Showing papers on "Electric discharge published in 2016"
TL;DR: In this article, an experimental investigation has been performed in order to study the effect of SiC microparticle suspended dielectric on machining Ti-6Al-4V with tungsten carbide electrode.
Abstract: Microelectric discharge milling is one of the variants of microelectric discharge machining process which acquire the attention of researchers due to its unique ability to produce microchannels and three-dimensional structures in difficult-to-machine materials like titanium. In the present work, an experimental investigation has been performed in order to study the effect of SiC microparticle suspended dielectric on machining Ti-6Al-4V with tungsten carbide electrode. The effects of major electric discharge milling process parameters—voltage, capacitance, and powder concentration in dielectric—on responses—viz., material removal rate (MRR) and tool wear rate (TWR)—were studied. Experiments were designed and performed based on response surface methodology (RSM)-Box–Behnken statistical design and the significance of in put parameters were identified with the help of analysis of variance. From the results, it is recommended to use powder concentration of 5 g/L, capacitance of 0.1 µF, and voltage of 115 V for...
92 citations
TL;DR: In this article, high resolution SEM micrographs were taken, covering the whole surface of small area samples (i.e., over a circular area of diameter about 0.9mm).
76 citations
TL;DR: In this paper, the authors presented a direct numerical experiment showing how the electron-positron plasma is created in an axisymmetric closed magnetosphere, where they showed the formation of an electric gap with unscreened electric field that continually accelerated particles along the magnetic field lines and sustains pair creation.
Abstract: The magnetospheres of magnetars are believed to be filled with electron-positron plasma generated by electric discharge. We present a first direct numerical experiment showing how the plasma is created in an axisymmetric closed magnetosphere. The $e^\pm$ discharge occurs in response to twisting of the magnetic field lines by a shear deformation of the magnetar surface, which launches electric currents into the magnetosphere. The simulation shows the formation of an electric "gap" with unscreened electric field ($\mathbf{E}\cdot \mathbf{B}
eq 0$) that continually accelerates particles along the magnetic field lines and sustains pair creation. The accelerating voltage is self-regulated to the threshold of the $e^\pm$ discharge. It controls the rate of energy release and the lifetime of the magnetic twist. The simulation follows the global evolution of the twisted magnetosphere over a long time and demonstrates its gradual resistive untwisting. A vacuum cavity forms near the star and expands, gradually erasing magnetospheric electric currents $j$. The active j-bundle shrinks with time and its footprints form shrinking hot spots on the magnetar surface bombarded by the created particles.
53 citations
TL;DR: In this paper, a lattice Boltzmann method was used to simulate the effect of the presence of such debris on the electric field strength, which was shown to be able to capture the local variation of electric field and predict qualitatively the correct trend of the electric fields strength increasing against the debris concentration.
52 citations
TL;DR: In this article, a tube electrode high-speed electrochemical discharge drilling (TSECDD) was used to machine a film-cooling hole in a nickel-based single-crystal superalloy (DD6).
40 citations
TL;DR: In this paper, the magnetic field was coupled with the conventional EDM plasma zone to test the hybrid process on Al-based metal matrix composites (MMCs) for improving process performance.
Abstract: The present study deals with an investigation of the hybrid electric discharge (ED) machining process executed in a magnetic field for improving process performance. Previous magnetic field-assisted electric discharge machining (MFAEDM) techniques, however, are limited to use with a class of magnetic workpieces. In this particular study, the magnetic field was coupled with the conventional EDM plasma zone to test the hybrid process on Al-based metal matrix composites (MMCs). The machining parameters, for instance, peak current as well as duration of pulse-on were selected to nail down thereafter effects on the response parameters like the material removal rate (MRR) and the surface integrity. The experimental results show an improvement of 12.9% MRR and reduction in recast layer formation at higher spark energy in the magnetic field environment. As the experimental outcome implied that the MFAEDM imparted appreciable process stability, a highly efficient pertinent process of EDM with high quality of the m...
38 citations
TL;DR: It shows that nanosecond pulse discharge has a significant advantage in energy cost and the main physiochemical processes for the generation of active species and the degradation of formaldehyde were discussed.
