Auxiliary Plasma Research Articles

Operando facet control of hydrophobic iron nitride nano-coral for surface protection via field-modulated plasma strategy

A facile facet reconfiguration has been considered as an essential issue for nitride coating in promoting surface protection behaviour. Compared to physical-chemical methods to achieve heterogeneous coating, plasma nitridation strategy is regarded as a favourable technique to in-situ deliver nitride protecting layer, but it is difficult to precisely control surface framework through plasma technique due to complicated interaction environment. To simply achieve nitride coating with favourable surface protection behaviour, we design a novel auxiliary insulator-confined plasma system to directly achieve hydrophobic iron nitride nano-coral (hFeNC) with desirable corrosion- and wear-resistant properties by controlling surface heating process during plasma nitridation. The resultant hFeNC nano-framework delivers corrosion rate of 1.2 mpy, 4- and 9-times lower than that of solid iron nitride film (sFeN) via normal plasma and initial Fe in NaCl condition, respectively. Operando plasma diagnostics along with numerical simulation further confirm the effect of surface heating on typical plasma parameters as well as the iron nitride nano-frameworks, indicating surface heating as the key factor responsible for the favourable surface protection coating.

Effect of Plasma Electric Field Assistance on the Freezing Process and Ice Crystal Formation of Bactrian Camel Meat

Background: The longissimus dorsi muscle of the camel was chosen as the experimental material in order to investigate the impact of plasma electric field assisted freezing on the quality and freezing process of Bactrian camel meat. Methods: The effect of the auxiliary plasma electric field of different field strengths (1 kV/m, 3 kV/m and 5 kV/m) on the freezing velocity of the camel meat and the distribution of ice crystals as well as the diameter and roundness of ice crystal in the frozen meat were studied and analyzing them with the help of the thermodynamic theory. Result: The findings demonstrated that the meat samples in the auxiliary 5 kV/m plasma field environment took 60 min and 30 min, respectively, at -20°C and -35°C, to pass the maximal ice crystal production zone. The tissue sections revealed that at -20°C and -35°C assisted 5 kV/m plasma field freezing, the smallest ice crystal area and grain size were formed, the roundness of the ice crystals was highest. Using Boltzmann’s entropic equation to calculate the system’s entropy, the results revealed that the meat samples frozen by the aided 5 kV/m plasma electric field had the lowest entropy at -20°C and -35°C. The electric field assisted freezing requires less energy to improve the subcooling degree and accelerate the freezing rate of meat samples, proving that the auxiliary 5 kV/m plasma electric field can significantly improve the system frozen meat moisture vitrification degree and can make the crystallization process more controllable.

Presence of hazardous chemical elements in low-cost children's toys: A risk to their development in early childhood

ObjectivesThe objectives of the current study was to study the presence of hazardous chemical elements (Ba138, Cd111, Cr52, Pb208, As75, Co59, Cu63, Mn55, Ni60, Se82, Sr88, Zn66 and Hg202) in low-cost children's toys, and the effect of color types on chemical element concentrations. MethodsChildren's toy samples were analyzed using microwave digestion and inductively coupled plasma/mass spectrometry (ICP/MS) method. Samples were prepared into small pieces, and 500 mg of homogenized sample was used for digestion by means of digesting regents HNO3 (65 %, 5 mL) and H2O2 (35 %, 1 mL). During the digestion process, the pressure was held constant at 90 bar and the temperature, hold time, and power were varied 150–170-40° C, 10–30-5 min, 70–90-0 %, respectively. The main operating conditions of ICP/MS were: spray chamber temperature (−20 °C), RF Power (1450 W), nebulizer gas flow (0.9 L/min), auxiliary gas flow (0.8 L/min) and plasma gas flow (14.85 L/min). Samples and blanks were analyzed for 30 s and system was operated in standard mode. ResultsThe excellent method performance was achieved in terms of limit of detection (LOD, 0.001–14.89 µg/L); limit of quantification (LOQ, 0.003–45.12 µg/L); correlation coefficient (R2, 0.975–0.999) with relative standard deviation values (RSD, 0.70–4.98 %). Chemical elements were found in all the toys (0.01–742.72 ng/g) except sample S2 where only Hg202 was found (0.01 ng/g). Outcomes revealed that the Hg202 was present at a very low level (0.01 ng/g) while Zn66 was present at very high level (742.72 ng/g). Furthermore, the toys contamination was also found to be color-specific, with significant amount of chemical elements was found in black type car sample (S5, 946.98 ng/g) whereas other color type samples constitute lower amounts (0.001–210.53 ng/g). Low-cost toys designed for children's use are found to contain chemical elements that should be addressed in the course of action. As a result of exposure to high amounts of chemical elements in toys, children have a high chance of developing cancer.

