Plasma Radiation Research Articles

A synthetic diagnostics platform for microwave imaging diagnostics in tokamaks

Interpreting experimental diagnostics data in tokamaks, while considering non-ideal effects, is challenging due to the complexity of plasmas. To address this challenge, a general synthetic diagnostics (GSD) platform has been established that facilitates microwave imaging reflectometry and electron cyclotron emission imaging. This platform utilizes plasma profiles as input and incorporates the finite-difference time domain, ray tracing and the radiative transfer equation to calculate the propagation of plasma spontaneous radiation and the external electromagnetic field in plasmas. Benchmark tests for classical cases have been conducted to verify the accuracy of every core module in the GSD platform. Finally, 2D imaging of a typical electron temperature distribution is reproduced by this platform and the results are consistent with the given real experimental data. This platform also has the potential to be extended to 3D electromagnetic field simulations and other microwave diagnostics such as cross-polarization scattering.

Evaluating Mass Spectrometry-Based Hydroxyl Radical Protein Footprinting of a Benchtop Flash Oxidation System against a Synchrotron X-ray Beamline.

Hydroxyl radical protein footprinting (HRPF) using synchrotron X-ray radiation (XFP) and mass spectrometry is a well-validated structural biology method that provides critical insights into macromolecular structural dynamics, such as determining binding sites, measuring affinity, and mapping epitopes. Numerous alternative sources for generating the hydroxyl radicals (•OH) needed for HRPF, such as laser photolysis and plasma irradiation, complement synchrotron-based HRPF, and a recently developed commercially available instrument based on flash lamp photolysis, the FOX system, enables access to laboratory benchtop HRPF. Here, we evaluate performing HRPF experiments in-house with a benchtop FOX instrument compared to synchrotron-based X-ray footprinting at the NSLS-II XFP beamline. Using lactate oxidase (LOx) as a model system, we carried out •OH labeling experiments using both instruments, followed by nanoLC-MS/MS bottom-up peptide mass mapping. Experiments were performed under high glucose concentrations to mimic the highly scavenging conditions present in biological buffers and human clinical samples, where less •OH are available for reaction with the biomolecule(s) of interest. The performance of the FOX and XFP HRPF methods was compared, and we found that tuning the •OH dosage enabled optimal labeling coverage for both setups under physiologically relevant highly scavenging conditions. Our study demonstrates the complementarity of FOX and XFP labeling approaches, demonstrating that benchtop instruments such as the FOX photolysis system can increase both the throughput and the accessibility of the HRPF technique.

Terahertz-induced second harmonic radiation from transient electron behavior in water

Laser-induced liquid plasma is expected to be an efficient medium for a new generation of terahertz (THz) devices. However, the mechanism of interaction between liquid plasma and THz waves is currently unclear. Here, we observed two phenomena related to THz wave interaction with water plasma: THz-induced second harmonic (TISH) radiation in water plasma and THz absorption by water plasma. We established an internal relationship between these two macroscopic phenomena by utilizing a photocurrent model and the Drude model. Using liquid water and air as examples, a scheme is proposed to analyze the photonic characteristics of plasma in different physical states. This study offers an experimental basis for predicting the TISH phenomenon across various substances and states and also provides the theoretical support for the practical implementation of liquid-based detection of THz waves.

Line-of-sight gas radiation effects on near-infrared two-color ratio pyrometry measurements during plasma wind tunnel experiments

Two-color ratio pyrometry is commonly used to measure the surface temperature of aerospace materials during plasma wind tunnel experiments. However, the effect of the plasma radiation on the measurement accuracy is often neglected. In this paper, we formulate a model of the instrument response to analyze the systematic error induced by the gas radiation along the optical path. CFD simulations of the plasma flow field, together with a radiation code, allow to compute the gas spectral radiance within the instrument wavelength range. The measurement error is numerically assessed as a function of the true object temperature and emissivity value. Our simulations explain the typical behavior observed in experiments, showing that a significant bias can affect the measured temperature during the material heating phase. For an actual experiment on a ceramic-matrix composite, a correction to the measured data is proposed, while comparative measurements with a spectrometer corroborate the results.

