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The plasma plume properties of a three-channel 100-kW-class nested Hall thruster were measured on xenon propellant for total powers up to 80 kW. The thruster was throttled through all seven availab...

In plasma material processing, vacuum ultraviolet (VUV) emission is released from gas discharges, leading to undesirable results. Energetic VUV photons enable the creation of an electron-hole pair current when their energy is larger than the bandgap energy of the plasma-facing top layer during plasma material processing. For example, the high energy of VUV photons from helium (21.2 eV), argon (11.6 eV), and oxygen (13.6 eV) is sufficient to generate induced currents in SiO2 thin films. These feedstock gases are widely used in many procedures utilizing low-temperature industrial plasmas. Thus, the VUV emission evolution with both the power ratio between high (60 MHz) and low (2 MHz) frequencies and pulse duty ratio of the low-frequency radio frequency (rf) power in a dual-frequency capacitively coupled plasma, which is indispensable in modern plasma etching processes, was investigated. Both the power ratio between high and low frequencies and the pulse duty ratio changed the electron temperature, leading to evolution of the VUV emission intensity.

The temperature field evolution and material removal process during picosecond (ps) laser micro-grooving of single crystalline germanium (Ge) are explored by developing a 2D two-temperature model (TTM). The transient temperature-dependent thermal and optical properties of electrons and lattice are incorporated for accurate calculations, and the electron-lattice coupling strength is estimated considering the electron transition from valence band (VB) to conduction band (CB) mainly caused by one photon absorption. Different material removal mechanisms, i.e. the thermal way caused by vaporization and the athermal manner resulted from covalent bonds breakage, are proposed and compared with experimental results. The variation trends of the thermal model predicted groove depths are similar and consistent with the measured ones within selected ranges, while the athermal model leads to groove depth far from reality, demonstrating that the vaporization-caused mechanism is the proper one. Employing the verified model, simulation study is conducted to explore the evolution of temperature field under different fluences. Under a low fluence of 0.071 J/cm2, the peak electron temperature shows a decreasing trend with pulse width, and the temperatures of electron and lattice evolve in a similar pattern when the pulse duration is wider than 200 ps. For a higher fluence of 7.074 J/cm2, lattice temperature increases up to melting and boiling point within 1 ps and 3 ps, respectively, and the groove depth produced by a 12 ps pulse heating is about 0.65 μm. Afterwards, residual heat diffusion during pulse interval and further material removal during following pulse heating will occur, leading to a deeper groove. Moreover, the effects of laser power and critical free electron density on the machining process are also analysed, demonstrating that an increase in any of these two parameters results in a faster element removal.

A high-efficiency microwave atmospheric pressure plasma jet (APPJ) has been developed in previous work. Long and stable plasma filament is excited directly in the open air with 2.45-GHz microwave power and double-channel argon flow by a double-coaxial structure. Unlike those plasma jets that strongly rely on a high flow rate to shape the plasma jet, this method produces a stable filamentous plasma jet at a low flow rate whose length and diameter are in a linear relationship with absorbed microwave power. This study aims to investigate the fundamental parameters of this special plasma filament under different power levels and gas flow rates by optical emission spectroscopy (OES), including the electron temperature and the spectrum. The electron temperature is determined to be 0.71–0.81 eV. It decreases slightly as the power increases, which is different from other high-voltage or radio frequency excited plasma jets under high power. The electron temperature does not change significantly with the change of microwave power and argon flow rate, more manifested as a change in the length, which indicates that this special plasma filament is related to the complex interaction of the microwave field and plasma. This study provides basic parameters for further investigation of this kind of plasma jet for theoretical and numerical simulation.

The results of an experimental study of breakdown of a cone-to-plane gap, filled with nitrogen at a pressure of 12.5–400 kPa at a negative polarity, and its numerical simulation by the XOOPIC code are presented. The formation of a diffuse discharge is observed within the entire range of pressures. At the nitrogen pressures of up 200 kPa, a large-diameter streamer is formed in the gap. At higher pressure, two streamers of smaller diameters are observed to form. At low nitrogen pressures, the streamer starts forming at a certain distance from the cathode. The numerical simulation demonstrates that under these conditions the electrons rapidly leave the near-cathode region due to the high reduced electric field strength. The excitation of nitrogen molecules is taken into account in the simulation. Using the R391/394 ratio of the emission intensities from the bands of the N2+ molecular ion and the N2 molecule, the dynamics of the electron temperature Te and the reduced electric field strength E/p in the plasma are determined. The streamer velocity is determined from the propagation velocity of the R391/394 maximum along the gap. The results are compared with the numerical simulation results.

Temperatures of singly and doubly charged krypton ions, along with electron temperature, were determined as functions of time in current sheets formed in the 2D and 3D magnetic configurations with an X-line. It is established that maximum temperature of krypton ions exceeds maximum electron temperature by more than an order of magnitude, and these temperatures exhibit different dependence on time and magnitude of the longitudinal magnetic field. Fast superthermal plasma jets directed along the largest of transverse dimensions of the current sheet, the sheet width, from the sheet center toward its periphery are discovered. It is demonstrated that Ampere’s forces are responsible for tangential acceleration of krypton plasma. Measured values of energy of accelerated krypton ions agree with estimates of the Ampere’s forces obtained on the basis of independent magnetic measurements.

