Plasma Properties Research Articles

The head-tail radio galaxy and revived fossil plasma in Abell 1775

Head-tail radio galaxies are characterized by a head, corresponding to an elliptical galaxy, and two radio jets sweeping back from the head, forming an extended structure behind the host galaxy that is moving through the intracluster medium (ICM). This morphology arises from the interaction between the diffuse radio-emitting plasma and the surrounding environment. Sometimes, in galaxy clusters, revived fossil plasma can be found, and it traces old active galactic nucleus ejecta with a very steep spectrum that has been re-energized through processes in the ICM, unrelated to the progenitor radio galaxy. We focus on the study of the central region of Abell 1775, a galaxy cluster in an unclear dynamical state at a redshift of z = 0.07203. It hosts two giant radio-loud elliptical galaxies, the head-tail radio galaxy that ‘breaks’ at the position of a cold front detected in the X-rays, filamentary revived fossil plasma, and central diffuse emission. This study aims to investigate and constrain the spectral properties and trends along the head-tail, as well as the revived fossil plasma, to better understand the formation process of the non-thermal phenomena in A1775. We make use of observations at three frequencies performed with LOFAR at 144 MHz, and new deep uGMRT observations at 400 MHz and at 650 MHz. We observe an overall steepening along the tail of the head-tail radio galaxy. In the radio colour-colour diagram, ageing models reproduce the emission of the head-tail. An unexpected brightness increase at the head of the tail suggests a complex bending of the jets. We derived the equipartition magnetic field and minimum pressure along the tail. We recovered the structure of the revived fossil plasma, which appears as thin filaments with ultra-steep spectra. We show that high-sensitivity, high-resolution observations at low frequencies are essential for detecting the full extent of the tail, enabling a deeper spectral analysis and resolving the structure and spectral properties of revived fossil plasma.

Laser-Induced Breakdown Spectroscopy Using 2D Structured Light: A Case of Spectral Signal Enhancement on Metal Samples.

Laser-induced breakdown spectroscopy (LIBS), an elemental detection technique with great potential, faces many problems mainly caused by the nonideal plasma properties in the detection window. The 2D laser energy distribution on the sample surface has a crucial impact on the plasma properties and spectral emission. However, relevant studies are still limited, lacking a good degree of freedom (DOF) to systematically explore its influence. In this work, 2D structured light was generated by using a spatial light modulator (SLM). Various focal patterns with different cross-section areas were tested using metal samples so that the effects of the focal spot structure and cross-section area could be separated. The arrow-target and anticone of 200 μm diameter resulted in a line enhancement factor of more than 3 for a pure aluminum sample and a factor of about 6 for the pure copper sample over that without beam modulation. A significant improvement in the signal-to-noise ratio and a reduction in the limit of detection (LOD) of Cr, Mn, Si, Cu, and Al by a factor of about 6 were also achieved with the bearing steel sample. To better understand the mechanism behind such improvements, time-resolved spectra were measured, from which the electron density and plasma temperature evolution were calculated. The results showed that with anticone and arrow-target patterns, the electron density was increased by more than 50%, while the plasma temperature varied less than 500 K, suggesting an evident ablation enhancement. The fast images of plasma self-emission proved that the laser energy distribution substantially influenced the morphology of the plasma plume. The plasma cores produced by the anticone and arrow-target focal patterns were more compact after the expansion and cooling process, which could reduce the mixing of plasma plumes and ambient air. Thus, with the first application of SLM in LIBS, focal spot structures of micrometer resolution could be rationally designed and generated with a high DOF. Substantial spectral signal enhancement and a much lower LOD were achieved. This study provides new insights into the role of focal patterns in plasma properties, suggesting the future possibility of plasma control using structured light.

