Plasma Parameters Research Articles

Deposition of nanocomposite carbon-based thin films doped with copper and fluorine

This paper is focused on plasma-enhanced chemical vapor deposition (PECVD) of novel carbon-based thin films. Unique thin films were deposited from a mixture of methane, hydrogen, and a precursor containing fluorine and copper: (hfac)copperVTMS (hfac = hexafluoroacetylacetonato and VTMS = vinyltrimethylsilane). Using the (hfac)copperVTMS precursor in PECVD deposition results in the advantageous chemical composition of carbon-based thin films while maintaining sufficient mechanical properties. Furthermore, with optimized plasma parameters, the films deposited on the substrate exhibit a nanocomposite structure. This nanostructured surface can increase the surface area, which is beneficial for various applications, including antibacterial and antiviral properties. The radiofrequency glow discharge at low pressure (≈70Pa) and power P=25W and P=250W was used for deposition. Deposited thin films were analyzed using X-ray photoelectron spectroscopy, water contact angle measurement, atomic force microscopy, and nanoindentation techniques. Despite the doping of carbon-based thin films with soft copper, the prepared films exhibited sufficient mechanical properties, which are crucial for the future implementation of this deposition process.

Full-f gyrokinetic simulations of hydrogen isotope mixing in tokamak plasmas

Hydrogen isotope mixing phenomena in tokamak plasmas are analyzed using global full-f gyrokinetic simulations. Model plasma parameters are chosen based on hydrogen isotope pellet experiments on JET, in which fast hydrogen isotope mixing in the timescale of the energy confinement time τE occurred after injecting deuterium (D) pellets into hydrogen (H) plasmas. Two numerical experiments are conducted using plasma profiles before and after the pellet injection. In both cases, turbulent fluctuations in the plasma core are characterized by ion temperature gradient driven turbulence. In the former case, the density profile of bulk H ions is kept in a quasi-steady state, and the particle confinement time of bulk H ions τH is an order of magnitude longer than τE. In the latter case, the density profiles of bulk H ions and pellet D ions show transient relaxation in the timescale of τE, and both τH and the timescale of particle pinch τD become comparable to τE, indicating the fast hydrogen isotope mixing. In the toroidal angular momentum balance, it is found that the enhanced ion particle transport leading to the fast hydrogen isotope mixing is driven by the toroidal field stress.

Enhancement of OH spectra in atmospheric pressure plasma jet by femtosecond laser

A helium (He) atmospheric pressure plasma jet (APPJ) system with a single electrode was configured. A pulsed light of femtosecond (fs) laser was irradiated at the guided streamer of He APPJ through an objective lens to generate the laser induced plasma (LIP) inside the He APPJ. The optical emission spectra of LIP were measured as the light energy of the fs laser increased. The spectra of hydroxyl molecules and atomic oxygen were enhanced when the fs laser energy exceeded 114 μJ. The plasma parameters of LIP inside the APPJ were determined using He collisional-radiative model. Electron temperature and density increased to ∼7.2 eV and 1.7×1014 cm−3, respectively. The dominant processes underlying the enhancement were discussed in the interaction of fs laser and He APPJ.

Enhanced degradation of aqueous caffeine via cylindrical dielectric barrier discharge plasma: Efficacy and toxicity insights

An environmentally friendly approach for caffeine degradation was explored in this study utilizing cylindrical dielectric barrier discharge (CDBD) plasma. The current-voltage characteristics and the plasma parameters of the CDBD, such as the electron temperature, electron density, density of nitrogen excited states, vibrational temperature, and rotational temperature, were assessed through electrical and optical characterization respectively. Fourier-transform infrared spectroscopy (FTIR) was employed to evaluate the reactive oxygen and nitrogen species (RONS) in the plasma-treated air. The physicochemical properties of deionized water (DW) were measured. To gain a deeper insight into the role of RONS in caffeine degradation, their concentrations in DW were analyzed. Furthermore, the effects of initial concentration, sample volume, and pH on caffeine degradation were investigated. The highest degradation of caffeine was 94% at initial concentration of 50 mg L-1, sample volume 50 mL and in neutral pH. Liquid chromatography–mass spectrometry (LC-MS) was then used to propose the degradation pathway for caffeine. The major reactive species involved in caffeine degradation was ozone. Finally, the phytotoxicity and cytotoxicity of caffeine were assessed before and after plasma treatment with plasma-treated caffeine (PTC) showing minimal toxicity to both plants and cells.

