Increase In Electron Density Research Articles

Characteristics of electron temperature profile stiffness in electron-heated plasmas on EAST

A very high core electron temperature (T e0 ∼ 10 keV) plasma has been established and stably sustained by applying both lower hybrid wave (LHW) and on-axis electron cyclotron resonance heating (ECRH) in the Experimental Advanced Superconducting Tokamak (EAST). In this work, power balance analysis shows that the increase of ECRH power can increase the normalized T e gradient significantly at the plasma core region (ρ < 0.6), but does not change the T e profile stiffness in the low-density L-mode plasmas. This has been considered to be due to a strong synergistic effect between ECRH and LHW. Furthermore, three distinguishable stages characterized by different T e profile stiffnesses can be identified from the density ramp-up in the electron-heated plasma on EAST. A stronger T e profile stiffness at ρ = 0.3 has been observed in the Stage-II, where the LHW power deposition gradually moves away from the plasma core region, following the electron density increases. Furthermore, the formation of an internal plasma density transport barrier inside ρ ∼ 0.6, accompanied by a sudden drop in core T e and a rise in both core plasma density and ion temperature, has been observed for the first time during the transition from the Stage-II to the Stage-III when the central line-averaged plasma density reaches a threshold of 2.2 × 1019 m−3. This finding strongly affects further development of high-performance gas-fueled electron-heated plasma scenarios in EAST and suggests an advanced operational regime with a wide internal plasma density transport barrier.

Quantum effects on the propagation of surface magnetoplasmon polaritons in a graphene-plasmonic structure

We investigate the properties of surface magnetoplasmon polaritons (SMPPs) in a graphene-plasmonic structure which is constructed as a graphene film sandwiched with two semi-infinite dielectrics under a perpendicular configuration. By solving Maxwell equations and quantum magneto-hydrodynamic equations with considering the quantum statistical and quantum diffraction effects, we deduce the dispersion relation of graphene SMPPs (GSMPPs) in detail. We show how the graphene electron density, the external magnetic field, and the dielectric constant, affect the features of the dispersion of GSMPPs in both classical and quantum cases. We find that the quantum effects (QEs) significantly alter the properties of GSMPPs, which are entirely different from those in a classical model. We find that the propagation speed of classical GSMPPs has small increases while the propagation speed of quantum GSMPPs has fast and sharp increases along with the increases in graphene electron density. We further find that the propagation speed decreases gradually by increasing the applied magnetic field in both classical and quantum GSMPPs. Moreover, we also find that the propagation speed of classical GSMPPs has fast decreases tending to zero at large wavenumber while the propagation speed of quantum GSMPPs has slow decreases tending to infinity with increasing the dielectric constant. Our findings elucidate that QEs play a crucial role in the properties of GSMPPs and their response to different parameters.

Study on characteristics of electron parameters on inert gas addition in a capacitively coupled SF6/O2 plasma

In this paper, characteristics of electron parameters of SF6/O2 and inert gas mixture in a capacitively coupled plasma were studied. Here, gases such as He, Ar, and Xe were added to SF6/O2 mixture and electron energy probability functions (EEPFs) were measured. The electron parameters were acquired, which agreed well with EEPF behaviors. Normally, the inert gas functioned as an electron source and the electron density tended to increase. When the inert gas ratio exceeded other gases, the effect of the mixture varied on each gas. He showed its unique behaviors with the increase in electron temperature. Ar and Xe showed consistent behaviors with increasing electron density and decreasing electron temperature as the inert gas proportion increases. Different behaviors of the electron parameters in inert gases can be explained by the complex contribution of electron attachment of SF6 and the ionization rate of each inert gas.

Fluorinated triphenylphosphonium analogs improve cell selectivity and invivo detection of mito-metformin.