Abstract: In this study, needle-array to plate electrode configuration was employed to generate an atmospheric air diffuse discharge using both nanosecond pulse and sine AC voltage as excitation voltage for the purpose of improving indoor air quality. Different types of voltage sources and electrode configurations are employed to optimize electrical field distribution and improve discharge stability. Discharge images, electrical characteristics, optical emission spectra, and plasma gas temperatures in both sine AC discharge and nanosecond pulse discharge were compared and the discharge stability during long operating time were discussed. Compared with the discharge excited by sine AC voltage, the nanosecond pulsed discharge is more homogenous and stable, besides, the plasma gas temperature of nanosecond pulse discharge is much lower. Using packed-bed structure, where γ- Al2O3 pellets are filled in the electrode gap, has obvious efficacy in the production of homogenous discharge. Furthermore, both sine AC discharge and nanosecond pulse discharge were used for removing formaldehyde from flowing air. It shows that nanosecond pulse discharge has a significant advantage in energy cost. And the main physiochemical processes for the generation of active species and the degradation of formaldehyde were discussed.
35 citations
01 Nov 2016
TL;DR: In this article, the significance of discharge energy on the performance of wire electrical discharge turning process, namely, material removal rate, surface finish, thickness of recast layer and surface crack, is analyzed.
Abstract: Energy conservation is one of the most important aspects of electrical discharge machining process in which the material removal is by means of spark erosion. Metal removal in wire electrical discharge turning is a complex erosion mechanism which involves melting, vaporization and rapid cooling of molten material. In this work, the significance of discharge energy on the performance of wire electrical discharge turning process, namely, material removal rate, surface finish, thickness of recast layer and surface crack, is analyzed. New model to estimate material removal rate and surface finish in wire electrical discharge turning process have been proposed. Erosion energy and kinetic energy imparted by electrons and average physio-thermal properties of work material are utilized for the modeling. Proposed models are validated by conducting experiments on AISI 4340 steel material. The results obtained from the model are well in agreement with the experimental values. The influence of discharge energy on sur...
33 citations
TL;DR: In this paper, the influence of bubbles generated in the machining gap on the stability and accuracy of electrochemical machining was analyzed using a transparent electrode made of SiC single crystal, which is electrically conductive and optically transparent.
32 citations
TL;DR: In this paper, optical emission spectroscopy was used to characterize an electrical discharge plasma reactor with a liquid H2O film contacting different carrier gases, and the plasma gas temperatures for Ar, He, and 1% N2 in Ar were 1000-1200 K and did not vary significantly with liquid flow rate.
Abstract: Optical emission spectroscopy was used to characterize an electrical discharge plasma reactor with a liquid H2O film contacting different carrier gases. The plasma gas temperatures for Ar, He, and 1% N2 in Ar were 1000–1200 K and did not vary significantly with liquid flow rate. Increasing solution conductivity by adding KCl to deionized water in the Ar case lowered the temperature by 13%, increased the discharge power and lowered the H2O2 formation rates. The temperature was highest in the case of air (2400 K), and in the case of Ar the temperature increased with the addition of O2. The temperatures for this reactor are comparable to previous studies with discharges in humid gases, while the effects of liquid conductivity were similar to those reported with direct discharge in the liquid phase.
32 citations
TL;DR: In this paper, a closed-cycle repetitively pulsed DF laser is described and the Fitch circuit and thyratron switch are introduced to realize self-sustained volume discharge in SF6-D2 mixtures.
Abstract: The design and performance of a closed-cycle repetitively pulsed DF laser are described. The Fitch circuit and thyratron switch are introduced to realize self-sustained volume discharge in SF6–D2 mixtures. The influences of gas parameters and charging voltage on output characteristics of non-chain pulsed DF laser are experimentally investigated. In order to improve the laser power stability over a long period of working time, zeolites with different apertures are used to scrub out the de-excitation particles produced in electric discharge. An average output power of the order of 100 W was obtained at an operating repetition rate of 50 Hz, with amplitude difference in laser pulses <8 %. And under the action of micropore alkaline zeolites, the average power fell by 20 % after the laser continuing working 100 s at repetition frequency of 50 Hz.
TL;DR: In this article, an electrical discharge machining grinding using two block electrodes (EDG-TBE) was created in an effort to overcome the problem of measurement and reduce the complexity of the equipment.
TL;DR: In this paper, the formation of a double-headed streamer at three different oxygen concentrations: no oxygen, 1 ppm O2 and 20% O2, as in air was simulated with a cylindrically symmetric configuration at ambient electric field magnitudes three times the conventional breakdown field.
