Variation Of Plasma Parameters Research Articles

Correlation Cosmic Ray Intensity Based on Variation in Solar Activity and Interplanetary Plasma Parameters Using Principal Component Analysis (PCA)

Correlation Cosmic Ray Intensity Based on Variation in Solar Activity and Interplanetary Plasma Parameters Using Principal Component Analysis (PCA)

Effects of cavity resonance and antenna resonance on mode transitions in helicon plasma

Mechanisms of cavity resonance and antenna resonance and their coupling effects on mode transitions in argon helicon plasma excited by a half-helical antenna (14 cm in length) were investigated in this paper. Cavity length was changed to distinguish the effects of cavity and antenna resonances in experiments. Plasma parameters under various discharge conditions, such as input power (0–2500 W), magnetic field (0–1000 G) and cavity length (10–42 cm) were measured. Characteristics of helicon discharges and mode transitions in cases of fixed and continuously changing cavity lengths were compared. The results show that multiple axial eigenmodes (at least five in the present work) were observed in both cases. In fixed-length cavities, the helicon discharge changes abruptly during mode transitions, while in changeable-length cavities, discharge features can change continuously (e.g. in a large range of density from 1.7 × 1012 to 1.3 × 1013 cm−3) without mode transition. Mode transitions also occur as the cavity length increases at fixed input power and magnetic field with periodical variations of plasma parameters. Cavity resonance plays a dominant role in the formation of standing helicon waves of eigenmodes and mode transitions, while antenna resonance significantly affects the transition from inductively coupled modes to helicon wave modes. Enhanced inter-coupling of cavity resonance and antenna resonance appears at specific axial wavelengths of eigenmodes. The threshold conditions for mode transitions were deduced and the overall transition path of wave modes and the corresponding density were predicted quantitatively, which shows that cavity resonance determines the transition path of wave modes, while antenna resonance gives the lower limit of the transition path. Characteristics of helicon discharge and mode transition are closely related to the axial wavenumber. Cavity and antenna resonances influence the helicon discharge and mode transition by determining the axial wavenumber of eigenmodes.

Experimental studies and COMSOL 1-D simulation in Ar capacitively coupled plasmas

This work systematically studies a capacitively coupled plasma (CCP) source using experiments and 1-D COMSOL simulations relevant to Ar plasmas. Two radio frequency compensated Langmuir probes (LPs) and optical emission spectroscopy (OES) were purposefully used to measure the plasma parameters, and the experimental results were compared with those of simulations. We studied the axial variation of plasma parameters using an axial LP between the power and ground electrodes of the CCP at various operating pressures ranging from 10 to 150 mTorr. The electron density showed a gradual increase in its value with rising pressures. In addition, we employed a radial LP at the axial location L = 4 cm from the surface of the power electrode to measure the plasma parameters and compare these data with those of the axial LP and simulations. The variations of plasma potential measured by the radial LP showed an opposite trend of variation to those of simulations and the axial LP at pressures 10–60 mTorr, which is attributed to the plasma diffusion at low pressures. LP and OES measurements and simulation data suggest stochastic heating that generates high electron temperatures at low pressures. In addition, data revealed that the high-density plasma generation at high pressures could be due to the effects of both collisional heating and stochastic heating. Analysis showed that electrons could gain energy from the strong field regime of the sheath closed to the electrodes, which has a similar variation to electron temperature. The results of simulations have shown excellent agreement with experiments, and this work has the basis for plasma applications like plasma-enhanced chemical vapor deposition.

Compositional analysis of copper and iron-based alloys using LIBS coupled with chemometric method.

The present manuscript deals with the utility of the calibration-free LIBS and calibration curve methods for the compositional study of different alloys using laser-induced breakdown spectroscopy (LIBS). In the process of alloying in the smelting industry, metal concentration in different alloys affects the physical and chemical properties of the final products. Therefore, LIBS can be used as an efficient quantitative analysis tool for online monitoring of the quality of the products. This is because LIBS can be performed online, in situ, without any pre-processing, and need no sample preparation for the compositional analysis of any type of materials present in any phase (solid, liquid, gas or even molten alloys in the industries). In the present study, four alloys (three copper and one iron-based alloy) consisting of Cu, Al, Zn, Ni, Fe, Cr and Mn as major and Sn and Si as minor elements were selected for the study using calibration-free laser-induced breakdown spectroscopy (CF-LIBS) and calibration curve method i.e. partial least square regression (PLSR). For the CF-LIBS method, the temporal delay has been optimized in order to satisfy the optically thin and local thermal equilibrium (LTE) condition of the plasma. For the PLSR method, different regions of the strongest emission lines of constituents have been selected for quantitative analysis. The study of time-resolved LIBS spectra and the variation of plasma parameters with respect to the delay time is also discussed. The utility of the combined technique of CF-LIBS with the PLSR method for rapid monitoring and quality assessment of desired material/products without any sample pretreatment, thus reducing the cost of the analysis, is presented in this paper.