Low onset potential for oxygen evolution reaction on hematite electrodes processed with He plasma irradiation

In this study, we investigated the effects of helium (He) plasma irradiation and thermal treatment on the morphology, the surface characteristics, and the photoelectrochemical performance of bulk iron (Fe) sheets. After processing, all samples consisted mainly of an α-Fe2O3 surface. Helium plasma irradiation resulted in a cathodic shift in the onset potential of the photocurrent from 1.16 VRHE (no pretreatment) to 0.57 VRHE (plasma exposure at 660 °C), where VRHE represents the potential versus reversible hydrogen electrode (RHE). An increase in the surface roughness and a smaller amount of hydroxyl or oxygen vacancies at the surface after photoelectrochemical measurement are related to the decrease of the onset potential. The results show that He plasma irradiation does not only modify the surface morphology, but also affects the functional properties of the materials.

Evaluation of the Effects of Dielectric Barrier Discharge Plasma on Candida albicans Strains: An in vitro Study

Background: Antifungal resistance is increasing, posing a challenge for treating candidiasis. Cold atmospheric plasma (CAP) is a potential alternative, but its association with traditional antifungals is poorly understood. Objectives: This study aims to evaluate the effects of dielectric barrier discharge (DBD) plasma on Candida albicans. Methods: In this in vitro study, C. albicans strains were irradiated with DBD plasma for 5, 10, and 15 minutes, both with and without nystatin. The number of colonies was counted, and the MTT method assessed Candida's survival. Data were analyzed with SPSS26. Results: This study showed that in both experimental groups, with and without nystatin, the lowest C. albicans cell viability was observed following a 10 minute DBD exposure within the groups subjected to plasma treatment (P < 0.001). The positive control group (nystatin without plasma exposure) exhibited a diminished count of viable cells in comparison to the group with 10 minute plasma irradiation without nystatin (P < 0.001). The 10 and 15 minute DBD plasma exposures, along with their positive control counterparts, demonstrated a statistically significant reduction in colony count compared to the 5 minute DBD exposure and the negative control groups (P < 0.001). Conclusions: Nystatin was more effective than DBD plasma irradiation in reducing C. albicans cell viability. When used in combination, 10 minute DBD plasma irradiation with nystatin was more effective than 5 or 15 minute irradiation times in reducing the survival rate of C. albicans.

Analysis of the Mechanism of Microwave Radiation Generated by the Weak Interaction Between Relativistic Electron Beam and Plasma with a Transverse Magnetic Field

This article establishes a physical model of the interaction between a surface electron beam and the plasma with a transverse magnetic field. The dispersion relation of the beam-plasma interaction is derived by using the field matching method. The effects of magnetic field, electron beam electron density, and plasma density on the radiation frequency and z-direction wave vector are studied. The results indicate that the stronger the transverse magnetic field is, the higher is the cutoff frequency of plasma radiation. The higher the plasma density or electron beam electron density is, the higher are the corresponding radiation frequency and radiation wave number.

Atomic-scale smoothing of semiconducting oxides via plasma-enabled atomic-scale reconstruction