Triphenylphosphonium (TPP+) conjugated compounds selectively target cancercells by exploiting their hyperpolarized mitochondrial membrane potential. Todate, studies have focused on modifying either the linker or the cargo of TPP+-conjugated compounds. Here, we investigated the biological effects ofdirect modification to TPP+ to improve the efficacy and detection of mito-metformin (MMe), a TPP+-conjugated probe we have shown to have promising preclinical efficacy against solid cancer cells. We designed, synthesized, and tested trifluoromethyl and methoxy MMe analogs (pCF3-MMe, mCF3-MMe, and pMeO-MMe) against multiple distinct human cancer cells. pCF3-MMe showed enhanced selectivity toward cancer cells compared to MMe, while retaining thesame signaling mechanism. Importantly, pCF3-MMe allowed quantitative monitoring of cellular accumulation via 19F-NMR invitro and invivo. Furthermore, adding trifluoromethyl groups to TPP+ reduced toxicity invivo while retaining anti-tumor efficacy, opening an avenue to de-risk these next-generation TPP+-conjugated compounds.

Combined effects of temperature and humidity on the interaction between tomato and Botrytis cinerea revealed by integration of histological characteristics and transcriptome sequencing.

The environment significantly impacts the interaction between plants and pathogens, thus remarkably affecting crop disease occurrence. However, the detailed combined mechanisms of temperature and humidity influencing this interaction remain unclear. In this study, the interaction between tomato and Botrytis cinerea in various temperature and humidity conditions was analyzed by histological observation and a dual RNA-seq approach. Results showed that low humidity was not favorable for mycelial growth, resulting in infection failure. Both high and low temperatures at high humidity successfully inhibited pathogenic infection and disease incidence in the tomato plants, thus enhancing their resistance to B. cinerea. The high temperature and high humidity (HH) treatment induced the upregulation of light reaction genes, increased the net photosynthetic rate, and expanded the chloroplast morphology of infected tomatoes. The HH treatment also inhibited the expression of cell cycle-related genes of B. cinerea, interfered with conidial germination and mycelial growth, and damaged mycelial cell structure. Low temperature and high humidity (LH) treatment induced the expression of cell wall modification genes and remodeled the cell wall morphology of tomatoes in response to B. cinerea. In addition, the downregulated fungal catabolic genes and the abnormal increase in electron density of mycelial cells under LH treatment subsequently reduced the infection ability of B. cinerea. These results further explain the coupled effects of temperature and humidity on plant defenses and pathogen virulence, and provide a potential means to control gray mold.

Adsorption kinetics of 20 glucocorticoids at environmentally relevant concentrations in wastewater by powdered activated carbons and development of surrogate models

Glucocorticoids (GCs) are widely used in the treatment of the coronavirus disease of 2019 (COVID-19), and the toxicity of GCs to aquatic organisms has aroused widespread concern. Powdered activated carbon (PAC) has proven effective in removing various trace organic pollutants. In this study, the adsorption behaviors of 20 typical GCs onto PACs were investigated at environmentally relevant concentrations (ng/L) in real wastewater, using four commercially available PACs (HDB, WPH, 20BF, PWA). The results showed that PAC adsorption was feasible for GC removal at ng/L concentrations. After adsorption for 60 min, the GC removal efficiencies obtained by HDB, WPH, 20BF, and PWA were 90–98 %, 89–97 %, 84–96 %, and 71–90 %, respectively. The adsorption processes of 20 GCs on PACs were well fitted by the pseudo-second-order kinetics model (with R2 >0.98). Among the four PACs, HDB achieved the highest rates because of the electrostatic attraction between HDB (positively charged) and the complex of GCs and natural organic matter (GC-NOM, negatively charged). Among the 20 GCs, compounds with substitutions of halogen atoms or five-membered rings at C-17 achieved higher adsorption rates because of the enhanced formation of hydrogen bonds and a resulting increase in electron density. In addition, surrogate models with total fluorescence (TF) and ultraviolet absorbance at 254 nm (UV254) were developed to monitor the attenuation trend of GCs during adsorption processes. Compared with the UV254 model, the TF model showed better sensitivity to GC monitoring, which could greatly simplify the water quality monitoring process and facilitate online monitoring of GCs in water.