Characterization of transversely confined electron beam-generated plasma using two-dimensional particle-in-cell simulations

Electron beam-generated plasmas (EBPs) have been used to modify the surface properties. In certain applications, EBPs are transversely confined and their properties are of value to the treatment. In this paper, the characteristics of an electron beam-generated argon plasma, confined within a narrow gap, are investigated using a two-dimensional particle-in-cell simulation. The employed particle-in-cell/Monte Carlo collision model accounts for the electron and ion kinetics, as well as collisions between electrons and the background gas, including the elastic scattering, excitation, and impact ionization. Our simulations reveal a strong correlation between the plasma density and the beam density within the plasma bulk. The excitation of obliquely growing waves is observed, which is found to have a significant impact on the transport of beam electrons, thereby leading to the non-uniformities of plasma density and electron temperature. Specifically, the obliquely growing waves increase the local plasma density while reducing the electron temperature. These contrasting effects compensate for each other, and therefore, to some extent, smooth out the distributions of ion flux and energy flux. We further examine the variations of plasma parameters with respect to the beam current density, beam energy, and gas pressure. Increasing the beam current density or decreasing the beam energy results in higher plasma density and electron temperature, while increasing pressure leads to a higher plasma density but electron temperature scarcely changes. Based on the simulation results, we propose an approach to achieve independent control of the ion flux and energy flux by adjusting beam current density, beam energy, and pressure.

Analytical study of ion-acoustic soliton in single temperature nonisothermal electron

In presence of warm negative ion, propagation of ion-acoustic solitary waves has been investigated analytically in a plasma consisting of warm positive ion, warm positron and single-temperature non-isothermal electron. The necessary and sufficient conditions for the existence of compressive solitary waves are discussed critically along with the calculation of phase velocity, kinetic energy (K.E) and force (F) found out in this paper by this new analytical method. Some important general observations and Theorems related with this problem are highlighted that supports the results of previous authors. The Sagdeev potential function ψ(𝜙) [= - L(𝑢𝛼 )] against ϕ depicted graphically under the variation of different plasma parameters is the most important and interesting situations by this analytical method.

Optical emission features of laterally colliding laser-produced plasmas at different ambient pressures

Optical emission characteristics of seed plasma and stagnation region of laterally colliding laser produced aluminium plasmas are investigated under various background gas pressures of air and argon ambient. The intensity of ionic and neutral emissions from seed plasma region increases with the increase of ambient pressure. Neutral emission from the stagnation region increases whereas the intensity of ionic emission decreases with the increase of ambient pressure. Decrease of collision rate between the seed plasmas results in the decrease of ionic emission from the interaction region. For higher inter seed plume separation, maximum spectral emission from stagnation region is observed at an intermediate pressure range of 10−2 mbar. Emission intensity and the life time of both ionic and neutral emission are greater in heavier Ar ambient. In the case of seed plasmas, the electron density decreases whereas the electron temperature increases with the increase of ambient gas pressure and is greater in Ar ambient. The variations of plasma parameters are quite less in stagnation region.

The influence of plasma evolution on a kinetic scenario of collisional relaxation of a magnetized plasma

For a magnetized plasma, a reduction of the two-time formalism (Erofeev 2019 J. Plasma Phys. 85 905850104, Erofeev 2022 Contrib. Plasma Phys. 62 e202100140) to a highly informative scenario of redistribution of charged particles in momentum due to Coulomb collisions is reported. The consideration focuses on the standard case of an ideal classical ionized homogeneous plasma. It is found that the leading-order approximation of the scenario is consistent with the well-known generalizations of the Lenard–Balescu equation (Lenard 1960 Ann. Phys. 10 390–400, Balescu 1960 Phys. Fluids 3 52–63) that take into account the leading magnetic field effect (Rostoker 1960 Phys. Fluids 3 922–7, Hassan and Watson 1977 Plasma Phys. 19 237–47). A correction to the collision integral of this equation is developed that is due to time variations of plasma parameters.