INFLUENCE OF DOPING WITH CARBON AND NITROGEN ON THE PHOTOACTIVITY OF TiO2 THIN FILMS OBTAINED WITH MePIIID

Titanium dioxide is well known as a photoactive material activated under ultraviolet irradiation. It is either employed as a photocatalyst or it exhibits superhydrophilic behavior after obtaining reduced surface energy under illumination used for self-cleaning or anti-fogging surfaces. For increasing the reactivity of thin films under solar illumination, a reduced band gap is desired. Doping with transition metals or nitrogen has been reported in the literature. However, the incorporation of nitrogen into a growing film is a much more complex process that is presently not completely understood. TiO2 thin layers were produced by metal plasma immersion ion implantation and deposition at room temperature at a pulse voltage of 0–5 kV and a duty cycle of 9 % for an apparently amorphous layer. An auxiliary rf plasma source was employed to increase the growth rate at low gas flow ratios. By adjusting the geometry between the incident ion beam, sputter target and substrate independently of the primary ion energy and species, a controlled deposition of samples was possible. Conventional ion implantation was employed to implant either carbon or nitrogen ions below the surface for bandgap engineering. The resulting thin films were subsequently investigated for optical properties, stoichiometry, structural properties, surface topography and photoactivity.

PB0159 Relative Role of Auxiliary Plasma Protease Inhibitors in Thrombin Inhibition at Reduced Antithrombin Levels

PB0159 Relative Role of Auxiliary Plasma Protease Inhibitors in Thrombin Inhibition at Reduced Antithrombin Levels

Parallelization of a 3D FDTD code and physics studies of electromagnetic wave propagation in fusion plasmas

Numerical codes for electromagnetic wave propagation in magnetized plasmas are mainly based on frequency-domain asymptotic methods, which provide a fast solution and are thus valuable for experiment design and control applications. However, in several cases of practical interest (e.g. mode conversion), these tools run close to their limits of validity and should be compared to full-wave solutions. The code RFFW solves Maxwell's equations with the finite-difference time-domain method in 3D geometry, for scenarios involving high-frequency waves with arbitrary electric field spectrum in plasmas with axisymmetric equilibrium. In fusion-related problems, the code may conduct investigations of wave propagation and absorption relevant to auxiliary plasma heating and current drive, reflectometry and instability control. The code has been parallelized with a hybrid OpenMP-MPI scheme, which has allowed exploiting the much larger processing power and memory of current-day supercomputers. In this work, we present the main aspects of the physics implemented in the code, and also refer shortly to the parallelization scheme. Furthermore, we show results that exhibit the strong scaling performance of the code, and examine cases of electron-cyclotron heating application in medium-sized tokamaks.

Structural control of heterostructured Co3N-Co nano-corals for boosting electrocatalytic hydrogen evolution based on insulator-confined plasma engineering

A facile phase reconfiguration has been considered as an essential issue in achieving heterostructures for boosting the electrocatalytic H2 production. Compared to chemical approaches, plasma-based technique serves as a favorable strategy to achieve hetero-structured nano-frameworks, but its modulation on nano-structured precursor inevitably leads to multi-step fabrication process and it is difficult to precisely control the partial surface modulation through plasma technique due to complicated interaction environment. To achieve heterostructures with optimized hydrogen evolution reaction (HER) behavior, we design a novel auxiliary insulator-confined plasma system to directly achieve Co3N-Co heterostructure (hCNC) with favorable activity by controlling surface heating process during plasma nitridation. The resultant hCNC nano-framework delivers excellent catalytic performance, evidenced by its overpotential of 97 and 229 mV at current density of 10 and 100 mA cm−2 for HER in alkaline condition, in stark comparison with that of normal plasma fabricated Co3N. Operando plasma diagnostics along with numerical simulation further confirm the effect of surface heating on typical plasma parameters as well as the Co3N-Co nano-structure, indicating the key factor responsible for the high-performance hetero-structured electrocatalyst.

