Discharge Chamber Research Articles

A novel method for measuring the width and angle of corrosion in Hall thrusters using three-dimensional point cloud

Hall thrusters are electric propulsion devices that are widely used in modern spaceflight. To obtain the critical corrosion data effectively and accurately during long-life tests of Hall thrusters, this paper proposes an automated corrosion measurement method based on three-dimensional point cloud technology. This method uses binocular structured light scanning method to obtain surface point cloud data. The point cloud topology relationship of these disordered data is also established by KD-tree and radius filtering. The base plane is determined according to the average of the outer circle plane in the discharge chamber, and the original point cloud data is sliced transversely and longitudinally. The point cloud of section data is extracted and the corrosion width data is obtained according to the round hole feature extraction and center of circle calculation. The corrosion angle is calculated according to the angle between the straight line and the normal of the section. The proposed method has been verified and the results show that the overall error accuracy is within 60 μm, which meets the requirements for automatic measurement of Hall thruster corrosion. It is a real and effective method to obtain the critical corrosion data during long-life tests of Hall thrusters.

Impact of the electrode structure on post‐cathode plasma in the grid electrode DC glow discharge

AbstractThe discharge properties of post‐cathode plasma generated by grid electrode discharge were investigated. Post‐cathode plasma is the plasma, generated in an open discharge, at the other side of the cathode that is different from the electrode gap. Based on the unique electron transport, discharge chamber parameters were adjusted to compare their impact on the electron density of the post‐cathode plasma. The peak of the electron flow in the grid cathode hole and the peak of the post‐cathode plasma thickness appear in the same diameter of the grid electrode holes, which shows the crucial influence of the electron transport within the grid cathode on the post‐cathode plasma. The study also investigated the combined effects of cathode thickness and gas pressure on post‐cathode plasma thickness. The findings suggest that the primary factor influencing post‐cathode plasma thickness is the electron transport within the grid cathode.

Formation of Extended Tubular Plasma in Argon at Low Pressure and in a Weak Longitudinal Magnetic Field

The results of experimental studies on the formation and subsequent evolution of extended (l = 300 mm) and thin-walled (Δr ≈ 10 mm) tubular (2r ≈ 110 mm) plasma in a weak longitudinal magnetic field (B = 175 G) without the use of a thermionic cathode are presented. The cylindrical chamber in which the tubular plasma was formed was pumped with high purity argon (99.998%) at an average velocity of about 1 m/s at a pressure of P = 10–3–10–2 Torr. Two methods of creating seed electrons initiating the development of ionization avalanches were used. The difference inherent to these methods has been established in the dynamics of breakdown, completing in the formation of a tubular discharge. In the first of them, a pulsed discharge preceding the high voltage supply of the main discharge created gas preionization in a small area around the sectioned cathodes. In the second method, seed electrons were created in the entire working area of the discharge chamber by an RF discharge with a frequency of 85 kHz and duration of about 1 s. High-speed shooting with a 4-frame ICCD camera allowed us to establish the dynamics of tubular discharge formation at all its stages. Measurements of the longitudinal and radial discharge current were carried out. The results we obtained showed the possibility of spatial isolation of an extended tubular plasma from the close located metal wall of the discharge chamber by using a weak longitudinal magnetic field.

Design and testing of a Mini-RF plasma thruster with permanent magnets

Compared with traditional electric propulsion, RF plasma thruster have attracted much attention due to their characteristics of no electrodes, long life, and high ionization rate. In recent years, the development of micro-nano satellites has put forward requirements for the miniaturization, modularization, and integration of satellite thrusters, and the miniaturization of RF plasma thrusters has a broad prospect. In this paper, a mini-RF plasma thruster with a discharge chamber inner diameter of 10 mm is designed, and a magnetic field is generated around it by two annular samarium cobalt permanent magnets. The discharge state and plasma parameters of the mini-RF thruster are tested using optical emission spectrometry (OES) and target thrust stand. In the experiment, we changed the flow rate of argon gas, the presence or absence of a magnetic field, the power of the RF source and analyzed the effects of these factors on the mode transition, plasma density, electron temperature, and thrust. According to the experimental results, it is found that the magnetic field (maximum strength 0.14T) helps to increase the plasma density at low power but delay the jump power threshold of the CCP-ICP.