First Thomson scattering results from AWAKE’s helicon plasma source

Abstract We present the first results of electron density and temperature measurements obtained from Thomson scattering at the helicon plasma source (HPS) for the AWAKE project. These measurements are compared to simulation results from a 1D power and particle balance model (PPM), confirming that the plasma can be fully sustained by collisional power dissipation. The variations in plasma parameters under different experimental conditions are evaluated in the PPM framework. We discuss current limitations of the model and propose possible improvements. Additionally, we suggest modifications to the existing HPS setup to enhance axial plasma homogeneity.

Bioavailability of Supplemented Free Oleanolic Acid and Cyclodextrin-Oleanolic Acid in Growing Pigs, and Effects on Growth Performance, Nutrient Digestibility and Plasma Metabolites.

Oleanolic acid (OLA) has beneficial health effects in animals, but in vivo efficacy in monogastric animals is questioned due to its low bioavailability. To gain further insight on the nutritional effects of OLA it was administered as part of a diet. We investigated digestibility and plasma OLA in pigs and the associated influence on growth, organs, digestibility of nutrients and plasma biochemical profile. Twenty-four crossbred barrows (23.7 ± 1.0 kg BW) were assigned one of three treatments: Control (basal diet without OLA), OLA-1 (basal diet with 260 mg/free OLA) and OLA-2 (basal diet with 260 mg/kg cyclodextrin-OLA). Diets included chromium oxide to estimate digestibility. Blood samples were collected on day 14 for OLA analysis and feces on days 22-24 for determining digestibility. Pigs were slaughtered on day 31 (39.9 ± 2.43 kg BW) and their blood collected for analysis. Growth and organ weights were not affected (p > 0.05). OLA-1 decreased apparent total tract digestibility (ATTD) of energy (p < 0.05). OLA-2 increased ATTD of dry and organic matter compared with Control pigs (p < 0.05). OLA-1 increased plasma calcium and alkaline phosphatase (p < 0.05). Ileal digestibility of OLA was not affected (0.88), although OLA ATTD increased in OLA-1 compared to Control pigs (0.75 vs. 0.82; p < 0.05). OLA-1 and OLA-2 increased plasma OLA compared to Control pigs (p < 0.05 and p = 0.083). In conclusion, although the OLA was digested and absorbed, plasma concentration was low (4.29 µg/L), and pig growth, organs and plasma parameters were not affected.

Helical resonant magnetic perturbation coils for controlling edge localized modes: a robustness study

Abstract Plasma response to helical resonant magnetic perturbation coil current is numerically computed for tokamak plasmas, with optimization results compared with that for conventional window-frame coils. The key aspect of study is the robustness of the proposed new concept against variation of plasma equilibrium parameters including (i) the plasma resistivity, (ii) the toroidal rotation and (iii) the plasma shaping (both elongation and triangularity). Toroidal modeling results yield several important conclusions. First, assuming the same coil current, the optimal helical coils robustly outperform the optimal window-frame coils against variation of the aforementioned plasma equilibrium parameters. Secondly, for a chosen toroidal spectrum, the optimal helical coil geometry including the poloidal location, poloidal coverage and the overall shape, is robust against variation of plasma parameters except the safety factor. Finally, in all cases, optimization based on the plasma response naturally yields a single row of helical coils located near the outboard mid-plane of the torus, ensuring a relatively simple design of the coil geometry.

