This paper introduces a deep learning-based methodology for reconstructing particle beam energy spectra from experimental attenuation curves. This task involves solving a classic ill-posed inverse problem for a Fredholm integral equation of the first kind. Unlike traditional Arsenin–Tikhonov regularization, the proposed framework utilizes two coupled neural networks for spectrum approximation and adaptive kernel correction. This approach explicitly accounts for measurement uncertainties in the experimental data. As a mesh-free technique, it operates directly on raw sparse experimental datasets without preprocessing. Validation using data from subnanosecond electron beams in gas-filled and vacuum diodes demonstrates that the method successfully resolves non-trivial two-peak spectral structures. In particular, it reliably identifies populations of “anomalous” high-energy electrons that are often obscured by classical regularization artifacts.

We have explored the evolution of the spatial distribution of radiation emitted from a repetitively pulsed glow discharge in an argon flow at atmospheric pressure with the following parameters-current 40-100 mA, voltage 250-300 V, pulse duration 10 mu s, repetition rate 50-100 kHz, argon flow rate 1000 sccm, and an inter-electrode gap of 6 mm. We find that at a threshold current of 40-60 mA, the uniform spatial distribution of plasma radiation changes to a regular structure with bright glowing spots separated by dimmer intervals similar to bead lightning. Time-resolved visualization reveals that the area of the cathode glow varies cyclically from pulse to pulse, and the spatial distribution of plasma radiation becomes uniform when the current pulse reaches its maximum and the discharge transitions to a quasi-stationary regime. As the current decreases, a spatially periodic non-uniform glow is formed in the discharge column that persists over the time intervals between the discharge current pulses during the off-voltage phase, as well as during breakdown of the discharge gap at the leading edge of the next pulse. We show that this phenomenon is caused by gas-dynamic instability of the boundary interface between the argon flow, cold and heated in plasma, surrounding the current channel as a result of convective cooling of the discharge gap.

The work studies the glow of diffuse plasma jets (DPJ), which make it possible to simulate some properties of red sprites, which are pulsed discharges observed in the upper layers of the Earth’s atmosphere at altitudes of 40–100 km, in low-pressure atmospheric air. DPJs are initiated by pulse-periodic capacitive discharge plasma created in a quartz tube between two external electrodes and simultaneously propagate in opposite directions. Two pairs of ring electrodes spaced 66 cm apart are used to generate DPJs which move towards each other. Bright areas of luminescence (BAL) similar to those observed in the lower part of column sprites appear when unipolar voltage pulses from generators are applied to each pair of ring electrodes with a delay of hundreds of nanoseconds. Air pressure of 1–2 Torr is shown to be optimal for the appearance of BAL at a generator voltage of 7 kV, and BALs are shown to appear due to the interaction of streamers which make up the DPJs. The speed of propagation of the DPJ front is measured for voltage pulses of positive polarity applied to the ring electrodes. Pictures of DPJs and BALs in them are made and their emission spectra are measured. Using the SPECAIR program, plasma parameters are calculated in different areas of DPJs. A decrease in the average electron temperature is found in the region where BALs appear. The results will be useful for studying the properties of red sprites.

This work presents a continuation of the study on the scattering of particles in a nanosecond spark discharge between two needle electrodes. Additional data were obtained on the scattering of electrode particles during voltage pulses of positive polarity with a half-maximum duration of 10 ns and a rise time of 2.2 ns, at atmospheric air pressure. Images of a discharge with particles flying away from a high-voltage electrode, obtained using a four-channel ICCD camera, are also presented. The study confirms that the formation of thin luminous tracks during diffuse and spark discharges is associated with the emission of metal particles from the surface of the electrodes. It is hypothesized that this process, similar to discharges in a vacuum, may involve mechanical phenomena that arise under the influence of a high electric field near needle electrodes.