A study of the discharge plasma with a vortex flow of an argon + water vapor mixture with aluminum particles in a tube of a plasma vortex reactor (PVR) was carried out. The parameters of the discharge, plasma, and working flow in the PVR have been measured. Spectral methods were used to estimate the electron temperature, rotational and vibrational temperatures of excited molecular complexes, the temperature of metal clusters, and the electron density of plasma. A kinetic scheme is proposed for calculating the operating modes in a reactor using a water vapor discharge with aluminum particles. Numerical simulation of a vortex flow of pure water vapor with aluminum particles in the presence of a heating source is carried out.

A considerable enhancement of the catalytic activity of graphene oxide (GO) was achieved as a result of plasma treatment in a hydrogen glow discharge. The results obtained for the hydroisomerization of 1-octene, together with the catalyst characterization showed that plasma exposure leads to the formation of defects in the material and of surface acidic species. Optical emission spectroscopy diagnostics of the plasma revealed that the electron temperature and the dissociation of molecular hydrogen are important parameters that can be tuned for optimization of the treatment process.

In this article, the effects of the O2 ratio on the electrical characteristics, including the I-V characteristic curve, Panchen’s curve, and I-P curve, were tested in a sample of O2/Ar gaseous mixture . The sample was produced by plasma-based DC magnetron sputtering with niobium metal as a target material. The inter-electrode spacing value was 4 cm. Plasma diagnosis via the Optical Emission Spectroscopy (OES) method was used to achieve Te and Ne mixture values of 20 %, 30 %, 50%, and 70% in the Ar/O2 system. The results showed that the discharge is operating in the abnormal glow region and the discharge current was decreased by increasing O2 percentage. In addition, the experimental results showed that the discharge is optimal at 30% gas ratio. It was found that the electron temperature was decreased with increasing working pressure and increased with increasing the O2 percentage, while electron density was increased with increasing both working gas pressure and O2 percentage.

The temperature evolution of singly and doubly charged krypton ions in current sheets formed in magnetic fields with an X-line is studied. The electron temperature is determined; it is shown to be lower than the ion temperature by an order of magnitude, which points to different heating mechanisms of ion and electron components of current sheet plasma.

The electron temperature and the density of argon arc plasma plume injected into water were observed through optical emission spectroscopic measurement. Argon arc plasma jets were generated with a DC arc current of 40–200 A by a non‐transferred arc discharge plasma torch under atmospheric pressure, and ejected through a nozzle on the anode into water or gas‐phase argon. The electron temperature of the plasma plume was determined by the Boltzmann plot with line intensity measurement of atomic argon lines, while the electron density is examined with the Stark broadening measurement of Hα line. It was found that the electron temperature increased from approximately 6500–8000 K, and the electron density also increased up to the order of 10^{16}cm^{−3}, as the discharge current increased for the underwater argon arc plasma plume, both of which were observed at 20 mm in the downward direction from the plasma generator nozzle. In addition, the electron temperature of the underwater plasma plume was slightly lower than that of the gas‐phase argon plasma plume, while the electron density of the underwater plasma was slightly higher than that of the gas‐phase plume. Longitudinal variation of the electron temperature and density of the underwater plasma plume was also observed, and the lowering rate was found to depend on the arc discharge current.

Low-pressure inductively coupled plasma of gaseous CF3Br has been studied by Langmuir probe and optical emission spectroscopy (actinometry) techniques. The electron temperature, electron and positive ion concentrations, and concentrations of fluorine- and bromine-containing radicals are determined. An explanation of the previously reported significant degradation of ultralow-k dielectrics during etching in this plasma is proposed.

The effect of a shock wave on the temperature of plasma electrons of the positive discharge column in argon is simulated. A one-dimensional hydrodynamic model of a gas discharge plasma along with a formula for the relationship between the relative electron temperature and the reduced electric field strength has been used. The distribution of the electron temperature in the shock wave has been obtained and the effect of the shock wave intensity has been estimated. The simulation results were compared with the experimental data.

We fabricated a cascade arc discharge source with a channel diameter of 8 mm for application to plasma window as an alternative differential pumping. Helium arc plasmas up to a discharge current of 100 A were generated, and the performance as the plasma window was investigated. The pressure ratio of high-pressure discharge section to low-pressure vacuum side was about 200 at a gas flow rate of 0.05 L/min. In order to characterize the plasma parameters around the anode electrode, vacuum UV and visible emissions of He I were measured. The electron density was determined to be $4 \times 10^{13}$ cm−3 for a discharge current 100 A and a gas flow rate of 0.05 L/min, while the electron temperature was 0.11 eV. Moreover, the forbidden transition of He I 2s1 S–2p3 P was observed. The effect of radiation trapping of He I Ly- $\alpha $ was studied by the intensity ratio of Ly $\alpha $ to forbidden line and the collisional radiative (CR) model. As a result, it was found that the plasma generated was optically thick with an optical escape factor of 10−5.