Abstract: Streamers are ionization filaments of electric gas discharges. Negative polarity streamers propagate primarily through electron impact ionization, whereas positive streamers in air develop through ionization of oxygen by UV photons emitted by excited nitrogen; however, experiments show that positive streamers may develop even for low oxygen concentrations. Here we explore if bremsstrahlung ionization facilitates positive streamer propagation. To discriminate between effects of UV and bremsstrahlung ionization, we simulate the formation of a double headed streamer at three different oxygen concentrations: no oxygen, 1 ppm O2 and 20% O2, as in air. At these oxygen levels, UV-relative to bremsstrahlung ionization is zero, small, and large. The simulations are conducted with a particle-in-cell code in a cylindrically symmetric configuration at ambient electric field magnitudes three times the conventional breakdown field. We find that bremsstrahlung induced ionization in air, contrary to expectations, reduces the propagation velocity of both positive and negative streamers by about 15%. At low oxygen levels, positive streamers stall; however, bremsstrahlung creates branching sub-streamers emerging from the streamer front that allow propagation of the streamer. Negative streamers propagate more readily forming branching sub-streamers. These results are in agreement with experiments. At both polarities, ionization patches are created ahead of the streamer front. Electrons with the highest energies are in the sub-streamer tips and the patches.
01 Jan 2016
TL;DR: In this paper, the authors provide a fundamental review about common APNTP technologies, which are mainly based on the direct application of electric fields across the electrodes, including corona discharge, dielectric barrier discharge, glow discharge, and plasma jet.
Abstract: Nonthermal plasmas, especially atmospheric pressure plasmas, are used increasingly for physical and chemical processing in widespread applications. Driven by emerging novel applications, atmospheric pressure nonthermal plasma sources (APNTPs) have been progressing to a broad technological field. The wide variety of APNTPs that exist span a range of electron densities and electron energies. The objective of this chapter is to provide a fundamental review about common APNTP technologies, which are mainly based on the direct application of electric fields across the electrodes. Common nonthermal electric discharge, including corona discharge, dielectric barrier discharge, glow discharge, and plasma jet are reviewed in the terms of discharge technologies, mechanisms, and mode characteristics. Recently developed nanosecond pulsed discharge produced APNTP also is introduced.
TL;DR: In this article, a 1D model for the simulation of transition from glow microdischarge to arc discharge with a thermionic cathode was built using COMSOL multiphysics, coupled with the gas heating equation for the self-consistent simulation of discharge at atmospheric pressure in a wide range of currents.
Abstract: A 1-D model for the simulation of transition from glow microdischarge to arc discharge with a thermionic cathode was built using COMSOL Multiphysics. The extended fluid model was coupled with the gas heating equation for the self-consistent simulation of discharge at atmospheric pressure in a wide range of currents. Both the secondary electron emission and the thermionic emission were taken into account simultaneously to allow for the transition. In order to properly account for thermionic emission, cathode heating was considered—heat flux equation was solved in a 1-D solid domain with heat fluxes on the cathode surface from the discharge domain used as boundary conditions. A thorough set of plasma-chemical reactions with account of molecular ions of argon was used. Using the external circuit allowed for obtaining stable solutions in a wide range of currents. By changing ballast resistance, the classical current–voltage characteristic of direct current discharge with transition from glow to arc was obtained. The distributions of such discharge parameters as charged and excited particle densities and fluxes, electron mean energies and temperatures, gas temperature, and electric potential were obtained for microdischarge, arc discharge, and transitional state. Time-dependent simulations allowed for obtaining the dynamics of discharge formation. It is shown that after the breakdown, the cathode is heated by the discharge current for a time of tens of milliseconds, and then, transition to stable arc discharge with thermionic cathode takes place.
TL;DR: In this paper, the authors present an experimental study of nanosecond discharges in distilled water bubbled with the monoatomic gas argon and with the polyatomic gases methane, carbon dioxide, and propane.
Abstract: Electric discharge in liquids with bubbles can reduce the energy consumption, which increases treatment efficiency. We present an experimental study of nanosecond discharges in distilled water bubbled with the monoatomic gas argon and with the polyatomic gases methane, carbon dioxide, and propane. We monitor the time evolution of the voltage and current waveforms, and calculate the injected charges to characterize the discharge. We establish a relationship between the injected charges and the shape of the plasma by time-resolved imaging to find that increasing the size of the gap reduces the injected charges. Moreover, we determine the plasma characteristics, including electron density, excitation temperatures (for atoms and ions), and rotational temperature of the OH and C2 radicals found in the plasma. Our space- and time-averaged measurements allow us to propose a spatial distribution of the plasma that is helpful for understanding the plasma dynamics necessary to develop and optimize applications based on nanosecond discharges in bubbled liquids.