Time-resolved plasma diagnostics of cathodic cage plasma nitriding system with variable pulsed duty cycle and surface modification of plain carbon steel

Cathodic cage plasma nitriding (CCPN) is an efficient technique to improve the surface properties of metallic and non-metallic materials, including steels. Usually, CCPN is powered by pulsed voltage sources due to additional control of the nitrided layer's thickness and composition as well as the discharge transition to the arc region can be controlled by varying the pulsed duty cycle. As the behavior of pulsed plasma varies with time, it is important to monitor variation in plasma parameters by using time-resolved plasma diagnostics. Unfortunately, the fundamental time-resolved diagnostics of such discharges are still very limited. Here, we report time-resolved measurements of current, voltage, plasma emission, space, and time-resolved emission from a single hole in the cathode as a function of pulsed duty cycle (15–75 %) at constant total current. The results show that the electron temperature is higher if a higher peak current and the shortest 15 % pulsed duty cycle are used. The results obtained from plasma diagnostics are confirmed by treatment of plain carbon steel samples in identical conditions and found that the best hardness, wear, and corrosion resistance is obtained at the lowest pulsed duty cycle. The study suggests that plasma generated at a low pulsed duty cycle and a higher peak discharge current exhibits higher electron temperature and less fluctuations in plasma emission which are more efficient in attaining high surface hardness, better wear, and corrosion resistance to nitride plain carbon steel.

Uniform plasma generation with filament assisted DC discharge in a linear plasma device

Uniform and quiescent (δ n/n < 0.5%) laboratory plasma has been produced in a linear plasma device with a simple filament-assisted DC source without using any magnetic field for plasma confinement. A filament-assisted DC plasma source has been designed, fabricated in-house, and operated successfully to achieve the desired plasma parameters. A stainless steel(ss)-grid is placed in-front of the filament assembly and biased appropriately using a DC-regulated power supply to accelerate thermionically emitted electrons from the heated filaments along the length of the main chamber and facilitate the production of uniform plasma. Heating of the filaments was done by passing a current of ∼3.8 − 4.2 A through it using another DC-regulated power supply. 2-dimensional spatial profiles of plasma density (n e ), electron temperature (T e ) and plasma potential (V P ) obtained from the Langmuir Probe measurements by inserting 4 number of Langmuir Probes inside the plasma from 4 co-linear radial ports of the plasma chamber and scanning them radially with the help of indigenously built probe drive setups reveal spatially uniform plasma generation with n e in the range ∼(1 − 2) × 1015 m−3 and T e ∼ (2.5 − 3.5) eV. Variations of plasma parameters and its spatial uniformity with neutral pressure are also investigated. It is observed that the spatial uniformity of the plasma produced at neutral pressures in the range of ∼(3 − 6) × 10−4 mbar is very good with δ n/n < 0.5%.

Metrology of Ar-N2/O2 Mixture Atmospheric Pressure Pulsed DC Jet Plasma and its Application in Bio-Decontamination.

Atmospheric pressure plasma jets are gaining a lot of attention due to their widespread applications in the field of bio-decontamination, polymer modification, material processing, deposition of thin film, and nanoparticle fabrication. Herein, we are reporting the disinfection of Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli bacteria using plasma jet. In this regard, Ar-O2, Ar-N2, and Ar-O2-N2 mixture plasma is generated and characterized using optical and electrical characterization. Variation in plasma parameters like electron temperature, electron density, and reactive species production is monitored with discharge parameters such as applied voltage and feed gas concentration. Results show that the peak average power consumed in Ar-O2, Ar-N2, and Ar-O2-N2 mixture plasma is found to be 4.45, 2.93, and 4.35 W respectively, at 8 kV. Moreover, it is noted that by increasing applied voltage, the electron temperature, electron density, and reactive species production also increases. It is worth noting that electron temperature increases with increase in oxygen concentration in the mixture (, while it decreases with increase in nitrogen concentration in the mixture (Ar-N2). Similarly, a decreasing trend in electron temperature is noted for Ar-O2-N2 mixture plasma. On the other hand, a decreasing trend in electron density is noted for all the mixtures. Reduction in viable colonies of Pseudomonas aeruginosa, Staphylococcus Aureus, and Escherichia coli were confirmed by the serial dilution method. The inactivation efficiency of pulsed DC plasma generated, in the Ar-N2 mixture at 8 kV and 6 KHz, was evaluated against P. aeruginosa, S. aureus and E. coli bacteria by measuring the number of surviving cells versus plasma treatment time. Results showed that after 240 s of plasma treatment, the number of survival colonies of the mentioned bacteria was reduced to less than 30 CFU/mL.