Complexed Semiconductor Cores Activate Hexaniobate Ligands as Nucleophilic Sites for Solar-Light Reduction of CO2 by Water.

Although pure and functionalized solid-state polyniobates such as layered perovskites and niobate nanosheets are photocatalysts for renewable-energy processes, analogous reactions by molecular polyoxoniobate cluster-anions are nearly absent from the literature. We now report that under simulated solar light, hexaniobate cluster-anion encapsulated 30-NiII -ion "fragments" of surface-protonated cubic-phase-like NiO cores activate the hexaniobate ligands towards CO2 reduction by water. Photoexcitation of the NiO cores promotes charge-transfer reduction of NbV to NbIV , increasing electron density at bridging oxo atoms of Nb-μ-O-Nb linkages that bind and convert CO2 to CO. Photogenerated NiO "holes" simultaneously oxidize water to dioxygen. The findings point to molecular complexation of suitable semiconductor "fragments" as a general method for utilizing electron-dense polyoxoniobate anions as nucleophilic photocatalysts for solar-light driven activation and reduction of small molecules.

Complexed Semiconductor Cores Activate Hexaniobate Ligands as Nucleophilic Sites for Solar‐Light Reduction of CO2 by Water

AbstractAlthough pure and functionalized solid‐state polyniobates such as layered perovskites and niobate nanosheets are photocatalysts for renewable‐energy processes, analogous reactions by molecular polyoxoniobate cluster‐anions are nearly absent from the literature. We now report that under simulated solar light, hexaniobate cluster‐anion encapsulated 30‐NiII‐ion “fragments” of surface‐protonated cubic‐phase‐like NiO cores activate the hexaniobate ligands towards CO2 reduction by water. Photoexcitation of the NiO cores promotes charge‐transfer reduction of NbV to NbIV, increasing electron density at bridging oxo atoms of Nb‐μ‐O‐Nb linkages that bind and convert CO2 to CO. Photogenerated NiO “holes” simultaneously oxidize water to dioxygen. The findings point to molecular complexation of suitable semiconductor “fragments” as a general method for utilizing electron‐dense polyoxoniobate anions as nucleophilic photocatalysts for solar‐light driven activation and reduction of small molecules.

The Great Flare of 2021 November 19 on AD Leonis

We present a detailed analysis of a superflare on the active M dwarf star AD Leonis. The event presents a rare case of a stellar flare that was simultaneously observed in X-rays (with XMM-Newton) and in the optical (with the Transiting Exoplanet Survey Satellite, TESS). The radiated energy in the 0.2 − 12 keV X-ray band (1.26 ± 0.01 × 1033 erg) and the bolometric value (EF, bol = 5.57 ± 0.03 × 1033 erg) place this event at the lower end of the superflare class. The exceptional photon statistics deriving from the proximity of AD Leo has enabled measurements in the 1 − 8 Å GOES band for the peak flux (X1445 class) and integrated energy (EF, GOES = 4.30 ± 0.05 × 1032 erg), which enables a direct comparison with data on flares from our Sun. From extrapolations of empirical relations for solar flares, we estimate that a proton flux of at least 105 cm−2 s−1 sr−1 accompanied the radiative output. With a time lag of 300 s between the peak of the TESS white-light flare and the GOES band flare peak as well as a clear Neupert effect, this event follows the standard (solar) flare scenario very closely. Time-resolved spectroscopy during the X-ray flare reveals, in addition to the time evolution of plasma temperature and emission measure, a temporary increase in electron density and elemental abundances, and a loop that extends into the corona by 13% of the stellar radius (4 × 109 cm). Independent estimates of the footprint area of the flare from TESS and XMM-Newton data suggest a high temperature of the optical flare (25 000 K), but we consider it more likely that the optical and X-ray flare areas represent physically distinct regions in the atmosphere of AD Leo.