Drastic effects of N2 addition in the chemical composition of C2H2/Ar glow discharges

Abstract The effects of nitrogen on the physicochemical properties of cold acetylene plasmas have been experimentally studied in C2H2/Ar capacitive RF discharges. Two discharges containing respectively 0.8% and 6.3% N2 in the initial gas mixture were investigated under conditions of incipient polymerization, using mass spectrometry, light scattering, and optical emission spectroscopy. During the initial transient, dust particles, small polyynes, and C2 radicals were found to form and decay in parallel with a steep drop in the C2H2 concentration and an increase in the concentration of HCN, which was more prominent for the 6.3 % N2 mixture, and participated actively in the plasma chemistry. Over this time interval, relevant plasma parameters including the electron density and excitation temperature, the self-bias voltage, and the density of electronic excited states of various plasma species were found to undergo sharp variations. After this initial transient, lasting for about 20 s, a steady state was reached with stable plasma properties. Ion distributions were measured in the steady state, where no dust particles remained. The distributions of positive ions were dominated by species with an even number of carbon atoms, reflecting the prevailing polymerization mechanisms. The increase in the N2 concentration from 0.8% to 6.3% led to a decrease in the global cation signal and to a marked growth in the intensity of detected anions. The cation distributions did not change much, but in the anion distributions, the peaks corresponding to the masses of the C2n-1N- (n= 1-4) ions grew by orders of magnitude, in contrast with those of the adjacent C2nH-peaks, which showed comparatively modest changes. These results could help identify anionic polymerization routes. Note that the two anion families mentioned correspond to the negative ions observed thus far in interstellar and circumstellar media.

Characterization and bacterial inactivation application of multiple pin-to-plate electrode-based DBD plasma driven by nanosecond-pulsed high voltage

A diffuse and large-area dielectric barrier discharge (DBD) filled with air and helium gas mixtures was generated by a unipolar nanosecond-pulsed high voltage. A large-gap multiple pin-to-plate electrode was employed to facilitate the insertion of well plates into the plasma discharge. The nanosecond high-voltage-pulsed discharge has unique advantages in producing a diffuse DBD plasma. We examined the changes in the plasma properties upon varying operating parameters such as the gas composition and flow rate, as well as the pulse voltage. Various types of liquid (de-ionized, tap, and saline water, as well as phosphate buffered saline and LB broth) were exposed to the DBD plasma. The physicochemical properties (pH and electrical conductivity) and concentrations of reactive species generated in the treated liquids (such as H2O2, NO2−, and O3, which play central roles in the aqueous-phase chemistry of plasma-treated liquids for bacterial inactivation) were measured as a function of the operating parameters. The nanosecond-pulsed DBD was observed to generate significantly higher level of reactive species in various types of liquid. For investigating the plasma treatment of liquids containing suspended microorganisms, 1 ml of Escherichia coli (E. coli) stock suspension was pipetted into 9 ml of DW. The resulting bacterial suspensions were treated with the DBD plasma for a selected time. Six-log E. coli reduction was achieved after 19 h of incubation. A DBD plasma generated in a gas mixture of ambient air and 2 slm helium exhibited an enhanced inactivation efficacy, which was correlated with the RONS concentration and pH in the plasma-treated liquids.

On the origins of the continuum radiation of an underwater nanosecond pulsed discharge: an absolute-intensity optical emission spectroscopy study

Abstract The plasma properties of an underwater nanosecond pulsed discharge remain not fully understood despite being extensively studied for several decades. In this work, we focus on the absolute continuum radiation generated in such discharges. The discharge is characterized by power measurements as well as by absolute emission spectroscopy. When observed, Stark broadenings of Hα, Hβ and O (777 nm) are employed for electron number densities measurements. The discharge was generated by a 10 ns main voltage pulse followed by multiple secondary pulses, which last up to 4 µs after the primary pulse. It is shown that a peak power of 3.5 MW and energy of 35 mJ is coupled during the main voltage pulse. A quantitative estimation of the different possible continuum radiation sources is performed through analytical calculations. This includes emission (blackbody, free-bound and free-free bremsstrahlung radiations) and absorption (electron-ion and electron-neutral free-free inverse bremsstrahlung) mechanisms. Our results suggest that electron-neutral free-free bremsstrahlung is the principal mechanism responsible for the strong continuum radiation observed experimentally during the primary pulse. We also show that self-absorption through electron-neutral (and electron-ion) inverse bremsstrahlung plays an important role in the main discharge pulse. Further, our results indicate the non-negligible additional contribution of the H2 continuum during the first reflected pulse which is likely ignited in bubbles generated by the first discharge pulse.