Construction of Multi-Channel Radio Frequency Plasma Jet System in Atmospheric Pressure and the Diagnosis of Plasma Parameters and I-V Characteristics

In order to produce cold plasma at atmospheric pressure, a multi-channel RF, of (1, 2, 3, and 4 MHz) frequencies, plasma jet system is developed using argon as the working gas. This system consists of two parts, a multi-channel power supply (of a power of 100 W) and a plasma jet. A strong electric field is created that ionizes and excites argon ions. The I-V characteristics of the system and the electron temperature and density for different powers (20, 50, 70, and 80 W), gas flow rates (10, 20, 30, and 40 sccm) (standard centimeter cubic per minute) at different frequencies (1, 2, 3, and 4 MHz) are studied, using the optical emission spectroscopy method. This system can be used in medical applications and material treatment with high efficiency.

Importance of the electron plasma parameter for excitation of chorus and formation of magnetic field irregularity in the region of their excitation

A threshold condition has been established for excitation of VLF electromagnetic radiation with a chorus structure of the dynamic spectrum in the daytime magnetosphere using the BPA (Beam Pulse Amplifier) mechanism for amplifying short noise electromagnetic pulses. The kappa distribution was used as a model function of the electron velocity distribution in the magnetosphere. Calculations performed for this distribution have shown that the threshold for excitation of chorus largely depends on the electron plasma parameter equal to the ratio of gas-kinetic pressure of electrons to magnetic pressure. This pattern is not contradicted by the dependence of the probability of excitation of chorus on the degree of magnetic field irregularity, which we derived from observations made by the Van Allen Probe spacecraft. It is sharp fluctuations in the magnetic field strength near its local minima outside the plasmasphere where the radiation under study can be excited. If there is an irregularity, the probability of detecting chorus is &gt;70 %; and if there is no or very low irregularity, the probability of the absence of any emissions is ~80 %. The results indicate a common reason for the excitation of chorus and the magnetic field irregularity — a small but finite value of the plasma parameter.

Существенность величины плазменного параметра электронов для возбуждения хоров и формирования нерегулярности магнитного поля в области их возбуждения

A threshold condition has been established for excitation of VLF electromagnetic radiation with a chorus structure of the dynamic spectrum in the daytime magnetosphere using the BPA (Beam Pulse Amplifier) mechanism for amplifying short noise electromagnetic pulses. The kappa distribution was used as a model function of the electron velocity distribution in the magnetosphere. Calculations performed for this distribution have shown that the threshold for excitation of chorus largely depends on the electron plasma parameter equal to the ratio of gas-kinetic pressure of electrons to magnetic pressure. This pattern is not contradicted by the dependence of the probability of excitation of chorus on the degree of magnetic field irregularity, which we derived from observations made by the Van Allen Probe spacecraft. It is sharp fluctuations in the magnetic field strength near its local minima outside the plasmasphere where the radiation under study can be excited. If there is an irregularity, the probability of detecting chorus is &gt;70 %; and if there is no or very low irregularity, the probability of the absence of any emissions is ~80 %. The results indicate a common reason for the excitation of chorus and the magnetic field irregularity — a small but finite value of the plasma parameter.

One-Year Impact of Occupational Exposure to Polycyclic Aromatic Hydrocarbons on Sperm Quality.

Polycyclic aromatic hydrocarbons (PAHs) have toxic potential, especially as carcinogens, neurotoxins, and endocrine disruptors. The objective of this study is to know the impact of exposure to PAHs on the reproductive health of male workers who operate in solar thermal plants. Case-control study. A total of 61 men were included: 32 workers exposed to PAH at a solar thermal plant and 29 unexposed people. Seminal quality was studied both at the cellular level (quantity and quality of sperm) and at the biochemical level (magnitudes of oxidative stress in seminal plasma). In exposure to PAHs, a significantly higher seminal leukocyte infiltration was observed, as well as lower activity in seminal plasma of superoxide dismutase (SOD) and a reduced glutathione/oxidised glutathione (GSH/GSSG) ratio. The oxidative stress parameters of seminal plasma did not show a relationship with sperm cellularity, neither in those exposed nor in those not exposed to PAH. One year of exposure to PAH in a solar thermal plant does not have a negative impact on the sperm cellularity of the worker, either quantitatively (sperm count) or qualitatively (motility, vitality, morphology, or cellular DNA fragmentation). However, PAH exposure is associated with lower antioxidant capacity and higher leukocyte infiltration in seminal plasma.