Low-pressure plasma of gas mixture of Ar, O2 and N2 generated by RF magnetron sputtering was characterized by Langmuir probe and optical emission spectroscopy (OES). The electron temperature (Te), ion density (ni) and electron energy distribution function (EEDF) in Ar-O2-N2 plasma atmosphere were calculated from I-V characteristic of Langmuir probe. Boltzmann plot method was applied for calculating the vibrational temperature (Tvib) of the second positive system of N2 (N2SPS) in Ar-O2-N2 plasma. The Te, ni, EEDF and Tvib in Ar-O2-N2 plasma were studied as a function of O2 percentages. It was found, the Tvib increased from 0.47 eV to 0.55 eV as the oxygen percentage in Ar-N2-O2 plasma increased from 10% to 40%. Further, the Te increased from 1.6 eV to 3 eV as the O2 concentration increased from 10% to 40%.

A planar probe and optical emission spectroscopy were employed to analyze parameters in an inductively coupled plasma (ICP). The analyses were performed in Ar, Ar+SF6 and O2 plasmas at 40 mTorr. Typical probe results indicate an ion current of 10-3 A/cm2 and an electron temperature (high energy tail) between 1-2 eV in measurements at high powers. At low powers a distinct discharge regime is observed, typically with low density (low ion current) and high electron temperature. The optical emission studies also showed the presence of these two regimes. Moreover, the electron temperature determination using this diagnostic is also in good agreement with planar probe results.

In this study, many plasma parameters including excitation temperature $$({{T}_{{{\text{exc}}}}})$$ , electron temperature $$({{T}_{e}})$$ , skin depth $$({{\delta }_{p}})$$ , plasma potential $$({{V}_{p}})$$ , and electron energy distribution function (EEDF) are inspected in the two modes of magnetic pole enhanced-inductively coupled (MaPE-ICP) neon–argon mixture plasma by employing Langmuir probe (LP) and optical emission spectroscopy (OES) diagnostics. The major purpose of this effort is to explore the validity of spectroscopic temperatures, including excitation temperature $$(kT_{{{\text{exc}}}}^{{{\text{OES}}}})$$ and electron temperature ( $$kT_{e}^{{{\text{OES}}}}$$ ) as a substitute diagnostic tool to the measured electron temperature $$(T_{e}^{{{\text{LP}}}})$$ by Langmuir probe. The spectroscopic and LP temperatures are measured in various input powers and argon contents in the discharge. It is observed that LP and spectroscopic temperatures both display falling dependence with input power and argon content, but the spectroscopic temperature is consistently lesser than the probe temperature.This study can be very useful in reactive plasma processing, where the LP has many limitations.

A bipolar nanosecond discharge with a voltage amplitude of one polarity of 15–40 kV and a current amplitude of 50–150 A in a pulse was ignited at an inter-electrode distance of 0.1 cm and the pressure of argon 101 or 202 kPa, at a frequency of the pulse voltage 40–100 Hz. The pulsed electric discharge power was in a range of 5–11 MW, with a plasma energy input of 0.40 and 0.44 J per pulse. Spectroscopic plasma diagnostics showed that the spectral lines of the copper atom in the range 200–230 nm and the spectral lines of the indium atom and Cu+ and In+ ions in a longer wavelength range of the spectrum are the most intense. The following lines from the spectral range of 300–460 nm can be used to diagnose the deposition of chalcopyrite films in real time: 307.38 nm Cu(I), 329.05 nm Cu(I), 410.17 nm In(I), 451.13 nm In(I). By solving the Boltzmann kinetic equation for the electron energy distribution function, the temperature and the density of electrons, the specific losses of the discharge power on the main electronic processes and the rate constants of the electronic processes depending on the value of the parameter of the ratio of the electric field strength E to the total concentration of Ar atoms and a small admixture of a Cu vapor N (E/N) are simulated. In a discharge in a mixture of copper vapor with argon, the electron temperature increased in a range of 300–110 000 K, with a change in the E/N parameter from 1 to 1800 Td. The electron concentration was in a range of 2.1 × 1020– 2.7 × 1020 m–3, at a current density (612–765) × 106 A/m2 on the electrode surface (at E/N = 1676 Td). Thin films of chalcopyrite were synthesized on substrates of transparent solid dielectrics, which, in a wide spectral range of 200–800 nm, absorb radiation incident of their surface quite effectively. This opens up prospects for their use in photovoltaic devices. It was shown that the smallest transmission of radiation is characteristic of chalcopyrite films synthesized at atmospheric pressure of argon and air.

LTX-β, the upgraded Lithium Tokamak Experiment, recently began its first campaign with a goal to study the transport properties of gradient-free electron temperature profile equilibria with increased toroidal field and neutral beam injection. The temperature-gradient-free equilibria in LTX were enabled by the lithium plasma-facing surface. To make the lithium surface conditions more consistent for LTX-β, a new, faster lithium evaporator system has been developed. The toroidal magnetic field has been nearly doubled to ≥0.3 T. Auxiliary heating and fueling with a high flux (35 A, 20 kV) neutral beam has begun. The beam provides core fueling without cold edge neutrals, to test whether flat temperature profiles can be sustained, and makes possible core ion temperature measurements via charge exchange recombination spectroscopy. Neutral beam fueling has been demonstrated with increases in line-integrated density. The coupling of the beam matches well with NUBEAM predictions for shine through. Improved performance has been observed following lithium evaporative coatings and an increase in field strength.

