree of correspondence of the printed 3D model to its standard, and, consequently, high quality printing on a 3D printer.

Electrical measurements and numerical modelling of dc tungsten-inert gas arcs are carried out in order to determine the electric field and the voltage, and to study their importance to the plasma-electrode interaction. The configuration under consideration is very typical for tungsten-inert gas welding processes and includes a conically shaped cathode made of doped tungsten and atmospheric pressure argon as a shielding gas. The studies analyze the effects of the inter-electrode distance and the electric current over wide ranges of variation—currents from below 10 A up to 200 A, and distances from 20 mm down to 2 mm in the modelling and to the short-circuit in the experiment. The comparison of the experimentally obtained and the computed current–voltage and arc length-voltage characteristics clearly prove the predictive capability of the advanced non-equilibrium model of the arc and the electrodes. Moreover, the self-consistent model yields the structure of the electric potential and the electric field and is capable of describing the peculiarities of the plasma-electrode interaction.

Results from simulations of plasma and neutrals under conditions predictively characterizing the detached plasma regime in the linear machine MAGNUM-PSI are presented. The relaxation of the vibrationally excited hydrogen molecules is investigated in order to establish a relation between their relaxation and dwell times, and the role of the various mechanisms of the molecular vibrational kinetics. The results obtained show that the individual vibrational states have to be included in the transport code for neutrals as distinct species, since the relaxation time of the vibrational states is sufficiently longer than the typical dwell time of hydrogen molecules in the detached plasma region. The parameters of plasma and neutrals are affected by the transport of the vibrationally excited hydrogen molecules. Furthermore, the rate of molecular recombination is overestimated by a factor of similar to 5 provided that the transport of hydrogen molecules only in their ground vibrational state is considered. The role of the various processes of vibrational kinetics is studied. The vibrational excitation through singlet electronic states has a strong influence on the molecular densities for levels with vibrational quantum numbers v >= 5. Vibration-vibration (V-V) collisions between vibrationally excited hydrogen molecules and vibration-translation (V-T) collisions between vibrationally excited hydrogen molecules and ground state molecules and atoms are of minor importance in MAGNUM-PSI.

The temporal and spatial characteristics of atomic nitrogen in a pulsed microwave discharge with 2.46 GHz field frequency with 20 Hz microwave pulse repetition rate, between 50 and 500 µs pulse duration and pressures from 2.5 to 20 mbar have been analysed experimentally by TALIF and explained by modelling. In the temporal profiles, in the middle of the plasma an unexpected increase in atomic nitrogen density within 20 µs after switching off microwave power supply has been observed. This could be explained by a kinetic plasma model taking into account the excitation of ground state nitrogen atoms N(4S) to the electronically excited states N(2D) and N(2P) by electron impact. As a second effect, the spatial and temporal density profiles of atomic nitrogen in the pulsed plasma showed a dominant diffusion behaviour in the phase of decreasing atomic nitrogen density between two microwave pulses. Fitting a model of diffusion led to diffusion coefficients of the order of 100 cm2 s−1, which correspond to translational temperatures of about 500 K. In this model, additional production of atomic nitrogen during the late afterglow proved to be important in weakening the density decrease.

A kinetic model is developed to study NOx removal in N2/O2/NO gas mixtures treated by a pulsed microwave discharge at atmospheric pressure. The model considers the coupling between electronic, vibrational and chemical kinetics, taking into account a large set of neutral, excited and charged species. The time behaviour of the species densities is calculated for the given input parameters, namely the reduced electric field, the initial gas composition (N2, 500 ppm NO and 0%, 2%, 5% O2), the effective pulse duration (1.5 µs) and repetition rate (40 Hz), and the gas temperature. The rate coefficients of the processes considered are either calculated from the electron energy distribution function or taken from published data. The vibrational temperature of N2 is derived from the calculated population densities of the first two vibrational levels of N2, and the results obtained are compared with those observed by coherent anti-Stokes Raman scattering (CARS) technique. The experimental data from the FTIR measurements of the NOx densities after reduction agree well with the calculations. The kinetic study shows the dominant role of the N4+ ions during the discharge phase. The calculated N density is about an order of magnitude lower than the O density. Nevertheless, it is the N radical that plays the major role in the reduction of the NO concentration even in O2-containing gas mixtures. Although there is oxidation of NO to NO2, an overall NOx reduction can be achieved, provided the microwave pulses are short enough (~1 µs) and the gas temperature low (~500 K).

A collisional-radiative model for the ground state and fifty effective excited levels of atomic iron, and one level for singly-ionized iron, is set up for technological plasmas. Attention is focused on the population of excited states of atomic iron as a result of excitation, de-excitation, ionization, recombination and spontaneous emission. Effective rate coefficients for ionization and recombination, required in non-equilibrium plasma transport models, are also obtained. The collisional-radiative model is applied to a thermal arc plasma. Input parameters for the collisional-radiative model are provided by a magnetohydrodynamic simulation of a gas-metal welding arc, in which local thermodynamic equilibrium is assumed and the treatment of the transport of metal vapour is based on combined diffusion coefficients. The results clearly identify the conditions in the arc, under which the atomic state distribution satisfies the Boltzmann distribution, with an excitation temperature equal to the plasma temperature. These conditions are met in the central part of the arc, even though a local temperature minimum occurs here. This provides assurance that diagnostic methods based on local thermodynamic equilibrium, in particular those of optical emission spectroscopy, are reliable here. In contrast, deviations from the equilibrium atomic-state distribution are obtained in the near-electrode and arc fringe regions. As a consequence, the temperatures determined from the ratio of line intensities and number densities obtained from the emission coefficient in these regions are questionable. In this situation, the collisional-radiative model can be used as a diagnostic tool to assist in the interpretation of spectroscopic measurements.