High resolution, sub-picosecond x-ray spectroscopy of K-shell emitters to characterize plasma emissivity measurement.

Short pulse laser (SPL) heated matter has opened an avenue to studying matter at conditions previously unattainable. While SPLs can generate matter at extreme densities and temperatures, characterization of the heated matter can be extremely challenging. The conditions are dynamic and require careful monitoring of the plasma evolution. Atomic processes under these conditions can provide a powerful tool to study fundamental plasma properties as they evolve. When utilizing the x-ray emission from these plasmas, it is often useful to resolve spectral details with high resolution. Sub-picosecond, time-resolved, high-resolution spectroscopy has previously been reported. We present a similar diagnostic (STreaked Orion High-Resolution X-ray spectrometer, or STOHREX) to measure the temporal evolution of spectral features with high spectral resolution. The diagnostic is the result of combining a high-resolution x-ray spectrometer with the LLNL sub-picosecond x-ray streak camera. The diagnostic was demonstrated in two campaigns: (1) To study spectral lineshapes using the 40fs, 400nm, Colorado State University ALEPH laser, and (2) to study buried layers using the 500fs, 532nm Atomic Weapons Establishment's Orion laser.

Experimental characterization of turbulence properties in negative triangularity DIII-D plasmas

Abstract Negative Triangularity (NT) plasmas have demonstrated robustly ELM-free high-performance operation and provide a unique testbed to study how plasma shaping affects turbulent transport. The Beam Emission Spectroscopy (BES) diagnostic provides localized 2D measurements of low-k ($k_{\theta} \rho_s < 1$) density fluctuations. In a sweep of upper triangularity at fixed power, H-mode access is suppressed and an NT-edge is observed. The turbulence amplitude ($\tilde{n}/n$) is shown to decrease by $\sim50\%$ for $\rho<0.9$ in the NT-edge phase as compared to the H-mode phase. Additionally, low-velocity edge modes below 70 kHz are suppressed by triangularity and the dominant mode propagating in the electron diamagnetic direction is seen to broaden in wavenumber space in the NT-edge phase. In a strong NT plasma ($\delta_{avg}\sim-0.5$), low amplitude modes ($\tilde{n}/n <0.5\%$) propagating in the ion-diamagnetic direction with radially-poloidally symmetric eddy structure are identified for $\rho \sim 0.65-0.83$ consistent with Ion Temperature Gradient (ITG) turbulence. Modes consistent with Trapped Electron Mode (TEM) turbulence are observed propagating in the electron-diamagnetic direction for $\rho\gtrsim0.83$ with poloidally extended eddy structure and reduced amplitudes observed at the separatrix. The turbulence properties presented in this paper help validate our understanding of NT turbulence and help explain the improved confinement and unique edge features of NT plasmas.

Freeze-dried plasma: Hemostasis and biophysical analyses for damage control resuscitation.