β-Ga2O3, known as a next-generation wide-bandgap transparent semiconducting oxide (TSO), has considerable application potential in ultra-high-power and high-temperature devices. However, fabricating a smooth β-Ga2O3 substrate is challenging owing to its strong mechanical strength and chemical stability. In this study, an atomic-scale smoothing method named plasma-enabled atomic-scale reconstruction (PEAR) is proposed. We find that three reconstruction modes, namely, 2D-island, step-flow, and step-bunching, can be identified with the increase in the input power; only the step-flow mode can result in the formation of an atomically smooth β-Ga2O3 surface (Sa = 0.098 nm). Various surface and subsurface characterizations indicate that the smooth β-Ga2O3 surface shows excellent surface integrity, high crystalline quality, and remarkable photoelectric properties. The atomic-scale density functional theory-based calculations show that the diffusion energy barrier of a Ga atom is only 0.46 eV, thereby supporting the atomic mass migration induced by high-energy plasma irradiation in the experiment. Nanoscale molecular dynamics simulations reveal that O atoms firstly migrate to crystallization sites, followed by Ga atoms with a lower migration rate; reconstruction mainly proceeds along the <010> direction and then expands along the <100> and <001> directions. The millimeter-scale numerical simulations based on the finite element method demonstrate that the coupling of the thermal and flow fields of plasma is the impetus for PEAR of β-Ga2O3. Furthermore, the smoothing generality of PEAR is demonstrated by extending it to other common TSOs (α-Al2O3, ZnO, and MgO). As a typical plasma-based atomic-scale smoothing method, PEAR is expected to enrich the theoretical and technological knowledge on atomic-scale manufacturing.

Modification of AgNP-Decorated PET: A Promising Strategy for Preparation of AgNP-Filled Nuclear Pores in Polymer Membranes.

Polymer-based membranes represent an irreplaceable group of materials that can be applied in a wide range of key industrial areas, from packaging to high-end technologies. Increased selectivity to transport properties or the possibility of controlling membrane permeability by external stimuli represents a key issue in current material research. In this work, we present an unconventional approach with the introduction of silver nanoparticles (AgNPs) into membrane pores, by immobilising them onto the surface of polyethyleneterephthalate (PET) foil with subsequent physical modification by means of laser and plasma radiation prior to membrane preparation. Our results showed that the surface characteristics of AgNP-decorated PET (surface morphology, AgNP content, and depth profile) affected the distribution and concentration of AgNPs in subsequent ion-track membranes. We believe that the presented approach affecting the redistribution of AgNPs in the polymer volume may open up new possibilities for the preparation of metal nanoparticle-filled polymeric membranes. The presence of AgNPs on the pore walls can facilitate the grafting of stimuli-responsive molecules onto these active sites and may contribute to the development of intelligent membranes with controllable transport properties.

Biopolymer-loaded plasma-mediated multi-functional finishes of polypropylene fabrics

Polypropylene (PP) has unique competitiveness with other synthetic fibers due to its suitable spinnability, availability of raw materials, and low processing cost. PP fabric exhibits excellent chemical, physical, and mechanical properties, such as a light texture, adequate tensile strength, and resistance to most chemicals. However, the absence of reactive functional groups in PP fiber, besides its high crystallinity, results in hydrophobic surface, low affinity to dyestuffs, and poor antistatic properties, which restrict its use in the clothing field. Herein, a water- and energy-saving, eco-friendly finish is proposed to render PP desired properties suitable for textile applications. The surface of PP fabric was activated using oxygen and nitrogen plasma radiations. The plasma-irradiated PP fabric was post-treated with two renewable eco-friendly proteinic biopolymers, namely gelatin and sericin, in the presence and absence of a crosslinking agent. The effects of different process conditions on the properties of the modified PP, including the duration of plasma exposure, the concentration of biopolymer, and treatment temperature were monitored. The affinity of the treated PP fabric towards anionic and cationic dyes was evaluated. The findings of this study demonstrated that the comfort attributes of the plasma/biopolymer-finished fabrics, such as the induced antistatic properties, wettability, and ultraviolet protection, were remarkably improved. The plasma-mediated biopolymer-finished PP fabrics were found dyeable with cationic and anionic dyes. The change in the chemical and morphological structures of PP fabrics was monitored using Fourier transform infrared spectroscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy.