Ultralong-lasting plasma-activated water: production and control mechanisms

Despite the rapidly growing interest stemming from the broad-spectrum, high inactivation capacity, and environmental friendliness of the plasma-activated water (PAW), practical applications are limited because of the PAW’s short lifetime. While low-temperature storage can extend the lifetime, but the freezing and thawing processes are energy- and labor-intense and are generally not suitable for large-scale applications such as environmental and biomedical disinfection. This work addresses this issue by developing the ultra-long-life PAW at room temperature. The innovative approach is based on using DC needle-water discharges, wherein the gaseous products are blown out and absorbed separately by a gas flow. By simply adjusting the voltage and gas flow rates, two distinctive types of PAW with acidic hydrogen peroxide and nitrite as the main products are produced and separated in the discharge chamber and gas bubbling chamber. Intentional mixing of these two PAWs causes a chain chemical reaction dominated by peroxynitrite (ONOOH). This reaction can generate a variety of short-lived reactive species, thereby achieving the ultralong-lasting PAW with very stable bactericidal ability. This study further demonstrates the ability to effectively control the reaction products in both chambers and provides insights into the secondary activation mechanism of short-lived reactive species stimulated by ONOOH.

Dusty Plasma: A Comprehensive Review

Dusty plasmas, characterized by the presence of micron or submicron-sized particles (dust) within a plasma of ions, electrons, and neutral species, represent a complex and intriguing state of matter. This review article provides a comprehensive overview of dusty plasmas, covering their formation mechanisms, fundamental properties, theoretical models, experimental techniques, and diverse applications. Dusty plasmas occur naturally in environments such as space, planetary atmospheres, and industrial processes, where they are formed through various mechanisms including micrometeorite impacts, volcanic eruptions, and cometary outgassing. In laboratory settings, they are generated in controlled discharge chambers using radio frequency or direct current sources, facilitating studies on their dynamic interactions and behavior. The physical characteristics and behavior of dusty plasmas are influenced by a range of forces including electrostatic, ion drag, gravitational, thermophoretic, and magnetic forces. These interactions give rise to collective phenomena such as dust acoustic waves, ion-dust interactions, and the formation of ordered structures like Coulomb crystals. Understanding these phenomena is essential for applications in astrophysics, materials science, semiconductor manufacturing, and environmental research. Theoretical approaches, including fluid dynamics, kinetic theories, and Particle-in-Cell (PIC) simulations, provide insights into the complex dynamics of dusty plasmas. Experimental methods such as Langmuir probes, laser scattering, and high-speed imaging are employed to characterize their properties and behaviors. Applications of dusty plasmas span diverse fields, from studying planetary formation processes to enhancing semiconductor device fabrication and environmental monitoring. Despite significant advancements, challenges remain in accurately modeling plasma dynamics and controlling dust particles in industrial applications. Future research directions include advancing diagnostic techniques, refining theoretical models, and exploring novel applications in materials science and technology. The interdisciplinary nature of dusty plasma research ensures continued exploration and innovation in understanding and utilizing this unique state of matter.