Investigation of the plasma parameters induced from a silver source in air using Boltzmann–Blott approach

In this paper, the influence of laser irradiance on the plasma characteristics of a silver target is investigated in relation to one another. A Q-switched nanosecond Nd:YAG laser with the fundamental harmonic wavelength (1064 nm) and an irradiance ranging from [Formula: see text] W/cm2to [Formula: see text] W/cm2was used to irradiate these matrices. The irradiance was measured at atmospheric pressure. Temperature of the plasma and the electron density were calculated for different laser intensities of silver based on their oxidation states. The Boltzmann plot and the Stark broadening technique were used to compute the properties of the plasma ([Formula: see text] and [Formula: see text]. Based on the findings, it is clear that the temperature of the electrons in the Ag plasma does not increase linearly with increasing laser irradiation. These variations in the temperatures of the electrons in those matrices are brought on by matrix effects. On the other hand, an increase in laser irradiance was shown to cause an increase in electron density, which resulted in a widening of the line profiles associated to electron density.

Optimization of heterostructure design for switching pHEMT transistors

In this work, the design of one-side-doped pHEMT heterostructures was varied to obtain better microwave switching transistor parameters. For this purpose, the doping level, the method of introducing the doping impurity and the type of spacer were varied. It was obtained that the electron density in the heterostructures increases without saturation up to a sheet donor concentration of 9 × 1013 cm−2. In the sheet donor concentration range of (5–6) × 1012 cm−2 a sharp increase in electron density in δ-doped heterostructures was observed. At an optimum concentration of the donors of 6 × 1012 cm−2 the conductivity of heterostructures with modulation doping from the supply layer is 9% higher than that of δ-doped heterostructures. The use of a spacer in the form of an AlAs/GaAs superlattice leads to a decrease in the electron density, which is more pronounced for δ-doped heterostructures. But the conductivity of heterostructures with AlAs/GaAs spacer is higher due to better mobility. Measurements of electron density and mobility, as well as the conductivity of heterostructures together with the calculation of electron concentration at different gate biases by the self-consistent solution of Schrödinger and Poisson equations showed that δ-doped heterostructures at 6 × 1012 cm−2 and AlAs/GaAs spacers are most preferable for switching transistors. These heterostructures were used to fabricate monolithic integrated circuits of single-pole double throw pHEMT-based switches with gate length and widths of 0.5 μm and 100 μm, respectively. The resulting transistors had the following parameters: gm = 400 mS/mm, saturation current density ID = 380 mA/mm, ON-state resistance 1.0 Ohm × mm, OFF-state capacitance 0.37 pF/mm. Parameters of the fabricated switches at frequency of 20 GHz are the following: insertion loss 2.2 dB, isolation 56 dB, return loss 11.7 dB, linearity P1dB 21 dBm and IIP3 - 40 dBm.

Cover Feature: Ligand Substituent Effects on Light‐Driven Hydrogen Evolution by Cobalt(II) Tripodal Iminopyridine Catalysts under Precious‐Metal‐Free Conditions (Eur. J. Inorg. Chem. 31/2022)

The Cover Feature shows light-driven hydrogen evolution mediated by cobalt(II) tripodal iminopyridine complexes, using tri(n-butyl)triazatriagulenium (TATA+) as the organic sensitizer and triethylamine (TEA) as the sacrificial donor in aqueous acetonitrile. The activity of the complexes depends highly on the electronic properties of the substituents on the pyridine moieties. Under acidified conditions, the activity for H2 production was enhanced for the substituted catalysts. The 5-Cl derivative showed higher activity and lower catalytic potential (Ecat), which can be attributed to the stabilized CoI, favorable for the formation of CoIII(H). The improved H2 productivity and lower Ecat of the 5-CH3O, 6-CH3O, and 5-CH3 derivatives are suggested to be associated with the increased electron density on the CoIII(H) intermediate, which is more susceptible to protonation. More information can be found in the Research Article by J. Xiang, C.-F. Leung, C.-C. Ko and co-workers.