The results of one-dimensional time-dependent simulation modeling of hydrogen production from water vapor dissociation using non-thermal discharge plasma in a plate-type reactor were developed. Three different water vapor dissociation reaction mechanisms pathway models were simulated at a water vapor temperature of 573 K and same boundary conditions. The electron collision cross sections of electron water vapor were utilized based on the reaction mechanisms. The electron attachment and detachment processes were described in detail; additionally, the surface charge accumulation, recombination of charged species, positive and negative ions production and losses are considered. The electron density, electric field, electric potential, electron temperature and the hydrogen mass fraction are presented across the plasma discharge gap and over time. The first model was described as direct water vapor decomposition into their constituent’s elements hydrogen and oxygen molecules. It was revealed that the formed hydrogen molecules increased across the plasma discharge gap over time. In model II, the simulation reaction mechanisms pathway included products of H2O+, OH+, and O+ ions. It was found a significant change in the electric potential and electric field across the discharge gap due to the charged species inside the plasma gap. In model III, it was introduced H− radicals which controlled H atoms production by the electron detachment reaction. The most interesting results of these simulation models were the growing of hydrogen molecules across the plasma gap over time. Further, it was observed that the produced hydrogen mass fraction from model III was higher than model II and model I.

The multifluid computational framework Hall2De is updated to perform simulations of Hall thrusters operating with krypton propellant. The implementation is validated by comparison to past experimen...

The results of a spectroscopic study of the conversion of acetylene and methane in a helium plasma jet produced by a direct current plasma torch are presented. The operating mode of the plasma torch corresponds to conditions that provide a high yield of carbon nanostructures. In the emission spectra recorded during the transverse observation of a 20-mm jet section following the outlet of the anode channel of the plasma torch, high-intensity Swan bands of the С2 molecule are the dominant component in the visible wavelength range. The spectra show atomic hydrogen lines of the HI Balmer series from Hα to He, numerous CI carbon lines from ultraviolet 247.9 nm to infrared 962–966 nm, and a number of HeI helium lines. The axial temperature values of the plasma jet were spectrally determined by the observed ionized carbon CII lines 283.7 nm, 392.0 and 426.7 nm. A joint analysis of the emission spectra and the mixture composition calculated in the Saha–Boltzmann approximation revealed the nature of the spatial heterogeneity of the studied He : C : H plasma jet. It is manifested by the difference in the electron temperature of the axial region of the jet, which is measured with ionized carbon lines CII (Te(0) = 12 000–14 000 K) from the vibrational and rotational temperatures of C2 molecules (TV = TR ≅ 5000 K) that emit intensely at the jet periphery. The electron density measured along the Hβ and Hγ line widths, which varies in the range of the observed jet region of ne = (4–2) × 1016 cm–3, corresponds to the ionization equilibrium in a plasma He : C : H mixture with an electron temperature close to Te measured by carbon-ion lines.

This article aims to understand the physics of pulsed plasmas by investigating the ionization and recombination of pulsed plasmas on the nanosecond timescale and how operating conditions affect the time-resolved electron temperature and electron density of a pulsed plasma. A nanosecond-pulsed argon plasma discharge was generated at various pulse frequencies, widths, and pressures. The argon emission lines were analyzed with a time-synchronized, intensified charge-coupled device (ICCD) spectrometer assembly that gated at 4 ns, and relative intensities of strong argon neutral and ion lines were used in line-ratio calculations. These experimentally determined ratios were compared to theoretical ratios generated from PrismSPECT, a collisional-radiative spectral analysis software, to obtain time-resolved electron temperature ( $\sim 1$ eV) and electron density ( $10^{14}-10^{15}$ cm $^{-3}$ ) over the various operating conditions as well as to discover trends of these plasma parameters over the lifetime of the pulsed plasma. Increasing pulse repetition frequency of the plasma increased the value of maximum $T_{e}$ , shortened the $T_{e}$ rise and decay times, and increased the excited argon neutral population. While $n_{e}$ was relatively independent of pulse frequency, higher pulse frequencies resulted in a faster $n_{e}$ decay. Maximum $T_{e}$ and $n_{e}$ were weakly dependent on applied discharge voltage, but both parameters decayed sooner in time with increasing voltage. Lastly, $T_{e}$ was inversely proportional to pressure, but $n_{e}$ was approximately linear. All three pressures had similar but time-shifted temporal profiles for $n_{e}$ . Plasmas in all operating conditions had ionization and recombination times in the tens of nanoseconds.

In this work, a krypton Hall thruster is used to study the influence of low-frequency oscillation on the focusing characteristics of the plasma beam. The experiment results show that the plume dive...