A Highly Reliable Nanoscale Biodevice Benefitting from the Charge Plasma Concept – Si and InAs Source

A nanoscale biodevice based on the tunneling field effect transistor (TFET) has been reported for the detection of the target biomolecules. Two kinds of materials in the cases of silicon and InAs have been incorporated inside the source region for the sensitivity performance comparison. In order to prevent the diffusion of the impurities in the nanoscale biodevice during thermal proceeding, whole the structure has been doped at a N-type doped same level forming a junctionless device. The approach that we have benefited is the utilization of the charge plasma for converting the N-type source into the P-type source resulting in the creation of the TFET device, electrically. Indeed, the hole plasma will be appeared inside the source by the auxiliary plasma gate electrodes. The obtained results performed by the SILVACO simulator has shown the improvement of the sensitivity of the proposed biodevice while keeping the reliability high. Also, the fill-factor impact and trap-assisted-tunneling (TAT) issue as serious challenges on sensing performance are monitored for the biodevices under the study and the interesting results are presented.

Multi-code estimation of DTT edge transport parameters

The main goal of the Divertor Tokamak Test facility (DTT) is to operate with a high value of power-exhaust-relevant parameter P S O L /R in plasma scenarios similar to those foreseen for the Demonstration Fusion Power Plant (DEMO) in terms of low collisionality and neutral opacity. For these unique characteristics, accurate modelling of the principal scenario is necessary for machine designing. In edge numerical codes, cross-field transport profiles have a high impact on modelling results. This work aims at providing a coherent set of transport parameters for DTT full-power (FP) single-null (SN) scenario edge modelling. To evaluate such parameters for DTT, a transport analysis on the current machine has been performed using SOLEDGE2D-EIRENE and SOLPS-ITER. The transport parameters to be used in the simulations of the DTT single-null scenario were selected using two complementary methods. The first is the modelling of JET and Alcator C-Mod (C-Mod) with SOLEDGE2D-EIRENE and SOLPS-ITER, validating transport parameters by comparing modelling results to experimental data from pulses which are considered DTT-relevant . JET pulses were selected with the highest auxiliary input power (from 29 to 33 MW), plasma current and toroidal field to better match DTT parameters; nitrogen and neon seeded pulses were selected to check possible seeding material dependencies. The considered C-Mod pulse better matches DTT plasma density and neutral opacity. Transport parameters are then scaled to DTT according to scaling laws. The second method derives the transport parameters by tuning their values inside the DTT separatrix to reproduce the pedestal profiles predicted by the EPED model via the Europed code and applied in DTT. The derived set of DTT transport parameters is consistent with the results obtained by modelling present machines, reproduces the expected heat flux decay length in detached conditions and, inside the separatrix, reproduces the predicted pedestal using transport parameters which are coherent with what is predicted by the quasi-linear turbulent model QuaLiKiz. • Edge and divertor transport parameters of the DTT single-null scenario were studied. • The edge transport parameters of JET and C-Mod pulses were derived by SOLEDGE2D-EIRENE and SOLPS modelling. • Transport parameters were scaled from present machines to DTT. • First principles core modelling with JETTO confirms the validity of the previous estimations.

Spectral Intensity of Electron Cyclotron Radiation Emerging from the Plasma to the First Wall in ITER

It is predicted that in ITER, due to high values of electron temperature and magnetic field strength, electron cyclotron (EC) radiation emitted by plasma will be a significant source (together with external EC radiation injected for auxiliary plasma heating and non-inductive current drive) of additional thermal and electromagnetic loads for microwave and optical diagnostics. The spectral distribution of plasma EC radiation is particularly important to consider in millimeter-wave diagnostics, namely for high- and low-magnetic-field side reflectometry, plasma position reflectometry, and collective Thomson scattering diagnostic, because the transmission lines of these diagnostics yield the transport of EC waves emitted by the plasma. The development of semi-analytical methods used to describe the spectral distribution of plasma-generated EC radiation in tokamaks, starting from the work of S. Tamor, is based on the dominance of multiple reflections of this radiation from the first wall in a toroidal axially symmetric vacuum chamber. Here, we present calculations using the CYNEQ code of the spectral intensity of the EC radiation emerging from the plasma to the first wall and port plugs for five scenarios of ITER operation. This code uses the symmetry-based effect of approximate isotropy and homogeneity of radiation intensity in a substantial part of the phase space and has been successfully tested by comparison with first-principles codes. The energy flux density in the range of 30–200 kW/m2 is predicted for wall reflectance in the range of 0.6–0.95. The possible effect of this radiation on in-vessel components and diagnostics is assessed by calculating the surface density of the energy absorbed by various materials of the ITER first wall.