TL;DR: In this article, the first MEMS type ionization vacuum sensor corresponding to the classical gauges with cold cathodes is presented, which operates on the principle of ionization of gases in an electric discharge, similarly to the Penning gauge.
Abstract: The paper presents the first MEMS type ionization vacuum sensor corresponding to the classical gauges with cold cathodes In contrast to the other MEMS sensors, it works both in medium and high vacuum It covers a pressure range from 20 down to 10−4 Pa The sensor is made of silicon and glass substrates by the use of microengineering techniques The overall dimensions of the sensor are 20 × 12 × 10 mm3 It operates on the principle of ionization of gases in an electric discharge, similarly to the Penning gauge The value of the discharge current is a measure of pressure The sensor can also be used for residual gas composition analysis in pressure range from 1000 Pa to 10−1 Pa The composition of gas species is determined on the basis of spectra of the glowing gases, recorded by a miniature fiber spectrometer Properties of the sensor: relations between discharge current, pressure, and power supply conditions, as well as characteristic spectral lines have been measured in a reference vacuum chamber for air and several gases
TL;DR: In this article, an electrical conductive layer is formed on the surface of the insulating ceramics, which maintains stable machining, and the layer control sequence is applied to the wire electrical discharge milling method (WED-milling) with a wire guide on a hemisphere tip.
TL;DR: In this article, a new phenomenon is observed in a spark discharge developing under normal conditions in air in a discharge circuit with a capacitive decoupling, which consists in the current channel bending becoming a source of a 4-6 cm long plasma jet directed across the channel.
Abstract: A new phenomenon is observed in a spark discharge developing under normal conditions in air in a discharge circuit with a capacitive decoupling. It consists in the current channel bending becoming a source of a 4–6 cm long plasma jet directed across the channel. The phenomenon is termed an apokampic discharge or an apokamp. Its emission spectrum contains the bands of electron-vibration transitions from the second positive group of molecular nitrogen. The conditions of formation of an apokamp are experimentally determined. A conclusion is drawn that in order construct a physical model of an apokamp, one has to take into account: 1) the presence of a local gas overheating in the site of the current channel bending, 2) the similarity of the current and voltage time dependences in the corona discharge and in the current channel (becoming a source of an apokamp), and 3) the length of the apokamp plasma jet.
TL;DR: In this paper, electrical discharge in a conductive solution of isopropyl alcohol in tap water (330 S cm−1) has been studied experimentally applying high voltage millisecond pulses (rise time ~0.4, amplitude up to 15 kV, positive polarity) to a pin anode electrode.
Abstract: Electrical discharge in a conductive solution of isopropyl alcohol in tap water (330 S cm−1) has been studied experimentally applying high voltage millisecond pulses (rise time ~0.4 , amplitude up to 15 kV, positive polarity) to a pin anode electrode. Dynamic current–voltage characteristics synchronized with high-speed images of the discharge were studied. The discharge was found to develop from high electric field region in the anode vicinity where initial conductive current with density ~100 A cm−2 results in fast heating and massive nucleation of vapor bubbles. Discharges in nucleated bubbles then produce a highly conductive plasma region and facilitate overheating instability development with subsequent formation of a thermally ionized plasma channel. The measured plasma channel propagation speed was 3–15 m s−1. A proposed thermal model of plasma channel development explains the low observed plasma channel propagation speed.
TL;DR: In this paper, a gas phase pulsed discharge over water surface and an underwater bubbling pulsing discharge was evaluated through diagnosis of H2O2 by a chemical probe method.
Abstract: Pulsed electric discharge over water surface/in water has been used to generate reactive species for decomposing the organic compounds in water, and hydrogen peroxide (H2O2) is one of the strong reactive species which can be decomposed into another stronger oxidative species, hydroxyl radical. The production efficacy of H2O2 by a gas phase pulsed discharge over water surface and an underwater bubbling pulsed discharge was evaluated through diagnosis of H2O2 by a chemical probe method. The experimental results show that the yield and the production rate of H2O2 increased with the input energy regardless of the electric discharge patterns, and the underwater bubbling pulsed discharge was more advantageous for H2O2 production considering both the yield and the production rate of H2O2. Results also indicate that the electric discharge patterns also influenced the water solution properties including the conductivity, the pH value and the water temperature.
TL;DR: In this paper, the authors present the results of studies concerning the assessment of propagation modes of electrical discharges developing in different liquid dielectrics, based on measurements of light emitted during discharge development.