Simulation of lighting characteristics of pulse discharge in cesium vapor

Mathematical modeling of characteristics of intense light source on the basis of high pressure pulse discharge in cesium vapor is performed. The investigated discharge is realized in a long ceramic tube from Al2O3 with an internal diameter of 5 mm. The amount of cesium in the discharge is determined by the value of the saturation pressure at the cold end of the tube. A current pulse with amplitude of 40 A to 250 A is periodically passed through the discharge plasma, with a frequency of 400- 1700 Hz. In the work, a mathematical model based on the equations of radiation gas dynamics is used to simulate discharge. When calculating heat exchange by radiation in plasma and light characteristics of discharge, direct integration of the radiation transfer equation is performed. The model takes into account two mechanisms for heating the walls of the gas discharge tube. Firstly, it is the molecular thermal conductivity of the near wall plasma and secondly, it is the absorption of discharge plasma radiation by walls. As a result of the simulation, the dependencies of plasma pressure and temperature, luminous flux and luminous efficacy of the discharge on the temperature of the cold tube end were investigated for different values of amplitudes of current pulses. It is shown that at all current amplitudes there is a pronounced maximum of luminous efficacy. In all studied modes of discharge combustion color rendering index exceeds Ra &gt; 95. It is shown in particular that if the power embedded per unit of discharge length increases to 400 W/cm, the luminous flux reaches 36000 lm/cm.

Composition and thermal properties of Ganymede’s surface from JWST/NIRSpec and MIRI observations

Context. We present the first spectroscopic observations of Ganymede by the James Webb Space Telescope undertaken in August 2022 as part of the proposal “ERS observations of the Jovian system as a demonstration of JWST’s capabilities for Solar System science”. Aims. We aimed to investigate the composition and thermal properties of the surface, and to study the relationships of ice and non-water-ice materials and their distribution. Methods. NIRSpec IFU (2.9–5.3 μm) and MIRI MRS (4.9–28.5 μm) observations were performed on both the leading and trailing hemispheres of Ganymede, with a spectral resolution of ~2700 and a spatial sampling of 0.1 to 0.17″ (while the Ganymede size was ~1.68″). We characterized the spectral signatures and their spatial distribution on the surface. The distribution of brightness temperatures was analyzed with standard thermophysical modeling including surface roughness. Results. Reflectance spectra show signatures of water ice, CO2, and H2O2. An absorption feature at 5.9 μm, with a shoulder at 6.5 μm, is revealed, and is tentatively assigned to sulfuric acid hydrates. The CO2 4.26-μm band shows latitudinal and longitudinal variations in depth, shape, and position over the two hemispheres, unveiling different CO2 physical states. In the ice-rich polar regions, which are the most exposed to Jupiter’s plasma irradiation, the CO2 band is redshifted with respect to other terrains. In the boreal region of the leading hemisphere, the CO2 band is dominated by a high wavelength component at ~4.27 μm, consistent with CO2 trapped in amorphous water ice. At equatorial latitudes (and especially on dark terrains), the observed band is broader and shifted toward the blue, suggesting CO2 adsorbed on non-icy materials, such as minerals or salts. Maps of the H2O Fresnel peak area correlate with Bond albedo maps and follow the distribution of water ice inferred from H2O absorption bands. Amorphous ice is detected in the ice-rich polar regions, and is especially abundant on the northern polar cap of the leading hemisphere. Leading and trailing polar regions exhibit different H2O, CO2, and H2O2 spectral properties. However, in both hemispheres the north polar cap ice appears to be more processed than the south polar cap. A longitudinal modification of the H2O ice molecular structure and/or nanometer- and micrometer-scale texture, of diurnal or geographic origin, is observed in both hemispheres. Ice frost is tentatively observed on the morning limb of the trailing hemisphere, which possibly formed during the night from the recondensation of water subliming from the warmer subsurface. Reflectance spectra of the dark terrains are compatible with the presence of Na- and Mg-sulfate salts, sulfuric acid hydrates, and possibly phyllosilicates mixed with fine-grained opaque minerals, with a highly porous texture. Latitude and local time variations of the brightness temperatures indicate a rough surface with mean slope angles of 15°–25° and a low thermal inertia Γ = 20 − 40 J m−2 s−0.5 K−1, consistent with a porous surface, with no obvious difference between the leading and trailing sides.