We present observations and modeling of argon gas at pressures of a few Torr that have been excited with high-voltage pulses (hundreds of volts) on the order of nanoseconds in duration. These tests are motivated by an effort to determine the feasibility of utilizing pulsed argon plasma as a conducting media in a novel antenna configuration. A vacuum chamber is constructed with plate electrodes inserted. An optical observation system is constructed to observe the temporal response. The rise time and fall time of the plasma’s optical emissions, taken as a proxy of the electron density, are measured as a function of pulse voltage and pressure using the captured optical light curve. In addition, spectroscopy measurements are made on a longer time scale. The maximum electron density of the plasma is then inferred through the use of PrismSPECT, a commercially available collisional radiative model, via the line ratio method. Measured pulsed plasmas reached their maximum ionization in as low as 5 ns and recombine in as low as 140 ns. Spectral measurements show that a 1-Torr plasma ionized with 5-ns long pulses had a maximum electron density of $5.2\times10\,\,^{\mathrm{ 20}}$ /m3 and maximum electron temperature of 1.28 eV.

This paper investigates the characteristics some of argon plasma parameters of glow discharge under axial magnetic field. The DC power supply of range (0-6000) V is used as a breakdown voltage to obtain the discharge of argon gas. The discharge voltage-current (V-I) characteristic curves and Paschen’s curves as well as the electrical conductivity were studied with the presents of magnetic field confinement at different gas pressures. The magnetic field up to 25 mT was obtained using four coils of radius 6 cm and 320 turn by passing A.C current up to 5 Amperes. Spectroscopic measurements are employed for purpose of estimating two main plasma parameters electron temperature (Te) and electron density (ne). Emission spectra from positive column (PC) zone of the discharge have been studies at different values of magnetic field and pressures at constant discharge currents of 1.5 mA. Electron temperature (Te) and its density are calculated from the ratio of the intensity of two emission lines of the same lower energy levels. Experimental results show the abnormal glow region characteristics (positive resistance). Breakdown voltage versus pressure curves near the curves of paschen and decrease as magnetic field increases due to magnetic field confinement of plasma charged particles. Also the electrical conductivity increases due to enhancing magnetic field at different gas pressures. Both temperature density of electron and the intensities of two selected emission lines decrease with increasing pressure due decreasing of mean free path of electron. Electron density increase according to enhancing magnetic field, while the intensity of emitting lines tends to decrease.

A gliding arc discharge (GAD) with a water spray system was constructed. A non-thermal plasma, generated between two V shaped electrodes in an ambient argon driven by 100 Hz AC voltage, was investigated using optical emission spectroscopy (OES) with different gas flow rates (0.5, 1, 1.5, 2 , 2.5 , 3 1/min). Boltzmann plot method was used to calculate electron temperature (Te) and electron density (ne). The electrodes design was spectrally recognized and its Te value was about 0.588-0.863 eV, while the ne value of 6.875×1017-10.938×1017 cm-3. The results of the plasma diagnostics generated by gliding arc showed that increasing gas flow rates was associated with decreased electron temperature (Te), Debye length, and Debye Number, along with decreased electron density (ne) and plasma frequency.

Optical emission of selected nitrogen bands is analyzed for different nitrogen fill pressure and input electrical power to find the changes in spectral intensities with changing discharge conditions. The electron temperature Te is inferred from the intensity ratio $$\left( {{{I_{{BX}}^{ + }} \mathord{\left/ {\vphantom {{I_{{BX}}^{ + }} {{{I}_{{CB}}}}}} \right. \kern-0em} {{{I}_{{CB}}}}}} \right)$$ of (0–0, 391.44 nm) and (0–2, 380.49 nm) band heads whereas electron number density ne from the intensity ratio and the corresponding rate coefficient X (cm3 s–1) for the given temperatures. Both band heads belonging to the first negative system and second positive system of nitrogen have a different threshold of excitation energies, and therefore the corresponding emission intensities provide a direct correlation between the group of electrons involved in optical emission (a part of electron energy distribution function above the excitation and ionization thresholds) and electron temperature. Measured intensity ratio $$\left( {{{I_{{BX}}^{ + }} \mathord{\left/ {\vphantom {{I_{{BX}}^{ + }} {{{I}_{{CB}}}}}} \right. \kern-0em} {{{I}_{{CB}}}}}} \right)$$ and resulting Te both increase with input power and decrease with gas fill pressure following almost the same trend. Besides, time-averaged triple probe measurements have been performed to determine Teff and ne under the same discharge conditions for the sake of comparison. The spectroscopic method provides the variation of Te and ne at various discharge power and gas pressure in comparison with probe measurements. This study will help to optimize the discharge conditions in terms of active species concentration, electron temperature and electron number density for technological applications.