Efficacy of Temozolomide-Conjugated Gold Nanoparticle Photothermal Therapy of Drug-Resistant Glioblastoma and Its Mechanism Study.

Temozolomide (TMZ) is a standard-of-care chemotherapeutic drug for the treatment of glioblastoma (GBM), but TMZ-acquired resistance limits its therapeutic effect. In this study, TMZ-loaded gold nanoparticles (TMZ@GNPs) with anti-EphA3 modification on the surface (anti-EphA3-TMZ@GNPs) were synthesized for chemical and auxiliary plasma photothermal treatment (GNPs-PPTT), aiming to overcome the problem of glioma resistance to TMZ and improve the therapeutic effects of GBM. The prepared anti-EphA3-TMZ@GNPs were spherical with a particle size of 45.88 ± 1.9 nm, and the drug loading was 7.31 ± 0.38%. In vitro, cell-culture-based experiments showed that anti-EphA3 increased the cellular uptake of GNPs in T98G cells. Upon laser irradiation, the cytotoxicity and apoptosis rate in the anti-EphA3-TMZ@GNPs-treated group were significantly higher than those in the GNPs and nonphotothermal groups (p < 0.001). The Western blot analysis showed that the GNPs-PPTT-mediated killing of tumor cells induced apoptosis by regulating the apoptotic signaling molecules and cell cycle inhibitors; the expression of MGMT significantly decreased upon p53 induction, thereby reversing drug resistance. After photothermal treatment, the survival time of the subcutaneous GBM model of nude mice in the anti-EphA3-TMZ@GNPs group was prolonged to 46 days, 1.64-fold longer as compared to that in the TMZ group. Based on H&E and TUNEL staining, GNPs-PPTT could elevate apoptosis in T98G cells. In vivo thermal imaging results showed that GNPs could enter the brain via intranasal administration and be eliminated in 2 days, indicating that GNPs are safe for brain. In conclusion, GNPs-PPTT could effectively induce apoptosis in glioma cells and reverse TMZ resistance, thereby, indicative of a promising treatment strategy for GBM.

In-plasma photo-assisted etching of Si with chlorine aided by an external vacuum ultraviolet source

Photo-assisted etching of p-type Si was previously found to occur in a chlorine-containing, Faraday-shielded, inductively coupled plasma (ICP), and this was attributed to the vacuum ultraviolet (VUV) light generated by the plasma. Other causes for the very high etching rates were ruled out, including ion bombardment. In the present study, the substrate in the main Cl2/Ar ICP was subjected to extra VUV light that was generated in an independently controlled, auxiliary Ar/He ICP in tandem with the main ICP. The ICPs were separated by a tungsten mesh and a bundle of high-aspect-ratio quartz tubes in a honeycomb configuration. There was no measurable perturbation of the main plasma by the auxiliary plasma. The etching rate was found to be enhanced by 11%–51% with the additional VUV light provided by the auxiliary ICP. With absolute measurements of the auxiliary ICP photon flux at the sample surface, as described elsewhere, incredibly large etching yields of 90–240 Si atoms per photon were obtained. It is argued that etching is not a result of electron–hole pair formation but is instead ascribed to a photocatalytic chain reaction.