Surface chemical reactions of etch stop prevention in plasma-enhanced atomic layer etching of silicon nitride

Molecular dynamics (MD) simulations were performed to examine the influence of oxygen (O) ion irradiation at the end of each cycle of plasma-enhanced atomic layer etching (PE-ALE) of silicon nitride (SiN). The main concern during the SiN PE-ALE process is that it can lead to an etch stop due to excessive hydrofluorocarbon (HFC) polymer accumulation, which hinders ion impact in the desorption step. Such an etch stop can be avoided by incorporating an oxygen (O2) plasma irradiation step after the desorption step of a conventional two-step PE-ALE process of SiN. In this study, the differences between the two- and three-step PE-ALE processes of SiN with and without O2 plasma irradiation are discussed. In the simulations of this study, low-energy CH2F radicals are deposited on a SiN surface in the adsorption step, and the modified surface is then irradiated with energetic Ar+ ions and removed in the desorption step. In the O2 plasma irradiation step, the resulting surface is irradiated with low-energy O species, and excess carbon (C) atoms are removed. It has been found that the O irradiation step effectively prevents the accumulation of C atoms by promoting the formation of volatile CO molecules.

Increasing growth of monobulb garlic through the application of corona glow discharge plasma radiation and organic fertilizers

&lt;abstract&gt; &lt;p&gt;Monobulb garlic, distinguished by its elevated allic.in content, has garnered heightened consumer interest due to its perceived health benefits. However, the challenge lies in scaling up production to meet this demand. This study investigates the potential enhancement of monobulb garlic growth by employing a novel approach that combines corona glow discharge plasma radiation technology and organic fertilizers. By employing a factorial complete randomized design with nine treatments and three repetitions, the research evaluates the impact of varying durations of plasma radiation (0, 15, and 30 minutes) and levels of organic fertilizers (0, 31.25, and 62.5 grams). Key growth parameters, including plant height, leaf count, root length, and root quantity, were measured. Results indicate that the optimal combination for growth enhancement involves 30 minutes of radiation coupled with 31.25 grams of organic fertilization. In conclusion, the integration of corona glow discharge plasma radiation technology and organic fertilization proves effective in promoting the growth of monobulb garlic plants.&lt;/p&gt; &lt;/abstract&gt;

Origin of sputter damage during transparent conductive oxide deposition for semitransparent perovskite solar cells

The origin of sputter damage during transparent conductive oxide deposition is ion bombardment rather than plasma radiation. Ion bombardment increased recombination, whereas plasma radiation reduced recombination.

Highly stable localized surface plasmon resonance of Cu nanoparticles obtained via oxygen plasma irradiation.

Copper nanoparticles (CuNPs) possess strong localized surface plasmon resonance (LSPR) in visible light. However, CuNPs are not chemically stable in air, which has seriously hindered the applications based on the LSPR of CuNPs. We developed an artificial method to passivate CuNPs as Al naturally does in air, preventing the oxidation of CuNPs through swift oxidation of the surface atoms via oxygen plasma irradiation. A hemispheric core-shell structure of CuNPs uniformly covered by a dense CuO shell (CuNPs@d-CuO) was constructed. The 4 nm d-CuO shell can prevent CuNPs from further oxidation. As a result, the LSPR of the CuNPs is stable in air over 180 days.

Effects of oxygen vacancies and interfacial strain on the metal-insulator transition of VO2 nanobeams.