Lactobacilli-Based Pro and Postbiotic Efficacy Are Also Influenced by Other Factors Than Dietary Challenging Conditions.

The present study aimed to confirm the previously reported 'recovery' effect to a challenging diet (CD) of a Lactobacilli-based probiotic (Pro) and its derived postbiotic (Post) in broilers. Identical diet compositions were used, and observations were extended to a second CD diet. A completely randomised block design of 2 × 3 treatment groups with two CDs and three additive conditions (Control, Pro, Post) was used. One additional group received a standard diet (SD). The study involved 1600 one-day-old Ross 308 male broilers. All diets, fed from d1 to 35, were formulated to contain identical nutrients levels, with CDs formulated to be greater than SD in nonstarch polysaccharides using rye and barley (Rye CD) or dry distiller grains with soluble, sunflower and rapeseed meal (DDGS CD). Growth performance parameters, footpad lesions (FPL) score and plasma Ca, P and uric acid concentrations were measured. Compared to SD, birds fed Rye CD and DDGS CD had a higher 1-35 days feed conversion ratio (+3.4 and +4.1%, respectively), due to a higher feed intake for Rye CD (+2.9%) and a lower body weight for DDGS CD (-4.1%). An effect of additive was restricted to Rye CD where Post depressed BW at d28 and d35 (-3.7 and -2.4%, respectively). Compared to Rye CD, DDGS CD lowered plasma Ca/P at d21 (-9.0%) and d35 (-8.1%) and uric acid at d21 (-26%). Pro increased plasma Ca in Rye CD at d21 (+12%) and Post decreased plasma uric acid in DDGS CD at d35 (-25%). All other plasma parameters were not affected. The previously observed recovery effect of a commercial probiotic and postbiotic were not reproducible under highly similar growth conditions, which suggests that both may have specific physiological effects which are only expressed under specific circumstances.

Analysis of discharge parameters of an argon cold atmospheric pressure plasma jet and its impact on surface characteristics of White Grapes

An argon cold atmospheric-pressure plasma (CAP) jet operated using bipolar pulsed power supply has been characterised electro-optically and the discharge parameters are optimized. An analysis has been done on the impact of the argon CAP jet treatment on the surface properties of white grapes for different treatment time period. The developed argon CAP jet is a plasma source based on dielectric barrier discharge (DBD) that has been tuned at various input parameters including applied voltage, frequency, average power consumption, and argon flow rate. Optical Emission Spectroscopy (OES) is used to identify the generated species along with plasma parameters. The collisional–radiative (CR) model is employed to extract the electron density (ne) and electron temperature (Te) from the spectra at the optimised applied voltage of 4 kV, frequency 20 kHz and argon flow rate of 4 slpm. The OES results coupled with the CR model (ne ∼ 1014 cm−3 and Te ∼ 1 eV) and the plasma gas temperature measurement through OH (A-X) transitions (Tg ∼ 310.5 K) show the non-equilibrium nature of the argon CAP jet. A comparative analysis between untreated and treated white grapes reveals that the argon CAP jet treatment influences surface microstructure, increasing hydrophilicity (with a ∼49.3% decrease in water contact angle) along with slight changes in surface temperature (∼5 °C increase), colour (ΔE* < 1.5), and physiochemical properties such as chemical composition (no change) and Total Soluble Solid (TSS) content (∼8.3%). It is inferred that this type of CAP jet treatment of white grapes only affects the physical characteristics of the grape surface and does not alter any chemical compositions.

