Inductive Radio-frequency Discharge Research Articles

Selection of Dust Particles in Radio Frequency Inductive Discharge

Selection of Dust Particles in Radio Frequency Inductive Discharge

Promising methods for improving the radio-frequency ion thruster performance

Improving the reliability and efficiency of available electric propulsion schemes is one of the priority areas of space technology development. In particular, this should be done for ensuring the guaranteed removal of spacecraft to a disposal orbit at the end of their active life, which, in turn, will slow down the growth in the number of space debris objects in the most exploited regions of near-Earth space. The paper considers ways to improve the power and mass efficiency of one of the modern electric propulsion types - a radio-frequency ion thruster with an inductive radio-frequency discharge. Using an engineering physico-mathematical model, computational studies were performed to optimize the shape of the radio-frequency ion thruster main components, namely the discharge chamber and the grids of ion-extraction system. The thrust of the thruster was used as the optimization criterion; it was determined from the calculated ion density distributions in the radio-frequency discharge plasma. Such an approach to refine the performance improvement methods has not previously been applied to radio-frequency ion thruster. The ion density distributions, as well as the thruster integral characteristics determined from them, such as the thrust, total ion current from the thruster, propellant utilization factor, ionization cost and a number of others, were calculated for two actual standard sizes of radio-frequency ion thruster with the beam diameters of 80 mm and 160 mm, which can be used to solve the problems listed above. Besides, for the defined optimal configurations of thruster with two standard sizes the calculations were made to assess the possibility for increasing the thruster integral characteristics by applying an additional magnetostatic field in the radio-frequency discharge region. The study revealed the possibility of noticeable performance improvement compared to the basic radio-frequency ion thruster design with hemispherical discharge chamber and flat grids of the ion-extraction system.

Inductively-coupled plasma discharge for use in high-energy-density science experiments

Inductively-coupled plasma discharges are well-suited as plasma sources for experiments in fundamental high-energy density science, which require large volume and stable plasmas. For example, experiments studying particle beam-plasma instabilities and the emergence of coherent macroscopic structures — which are key for modelling emission from collisionless shocks present in many astrophysical phenomena. A meter-length, table-top, inductive radio-frequency discharge has been constructed for use in a high-energy density science experiment at CERN which will study plasma instabilities of a relativistic electron-positron beam. In this case, a large volume is necessary for the beam to remain inside the plasma as it diverges to centimeter-scale diameters during the tens-of-centimeters of propagation needed for instabilities to develop. Langmuir probe measurements of the plasma parameters show that plasma can be stably sustained in the discharge with electron densities exceeding 1011 cm-3. The discharge has been assembled using commercially-available components, making it an accessible option for commissioning at a University laboratory.

Distributed ferromagnetic enhanced inductive plasma source for plasma processing

New experimental data on the plasma density profiles have been obtained for a low-frequency (100 kHz) distributed ferromagnetic enhanced inductive plasma source at different locations of inductive discharges. An ability to control the plasma density profiles in a large gas discharge chamber in order to achieve a uniform treatment of a substrate is demonstrated. The differences between the obtained results and literature data for a distributed ferromagnetic enhanced inductive plasma source combined with a radio-frequency inductive discharge are discussed.

Ion-plasma sputtering of Co and Mo nanometer thin films near the sputtering threshold

In this work, we present results of a study of low-energy (Е i < 200 eV) sputtering of Co and Mo nanometer thin films in high-density argon plasma of a low-pressure radio-frequency inductive discharge with a controlled incident ion energy and ion current density onto the sample. The average ion energy was determined by the negative self-bias potential, which arises when the RF bias power is applied to the substrate. The ion current density was determined from the ratio of the increments in the RF bias power and the self-bias potential. The sputtering rate was determined in situ by a refractometric method from a sharp change in the intensity of a reflected laser beam signal at the moment of a removal of a metal film. Precise control of sputtering made it possible to detect a formation of nanoscale structures at a stage near the end of sputtering of metal films. The experimentally determined sputtering yields of Co and Mo were in agreement with the results of semiempirical calculations. We demonstrate that for ion-plasma sputtering, removal of Co and Mo atoms occurs at ion energy lower than the sputtering threshold.

A the one-dimensional J.J. Thomsons model of radio frequency induction discharge

In this paper, the Thomson’s one dimensional model of radio-frequency induction discharge is considered and some important relations for investigation of its structure are obtained.

Modeling and experimental study of an ion source with a weakly diverging ion beam

An ion source was developed for transporting space debris to the disposal orbit by acting on such objects with an intense ion beam injected from a “service” spacecraft. The ion source differs by weakly diverging ion beam, radio-frequency inductive discharge, and a three-electrode slit ion-extraction system with quasi-Pierce geometry.