Electron extraction mechanism of magnet array microwave discharge neutralizer

Microwave discharge neutralizer is an important part of microwave discharge ion thruster system, which plays a vital role in maintaining potential balance between spacecraft and neutralizing ion beam. Its electron extraction property directly affects the operation condition of ion thruster system. In order to break through the power limit of miniature microwave discharge ion thruster, a magnet array microwave discharge ion thruster system is designed and tested. In the experiment on finalizing magnetic field structure of magnet array microwave discharge neutralizer, an interesting phenomenon is found that the <i>I</i>-<i>V</i> curves of electron current, after rotating the magnetic array orientation, are very different. Defining forward direction of magnet array can normally extract electrons, then backward direction of magnet array can hardly extract electrons. Because the diameter of discharge chamber is only 10 mm, it is too small to perform Langmuir probe diagnosis. And thus, an integrative particle-in-cell method is used to simulate the neutralizer operation processes of two different magnetic field structures, and for the sake of accuracy, real vacuum permittivity is used. The simulation results show good consistence with experimental phenomenon. In the initial discharge process, it is found that the magnetic field gradient leads to different plasma distributions; in electron extraction process, it is found that the potential distribution near the orifice determines the electron extraction property of the neutralizer. Through comparing the plasma parameter distributions under different magnetic field structures and operating voltages, an assumption that the ion is an important factor in electron extraction process is proposed. Then, a simulation that ions disappear artificially outside the orifice is conducted, and the simulation results show that electrons cannot be effectively extracted without ions near the orifice. According to the simulation and experiment results, two necessary conditions are summarized for electron extraction of the neutralizer. The first condition is magnetic field structure: the magnetic field gradient should point towards the orifice to guide plasma migration towards the orifice, the second one is potential distribution: there should be enough ions to lift the potential near the orifice for reducing or breaking the potential well. These two conditions can help understand the electron extraction mechanism of microwave discharge neutralizer and provide theoretical reference for optimizing the performance of neutralizer in future.

Wall material effects in a minimized electron cyclotron resonance ion thruster

Wall material effects in micro-ion thrusters attracts significant research attention with respect to weakening plasma wall loss, and increasing propellant utilization to obtain high-precision and low-thrust of micro-Newton propulsion, as required in new generation space observation missions. In this study, we compare the performance and discharge characteristics of different wall materials, namely, Mo and Al2O3 in a minimized electron cyclotron resonance ion thruster. The results show that the propellant utilization and specific impulse of the ceramic are about three times higher than those of the Mo at a low mass flow rate of 0.03 sccm. In addition, a planar Langmuir probe is used in the discharge chambers, and the results show that the secondary electron emission of Al2O3 effectively reduces the electron temperature, increases the electron density, and results in high efficiency. These results are helpful for improving the performance of micro-ion propulsion devices for microsatellites and space-borne gravitational wave detection missions.

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.

The use of low-temperature plasma for disinfection of open surfaces of industrial premises

The results of research on inactivation of microorganisms on open surfaces of poultry houses using low-temperature non-equilibrium plasma are presented. AC electrospark discharge at atmospheric pressure was used as its source. Discharge types are streamer, flare. The simultaneous effect of electromagnetic fields, charged particles and chemically active compounds formed by electrospark discharge on the efficiency of pathogenic microflora inactivation for various surfaces (acrylic primer, epoxy resin, yacht varnish, concrete-graphite mixture) is considered. The material to be treated (a biological model of the bedding surface of the floor in the poultry house with the applied protective layer) is installed after the electrospark discharge chamber blown with plasmaforming gas (atmospheric air). The main affecting factors are active chemical compounds: ozone; free radicals (OH, O, O2), ultraviolet radiation in the range of 750–1600 THz, electromagnetic radiation from 50 Hz to 980 MHz, charged particles and vibrationally excited nitrogen and oxygen molecules. Characterizations of electromagnetic radiation flux density at electrospark discharge are obtained. According to the research results, the maximum effect of treatment of exposed surfaces with low-temperature non-equilibrium plasma is achieved when epoxy resin is used as a surface protection material. The number of inactivated microorganisms at exposure of 10-20 s reaches 100%. When inactivating microorganisms on exposed surfaces, it is not economically feasible to take exposure time longer than 20 s. The studies found no significant difference when using streamer or flare discharges to treat outdoor facility surfaces.

Simulation Study on the Influence of Different Molten Steel Temperatures on Inclusion Distribution under Dual-Channel Induction-Heating Conditions.

Impurity elimination in tundishes is an essential metallurgical function in continuous casting. If inclusions in a tundish cannot be effectively removed, their presence will have a serious impact on the quality of the bloom. As a result, this research investigates the locations of inclusion particles in a six-strand induction-heating tundish in depth, combining the flow, temperature, and inclusion trajectories of molten steel under electromagnetic fields. The results show that a pinch effect occurred in the induction-heating tundish, and a rotating magnetic field formed in the channel, with a maximum value of 0.158 T. The electromagnetic force was directed toward the center of the axis, and its numerical distribution corresponds to the magnetic flux density distribution, with a maximum value of 2.11 × 105 N/m3. The inclusion particles' movement speed accelerated as the molten steel's temperature rose, and their distribution in the channel was identical to the rotating flow field distribution. When the steel's temperature rose from 1750 K to 1850 K, the removal percentage of inclusion particles in the discharge chamber rose by 9.20%, the removal rate at the outlet decreased from 8.00% to 3.00%, and the adhesion percentage of inclusion particles in the channel decreased from 48.40% to 44.40%.