Pedestal properties of negative triangularity discharges in ASDEX Upgrade

Abstract In this work, we explore the pedestal properties of negative triangularity discharges with upper triangularity of δ u ≈ − 0.35 and with both ion ∇ B drift directions. In all cases, the discharges undergo a transition to H-mode with accompanying edge-localized modes (ELMs) that are not explained by the peeling-ballooning stability analysis alone. A variation in the ion ∇ B drift direction is observed. A lower pressure gradient, shallower radial electric field well and increased temperature fluctuations are measured in the favorable case. In addition, irregular ELMs are present. This difference is more pronounced in electron cyclotron resonance heating (ECRH) plasmas compared to plasmas with combined neutral beam injection and ECRH. A comparative analysis between two discharges, featuring similar plasma parameters but varied shaping, suggests that an interplay between other parameters, such as magnetic shear, the timing of the auxiliary heating and shaping, might play a strong role in low- to high-confinement transitions. While the low shaping discharge maintained L-mode, the high shaping discharge entered H-mode with ELMs, contrary to expectations.

X-ray imaging crystal spectrometer (XICS) diagnostic on the HL-3 tokamak

The construction of an X-ray imaging crystal spectrometer (XICS) diagnostic system on the HL-3 tokamak plays a crucial role in measuring core plasma parameter profiles, including ion temperature, electron temperature, rotational velocity, and impurity radiation profiles. This diagnostic system has been specifically designed to provide detailed and accurate data essential for understanding the behavior and characteristics of tokamak plasma. The resonance spectral line (w line of Ar XVII at 3.9494 Å) and its satellites of helium-like argon ions were chosen on the basis of the HL-3 parameter range. A spherically bent quartz crystal (1012) with a lattice constant of 2d = 4.562 Å, a curvature radius of Rc = 3.0 m, and a size of 10 cm (high) × 5 cm (wide) was mounted on an adjustable displacement platform in the XICS system. The position was adjusted in three dimensions (vertical, inclined, rotation) to effectively record the spectra of the helium-like argon ions. The XICS has a tangential angle of 49° for the toroidal direction in the magnetic axis. This layout accounts for 65.6 % of the toroidal rotation velocity component. The XICS system was set at an 11° poloidal angle in the mid-plane to cover a plasma range of 10 cm above to 50 cm below the mid-plane, which corresponds to the q = 1 surface of the HL-3 plasma (elongation κ > 1.8). This XICS layout produced a spectrum with poloidal and toroidal rotational contributions, requiring decoupling through data processing. In general, because the contribution of the poloidal rotation velocity is much smaller than that of the toroidal rotation velocity, it can be ignored. The XICS system offers a spatial resolution of ∼1.5 cm and a temporal resolution of 5–10 ms on the basis of a high-performance PILATUS3 × 900 K detector. The spectral resolution is λ/Δλ∼4×104, which satisfies the experimental measurement requirements. Preliminary results of ion and electron temperature profiles were obtained for the HL-3 tokamak.

Velocity profile shapes in Alcator C-Mod plasmas

Abstract Toroidal rotation velocity spatial profiles ( r / a &lt; 0.8) have been obtained from C-Mod over a wide range of operational conditions, including H-mode, I-mode, ICRF-heated L-mode and Ohmic L-mode (LOC and SOC), and in plasmas with ITBs, LH wave injection and MCFD. Peaked, flat and hollow rotation profiles have been observed. In H- and I-mode plasmas, generally with co-current peaked profiles, the peaking is correlated with temperature profile peaking, and both increase with toroidal magnetic field (decrease with ρ ∗ ). Any dependence on density peaking is unclear. For Ohmic L-mode discharges, with LOC, the velocity profiles are usually flat and most often directed co-current, while with SOC the profiles are hollow, mostly co-current at the edge and counter-current in the core. Both of these Ohmic rotation states exist with matched density and temperature profiles (and gradients), indicating that neither gradient is relevant during rotation reversals. For plasmas with LH wave injection and discharges with ITBs, the velocity profiles are hollow while the density and temperature profiles exhibit substantial peaking. Broadly speaking for all operational regimes, there is no unifying ordering of the velocity gradient with plasma parameters.