TL;DR: In this article, the physical characteristics of water surface discharges were reported, with the needle electrode driven by 47 kV (FWHM) positive voltage pulses of 2 µs duration.
Abstract: This paper reports physical characteristics of water surface discharges. Discharges were produced by metal needle-to-water surface geometry, with the needle electrode driven by 47 kV (FWHM) positive voltage pulses of 2 µs duration. Propagation of discharges along the water surface was confined between glass plates with 2 mm separation. This allowed generation of highly reproducible 634 mm-long plasma filaments. Experiments were performed using different atmospheres: air, N2, and O2, each at atmospheric pressure. Time- and spatially-resolved spectroscopic measurements revealed that early spectra of discharges in air and nitrogen atmospheres were dominated by N2 2nd positive system. N2 radiation disappeared after approx. 150 ns, replaced by emissions from atomic hydrogen. Spectra of discharges in O2 atmosphere were dominated by emissions from atomic oxygen. Time- and spatially-resolved emission spectra were used to determine temperatures in plasma. Atomic hydrogen emissions showed excitation temperature of discharges in air to be about 2 × 104 K. Electron number densities determined by Stark broadening of the hydrogen H β line reached a maximum value of ~1018 cm−3 just after plasma initiation. Electron number densities and temperatures depended only slightly on distance from needle electrode, indicating formation of high conductivity leader channels. Direct observation of discharges by high speed camera showed that the average leader head propagation speed was 412 km s−1, which is substantially higher value than that observed in experiments with shorter streamers driven by lower voltages.
TL;DR: In this article, the formation and development of plasma in single air bubbles submerged in water were investigated using a 900 000 frame per second high-speed charge-coupled device camera.
Abstract: The formation and development of plasma in single air bubbles submerged in water were investigated. The difference in the discharge dynamics and the after-effects on the bubble were investigated using a 900 000 frame per second high-speed charge-coupled device camera. It was observed that depending on the position of the electrodes, the breakdown could be categorized into two modes: (1) direct discharge mode, where the high voltage and ground electrodes were in contact with the bubble, and the streamer would follow the shortest path and propagate along the axis of the bubble and (2) dielectric barrier mode, where the ground electrode was not in touch with the bubble surface, and the streamer would form along the inner surface of the bubble. The oscillation of the bubble and the development of instabilities on the bubble surface were also discussed.
TL;DR: A short review of a porous materials production from the powders of titanium, niobium and tantalum with a highvoltage discharge current is presented in this article, where the experimental dependences of bending strength, porosity, specific electrical resistance, radial and axial shrinkage from the sizes of particles of the examined powders and from the parameters of the electric discharge are given.
Abstract: A short review of a porous materials production from the powders of titanium, niobium and tantalum with a high-voltage discharge current is presented. The experimental dependences of bending strength, porosity, specific electrical resistance, radial and axial shrinkage from the sizes of particles of the examined powders and from the parameters of the electric discharge are given. The maximum correlations of the diameters and the length of the experimental samples of porous powders are stated. The examples of perspective applications of produced porous materials in the manufactured articles of electronics and medicine are shown.
TL;DR: In this paper, the morphology, element composition, and crystal structure of the Nickle particles produced by the ultrasound-aided spark discharge were observed and analyzed by SEM, EDS and XRD respectively.
TL;DR: In this paper, an atmospheric pressure plasma discharge in argon was generated using a needle-to-ring electrode configuration driven by a sinusoidal excitation voltage, and the electric discharge processes and discharge characteristics were investigated by inspecting the voltage-current waveforms, Lissajous curves and lighting emission images.
Abstract: In this paper, an atmospheric pressure plasma discharge in argon was generated using a needle-to-ring electrode configuration driven by a sinusoidal excitation voltage. The electric discharge processes and discharge characteristics were investigated by inspecting the voltage-current waveforms, Lissajous curves and lighting emission images. The change in discharge mode with applied voltage amplitude was studied and characterised, and three modes of corona discharge, dielectric barrier discharge (DBD) and jet discharge were identified, which appeared in turn with increasing applied voltage and can be distinguished clearly from the measured voltage-current waveforms, light-emission images and the changing gradient of discharge power with applied voltage. Based on the experimental results and discharge mechanism analysis, an equivalent electrical model and the corresponding equivalent circuit for characterising the whole discharge processes accurately was proposed, and the three discharge stages were characterised separately. A voltage-controlled current source (VCCS) associated with a resistance and a capacitance were used to represent the DBD stage, and the plasma plume and corona discharge were modelled by a variable capacitor in series with a variable resistor. Other factors that can influence the discharge, such as lead and stray capacitance values of the circuit, were also considered in the proposed model.