A comparative study of some physicochemical properties of aqueous solutions resulted from the treatment of distilled and ground waters by pulsed discharges has been performed. Changes in the pH value, the conductivity of the solution, and the content of NO3anions and Ca++, Mg++, K+, and Na+ cations were studied. Water bodies were affected by active particles formed in the air under the action of a pulsed discharge, which is implemented in two options. The first option is conventionally called 'bubble discharge' since it assumes the ignition of a discharge in an air bubble in direct contact with a liquid. The second option is the case when active particles, which are formed in an air stream under the action of a barrier discharge, are blown into a liquid. It is shown that the bubble discharge in ground water gives the maximum performance for the NO3 anions, while in the case of barrier discharge the best performance in the formation of NO(3)anions is observed in distilled water. The pH value for ground water increases from 8.1 to 8.6 in the course of a 10-minute treatment using both discharges. However, in the case of distilled water treatment an inverse relationship is observed, so its value decreases from 7.5 to 3.5 pH. A multiple increase in the content of Ca++ and Mg++ cations in the water sample is observed when groundwater treating. Presumably, their increase in solution is associated with the transition of insoluble salts of calcium and magnesium carbonates (constant water hardness) into water-soluble nitrates (temporary hardness). In addition to magnesium and calcium ions, potassium and sodium cations were monitored in water samples. Their concentration in water was insignificantly affected by the treatments with discharges.

A compact emitter of a relatively simple design with argon filling has been developed, which can be used to create VUV and UV excilamps. Its characteristics were investigated. To increase the radiation power on the second continuum of argon dimers (λ ≈ 126 nm), a method based on gas flow through the discharge region was used. At an excitation pulse repetition rate of 96 kHz, the radiation power density at λ ≈ 126 nm behind the output window made of MgF2 greater than 5 mW/cm2 was obtained. It is shown that argon flow at a rate of 0.5–1 L/s through the discharge region makes it possible to stabilize the average power of VUV radiation at a level no worse than 2

The effect of a pulse repetition rate and a number of voltage pulses on the formation of a nanosecond discharge under a sharply inhomogeneous electric field, as well as on the generation of runaway electrons (REs), has been investigated. Trains consisting of 10, 20, 50, 100, 200, 500, and 1000 voltage pulses were applied across a point-to-plane gap filled with air. The pulse repetition rate was varied in the range of 10–1000 Hz. Waveforms of the voltage and RE current were recorded. Furthermore, the discharge formation dynamics were studied with fast-capturing optical methods. The data obtained were compared with the results obtained for the single mode. It was found that at the pulse repetition rate from 10 to 100 Hz, the amplitude of the RE current pulses decreases monotonously by 3–4 times and stabilizes to the tenth breakdown. The amplitude of the RE current pulses decreases by more than an order of magnitude at the pulse repetition rate of 1000 Hz. The reason is gas heating and a decrease in breakdown voltage. From the point of view of the practical application of the nanosecond discharge, pulse repetition rates up to 100 Hz are most preferable.

Представлены результаты исследований импульсного периодического тлеющего разряда в потоке аргона при атмосферном давлении, при частоте следования импульсов до 100 кГц, длительности импульса несколько микросекунд и при значениях тока в импульсе от нескольких десятков миллиампер до 1 А. Выявлены условия, при которых в разрядной плазме наблюдается присутствие ионов и атомов материалов катодной вставки, в качестве которых применялись легкоплавкие металлы. Показано, что при остывании атомов металлов происходит их слипание в наноразмерные частицы и формирование порошков оксидов металлов.

To date, the use of graphene in photodetecting devices has attracted great attention, since due to the absence of a band gap and the linear law of dispersion of free charge carriers, graphene has a wide range of photon registration and fast response time. However, due to the low amount of incident light absorption by graphene, the efficiency of graphene devices is limited, so improving the efficiency of light absorption remains one of the key tasks. In this paper, we present a method for enhancing the photoresponsivity and external quantum efficiency of graphene based on modification of the graphene surface by highly lightabsorbing titanium nanoparticles by magnetron sputtering.