Comprehensive Analysis of Copper Plasma: A Laser-Induced Breakdown Spectroscopic Approach

The emergence of diversified applications of laser-induced breakdown spectroscopy in the biomedical field, electronics, space physics, and material processing necessitates a comprehensive understanding of plasma parameters. The present work delineates the structure and evolution of copper plasma under different ambient pressures (0.01 mbar to 100 mbar) along with other plasma parameters. The study reveals the role of ambient pressure in the increase of plasma temperature (Te), electron density (Ne), number of particles in the Debye sphere, plasma frequency, inverse bremsstrahlung absorption coefficient, electron thermal velocity, electron–ion collision frequency and in the decrease of Debye length (λD) and plasma skin depth (PSD). The experimental techniques and the theoretical explanations for the variation of plasma parameters and their applications are also detailed. As the ambient pressure increases, the motion of plasma species becomes restricted, resulting in the increase of Te, calculated using the Boltzmann plot. From the values of λD, PSD, and Ne, it is understood that the copper plasma under investigation is thermally non-relativistic and satisfies McWhirter’s criterion, thus, revealing the local thermodynamic equilibrium condition of plasma. The effects of Debye shielding and stark broadening on the spectral lines are also investigated. Thus, the study helps bring newfangled dimensions to the application of plasma by exploring the possibility of tailoring plasma parameters.

Optical diagnosis of an inductively coupled plasma source for atmosphere-breathing electric propulsion system

Atmosphere-breathing electric propulsion (ABEP) systems capture atmospheric particles for use as propellant. In the best-case scenario, such systems can undertake long-life space missions without carrying propellant from the ground. The present research mainly focuses on plasma discharge processes based on inductively coupled plasma generation from atmospheric particles in very low Earth orbit (120–250 km). The optical diagnosis is done when the N2 and O2 mixture is injected into the low-pressure discharge chamber. Numerous active groups can be identified from the emission spectra, including excited molecules, molecular ions, atoms, and excited atoms. The generation mechanism of active groups is also clarified to understand the ionization process. The variations of plasma parameters are analyzed for different ratios of N2 to O2, which can also be expanded to describe the potential behavior of ABEP systems in low Earth orbit. Note that this research is only a preliminary study and is not fully representative of the potential of ABEP systems. However, to develop ABEP systems, it is essential to understand the plasma behavior of discharge systems.

On the validity of the classical plasma conductivity in capacitive RF discharges

The plasma conductivity is an important input parameter for various plasma models. It is typically obtained from a simplified version of the electron momentum balance equation, where only a single inertia term and a simplified description of the collisional momentum transfer are included. The electric field is assumed to be a harmonic function of the driving frequency, higher harmonics of the current and spatial variations are neglected. Through particle-in-cell/Monte Carlo collision (PIC/MCC) simulations and analysis of the electric field generation based on velocity moments of the Boltzmann equation, the validity of this classical model is studied in capacitively coupled plasmas (CCPs). We find that these assumptions/simplifications result in significant inaccuracies of the conductivity in many cases. In single frequency CCPs, a deviation of more than an order of magnitude from the effective PIC-conductivity obtained from the simulations is found at low pressures in the discharge center and at the maximum sheath edge. In the center, this deviation is caused by neglecting the temperature gradient term in the momentum balance equation and adopting an approximation of the Ohmic term in the classical model, while at the maximum sheath edge it is induced by neglecting the density gradient term that accounts for the effect of the ambipolar electric field. The inaccuracy in the discharge center is reduced at higher pressures where the Ohmic term dominates and the approximations made in the classical model are more applicable. Better performance of the classical model is also found under conditions at which the inertia term included in the model plays an important role. Generally, neglecting higher harmonics of the current and spatial variations of plasma parameters is found to cause strong inaccuracies. Thus, the classical model can result in an inaccurate calculation of the power absorbed by electrons. Our results indicate that its applicability must be evaluated for a given set of conditions before using it to avoid introducing errors to plasma models.