Clues of Lithosphere, Atmosphere and Ionosphere Variations Possibly Related to the Preparation of La Palma 19 September 2021 Volcano Eruption

On 19 September 2021, La Palma Cumbre Vieja Volcano started an eruption classified as Volcanic Explosive Index (VEI) 3. In this study, at least the six months prior to such an event have been investigated to search for possible lithosphere–atmosphere–ionosphere bottom-up interactions. The lithosphere has been analysed in terms of seismicity getting advantages from the high-density local seismic network. Possible atmospheric alterations related to the volcano emissions or release of gases due to the uplift of the magmatic chamber have been searched in SO2, aerosol, dimethyl sulphide, and CO. The magnetic field on Earth’s surface has been studied by ground geomagnetic observatories. The status of the ionosphere has been investigated with two satellite missions: China Seismo Electromagnetic Satellite (CSES) and European Space Agency Swarm constellation, with Total Electron Content (TEC) retrieved from global maps. We identified a temporal migration of the seismicity from November 2020 at a depth of 40 km that seems associable to magma migration, firstly to a deep chamber at about 15 km depth and in the last 10 days in a shallow magma chamber at less than 5 km depth. The atmospheric composition, ground geomagnetic field, and ionosphere showed anomalies from more than three months before the eruption, suggesting a possible influence from the bottom geo-layers to the upper ones. CSES-01 detected an increase of electron density, confirmed by TEC data, and alterations of vertical magnetic field on ground Guimar observatory that are temporal compatible with some volcanic low seismic activity (very likely due to the magma uplift), suggesting an eventual electromagnetic disturbance from the lithosphere to the ionosphere. A final increase of carbon monoxide 1.5 months before the eruption with unusually high values of TEC suggests the last uplifting of the magma before the eruption, confirmed by a very high shallow seismicity that preceded the eruption by ten days. This work underlines the importance of integrating several observation platforms from ground and overall space to understand geophysics better, and, in particular, the natural hazard affecting our planet.

Reagent-and solvent-mediated Fe2O3 morphologies and electrochemical mechanism of Fe2O3 supercapacitors

A solvothermal technique was used to synthesize nine different ferric oxide (Fe 2 O 3 ) morphologies: rhomb ( R ), flower ( F ), hollow sphere ( HS ), crystal ( C ), elongated hexagon ( EH ), hexagon ( H ), sugar apple ( SA ), sand/spherical particle ( SSP ) and mixed particle ( MP ). X-ray diffraction, high-resolution transmission electron microscopy and selected area electron diffraction reveal six of the nine powders to be composed of the pure α-Fe 2 O 3 structure, whereas the EH-Fe 2 O 3 , H-Fe 2 O 3 and SA-Fe 2 O 3 powders contain the mixed α-Fe 2 O 3 /Fe 3 O 4 structure. The F-Fe 2 O 3 powder has the highest total specific pore volume (0.059 cm 3 g −1 ), the largest average pore size (23.983 nm), and a high specific surface area (9.82 m 2 g −1 ), which subsequently produce the highest specific capacitance of 218.49 F g −1 . X-ray photoemission spectroscopy and energy dispersive spectroscopy detect H 2 O and K + adsorption on the F-Fe 2 O 3 electrode and the reduction of Fe 3+ to Fe 2+ in the charged state, whereas H 2 O molecules and K + ions are released from the F-Fe 2 O 3 electrode, and Fe 2+ is oxidized to Fe 3+ in the discharged state. The simulated K-inserted-α-Fe 2 O 3 structure shows an increased electron density surrounding Fe atoms, which is indicative of Fe 3+ reduction during the charged state. The F-Fe 2 O 3 film is able to retain 76.81 % of its 20 th cycle value after 1,000 cycles. Four series-supercapacitor coin cells constructed from the F - Fe 2 O 3 anode and the MnO 2 cathode deliver an outstanding energy density of 10.96 Wh kg −1 and power density of 0.461 kW kg −1 . • Nine Fe 2 O 3 morphologies were synthesized by different reagents and solvents. • F-Fe 2 O 3 electrodes have the highest specific capacitance of 218.49 F g −1 . • The charged/discharged F-Fe 2 O 3 electrode inserts/deinserts H 2 O molecules and K + ions. • K-inserted-α-Fe 2 O 3 structure displays increasing electron density on Fe atoms. • MnO 2 // F-Fe 2 O 3 gives high energy (15.58 Whkg −1 ) and power densities (399 Wkg −1 ).