Effective hemorrhage protocols prioritize immediate hemostatic resuscitation to manage hemorrhagic shock. Prehospital resuscitation using blood products, such as whole blood or alternatively dried plasma in its absence, has the potential to improve outcomes in hemorrhagic shock patients. However, integrating blood products into prehospital care poses substantial logistical challenges due to issues with storage, transport, and administration in field environments. We utilized hemostatic assays and advanced biophysical techniques, such as calorimetry, infrared spectoscopy, dynamic light scattering,and biolayer interferometry, to compare the functional and structural properties of freeze-dried plasma (FDP; OctaplasLG Powder, Octapharma AB) with those of fresh plasma controls. Hemostatic characterization of FDP revealed that clot formation properties and coagulation parameters were largely comparable to fresh plasma controls, with some variations observed in Von Willebrand factor-ADAMTS13 axis and fibrinolysis. No change to moisture content of FDP (~1% water content) was observed after 6-month storage at ambient conditions. Biophysical analyses of FDP during transfusion demonstrated spontaneous exothermic mixing of FDP in plasma, a dilution effect from saline, as well as comparable stability to plasma controls. Quantification of ligand-binding affinities of platelet receptors activated GPIIbIIIa and GPIbα showed comparable binding properties to plasma controls. Our results show that FDP exhibits hemostatic functionality and protein stability on par with fresh plasma, as assessed by novel, highly sensitive techniques. FDP therefore represents a viable alternative to conventional plasma in damage control resuscitation, offering significant logistical and storage advantages for prehospital and remote applications, especially in scenarios where whole blood is unavailable.

3D fluid simulation of the propagation of a nanosecond discharge in air above a liquid surface: investigation of the pattern formation under various conditions and comparison with experiments

Abstract Plasma-liquid interaction remains one of the fundamental processes influencing the various applications. Understanding the influence of external parameters on discharge properties, particularly the discharge dynamic at the liquid surface, is therefore essential. In previous studies, we investigated the impact of voltage polarity, gap distance, and liquid dielectric permittivity and electrical conductivity on nanosecond discharges initiated in air at atmospheric pressure in a pin-to-liquid configuration. Herein, we present a 3D fluid model, improved with stochastic photoionization, to simulate the discharge dynamics under the previously mentioned conditions. The model outputs are compared with the discharge dynamics measured experimentally. For instance, filamentation and the homogeneous emission over solution’s surface measured in positive and negative discharges, respectively, are well reproduced by the simulation. Furthermore, the simulation allowed us to report other plasma properties not accessible experimentally such as the spatio-temporal distributions of electric field (E-field) and electron density. Notably, we observe that the E-field at the front of the negative surface ionization wave (SIW) is nearly four times lower than that of the positive SIW, which may explain the absence of filaments for negative discharges. Furthermore, we find that increasing solution conductivity or gap distance reduce the radial propagation velocity of the circular SIW front and stopping its expansion before a destabilization can occur. The simulation allowed investigating the influence of photoionization strength, and we find that increasing the number of ionizing photons leads to supress the filamentation while keeping the ionization front circular and propagating at high speed.

Microstructure and electrical properties of supersonic plasma sprayed BKT-doped BNT coatings

Microstructure and electrical properties of supersonic plasma sprayed BKT-doped BNT coatings

Study of baryon-strangeness and charge-strangeness correlations in Pb–Pb collisions at √sNN = 5.02 TeV with ALICE

In the quest to unravel the mysteries of the strong force and the underlying properties of the quark-gluon plasma, the ALICE collaboration at CERN has carried out a comprehensive study focusing on the correlations between net-conserved quantities such as net-baryon, net-charge and net- strangeness. These correlations play a crucial role in the study of QCD phase structure as they are closely related to the ratios of thermodynamic susceptibilities in lattice QCD calculations. This work mainly focuses on the correlations between net-kaon and net-proton, and net-kaon and net-charge in Pb–Pb collisions at √sNN = 5.02 TeV using data recorded during LHC Run 2. The net-proton and net-kaon serve as proxies for net-baryon and net-strangeness, respectively, with measurements analyzed as a function of collision centrality. Theoretical predictions from the Thermal-FIST model are compared with experimental results, providing insights into the effects of resonance decays and charge conservation laws on the correlations.