Argon doped pellets for fast and efficient radiative power removal in ASDEX Upgrade

Argon doped deuterium pellets with about 1 per mille Ar atomic fraction have been injected into ASDEX Upgrade H-mode discharges and demonstrate fast and efficient power removal from the outer plasma region. Bolometer views directly on the pellet and in its very close vicinity observe a strong, non-toroidally symmetric radiation pattern on a fast, sub-ms time scale. This pattern is explained by the ionisation process of the delivered Ar neutrals, leading to non-coronal radiation by intermediate ionisation stages until the equilibrium He like stage is reached. Subsequently, a toroidally symmetric radiation increase is observed with a fast initial decay time of about 20 ms consistent with the radial particle transport time scale for a source located in the outer plasma. In the following, a radiation pattern related to Ar recycling develops comparable to the pattern observed with Ar midplane gas puffing which decays with the Ar divertor pumping time of about 200 ms. The energy radiated around each pellet is described by the radiative potential of Ar evaluated for non-coronal conditions with the ablation time as the relevant time scale. A factor 4 too low radiated energy is obtained by this simple model, which could be explained by stronger deviations from corona equilibrium and plasma parameter variations in the vicinity of the pellet. Injection of Ar-doped pellets into a no-ELM quasi-continuous exhaust H-mode discharge showed no triggering of ELMs by the pellet. Advantages of the pellet seeding scheme are the faster reaction time of the radiation compared to gas puffing, which may be important to counter-act transient re-attachment in ITER or in a reactor and an elevated radiative efficiency in the outer core plasma due to non-corona effects.

Multilayer SiNx:H films as passivation and anti-reflection coating for industrial PERC solar cells

ObjectiveDevelop high-quality multilayer SiNx:H film as anti-reflection and passivation coating for industrial PERC solar cells to improve cell efficiency. MethodsCombining OPAL2 software simulation and experimental design, high-quality multilayer SiNx:H films were realized using PECVD tool by variation of plasma and gas parameters, PERC cells were also fabricated with multilayer SiNx:H film structures to check the cell performance. ResultSimulation results showed that with the increase from double-layer to four-layer SiNx:H film, light absorption was reduced gradually, thus the light entering into the silicon bulk was increased from 95.6% to 97.5%. Corresponding experiment results showed that the short-circuit current density (Jsc) of three- and four-layer SiNx:H film were 0.11 mA/cm2 and 0.13 mA/cm2 higher than that of double layer SiNx:H film respectively, which was well aligned with simulation result, more current was generated due to more light reached to silicon bulk. However, the inner layer SiNx:H of double layer structure had higher refractive index (RI) with better passivation effect, resulting in higher open-circuit voltage (Voc). Finally, the experiment results showed that four-layer SiNx:H solar cells achieved 22.15% cell efficiency, which was absolutely 0.09% higher than that of double layers. The multilayer SiNx film technology can be applied directly to mass production without additional costs.

Coupled KIPP-EDGE2D modelling of parallel transport in the SOL and divertor of inter-ELM JET high radiative H-mode plasma

The Kinetic Code for Plasma Periphery (KIPP) models parallel (along magnetic field lines) propagation of charged particles in the scrape-off layer (SOL) and divertor of tokamaks. An iterative coupling between KIPP and a 2D edge fluid code EDGE2D, which in turn is coupled to the Monte-Carlo solver EIRENE for neutrals, was used to achieve a converged KIPP-EDGE2D-EIRENE solution. The original EDGE2D-EIRENE solution simulated SOL and divertor of JET high radiative inter-edge localized mode H-mode plasma conditions with strong nitrogen injection, leading to partial detachment at divertor targets. This work is a continuation of earlier studies of modelling kinetic electrons (Chankin et al 2018 Plasma Phys. Control. Fusion 60 115011) and ions (Chankin et al 2020 Plasma Phys. Control. Fusion 62 105022) with KIPP. For numerical reasons caused by large cell-to-cell plasma parameter variations near entrances to divertors, multipliers for parallel electron and ion conductive power fluxes (KIPP/EDGE2D ratios) which are passed onto EDGE2D, could only be used in the main SOL, outside divertors. There, the heat flux limiting effect led to an increase in maximum plasma temperatures in the main SOL and a decrease in power fluxes to divertor targets. Results of the coupling studies are consistent with earlier studies, suggesting that under investigated JET plasma conditions kinetic effects of charged particle parallel propagation do not drastically change target power deposition at divertor targets calculated by EDGE2D-EIRENE along.