Особенности генерации однородных газоразрядных пучково-плазменных образований в протяженном полом катоде сильноточного тлеющего разряда

The regularities of the generation of gas-discharge beam-plasma formations formed in a high-current non-self-sustained glow discharge at low (≈ 1 Pa) pressure in an extended, 1.2 m long, hollow cathode with a volume of 0.34 m3 with a length-to-diameter ratio of 2: 1 were investigated. It is shown that in a system with one electron source providing injection of electrons into the hollow cathode of a glow discharge, a sharp nonuniformity (≈ 40%) of the nitrogen plasma concentration distribution is observed. In an extended hollow cathode, the problem of inhomogeneity of the plasma concentration distribution is solved by using two sources of electrons that provides injection of electrons from the auxiliary arc plasma into the hollow cathode of the glow discharge. The use of two sources of electrons makes it possible to form beam-plasma formations with an inhomogeneity of no more than 18%. A source of beam-plasma formations based on a non-self-sustained glow discharge with an extended hollow cathode was used for ion-plasma treatment of Cr12MoV die steel products.

Electron beam generation in an arc plasma source with an auxiliary anode plasma

In a plasma-cathode electron source with a grid-stabilized emission boundary, a discharge in crossed fields was used to create an auxiliary anode plasma before the generation of an electron beam. Such a plasma formed in the beam transport region shortens the rise time of the beam current and eliminates or at least minimizes its high-frequency oscillations at low pressures, making possible electron beams of several microseconds long and stable lower-pressure modes with less probable acceleration gap breakdowns. These effects are explained primarily by gas pre-ionization in the beam acceleration and transport region and by ion flows from the acceleration gap to the plasma cathode of the source.

DFT and Experimental Studies on the Mechanism of Mercury Adsorption on O2-/NO-Codoped Porous Carbon.

The utilization of O2 and NO in flue gas to activate the raw porous carbon with auxiliary plasma contributes to an effective mercury (Hg)-removal strategy. The lack of in-depth knowledge on the Hg adsorption mechanism over the O2-/NO-codoped porous carbon severely limits the development of a more effective Hg removal method and the potential application. Therefore, the generation processes of functional groups on the surface during plasma treatment were investigated and the detailed roles of different groups in Hg adsorption were clarified. The theoretical results suggest that the formation of functional groups is highly exothermic and they preferentially form on a carbon surface, and then affect Hg adsorption. The active groups affect Hg adsorption in a different manner, which depends on their nature. All of these active groups can improve Hg adsorption by enhancing the interaction of Hg with a surface carbon atom. Particularly, the preadsorbed NO2 and O3 groups can react directly with Hg by forming HgO. The experimental results confirm that the active groups cocontribute to the high Hg removal efficiency of O2-/NO-codoped porous carbon. In addition, the mercury temperature-programmed desorption results suggest that there are two forms of mercury present on O2-/NO-codoped porous carbon, including a carbon-bonded Hg atom and HgO.

Preliminary design of the COMPASS upgrade tokamak

COMPASS Upgrade is a new medium size, high magnetic field tokamak (R = 0.9 m, Bt = 5 T, Ip = 2 MA) currently under design in the Czech Republic. It will provide unique capabilities for addressing some of the key challenges in plasma exhaust physics, advanced confinement modes and advanced plasma configurations as well as testing new plasma facing materials and liquid metal divertor concepts.This paper contains an overview of the preliminary engineering design of the main systems of the COMPASS Upgrade tokamak (vacuum vessel, central solenoid and poloidal field coils, toroidal field coils, support structure, cryostat, cryogenic system, power supply system and machine monitoring and protection system). The description of foreseen auxiliary plasma heating systems and plasma diagnostics is also provided as well as a summary of expected plasma performance and available plasma configurations.

Влияния условий горения разряда на распределения параметров плазмы, генерируемой в несамостоятельном тлеющем разряде внутри полого катода

The parameters of the plasma of a non-self-sustaining glow discharge generated inside a metal hollow cathode 300 mm long and 25 mm in inner diameter are investigated. A feature of this system is the additional injection of electrons from the auxiliary discharge plasma, formed by a plasma source with a combined heated and hollow cathode «PINK». The dependences and combustion modes of a non-self-sustaining glow discharge are presented and described at a pressure in the range (0.06 ÷ 1.4) Pa and a combustion voltage (70 ÷ 300) V. Studies of plasma parameters using double Langmuir probes have shown that this discharge system provides generation nitrogen plasma inside the hollow cathode with inhomogeneity from ± 12 to ± 63%.