International audience; This article reports on the characterization of a laboratory model 100 A-class hollow cathode with a sintered lanthanum hexaboride (LaB6) emitter for high-power Hall thrusters. The cathode has been fired up to 70 A with xenon as working gas. The cathode architecture, test setup, ignition procedure, and power consumption are described first. The second part of this contribution comments on the current–voltage characteristics and the discharge modes obtained for discharge currents in the 30–70 A range and flow rates in the 15–30 SCCM range. The cathode operates in a spot mode at high discharge currents and in a plume mode with large oscillations at low currents and low gas flow rate. Spectral analysis shows that most frequencies reside in the 10–200 kHz range with flat and sharp distributions in plume and spot modes, respectively. Finally, we present electron temperatures and densities measured in the cathode plasma plume by means of incoherent Thomson scattering. The two quantities decrease along the axis. The density is large (up to ∼1019m−3) and increases with both the ion current and the gas flow rate. The electron temperature increases with the current and decreases with the gas flow rate. The temperature remains relatively low (

In the atmospheric pressure anodic carbon arc, ablation of the anode serves as a feedstock of carbon for production of nanomaterials. It is known that the ablation of the graphite anode in this arc can have two distinctive modes with low and high ablation rates. The transition between these modes is governed by the power deposition at the arc attachment to the anode and depends on the gap between the anode and the cathode electrodes. Probe measurements combined with optical emission spectroscopy (OES) are used to analyze the voltage drop between the arc electrodes. These measurements corroborated previous predictions of a positive anode sheath (i.e. electron attracting sheath) in this arc, which appears in both low and high ablation modes. Another key result is a relatively low electron temperature (~ 0.6 eV) obtained from OES using a collisional radiative model. This result partially explains a higher arc voltage (~ 20 V) required to sustain the arc current of 50-70 A than predicted by existing simulations of this discharge., 38 pages, 25 figures, submitted to Journal of Physics D: Applied Physics

X-ray spectroscopy is an indispensable tool in the study of highly ionized high-Z plasmas. A new non-local thermodynamic equilibrium (non-LTE) model for M-shell xenon was developed, encompassing the 9-14 A wavelength range. We present comparison of this new M-shell xenon model to experimental data from reversed polarity gas-puff Z-pinch 1 and laser-irradiated gas-puff 2 xenon experiments. The model matches experimental spectral features which provides estimates of useful plasma properties, such as electron temperature, density, and presence of hot electrons. Specifically, the new M-shell xenon model is compared with x-ray spectra produced from the SHOTGUN-III device at Nihon University- Japan and from the Titan laser at Lawrence Livermore National Laboratory. Notably results include a robust description of ionization stages from Zn-like to Ar-like xenon and evidence of the effects of hot electrons in the reversed polarity gas-puff Z-pinch experiment, highlighted by the comparison of both experiments. Future applications of this model are discussed.

Electron density is one of the important parameters of inductively coupled plasma. It is of great significance to study the distribution of electron density in inductively coupled plasma. It is difficult to measure the electron density and its distribution at any position of the cavity only by using emission spectroscopy or probe method. To solve this problem, the electron density of inductively coupled argon plasma is diagnosed by using probe calibrated emission spectroscopy. The feasibility of the proposed method was verified by studying the electron density distribution in the axial direction of the cavity. The electron density and its distribution can be diagnosed by using probe calibrated emission spectroscopy for plasma with little change in electron temperature.

A series of experiments is described which were conducted to measure the absolute spectral irradiances of laser plasmas created from metal targets over the wavelength region of 123–164 nm by two separate 1.0 μm lasers, i.e., using 100 Hz, 10 ns, 2–20 kHz, 60–100 ns full-width-at-half-maximum pulses. A maximum radiation conversion efficiency of ≈3%/2πsr is measured over a wavelength region from ≈125 to 160 nm. A developed collisional-radiative solver and radiation-hydrodynamics simulations in comparison to the spectra detected by the Seya–Namioka-type monochromator reveal the strong broadband experimental radiations which mainly originate from bound–bound transitions of low-ionized charges superimposed on a strong continuum from a dense plasma with an electron temperature of less than 10 eV.

Argon helicon plasma is typically associated with a blue core, namely a radially localized central area of strong ion light emission. An experimental study was carried out to study the morphology and radiation characteristics of blue core in argon helicon plasma discharge. Experiments were carried out with two technics including Local Optical Emission Spectroscopy (LOES) and time-integrated images with digital camera. In particular, the helicon mode, characterized by the intense blue core plasma, can be achieved by adjusting the input parameters such as RF power, magnetic field, and operating pressure. Analysis of a prominent characteristic line (ArII 481.0 nm) of blue core indicates that the intensity of ion line increases linearly with the RF power, magnetic field, or operating pressure in certain intervals (when 1000 W 0 < 500 Gauss or 0.1 Pa< p< 1.0 Pa). Apart from this, blue core width increases with the power while decreases with an increase in magnetic field or operating pressure. In order to further understand the formation of the blue core, parameter regarding electron temperature is adopted to reveal that the increase of the intensity of ion line depends strongly on the increase of electron temperature.