Ultrarelativistic Fe plasma with GJ/cm3 energy density created by femtosecond laser pulses

The generation of a plasma with an ultrahigh energy density of 1.2 GJ/cm3 (which corresponds to about 12 Gbar pressure) is investigated by irradiating thin stainless-steel foils with high-contrast femtosecond laser pulses with relativistic intensities of up to 1022 W/cm2. The plasma parameters are determined by X-ray spectroscopy. The results show that most of the laser energy is absorbed by the plasma at solid density, indicating that no pre-plasma is generated in the current experimental setup.

Extreme ultraviolet emission spectra of a low-pressure microwave neon discharge

In this paper, in order to reveal the discharge mechanism and optimize the extreme ultraviolet (EUV) emission lines in intensity of a low-pressure microwave (MW) neon discharge, the EUV neon spectra is carefully characterized under varied MW powers and neon pressures. The corona balance is verified to be valid for the neon upper levels of the measured EUV lines, and the electron temperature T e is derived by the modified Boltzmann plot method and the line-ratio method. Both results of the methods present a decreasing trend of T e with growing neon pressure, but the values in a range of 1.87-5.77 eV deduced by the former method is in general lower than that calculated by the latter with a range of 2.23–5.58 eV in similar neon pressure range. It is also found that the increase of MW power from 90 to 135 W only leads to a slight increasing of T e . A global model is applied to estimate the electron density n e , which is found to lie in the order of magnitude of 1010 cm−3. The dependence of the plasma parameters on different discharge conditions is analysed in detail, which in turn provide a favourable basis for further optimization of the promising low-pressure MW discharge radiation source.

Tunable topological edge state in plasma photonic crystals

In this study, we found a kind of edge state located at the interface between plasma photonic crystals (PPCs) and traditional photonic crystals, which depends on the property of the photonic band gap rather than the surface defect. Simulation and theoretical analysis show that by adjusting the plasma density, we can change the topological characteristics of the photonic band gap of PPCs. This makes it different from the photonic band gap of traditional PCs, and thus excites or closes the topological edge states. We further discussed the influence of plasma parameters on edge state characteristics, and the results showed that as the plasma density increased, the first photonic band gap (PBG) of the PPCs closed and then reopened, resulting in band inversion and a change in the PBG properties of the PPCs. We can control the generation of edge states through plasma and adjust the frequency and strength of the edge states. After the appearance of edge states, as the plasma density further increases, the first PBG of the PPCs will shift towards high frequencies and deepen. The frequency of edge states will shift towards higher frequencies, and their strength will also increase. We increased the first PBG depth of the PPCs by increasing the number of arrays and found that when the number of the PPCs arrays increased, only the intensity of the edge states would increase while the frequency remained unchanged. Therefore, flexible adjustment of edge state frequency and intensity can be achieved through plasma density and array quantity parameters. Our study demonstrates the properties of topological edge states in plasma photonic crystals, which we believe can provide some guidance for applications based on edge states.

Optical emission spectroscopy as a method for evaluating the change in Si etching structures profile in ICP SF6/C4F8 plasma: Microstructures

In this work, a method for in situ diagnostics of the etching profile of silicon structures (etching window sizes 15–400 μm) using optical emission spectroscopy was proposed. To determine the relationship between the etching profile and plasma parameters, the influence of technological parameters on the etching characteristics (vertical and lateral etching rate, selectivity in relation to photoresist, and sidewall angle) was studied. As a general parameter, which reflects the changes in plasma characteristics depending on the selected technological parameters, the parameter X (C/F ratio in SF6/C4F8 plasma) was introduced. Based on the results obtained, a general pattern between the lateral etching rate, sidewall angle, and optical emission spectra was identified. Thus, ranges of X values, at which the lateral etching rate does not exceed 5 nm/min for 15–30 μm structures and 15 nm/min for 100 μm structures, were estimated: 0.38 ≤ X ≤ 0.77 and 0.28 ≤ X ≤ 0.46, respectively. For 250–400 μm structures, ranges of X values, at which the sidewall angle is acute, straight, and obtuse, were determined: 0.16 ≤ X &amp;lt; 0.29, 0.29 ≤ X ≤ 0.41, 0.41 &amp;lt; X ≤ 0.75, respectively.