Analysis on plasma and electric field property of TM<sub>011</sub> mode MPT and its tuning experiment

Microwave plasma thruster (MPT) is a kind of electrothermal thruster. Inside its cylindrical cavity, the plasma process, microwave electric field distribution, and TM<sub>011</sub> mode resonant state are important factors affecting the performance of MPT seriously. According to previous MPT formed through continuous regulation in the resonant sate of cylindrical cavity, the research is needed on a newly fixed and simple MPT, which will simplify the resonant state regulation and lays an important foundation for further study. Therefore the plasma process is analyzed to find the optimal gas discharge condition, and the microwave electric field intensity and power density distribution inside the cavity running in TM<sub>011</sub> resonant sate are calculated to analyse how the parameters are influenced by the cavity dimensions. The resonant state is finely regulated to study how it is influenced by the dimensions of cylindrical cavity and microwave coupling probe with ball and half ball structure. The results of theoretical analysis and calculation show that the discharge power of helium gas is the lowest under the condition of 489 Pa and when the ratio of length to diameter is greater than 1, the microwave electric density distribution inside the cavity is beneficial. Owing to the appropriate length and radius of microwave coupling ball probe, the experiment on resonant state regulation shows that the shortest cylinder cavity is in the optimal resonant sate, with a resonance frequency very close to 2.45 GHz. The helium discharge experiment proves that the cavity and matching ball probe enable high microwave utilization and easy helium gas discharge, and the structure scheme is correct and reliable.

Advanced perspective on heavily phosphorus-doped diamond layers via optical emission spectroscopy

Although heavily phosphorus-doped diamond (PDD) holds great potential for advanced device applications, incorporating phosphorus into diamond remains challenging with conventional growth methods. In this study, optical emission spectroscopy (OES) was used to correlate the emission intensity ratio of PH to CH radicals (IPH/ICH) with phosphorus concentration ([P]) in diamond layers synthesized under varying phosphine ([PH3]/[H2]) and methane ([CH4]/[H2]) concentrations using microwave plasma-enhanced chemical vapor deposition. OES results revealed a strong proportional relationship between IPH/ICH and [P] across different [PH3]/[CH4] ratios. However, beyond a maximum [P] of ∼7.0 × 1020 atoms/cm3, further increases in IPH/ICH did not lead to higher [P] with a significant reduction in phosphorus incorporation efficiency (η), consistent with the solubility limits of phosphorus in diamond. At lower [PH3]/[H2], [P] did not scale proportionally with [PH3]/[CH4], exhibiting nonlinear behavior due to phosphorus contamination (Pcont.) in the reaction chamber, which provided sufficient PHx radicals to grow heavily PDD without PH3 gas flow. By understanding plasma properties and their effects on [P], heavily PDD has been effectively achieved with enhancing [P] (up to 745%) and η (up to 143%) by alternating the dominant radical species in the plasma. Time-dependent control of precursor gas flow allowed modulation of IPH/ICH, improving control over phosphorus incorporation. This novel growth approach offers valuable insights for optimizing PDD synthesis, enabling more efficient phosphorus incorporation for electronic, electrochemical, and quantum applications.

Effects of cold electron emissions on thermal plasma measurements on board Solar Orbiter spacecraft

Aims. Emissions of photo and secondary electrons influence thermal electron measurements on board spacecraft, typically below a threshold determined by the spacecraft’s potential. We aim to examine and quantify this contamination of the observed low-energy electron fluxes. We seek to provide effective constraints for the correction methods used to accurately estimate unperturbed solar wind plasma parameters in the context of the Solar Orbiter mission. Methods. We performed a long-term statistical analysis of electron velocity distribution functions acquired by the Electron Analyser System experiment, which is part of the Solar Orbiter’s Solar Wind Analyser suite of instruments. We employed analytical fits of time-averaged phase space density spectra to identify the energy break separating ambient solar wind electron populations from cold electron populations emitted by the spacecraft body. We analysed correlations between the observed energy break and the spacecraft potential, as well as other relevant plasma properties. Results. Our analysis indicates that in contrast to other space missions, emitted electrons from the spacecraft are detected even above the spacecraft potential energy. The derived energy break is found to be uncorrelated with the measured spacecraft potential, but it is correlated strongly with the ambient electron temperature. We attribute this behaviour to the Solar Orbiter’s geometric configuration, which can result in the detection of electrons emitted from spacecraft surfaces that are located far from the instrument’s detector. We derived a theoretical expression for the energy break, assuming Maxwellian distribution functions for both the ambient and spacecraft electrons. This provides an effective constraint for the observed contamination by spacecraft electrons.