Superposition of low-pressure DBD and RF induction discharge for spectroscopic study of dissociative recombination in decaying plasma

The aim of the work was to find the optimal way to set up an experiment for spectroscopic study of the dissociative recombination of molecular ions with electrons in low electron density plasma at low gas pressure. In such an experiment, the influence of inelastic atom–atom collisions on the distribution of the DR flux over the excited atomic levels can be excluded. The first results of an experiment on combining a low-frequency barrier discharge (DBD) in neon at a pressure of less than 1 Torr with a pulsed radio-frequency (RF) induction discharge are presented. To create the plasma, we used DBD in a cylindrical glass tube with an inner diameter of 3.9 cm, which forms the spatial distribution of electron density with a minimum on the axis of the tube. The evolution of such a spatial distribution due to ambipolar diffusion in the initial stage of plasma decay provides an influx of charged particles to the center of the discharge tube, which increases the afterglow duration and helps to overcome the difficulties of detecting weak plasma radiation. The specific features of the DBD also appeared in the ionic composition of the plasma, which contained, in addition to Ne+ and Ne2+, the Ne++ ions, whose recombination with electrons significantly enriched the afterglow spectrum in the short-wavelength region. An RF discharge was used for pulsed heating of electrons in the afterglow. It is shown that, in accordance with the ionic composition, the radiation of a decaying plasma is presented by three groups of spectral lines with characteristic time behavior and the electron temperature dependence. The advantages of the proposed approach for studying the mechanism of dissociative recombination are discussed.

Increasing the capillary of fiberglass under the application of a relief coating in the low-pressure radio-frequency induction discharge

the article presents the results of experimental studies of the effect of low-pressure radio-frequency induction discharge on the glassfiber capillarity indexes after the formation of a functional microrelief of SiO2 particles on the surface of fiberglass.

A comparison of emissive and cold floating probe techniques for electric potential measurements in rf inductive discharge

A cold floating probe method was compared with the emissive floating probe method in terms of a low-pressure radio-frequency inductive discharge. The dependences of difference between the plasma potential and the floating potential on the electron temperature 1–8 eV, plasma density 109–1012 cm−3 and magnetic field 100–650 G were obtained. It was demonstrated that the difference between the potentials that obtained by these two methods can differ significantly from the expected value of 5.2 kTe/e for argon.

Improvement of Technological Properties of a Vegetal Tanning Agent in Gas Discharge Plasma

The article considers the possibility of modification of the vegetal tanning agent quebracho in the plasma of a radio-frequency induction discharge at low pressure. It is established that plasma treatment leads to a decrease in the size of colloid fractions and a decrease in the molecular weight, while the functionality of the vegetal tanning agent is preserved. Application of the obtained product in the process of leather retanning allows improving its physical, mechanical and consumer properties.

Creation of relief coatings on the surface of silicate materials in the plasma of radio-frequency induction discharge at low pressure

The paper shows the possibility to create relief coatings based on powdered nonmetallic materials (SiO2 and Al2O3) on a silicate substrate in the radio-frequency induction plasma at the low pressure. The features of the structure and properties of the obtained coatings have been studied.

Formation of Nanosized Coatings in Hybrid Plasma Reactor Combining Magnetron or Arc Deposition with RF Plasma Assistance

The hybrid plasma reactor is based on the combined magnetron or arc discharge and radio-frequency inductive discharge located in the external magnetic field. Magnetron or arc discharge provides the generation of atoms and ions of the target materials while the flow of accelerated ions used for the ion assistance is provided by the RF inductive discharge. An external magnetic field is used to optimize the power input to the discharge, to increase the ion current density in the realm of substrate and to enhance the area of uniform plasma. The high value of the ion flow bombarding the substrate gives the possibility to organize the effective ion assistance to the films growth in case of high rate deposition by the arc sources.The deposition of Ti, Al, Si and permalloy films showed that the presence of ion assistance leads to the substantial change of the films structure and properties.

Features of RF low-pressure discharge with inductive and capacitive channels

The present paper deals with the experimental and numerical study of radio-frequency (RF) low-pressure discharge having both inductive and capacitive or DC channels. Two discharge schemes are considered. In the first case the inductive and capacitive channels are powered by two independent RF power sources. In the second case the inductor and capacitor plates, being the main parts of inductive and capacitive channels, are connected in parallel to one RF power source. The properties of the mentioned discharges are compared with that of pure inductive RF discharge. It is shown that the presence of the capacitive component leads to changes of the fraction of RF power coupled through the inductive channel. This manifests with a reduction of the RF source power value, at which the transition from E- to H-mode takes place, and with the disappearance of hysteresis.

Plasma parameters in a dual-camera low-power inductive RF discharge with an external magnetic field

The results from studying a dual-camera inductive radio-frequency (RF) discharge that was placed in an external magnetic field are presented. The operating conditions were as follows: an argon pressure of 5 × 10–5–6 × 10–2 Torr, an external magnetic field strength of 0–60 G, and an RF generator power supply of 25–300 W. During the experiment the resonant RF power consumption and the correspondence between the local power-consumption maxima and spatial maxima of the plasma concentration as a function of the external magnetic field were observed. The comparison of the experimental results with the results of the mathematical simulation indicates that the resonant character of the discharge is associated with the excitation of helicons and Trivelpiece–Gould waves.