The high-speed etching of a silicon wafer was experimentally investigated, focusing on the duty factor of 150 kHz band high-power burst inductively coupled plasma. The pulse burst width was varied in the range of 400–1000 µs and the repetition rate was set to 10 Hz. A mixture of argon (Ar) and carbon tetrafluoride (CF4) gas was used as the etching gas and injected into the vacuum chamber. The impedance was changed with time, and the coil voltage and current were changed to follow it. During the discharge, about 3 kW of power was applied. The electron temperature and plasma density were measured by the double probe method. The plasma density in the etching region was 1018–1019 m−3. The target current increased with t burst width. The etching rate of Ar discharge at burst width of 1000 µs was 0.005 µm/min. Adding CF4 into Ar, the etching rate became 0.05 µm/min, which was about 10 times higher. The etching rate increased with burst width.

The information about time evolution of plasma electron temperature and density plays a fundamental role in numerous physics-related sciences. For CF DP-LIBS (calibration-free double-pulse laser-induced breakdown spectroscopy), not only may it serve to minimize the impact on the investigated sample, but also to optimize the laser and spectral parameters, or even to pave the way for real-time chemical analysis of the sample. To evaluate this impact and describe the plasma time behavior, electron temperature and density are calculated for plasma induced by double-pulse Nd:YAG laser with various (0–500 ns) inter-pulse delays. The parameters are calculated using various methods, such as Stark broadening, Boltzmann plot and Saha equation to provide complementary calculations for comparison. To ensure validity of the results, calibration of the measurement setup was performed. In the work, tungsten samples are investigated, because the W is chosen as the preferred material for plasma-facing components in future fusion devices such as ITER. Since LIBS method will be used to monitor tritium retention in ITER, the results may be utilized to improve the diagnostics.

At the present time, some ECR ion sources use a high-frequency powerful microwave radiation of modern gyrotrons for plasma heating. Due to high radiation power, such systems mainly operate in a pulsed mode. This type of ECR ion sources was developed at the Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS), and most experimental research was performed at the SMIS 37 facility, at which 37 gyrotrons with 37.5- and 75-GHz frequencies and 100- and 200-kW maximum powers, respectively, were used for plasma production. Such heating microwaves allow creating plasma with unique parameters: electron density >1013 cm–3, electron temperature of 50–300 eV, and ion temperature of about 1 eV. The principal difference between these systems and conventional ECR sources is a so-called quasi-gas-dynamic regime of plasma confinement. In accordance with the confinement regime, such sources have been called “gas-dynamic ECR sources.” Typically, plasma lifetime in such systems is about several tens of microseconds, which, in combination with the high plasma density, leads to the formation of plasma fluxes from a trap with a density of up to 1–10 A/cm2. The possibility of production of multiply charged ion beams (nitrogen, argon) and proton (or deuterium) beams with currents of up to a few hundred mA and normalized rms emittance of about 0.1π mm mrad was demonstrated. The next step in the research is a transition to continuous wave operation. For this purpose, a new experimental facility is under construction at the IAP RAS. A future source will utilize 28- and 37.5-GHz gyrotron radiation for plasma heating. An overview of the obtained results and the status of the new source development is presented.

In this study, hydrogen production via microwave plasma is investigated, analyzed and simulated in a novel way for practical applications. The water vapor when in proximity of a tungsten electrode is modeled for the generation of hydrogen gas. A numerical simulation study is performed using plasma and electromagnetic wave COMSOL modules to analyze the plasmolysis of water vapor within a vacuum concealed reaction vessel entailing a tungsten electrode. A kinetic model is therefore developed to represent the reaction mechanisms and interactions between the species within the plasmolysis reactor. The dynamic results of electron density, electron temperature, plasma rate, and species interactions are extracted through the kinetic model. Within the time domain of 10−16 to 10−14 s, the hydrogen concentration is found to increase to 4.5815 × 10−11 mol/m3 with a corresponding decrease in water vapor concentration of 1.782 × 10−8 mol/m3, respectively. The dynamic variations in the concentrations of other dissociated species are investigated across the geometry of the reaction domain studied, and it is therefore concluded that the tip of the electrode entails the highest species concentrations.

Decaying neon plasma has been investigated by kinetic spectroscopy. The experimental conditions were neon pressure of 0.2–152 Torr and electron density in the initial stage of decay [e] ≤ 5 × 1010 cm–3. The plasma was created by a pulsed barrier discharge with electrodes on the outer surface of a cylindrical glass tube. The discharge frequency was 40–160 Hz. It has been shown based on a comparative analysis of the dependences of the intensities of spectral lines on the time and electron temperature in the afterglow that the 2р54р levels are clearly divided into two groups in terms of population mechanisms. The lower levels (from 3р10 to 3р3 (Paschen notations)) are related to dissociative recombination of $${\text{Ne}}_{{\text{2}}}^{ + }$$ molecular ions with electrons, and the lines emitted by them behaved identically to the lines of the transitions 2p53s ← 2p53p and 2p53p ← 2p53d up to pressures of 0.6 Torr. The kinetics of the upper levels (3р5, 3р2, 3р4, and 3р1) had a more complicated character, and, at low pressures, the populations of all 2p54p levels were related to a collisional-radiative recombination of Ne+ ions. Significant differences in the dependences of the relative populations of 3d- and 4p levels on neon pressure are discussed.