Experimental Thermonuclear Installation Tokamak T-15MD

At present, the T-15MD tokamak is being built and its supporting technological systems are being modernized at the National Research Center Kurchatov Institute in the framework of the federal target-oriented program “New Generation Nuclear Power Technologies in 2010–2015 and in Prospect to 2020.” The T-15MD magnet system is to ensure producing and confinement of hot plasma in the divertor configuration. The T-5MD plasma parameters are as follows: major radius R0 = 1.48 m, minor radius a = 0.67 m, elongation k95 = 1.7–1.9, triangularity δ95 = 0.3–0.4, plasma current Ip = 2 MA, and toroidal magnetic field at the plasma axis BTO = 2 T. The tokamak will be equipped with an auxiliary plasma heating and current drive system (Paux = 15–20 MW), which will enable achieving a high plasma temperature (Ti ~ Te of 5–9 keV) and a plasma density (ne ≈ 1020 m–3) during a discharge with a pulse duration of up to 30 s. The magnet system includes a toroidal winding and a poloidal magnet system. The poloidal magnet system may generate the one- or two-null divertor magnetic configuration. The power supply system provides the necessary current scenarios in the magnet system windings. The T-15MD magnet together with the vacuum vessel was pre-assembled at the NPO GKMP Ltd. plant in Bryansk. All elements of the magnet system and the vacuum vessel are delivered to the National Research Center Kurchatov Institute in Moscow, where the T-15MD tokamak will be assembled. The technological systems are to be reconstructed by the end of 2019. The physical start-up of the T-15MD is scheduled for December 2020.

Generation of Plasma in Non-Self-Sustained Glow Discharge With Hollow Cathode for Nitriding Inner Surfaces of Elongated and Complex Shaped Cavities

This article describes a plasma-generating system based on a non-self-sustained glow discharge with external electron injection and a hollow cathode in the shape of a tube with an internal diameter of 25 mm and a length of 300 mm made of stainless steel AISI 321. It is proved that the parameters of the non-self-sustained glow discharge under (0.2–1) Pa, (100–280) V, and (2–6) A depend on the auxiliary discharge current to a great extent, which is due to the determining influence of electrons injected from the auxiliary discharge plasma on the physical processes in the main discharge. The study of uniformity of temperature distribution on the hollow cathode walls has shown that it can reach ±10% of the average value and greatly depends not only on electric characteristics of the discharge but also on its working pressure. The study further demonstrates that such discharge can burn not only in elongated hollow rectilinear cathodes but also in hollow cathodes of a complex shape produced by welding two tubes at a 90% angle. The efficiency of using emitted electrons to sustain discharge and uniformity of temperature distribution on the walls is improved in the latter configuration. The discharge can be used for ion plasma nitriding of inner surfaces with treatment uniformity of ±8.5% of the average value for complex-shaped hollow cathodes. The mean thickness of the nitrided layer after 1 h of processing steel AISI 321 at 630 °C was $\approx 50~\mu \text{m}$ and the hardness of the nitrided layer exceeded the original value by $\approx 3$ times.

Investigation of the Surface Properties and Wear Properties of AISI H11 Steel Treated by Auxiliary Heating Plasma Nitriding

This paper presents an auxiliary heating method to maintain a uniform specimen temperature and precisely control nitriding temperature during plasma nitriding. The surface properties and wear properties of AISI H11 steel treated by auxiliary heating plasma nitriding are investigated. Firstly, the specimens with different diffusion layers and different hardness levels are fabricated through changing the plasma nitriding temperature. Secondly, the surface properties of the plasma-nitrided H11 steel specimens are characterized by a scanning electron microscope (SEM), X-ray diffractometer, metallographic microscope and microhardness tester. The results show that the surface hardness of the plasma-nitrided specimen is almost twice as high as that of the untreated specimen. The thickness of diffusion layer increases with the increase of nitriding temperature. However, the surface hardness firstly increases and then decreases with the increase of the nitriding temperature. Finally, the wear properties of untreated and plasma-nitrided H11 steel specimens are investigated under different friction conditions. The results show that the plasma-nitriding method can significantly improve the wear resistance of AISI H11 steel. The friction coefficient fluctuations of the plasma-nitrided specimens are all lower than those of the untreated specimens. In addition, the wear rates of the plasma-nitrided specimens rise along with load, and reduce along with the sliding speed and friction temperature.