PIC/Fluid simulations of the plasma expansion in a planar magnetic arch

Abstract Magnetic arches (MA) (i.e. the magnetic topology that emerges when placing two magnetic nozzles with opposite polarities side by side) are an attractive option for the clustering of multiple electrodeless plasma thrusters, as they are characterized by a zero magnetic dipole moment and thus allow a reduction of perturbing magnetic forces on the spacecraft. This work employs the hybrid code EP2PLUS to simulate and study the plasma expansion for such a magnetic topology in the planar limit. First, a reference simulation is used to analyze the leading physical mechanisms that govern the plume properties. Ions are thus found to be characterized by a double peaked velocity distribution function close to the symmetry plane, where the plasma beams emitted by the two thrusters merge, while the magnetic force acting on electrons is shown to shape both the lateral confinement of the plume, and the thrust profile provided. Second, a parametric sweep on the strength of the magnetic field shows that its influence on the propulsive properties and on the characteristics of the plume saturates for values of the Hall parameter larger than around 10. Beyond this value of the Hall parameter, only the in-plane electron currents are found to be particularly sensitive both to the magnetization levels and the boundary conditions employed, although they are also largely decoupled from the rest of plasma properties. Finally, background pressure effects were considered by including collisions with neutral atoms in the simulations, highlighting the relevance of neutral entrainment in the modification of the plume properties and in the propulsive performance of the MA.

Analysis of the Temporal and Spatial Properties of Platinum Plasma Using Pulsed Nd:YAG and CO2 lasers

Background: The impact of laser light and pulse duration on the hydrodynamic properties of plasma was studied in terms of electron temperature (Te), ion temperature (Ti), and ion rate (Z*). Materials and methods: The study was carried out in two stages: in the first phase, five energy levels of the Nd:YAG laser (1, 3, 5, 7, 9 J) and a pulse duration of (10 ns) were used at Full Width at Half Maximum (FWHM). In the second phase, five energy levels of the CO2 laser (1, 3, 5, 7, 9 J) with a (10 ns ) pulse duration . Results: It was observed that at energy values of (1, 3, 5, 7, 9) J for the Nd:YAG laser with a 10 ns pulse duration, the electron temperature ranged from (214.79 to 690.97) eV. While the electron temperatures as a result of Co2 laser is ranged between (84.93 to 414.99) eV. Conclusion: We observe the electron temperatures of platinum plasma produced as a result of the ND:YAG laser was produced with with the same levels were higher than the electron temperatures of platinum plasma produced using a CO2 laser.

Shear and bulk viscosity of the quark-gluon plasma with Gribov gluons and quasiparticle quarks

In this study, we analyze the transport properties of the quark-gluon plasma (QGP), focusing on bulk (ζ) and shear (η) viscosities at vanishing chemical potential. To describe the QGP, we employ a quasiparticle model for quarks along with Gribov’s prescription for gluons, which effectively captures nonperturbative dynamics. The Gribov parameter γG and the dynamical mass mg are obtained by solving the one-loop gap equation in the MS¯ renormalization scheme and further using lattice QCD data for the equation of state (EOS) of pure gluonic matter. The interaction between quarks and gluons is reflected in the quark quasimass mq, again obtained using lattice EOS data for (2+1)-flavor QCD. Our primary goal is to investigate the influence of quasiquarks on the transport coefficients of QGP. Interestingly, we find a substantial decrease in the scaled transport coefficients with rising temperatures within the range (1≤T/Tc≤3.5). Published by the American Physical Society 2024

Current pathways model for hall thruster plumes in ground-based vacuum test facilities: measurements and observations