Combined spectroscopy and electrical characterization of La:BaSnO3 thin films and heterostructures

For La-doped BaSnO3 thin films grown by pulsed laser deposition, we combine chemical surface characterization and electronic transport studies to probe the evolution of electronic states in the band structure for different La-doping contents. Systematic analyses of spectroscopic data based on fitting the core electron line shapes help to unravel the composition of the surface as well as the dynamics associated with increasing doping. These dynamics are observed with a more pronounced signature in the Sn 3d core level, which exhibits an increasing asymmetry to the high binding energy side of the peak with increasing electron density. The present results expand the current understanding of the interplay between the doping concentration, electronic band structure, and transport properties of epitaxial La:BaSnO3 films.

Disturbances of electron density in the high latitude upper (F-region) ionosphere induced by X-mode HF pump waves from EISCAT UHF radar observations

The paper presents experimental results concerning disturbances of electron density in the high latitude ionosphere F-region, induced by powerfulHF radio waves (pump waves) with extraordinary (X-mode) polarization. The experiments were carried out at the EISCAT/Heating facility at Tromsø, Norway. The EISCAT UHF incoherent scatter radar (ISR), running at 930 MHz, co-located with a heating facility, was used to detect the disturbances of electron density. In the course of the experiments, the X-mode HF pump waves radiated into the F-region towards the magnetic zenith at different pump frequencies and ratios of the pump frequency to the critical frequency of the F2 layer.The effective radiated power was ERP = 360–820 MW. An increase in electron densities was found in a wide altitude range, giving rise to field-aligned ducts with enhanced electron density. The features and behavior of the ducts were investigated. It was revealed that the ducts are formed under quiet background geophysical conditions in a wide altitude range up to the upper altitude limit of EISCAT ISR measurements, when the pump frequencies were both below and above the critical frequency of the F2 layer (fH ≤ foF2 or fH &gt; foF2). A plausible formation mechanism of the ducts is discussed.

Increasing electron density by surface plasmon resonance for enhanced photocatalytic CO2 reduction

The photocatalytic CO2 reduction reaction is a multi-electron process, which is greatly affected by the surface electron density. In this work, we synthesize Ag clusters supported on In2O3 plasmonic photocatalysts. The Ag–In2O3 compounds show remarkedly enhanced photocatalytic activity for CO2 conversion to CO compared to pristine In2O3. In the absence of any co-catalyst or sacrificial agent, the CO evolution rate of optimal Ag–In2O3-10 is 1.56 μmol/g/h, achieving 5.38-folds higher than that of In2O3 (0.29 μmol/g/h). Experimental verification and DFT calculation demonstrate that electrons transfer from Ag clusters to In2O3 on Ag–In2O3 compounds. In Ag–In2O3 compounds, Ag clusters serving as electron donators owing to the SPR behaviour are not helpful to decline photo-induced charge recomnation rate, but can provide more electron for photocatalytic reaction. Overall, the Ag clusters promote visible-light absorption and accelerate photocatalytic reaction kinetic for In2O3, resulting in the photocatalytic activity enhancement of Ag–In2O3 compounds. This work puts insight into the function of plasmonic metal on enhancing photocatalysis performance, and provides a feasible strategy to design and fabricate efficient plasmonic photocatalysts.

Heterostructured V-Doped Ni2 P/Ni12 P5 Electrocatalysts for Hydrogen Evolution in Anion Exchange Membrane Water Electrolyzers.