The role of oxygen vacancies and interfacial strain on the metal-insulator transition (MIT) behavior of high-quality VO2 nanobeams (NBs) synthesized on SiO2/Si substrates employing V2O5 as a precursor has been investigated in this research. Selective oxygen vacancies have been generated by argon plasma irradiation. The MIT is progressively suppressed as the duration of plasma processing increases; in addition, the temperature of MIT (TMIT) drops by up to 95 K relative to the pristine VO2 NBs. Incorporating oxygen vacancies into VO2 may increase its electron concentration, which might shift the Fermi levels upward, strengthen the electronic orbital overlap of the V-V chains, and further stabilize the metallic phase at lower temperatures, based on first-principles calculations. Furthermore, in order to evaluate the influence of substrate-induced strain in our situation, the MIT in two distinct types of VO2 NB samples is examined without metal contacts by using the distinctive light scattering characteristics of the metal (M) and insulator (I) phases (i.e., M/I domains) by optical microscopy. It is found that the domain structures in the "clamped" NBs persisted up to ∼453 K, while the "released" NBs (transferred to a new substrate) did not exhibit any domain structures and turned into an entirely M phase with a dark contrast above ∼348 K. When combined with first-principles calculations, the electronic orbital occupancy in the rutile phase contributes to explaining the interfacial strain-induced modulation of MIT. The current findings shed light on how interfacial strain and oxygen vacancies impact MIT behavior. It also suggests several types of control strategies for MIT in VO2 NBs, which are essential for a broader spectrum of VO2 NB applications.

Effect of Helium Plasma Irradiation on Microstructures and Mechanical Properties of Tungsten

Effect of Helium Plasma Irradiation on Microstructures and Mechanical Properties of Tungsten

Enhancement mechanism of coaxial dual-pulse laser-induced breakdown spectroscopy plasma radiation signal

Enhancement mechanism of coaxial dual-pulse laser-induced breakdown spectroscopy plasma radiation signal

Theoretical investigation of electron-impact ionization of W&lt;sup&gt;6+&lt;/sup&gt; ion

&lt;sec&gt;Due to its unique characteristics, metal tungsten has been selected as the wall material for the tokamak magnetic confinement fusion device. The wall material directly interacts with the plasma for a long time, thus causing tungsten atoms and ions to be sputtered and ionized into different charge states, which then enter the tokamak device as plasma impurities. To ensure stable plasma combustion conditions, highly complex model is currently being used to evaluate the behavior of tungsten impurities and their influence on the tokamak plasma. This requires various high-precision atomic data for tungsten atoms and different ionized states of tungsten ions. Electron collision ionization, as a fundamental atomic physical process, is widely encountered in laboratory and astrophysical plasma environments. The parameters such as electron collision ionization cross-sections and rate coefficients are crucial for plasma radiation transport simulations and state diagnostics.&lt;/sec&gt;&lt;sec&gt;Electron-impact single-ionization (EISI) cross sections of the ground state and metastable state for W&lt;sup&gt;6+&lt;/sup&gt; ions are calculated by using the level-to-level distorted-wave (LLDW) method. The contributions of direct ionization (DI) cross section and excited autoionization (EA) cross section to the total EISI cross section are primarily considered.&lt;/sec&gt;&lt;sec&gt;Comparison of our calculation results with the experimental data from Stenke et al. (Stenke M, Aichele K, Harthiramani D, Hofmann G, Steidl M, Volpel R, Salzborn E &lt;ext-link ext-link-type="uri" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://iopscience.iop.org/article/10.1088/0953-4075/28/13/021"&gt;1995 &lt;i&gt;J. Phys. B: At. Mol. Opt. Phys.&lt;/i&gt; &lt;b&gt;28&lt;/b&gt; 2711&lt;/ext-link&gt;) reveals that the EISI cross section considering only the ground state is significantly smaller than the experimental result. Therefore, it is imperative to take into account the contribution from the metastable state. To determine the fraction of ions in long-lived energy levels within the parent ion beam, three models are employed.&lt;/sec&gt;&lt;sec&gt;Our results, which include the contribution of metastable states, accord well with the experimental results of Stenke et al. Compared with the theoretical calculation result of Pindzola et al. our calculaiton provides a more comprehensive understanding of the electron-impact single-ionization process for W&lt;sup&gt;6+&lt;/sup&gt; ions. The comparison is illustrated in the attached figure.&lt;/sec&gt;