A previous companion paper introduced a current pathways model that represents the electrical coupling between the Hall effect thruster (HET) and the ground-based vacuum test facility operational environment. In this work, we operated a 7-kW class HET at 4.5 kW, 15 A and 6 kW, 20 A on krypton to quantify aspects of the current pathways model to characterize the role metal vacuum chambers play in the thruster’s discharge circuit as a function of discharge current. During HET operation, far-field ion and electron saturation currents at 47 near-facility wall locations were measured using an array of 5.08 cm diameter, stainless-steel planar electrodes. In addition, the plasma properties at three distinct locations within the facility, 25 cm from the facility wall, were obtained using Langmuir probes. Experimental results show that thruster beam ions do not readily neutralize with cathode electrons and instead neutralize with the free electrons provided by the metallic chamber wall. In addition, significant charge-exchange (CEX) ion current was measured in the background plasma environment and constituted about 23% of the total ion current measured by the planar electrode array. Thus, the metallic vacuum chamber surfaces facilitate charge neutralization for both ion populations. Additionally, the plasma environment near the facility walls was characterized to be non-uniform with an estimated plasma sheath capacitance ranging between 0.45 µF and 1.79 µF. Further analysis shows that the plasma sheath at the facility wall behaves like a parallel RC circuit, potentially concealing the thruster’s AC characteristics. Inherent plasma oscillations give rise to inductive effects with inductances that varied between 76.5 nH and 101.4 nH. Hence, the dynamic characteristics of the HET’s discharge are influenced by the capacitive and inductive effects introduced by the vacuum test facility operational environment.

Impact of plasma discharge pressure on implant surface properties and osteoblast activities in vacuum-assisted plasma treatment

Nonthermal plasma has been extensively utilized in various biomedical fields, including surface engineering of medical implants to enhance their biocompatibility and osseointegration. To ensure robustness and cost effectiveness for commercial viability, stable and effective plasma is required, which can be achieved by reducing gas pressure in a controlled volume. Here, we explored the impact of reduced gas pressure on plasma properties, surface characteristics of plasma-treated implants, and subsequent biological outcomes. Implant materials were treated with plasmas under varying discharge conditions, with pre-pumping times of 10 s and 20 s, thereby modulating the pressure during plasma treatments. Through optical emission spectroscopy, we demonstrated that the 5 Torr operational condition, achieved by 20-s pre-pumping, generated a greater density of excited nitrogen species and provided more stable plasma compared to the 16 Torr condition, achieved by 10-s pre-pumping. We then assessed the surface hydrophilicity, chemical composition, protein adsorption, and osteoblast activities on plasma-treated implants compared with those of untreated controls. Our results reveal that the 5 Torr condition significantly enhances removal of carbon-based impurities and increased protein adsorption, leading to improved cell adhesion, proliferation, and differentiation. In particular, implants treated under the 5 Torr condition showed significantly higher carbon-based impurity reduction and osteoblast differentiation performance compared to those treated under the 16 Torr condition. These findings suggest that optimizing gas pressure in plasma devices is critical for effectively controlling excited nitrogen radicals, which improves plasma surface modification and enhances the biocompatibility of implant surfaces.

Modeling of arcs with binary gas mixtures in a multi‐arc plasma generator

AbstractUsing plasma as an energy source in thermal spraying allows the processing of feedstock materials with high melting temperatures. In plasma spraying, hydrogen or nitrogen is commonly injected into the argon plasma, which increases the specific enthalpy and thermal conductivity. The objective of this study is to improve the understanding of this process through numerical simulation and to investigate the impact on the plasma properties. A comprehensive modelling approach for the electrodes in the three‐cathode plasma generator is built upon the previous work of the authors. The plasma is described as an electromagnetically reactive fluid in local thermodynamic equilibrium using temperature‐dependent thermodynamic and transport properties. The increase of flow temperature and velocity as well as the temperature distribution at the electrodes can be successfully simulated. The simulation model could accelerate parameter development for new coating systems in the future. This study completes the simulation model for multi‐arc plasma spraying using binary gas mixtures.