Regulating the electronic structure and intrinsic activity of catalysts' active sites with optimal hydrogen intermediates adsorption is crucial to enhancing the hydrogen evolution reaction (HER) in alkaline media. Herein, a heterostructured V-doped Ni2 P/Ni12 P5 (V-Ni2 P/Ni12 P5 ) electrocatalyst is fabricated through a hydrothermal treatment and controllable phosphidation process. In comparison with pure-phase V-Ni2 P, in/ex situ characterizations and theoretical calculations reveal a redistribution of electrons and active sites in V-Ni2 P/Ni12 P5 due to the V doping and heterointerfaces effect. The strong coupling between Ni2 P and Ni12 P5 at the interface leads to an increased electron density at interfacial Ni sites while depleting at P sites, with V-doping further promoting the electron accumulation at Ni sites. This is accompanied by the change of active sites from the anionic P sites to the interfacial Ni-V bridge sites in V-Ni2 P/Ni12 P5 . Benefiting from the interface electronic structure, increased number of active sites, and optimized H-adsorption energy, the V-Ni2 P/Ni12 P5 exhibits an overpotential of 62mV to deliver 10mA cm-2 and excellent long-term stability for HER. The V-Ni2 P/Ni12 P5 catalyst is applied for anion exchange membrane water electrolysis to deliver superior performance with a current density of 500mA cm-2 at a cell voltage of 1.79V and excellent durability.

The generation of higher harmonics in capacitively coupled argon plasma driven by 8 MHz, 100 MHz and 8/100 MHz

The generation of higher harmonics in capacitively coupled argon plasma (CCP) driven by 8 MHz (60 W), 100 MHz (10-40 W) and dual frequency 8/100 MHz (high frequency power of 10-40 W) are studied when the pressure is 30 mTorr. At dual frequency 8/100 MHz, the number of harmonics in the voltage and current measured on the discharge electrode is the largest, and the number of harmonics increases with the increase of high frequency (HF) power. The amplitude of the corresponding harmonics of dual frequency 8/100 MHz is between single 8 MHz (60 W) and single 100 MHz (10-40 W). The measured voltages on the discharge electrode are used to calculate the electron density, electron temperature, electric field, current density and electron heating of 8 MHz (60 W), 100 MHz (10-40 W) and 8/100 MHz (high frequency power of 10-40 W) at the pressure of 30 mTorr by Particle-in-cell/Monte Carlo collision (PIC/MCC) methods. The simulated results show that the harmonics amplitude of the electric field and current density in the bulk center reach the largest with the HF power increase in 8/100 MHz. The sheath thickness gradually narrows at different HF power with the electron density increase. At dual frequency (8/100 MHz), the electron density and electron temperature are higher than 8 MHz and lower than 100 MHz. The electron heating mainly occurs at the boundary between the sheath and plasma. The plasma series resonance (PSR) effect and dual frequency coupling effect can generate multiple harmonics in dual frequency CCP discharge. The expansion and collapse of sheath indicate that the electrons gain and lose energy respectively because of PSR.

Numerical simulation of air DBD under standard atmospheric pressure

In order to study the mechanism of dielectric barrier discharge (DBD) producing non-equilibrium plasma, the DBD equipment was simplified into a one-dimensional model. The AC power supply voltage was set as 18 kV, the frequency was set as 10 kHz, and the discharge medium was N2 and O2 with a mass fraction of 4:1 to simulate the air. The impact cross-section, electron mobility and initial electron temperature of the discharge reaction were determined by BOLSIG+. The electric potential field diagram, voltage current relation diagram, electron density diagram, temperature distribution diagram and electron energy distribution function EEDF diagram are obtained. The results show that the electric field reaches the maximum near the gap sheath. Due to the generation of an additional electric field, the current density reaches the maximum at the rising edge of the air gap voltage. The continuous ionization of air particles in the discharge process leads to the accumulation of electrons and the formation of electron collapse, which leads to the increase in electron density and the decrease in electron temperature. As the reduced electric field E/N increases, the proportion of high-energy electrons in the total electron number increases. At this time, the reaction of non-equilibrium plasma intensifies, and more active substances can be produced.