Temporal Evolutions of Self-Organized Patterns Formed on the Water-Anode Surface of an Atmospheric Pressure Glow Discharge

Atmospheric pressure glow discharge above water anode has attracted much attention due to its extensive potential applications, where self-organized patterns can be formed. Usually, they are time-invariant under constant conditions. In this article, some peculiar time-dependent patterns are formed, among which concentric ring patterns like single, triple, quadruple, and quintuple rings are observed in water-anode discharge system for the first time. Accompanying the increasing complexity of patterns, results indicate that water conductivity evolves with time. Optical emission spectroscopy reveals that before reaching constant values, electron density decreases, while electron and gas temperatures increase as time elapses. Interestingly, the temporal variations of electric conductivity and plasma parameters are correlated with the evolution of patterns. Based on the phenomena mentioned above, the pattern evolution is qualitatively explained based on the Turing mechanism at last. We think these results will shed light on formation mechanism of patterns in atmospheric pressure glow discharge with water anode.

The influence of plasma evolution on a kinetic scenario of plasma collisional relaxation

AbstractA reduction of the two‐time formalism [V. I. Erofeev, Journal of Plasma Physics 85, 905850104 (2019)] to a highly informative scenario of redistribution of plasma particles in momentum due to Coulomb collisions is reported. The standard case of an ideal classical ionized homogeneous plasma is considered. It is found that the leading‐order approximation of the scenario is consistent with the well‐known Lenard–Balescu Equation [A. Lenard, Ann. Phys. 10, 390–400 (1960); R. Balescu, Phys. Fluids 3, 52–63 (1960)]. A correction to the collision integral of this equation is developed to account for the time variation of plasma parameters. This correction is shown to differ from its analogs related to the existing generalizations of the Lenard–Balescu kinetic equation [Yu.L. Klimontovich, Kinetic theory of nonideal gases and nonideal plasmas (Pergamon Press, Oxford [1982]); V.V. Belyi, Yu.A. Kukharenko, J. Wallenborn, Journal of plasma physics 59, 657–669 (1998)].

Study of the effects of detection times in laser-induced breakdown spectroscopy and missed variation of plasma parameters with gate width

The time control of signal acquisition in laser-induced breakdown spectroscopy (LIBS) is critical to the quantification of elements in samples. Upon interacting with the laser pulse, the plasma expands and then cools rapidly in tens of microseconds, undergoing temperature variations of over 50,000 K. In the LIBS technique, the signal acquisition is controlled with the delay time, which is the time between the emission of the laser pulse and the reading of the spectrum, and the gate width, which is the integration time of the spectrometer. Although the relationship of the delay time with the measured plasma temperature and electron density is well-known in the literature, little is known about how these parameters vary with different gate widths. Thus, the objective of this work was to evaluate how the measured plasma parameters and the signal-to-noise ratio (SNR) of an atomic line change with different values of delay time and gate width. For this study, two sets of samples were prepared: i) pure NaCl and ii) NaCl with 20 wt% H3BO3, and at concentrations of 1 and 3 wt% Ca. TiO2 and CuSO4 were also added to these samples to facilitate plasma temperature and electron density calculations, which were carried out using a Saha-Boltzmann plot corrected with the one-point calibration method. The results of this study indicated that the measured plasma parameters did not vary with the gate width, even though the SNR of the Ca I line at 643.9 nm increased as the gate width did. Furthermore, the use of the concept of local thermodynamic equilibrium was verified even with long gate widths (≥ 20 μs), except for the 4 μs delay time. Studies with other samples and other combinations of LIBS system parameters, e.g., at sub atmospheric pressure, should be done to confirm and expand these findings.