Growth of ZnO Thin Films by Spray Plasma Technique: Correlation Between Spectroscopic Measurements and Film Properties

Nanostructured ZnO thin films have been deposited on glass substrate at low substrate temperature (200 °C) using the Spray Plasma technique. The zinc nitrate or zinc chloride precursors (droplets) are injected in a low-pressure Ar/O2 radio-frequency inductive discharge. The O2 fraction and the distance between the inductive coil and the substrate holder were varied, and the resulting effect on the deposited film properties was investigated by means of X-ray diffraction, atomic force microscopy, transmittance electron microscopy and UV–visible spectroscopy. It was shown that the c-axis orientation growth depends on these two parameters but not on the precursor nature. The quality of the deposited film is optimal for 5 % O2 in argon when the inductive coil-substrate distance is small. The Ar/O2 plasma was also diagnosed by optical emission spectroscopy. The oxygen atom relative concentration was monitored by optical emission actinometry and the rotational spectrum of OH was recorded to estimate the gas temperature.

Radial inhomogenity of plasma parameters in a low-pressure inductive RF discharge

This work is devoted to systematic investigation into the radial dependence of the plasma parameters of a low-pressure inductive radio-frequency (RF) discharge on pressure within a wide range of 0.8–1 Torr. Experimental results that were obtained under the considered pressures make it possible to analyze the patterns of the changes in plasma parameters upon both a nonlocal mode of discharge and a transition from a nonlocal to local mode of the RF power input. Discharges in helium, neon, argon, and krypton were considered. Experimental data were compared to the results of the numerical simulation of the inductive RF discharge using the particle-in-cell (PIC) method.

Model of a low-pressure radio-frequency inductive discharge in Ar/O2 used for plasma spray deposition

A global (volume-averaged) model of a low-pressure radio-frequency (RF) inductive discharge used for nanostructured zinc oxide thin film deposition, the so-called spray-plasma device, is proposed. The plasma reactor is fed with an admixture of argon and oxygen and the pressure is typically several tens of mTorr. In the first step of the modelling, the injector and the substrate holder are not taken into account, and therefore zinc-containing species are not considered. The global model is based on the numerical integration of the particle balance equations and the electronic power balance equation. The model is first run until the steady state is reached to determine the equilibrium discharge parameters that are the species densities and the electron temperature. A parametric study is carried out varying the gas pressure, the RF power and the O2 fraction in the reactor. A parameter of great importance for the deposition process is the flux of the reactive species on the substrate holder and the model allows a fast exploration of this parameter. For continuous plasmas, the ratio of the reactive species flux to the total positive ion flux can be controlled varying the three basic parameters cited before (pressure, power and dilution). In the last part of the paper, we also investigate pulsed plasmas and the effect of the duty cycle variations on the neutral/ion flux ratio.

Low-pressure radio-frequency inductive discharge and possibilities of optimizing inductive plasma sources

Plasma reactors and ion sources whose operation relies on a low-pressure radio-frequency (RF) inductive discharge have been an important constituent of modern ground and space technologies for several decades already. However, the steadily toughening and varying requirements of plasma technologies call for improving the old models of devices and developing novel prospective models. Of vital importance in the development of inductive plasma sources is the provision of conditions whereat the plasma efficiently absorbs the RF power. In recent years it has become evident that in a low-pressure RF inductive discharge the RF-generator power is distributed between the active resistance of the external circuit and the plasma. In the latter case, the power is delivered to the plasma via two channels: an inductive channel, which exists due to the current flowing through an inductor or an antenna, and a capacitive one, which is due to the antenna–plasma capacitive coupling. RF inductive discharge properties related to the RF-power redistribution between the channels are considered and the mechanisms of RF-power absorption are analyzed. The feasibilities of optimizing RF inductive plasma sources are also discussed.

Methyl radical chemical reactions on a tungsten surface

In this paper an interaction of the inner dome surfaces of the International Thermonuclear Experimental Reactor with a gas mixture containing hydrocarbon radicals has been modelled. To study the processes of transport and deposition of methyl radicals in a C x H y –H2–H (x=1−3, y=1−6) flow, a stream technique has been used. A radiofrequency inductive discharge initiated in methane at the inlet of a quartz tube was a source of methyl and hydrogen atoms. Methyl radicals were transported by a gas flow that passed through cylindrical tungsten inserts and were deposited on the tube wall, on silicon samples and on tungsten samples, forming polymer-like hydrogenated amorphous carbon films. It has been shown that at the tungsten insert temperature increases to 420 K, and carbon deposition rate decreased significantly. However, in the gaseous phase the secondary hydrocarbon species accumulated and condensed on the tungsten surface at a temperature lower than 340 K.