The results of a study of the development of a nanosecond discharge in a point-to-point gap 2 mm long, filled with distilled water, are presented. Positive voltage pulses with a duration of 13 ns and an amplitude of a matched load of 25 kV (50 kV in the gap) were applied across the gap. Using a four-channel ICCD camera, the dynamics of streamer development was studied while simultaneously measuring voltage and current. It was observed that in the gap positive streamers develop alternately from each electrode when it is an anode. In the final stage, streamers collide and return ionization waves propagate in the direction of both electrodes. It has been established that in the spark stage of the discharge, the discharge current density reaches 6 × 107 A/cm2. A stratified structure is observed after the current declines. It is assumed that during the spark stage of the discharge, the plasma channel experiences self-compression under the influence of a strong magnetic field.

Physical principles and modern techniques for the formation of spontaneous vacuum ultraviolet radiation are described for three cases: the formation of line spectra of atoms, line spectra of multicharged ions and continuous spectra of excimer molecules. The parameters of the radiation sources are correlated with their applications: real and potential. The following schemes of the formation of vacuum ultraviolet radiation are described: H-type and E-type high frequencies discharges; discharge in a hollow cathode; glow, barrier, and arc discharges; high-voltage nanosecond discharge with a sharply inhomogeneous distribution of electric field strength in a gap; laser, discharge, and hybrid systems for multicharged ions formation; excitation of gas targets under conditions of gyrotron plasma heating. The review covers the state of the art over the last 20 years.

The development of a nanosecond discharge in a pin-to-pin gap filled with air at atmospheric pressure has been studied with high temporal and spatial resolutions from a breakdown start to the spark decay. Positive and negative nanosecond voltage pulses with an amplitude of tens of kilovolts were applied. Time-resolved images of the discharge development were taken with a four-channel Intensified Charge Coupled Device (ICCD) camera. The minimum delay between the camera channels could be as short as ≈ 0.1 ns. This made it possible to study the gap breakdown process with subnanosecond resolution. It was observed that a wide-diameter streamer develops from the high-voltage pointed electrode. The ionization processes near the grounded pin electrode started when the streamer crossed half of the gap. After bridging the gap by the streamer, a diffuse discharge was formed. The development of spark leaders from bright spots on the surface of the pointed electrodes was observed at the next stage. It was found that the rate of development of the spark leader is an order of magnitude lower than that of the wide-diameter streamer. Long thin luminous tracks were observed against the background of a discharge plasma glow. It has been established that the tracks are adjacent to brightly glowing spots on the electrodes and are associated with the flight of small particles.

AbstractDiffuse and volume discharges are currently used widely in various fields. This work compares the properties of diffuse and volume discharges, as well as considers the conditions for their formation at high pressures. The main attention is paid to a diffuse discharge (DD). It has been shown that the ignition of a diffuse discharges is preceded by the development of a wide streamers. In the case of a volume discharge, the streamers usually have a small diameter and an ionisation waves emerging from it passes into the spark leader with subsequent discharge constriction. There are images and emission spectra of diffuse discharges in air and nitrogen in the paper. It has been confirmed that a diffuse discharges initiated by a nanosecond voltage pulse in a point‐to‐plane gaps has a uniform effect on the surface of a flat electrode. It was found that thin tracks of luminous particles are observed against the background of the DD plasma glow. They are associated with sputtering of the pointed electrode material due to the large field enhancement on the macro‐ and microinhomogeneities.

Many scientific teams are currently studying the effects of plasma generated by nanosecond diffuse discharges on the surfaces of various materials in order to modify their properties. To achieve this, uniform plasma is required to act on the target being treated, which is often an electrode in a discharge system. Previously, the surface treatment uniformity of flat electrodes during a nanosecond discharge in a point-to-plane gap was studied by applying a carbon black layer, and a discharge mode was identified in which there was no erosion on the treated electrode. In this study, it was established that during a nanosecond discharge in air at atmospheric pressure in a non-uniform electric field, carbon black deposited on the surface of a flat anode can ignite. The conditions and dynamics of carbon black ignition during the nanosecond discharge were determined. It was observed that the carbon black is ignited on the surface and continues to combust in the gap in the form of flame plumes for tens of milliseconds. It was also found that the combustion of carbon black can occur in both diffuse and spark discharges.

Withdrawal This article has been withdrawn by IOP Publishing following the discovery that several authors are affiliated with an institution (Institute of High Current Electronics, Siberian Branch of the Russian Academy of Sciences) that is subject to sanctions by the US government. To ensure compliance with sanctions regulations, this article has been withdrawn from IOPscience.