A 3.0 GHz pulsed microwave source operated at atmospheric pressure with a pulse power of 1.4 MW, a maximum repetition rate of 40 Hz, and a pulse length of 3.5 µs is experimentally studied with respect to the ability to remove NOx from synthetic exhaust gases. Experiments in gas mixtures containing N2/O2/NO with typically 500 ppm NO are carried out. The discharge is embedded in a high-Q microwave resonator, which provides a reliable plasma ignition. Vortex flow is applied to the exhaust gas to improve gas treatment. Concentration measurements by Fourier transform infrared spectroscopy confirm an NOx reduction of more than 90% in the case of N2/NO mixtures. The admixture of oxygen lowers the reductive potential of the reactor, but NOx reduction can still be observed up to 9% O2 concentration. Coherent anti-Stokes Raman scattering technique is applied to measure the vibrational and rotational temperature of N2. Gas temperatures of about 400 K are found, whilst the vibrational temperature is 3000-3500 K in pure N2. The vibrational temperature drops to 1500 K when O2 and/or NO are present. The randomly distributed relative frequency of occurrence of selected breakdown field intensities is measured by a calibrated, short linear-antenna. The breakdown field strength in pure N2 amounts to 2.2×106 V m-1, a value that is reproducible within 2%. In the case of O2 and/or NO admixture, the frequency distribution of the breakdown field strength scatters more and extends over a range from 3 to 8×106 V m-1.

A low-pressure (1-10 hPa) pulsed microwave discharge (2.45 GHz) in oxygen of power 100-1000 W operated in a cylindrical vessel is investigated by miscellaneous diagnostic techniques to determine space- and time-resolved concentrations of the most important species. The electron density is measured by monitoring the detuning of a Fabry-Perot resonator, which is in resonance at = 337 ?m (HCN-laser). The same technique is used to detect those electrons generated when a sufficiently strong laser beam crosses laterally the intracavity HCN laser mode and destroys O- and O2 - ions in the discharge by photodetachment. During the release of photodetached electrons the microwave field in the discharge chamber changes. This field alteration is utilized to determine the n O- /n O2 - ratio, which is about 7 over the entire pulse. The concentration of rovibrational states of O2 and vibrational temperatures are measured by coherent anti-Stokes-Raman scattering (CARS) as well as O concentrations by two-photon-allowed laser induced fluorescence (TALIF). A global kinetic model has been developed to describe the production of various species such as oxygen atoms, metastable molecules, ozone and charged particles. The experimentally observed and theoretically predicted temporal behaviour of the oxygen atom density are in a good agreement, if wall losses of type O 1/2O2 with a probability of 0.004 are taken into account. Both experiment and modelling show a sharp enhancement of the electron density at the instant of the pulse switch-off. The effect has been explained to result mainly from the processes of collisional detachment of O- ions by collisions with metastable molecules O2 (a ) and oxygen atoms after switch-off.

Investigations on the breakdown and the maintenance phase in a pulsed N2 microwave plasma at 2.45 GHz under low pressure (1-10 mbar) have been carried out. The discharge chamber has a cylindrical geometry with a length of 80 mm and a radius of 45 mm. Microwave pulses with a duration of 50-200 microseconds and a repetition rate of 10-500 Hz were typical for the experiments. The behaviour of the electric field in the duct has been measured and calculated. The electron number density has been determined using an HCN laser interferometer and a Langmuir probe. The microwave power absorbed in the plasma was obtained measuring the forwardly directed and the reflected time resolved power flux. The vibrational excitation of the N2 molecules in the plasma was studied with spatial and temporal resolution on the basis of the coherent anti-Stokes Raman scattering (CARS) technique.

A pulsed microwave discharge burning close to the centre of a cylindrical chamber (/2 = 2.45 GHz) in pure nitrogen at low pressure (5 mbar) has been investigated theoretically. Boltzmann equation analysis is applied for the description of the breakdown and the consecutive maintenance phase of the discharge. The breakdown electric field is estimated using the calculated ionization frequency and the losses by the free electron diffusion. A self-consistent model for electron and heavy-particle kinetics coupling the rate master equations for the vibrational levels N2(X,v) of the electronic ground state of the nitrogen molecule to the Boltzmann equation of electrons has been developed. Besides the momentum transfer, inelastic as well as superelastic e-V collisions, ionization and free diffusion of electrons have been taken into account in the Boltzmann equation. The balance of the populations of the vibrational levels includes e-V, V-V and V-T exchanges, dissociation, atom re-association, vibrational deactivation on the walls and the effect of molecular diffusion. A further relation used is the global energy balance of electrons. The calculated breakdown electric field strength and the temporal course of the population of vibrational levels have been compared with experimental breakdown data and CARS measurements. Calculations and measurements are found to agree well.