TL;DR: In this article, a fluid model coupled with an external circuit is built to explain the discharge mode transitions mechanism and the applied voltage drop's influence on He-DBD. But the model is limited to a single image.
Abstract: The discharge mode transitions and the characteristics of atmospheric pressure dielectric barrier discharge in pure helium (He-DBD) are studied. Different discharge modes of He-DBD are clarified, including filament-diffuse mixed mode, filamentary mode, diffuse mode, and multichannels coupled mode. The transitions of different modes are explored by changing the gap width and applied voltage. According to the luminous structure of discharge [short exposure (100~300 ns) image], it is found that there should be only Townsend-like and glow-like discharges that appear in the above modes. In Townsend-like discharge, the secondary electron emission coefficient (SEEC) of dielectric is estimated. Based on which, a fluid model coupled with an external circuit is built to explain the He-DBD mode transitions mechanism and the applied voltage drop’s influence on He-DBD. Through the temporal evolution of a luminous structure, a discharge filament is believed to be a contractive state of discharge channel, which should be an unstable glow-like discharge. The radius of discharge channel, changing with gap width and applied voltage, is measured. The discharge contraction is attributed to the nonlinear relationship between Townsend ionization coefficient and electric field. The enhancing interaction between different discharge channels inhibits the appearing of diffuse discharge around discharge filament, leading to the transition from mixed mode to filamentary mode. In the end, the multichannels coupled mode is proven to be glow-like discharge, and its formation mechanism is explained by the overlap of discharge channels.
TL;DR: In this article, the possibility of dielectric barrier discharge contraction prevention by means of air flow has been experimentally investigated, where a plasma generator with coaxial configuration was used in the experiments, and the discharge medium was atmospheric pressure air under natural humidity (about 50%).
Abstract: The possibility of dielectric barrier discharge contraction prevention by means of air flow has been experimentally investigated. A plasma generator with coaxial configuration was used in the experiments. The discharge medium was atmospheric pressure air under natural humidity (about 50%). A rectangle voltage pulse of 16 kV amplitude and 60 us duration was applied to the discharge electrodes with a pulse repetition rate of 3 kHz. The air flow rate through the discharge gap was varied from 0 to 32 L · min
-1
. The discharge uniformity was evaluated on the basis on the discharge afterglow brightness distribution in the cross section of the gap. It was found that the discharge afterglow uniformity grows with increase in the flow rate. The explanation for this phenomenon is presented.
TL;DR: In this paper, the time evolution of electron density and electron temperature in a nanosecond pulse, diffuse filament electric discharge in H2−He and O2-He mixtures at a pressure of 100 Torr is studied by Thomson/pure rotational Raman scattering and kinetic modeling.
Abstract: Time evolution of electron density and electron temperature in a nanosecond pulse, diffuse filament electric discharge in H2–He and O2–He mixtures at a pressure of 100 Torr is studied by Thomson/pure rotational Raman scattering and kinetic modeling. The discharge is sustained between two spherical electrodes separated by a 1 cm gap and powered by high voltage pulses ~150 ns duration. Discharge energy coupled to the plasma filament 2–3 mm in diameter is 4–5 mJ/pulse, with specific energy loading of up to ~0.3 eV/molecule. At all experimental conditions, a rapid initial rise of electron temperature and electron density during the discharge pulse is observed, followed by the decay in the afterglow, over ~100 ns–1 µs. Electron density in the afterglow decays more rapidly as H2 or O2 fraction in the mixture is increased. In He/H2 mixtures, this is likely due to more rapid recombination of electrons in collisions with and ions, compared to recombination with ions. In O2/He mixtures, electron density decay in the afterglow is affected by recombination with and ions, while the effect of three-body attachment is relatively minor. Peak electron number densities and electron temperatures are n e = (1.7–3.1) 1014 cm−3 and T e = 2.9–5.5 eV, depending on gas mixture composition. Electron temperature in the afterglow decays to approximately T e ≈ 0.3 eV, considerably higher compared to the gas temperature of T = 300–380 K, inferred from O2 pure rotational Raman scattering spectra, due to superelastic collisions. The experimental results in helium and O2–He mixtures are compared with kinetic modeling predictions, showing good agreement.