Results of experimental studies of red-colored plasma diffuse jets are presented. Such jets are initiated by a capacitive discharge in air or nitrogen at pressures of 0.2–3 Torr fed by voltage pulses with an amplitude of 5–7 kV following with a frequency of 21 kHz. They can be considered as a lab analog of a columnar sprite. The jet is formed by successive ionization waves (streamers). A significant effect of the reduced electric field strength E/N on the color (emission spectrum) of a plasma diffuse jet has been established. It is shown that the transition from red to blue as the jet approaches the additional electrodes and the end flange of the discharge tube is due to an increase in E/N in these regions. This, in turn, explains the change in color of sprites as they approach the top of the storm clouds. An assumption about the influence of noctilucent clouds on the formation of the beaded structure of sprites is made. The plasma parameters (electron Te, vibrational Tv, rotational Tr, and translational Ttr temperatures, as well as E/N) in the region of the capacitive discharge and along the plasma diffuse jet were measured by optical emission spectroscopy. The measurements have shown that with the increase in distance from the electrode assembly, E/N decreases from ∼3500 to ∼200 Td, while Te changes from ∼50 to 3 eV. The gas temperature varies slightly from 400 to 360 K. The measurement results are compared with those of natural red sprites.

The comparison of ion concentrations, pH index, and conductivity in distilled and ground water after exposure to low-temperature plasma formed by barrier and bubble discharges is performed. It has been found that in the case of groundwater, the best performance for the production of NO3− anions is provided by the discharge inside the gas bubbles. For distilled water, the barrier discharge in air, followed by saturation of water with plasma products, is the most suitable from this point of view. In both treatments, the maximum energy input into the stock solution is ensured. After 10 min treatment of ground water, the pH index increases and then it decreases. The obtained numerical indicators make it possible to understand in which tasks the indicated treatment modes should be used, their comparative advantages, and disadvantages. From the point of view of energy consumption for obtaining approximately equal (in order of magnitude) amounts of NO3− anions, both types of discharge treatment are suitable. The research results point to a fairly simple way to convert salts (calcium carbonates) from an insoluble form to soluble one. Namely, when interacting with NO3− anions, insoluble carbonates pass into soluble nitrates.

Discharges with cathode spots can operate in a wide range of gas pressures. Erosion of the cathode material is an inherent property of such discharges. The erosion products are considered to be ionized atoms and electrically neutral microdroplets. In accordance with this concept, a plasma source based on a pulsed cathodic arc discharge in atmospheric-pressure argon with a current of up to 200 A, a pulse duration of 250 μs, and a pulse repetition rate of 10 Hz was implemented. Using this source, the synthesis of magnesium oxide powder was performed. The chemical composition of the erosion products was determined using the TEM/EDS method and the composition of the gas mixture in which the discharge system operated was evaluated by optical spectrometry. It was shown that particles of the synthesized powder have different morphological features, depending on the nature of the electrical erosion of the cathode material. Micron-sized particles are formed due to the removal of microdroplets from liquid–metal craters on the cathode surface at certain plasma pressures. Submicron particles are produced during the agglomeration of atoms originating from the plasma jets flowing out from cathode spots. These atoms are magnesium ions that are neutralized by collisions with gas particles. The advantages and disadvantages of this synthesis method are discussed in this paper. The reference methods for the powder synthesis of magnesium oxide are compared. The prospects of the studied method from the point of view of its application for obtaining ceramic materials are also evaluated.

The design and parameters of a compact excilamp with an original sealed-off emitter made of a quartz tube with an outer diameter of 21 mm are described. The characteristics of xenon radiation in the vacuum ultraviolet region of the spectrum have been studied. On the band of the second xenon continuum, which has a maximum at the wavelength λ ≈ 172 nm, at a pulse repetition rate of 96 kHz, a radiation power density of 30 mW/cm 2 was obtained. The excilamp was used for excitation of polymethyl methacrylate, in which a photoluminescence band was recorded in the spectral region of 380–480 nm.