The current study was carried out to reveal the plasma parameters such as ,the electron temperature ( ), electron density (ne) , plasma frequency (fp), Debye length ( ) , Debye number ( for CdS to employ the LIBS for the purpose of analyzing and determining spectral emission lines using . The results of electron temperature for CdS range (0.746-0.856) eV , the electron density(3.909-4.691)×1018 cm-3. Finally ,we discuss plasma parameters of CdS through nano second laser generated plasma .

This paper presents the results regarding the influence of cyclic growth of nanoparticles from the gas phase on the parameters of a low-temperature plasma. The measurements were carried out in an asymmetric RF (13.56 MHz) discharge in mixtures of argon and acetylene gases. The main plasma parameters such as the electron temperature, electron density and plasma potential were determined by a Langmuir probe and compared with the discharge self-bias voltage signal. The contamination problem of the electric probe tip in a reactive plasma due to the sticking of nanoparticles and radicals was minimized by applying a rapid “complex” sweep pattern of the probe voltage. The method based on the oscillation of the probe voltage with a frequency higher than the frequency of dust particles. The measurement results show a decrease in the electron density during the cyclic growth due to their absorption on the surface of the nanoparticles. On the contrary, the electron temperature and plasma potential increase. Additionally, a laser light scattering system was used to evidence the presence of the dust particle cloud in the vicinity of the probe position.

We report an experimental study of an electron cyclotron wave resonance (ECWR) plasma source. The dimensions of the source are considerably larger than in similar experiments. The excitation frequency is 27.12 MHz, the working gas is argon at very low pressures below 0.13 Pa. Spectroscopic data connected with a global model yield electron temperature $T_{\mathrm{ e}}$ , electron number density $n_{\mathrm{ e}}$ , population of the metastable state $n_{\mathrm{ m}}$ . The pressure dependencies of these quantities are discussed. Starting from $T_{\mathrm{ e}}\sim 5$ eV at pressure $p=0.13$ Pa the temperature grows as the pressure goes down until the discharge extinguishes at ${\sim }0.6\times 10^{-2}$ Pa. It becomes in the meantime so high that the emission spectra feature strong Ar(II) lines in the region 400–500 nm. At $p=0.13$ Pa and power 300 W the electron density on the axis is about $4\times 10^{10}~{\mathrm{ cm}}^{-3}$ and falls down due to the increase in $T_{\mathrm{ e}}$ as the pressure drops. The discharge was also electrically characterized to determine the plasma impedance $Z$ . The impedance and the plasma resistance ${\mathrm{ Re}}(Z)$ are presented as functions of the static magnetic field $B_{\mathrm{ 0}}$ . The distribution of power losses are also shown as $B_{\mathrm{ 0}}$ -dependencies.

Laser-induced arc was initiated on a nanostructured “fuzz” tungsten cathode with simultaneous exposure to a stationary helium (He) plasma. Arc spots moved randomly and eroded almost all the surface area. The diameter of each arc spot was measured to be 5– $10~\mu \text{m}$ . A linear relationship was observed in the arc current–voltage characteristic, which was affected by the presence of resistance through a He plasma column. The specific resistance of He plasmas was estimated from the current–voltage characteristic, which showed a good agreement with theoretical calculations. A greater potential gap should be maintained to keep a higher arc current, indicating a good sign for preventing a high-current arc in fusion devices. The condition of arc ignition was investigated in detail by changing the He plasma parameters and the sheath potential drop. The ignition and sustainment of arcs were very sensitive to both the sheath potential drop and the sheath electric field. Arcs ignited when the sheath potential drop was negatively deeper than −100 V and the sheath electric field was above 2 MV/m. The relatively low electric field threshold would result from the thermofield emission aided by heating of spots from adjacent former spots. This result indicates that the electron density and the electron temperature should be reduced in order to lower the potential drop and the sheath electric field in front of the plasma-facing material surface, which can prevent arcs from igniting in fusion devices.

With the purpose to create new methods for monitoring the parameters of low-temperature nonequilibrium plasma, a numerical drift-diffusion model of an inductive RF discharge in argon is developed and a study is made of ion transport onto the surface of the processed material. The model was tested against the available experimental and theoretical data. The calculations were performed for an inductive discharge in argon with parameters typical of modern plasmachemical reactors (a frequency of 13.56 MHz and a gas pressure in the chamber of 10 mTorr). The plasma density, electron temperature, and ion flux onto the processed surface are calculated; the gas temperature is found as a function of the input RF power; and the discharge parameters are determined as functions of the gas flow rate.

A helium-based atmospheric pressure plasma jet (APPJ) with various flow rates of argon gas as a variable working gas was characterized by utilizing optical emission spectroscopy (OES) alongside the plasma jet. The spectroscopic characterization was performed through plasma exposure in direct and indirect interaction with and without de-ionized (DI) water. The electron density and electron temperature, which were estimated by Stark broadening of atomic hydrogen (486.1 nm) and the Boltzmann plot, were investigated as a function of the flow rate of argon gas. The spectra obtained by OES indicate that the hydroxyl concentrations reached a maximum value in the case of direct interaction with DI water as well as upstream of the plasma jet for all cases. The relative intensities of hydroxyl were optimized by changing the flow rate of argon gas.