Influence of the Electrical Characteristics of Pulsed Microwave Magnetron Power Supply on the Conditions for Plasma Formation in the Vacuum Chamber of Resonator-Type Plasmatron

The paper presents the research results of the influence of the electrical characteristics of a pulsed microwave magnetron power supply on the microwave discharge generation conditions, determined by the operating mode of the generating system as a whole. Plasma was formed in a vacuumized reaction-discharge volume located inside a rectangular resonator chamber. Depending on the operating modes of the microwave magnetron power supply, studies have been conducted for three modes of microwave discharge plasma generation: pulsed mode with a duty factor S ≈ 2; pulsed mode with a duty factor S ≈ 1.15; continuous mode. Probe measurements of the microwave power in the microwave discharge plasma volume and its local conductivity have been carried out. The paper presents the dependence of the power of microwave energy in the central area of the reaction-discharge quartz chamber of a microwave plasmotron on the amount of power consumed by the microwave magnetron, as well as the distribution of the electrical component of the microwave discharge plasma along the length and cross-sectional plane of the working volume. It has been established that for all studied modes of operation of the power source, with an increase in the power consumption of the microwave generator system, an increase in the microwave power recorded in the central region of the plasma discharge is characteristic. The continuous generation mode is characterized by a decrease in the uneven distribution of electromagnetic energy along the axis of the discharge chamber. It is shown that the transition from a pulsed to a continuous mode of microwave plasma discharge generation at the same level of power consumption by the generating system is characterized by a decrease in the value of the registered microwave power in the microwave discharge plasma volume and an increase in its local conductivity in particular areas of the reaction-discharge volume.

Laboratory ECR Source of Light Ions with a Resonant Discharge Chamber for Installation on a High-Voltage Platform

Laboratory ECR Source of Light Ions with a Resonant Discharge Chamber for Installation on a High-Voltage Platform

Influence of the Volume of a Cylindrical Discharge Chamber with Rigid Walls on the Pressure Field in the Water Filling It

Influence of the Volume of a Cylindrical Discharge Chamber with Rigid Walls on the Pressure Field in the Water Filling It

An integrative mathematical model of microwave ion thruster for mHz-frequency thrust noise analysis

Many high-precision space missions need thrusters to produce thrust with low noise to compensate for disturbances and ensure satellite platform stability. Microwave ion thruster is characterized with a wide thrust range and potential for these missions. A cost-effective and accurate mathematical model is crucial for mHz-frequency thrust noise analysis and feedback controller design. The Particle-In-Cell (PIC) and global models are two common simulation tools. The PIC model is characterized with high accuracy but huge computation cost, which is difficult to analyze long-time performance characteristics. Now, the global model is only used for the discharge chamber with low accuracy and cannot reflect ion extraction properties. In this paper, an integrative mathematical model is built for a 1-cm microwave ion thruster and can reflect ion beamlet divergence and impingement on the Accelerator Grid (AG). Simulation results show good agreement with experiments at 0.06 sccm. However, the model demonstrates worse consistency with experiments when the flux increases to 0.1 sccm, which may be because the influence of neutral gas on the Electron Cyclotron Resonance (ECR) is not considered in the model. A long-time (1000 s) simulation is conducted with this model under 35 μN. It takes 3 hrs, and the thrust noise reaches 1 μN/Hz0.5 at 1 mHz.

Linear Plasma Device for the Study of Plasma–Surface Interactions

At the research and production company “PlasmaScience” (Ust-Kamenogorsk, Kazakhstan), a linear plasma generator installation, KAZ-PSI (Kazakhstan Plasma Generator for Plasma Surface Interactions), has been developed and constructed for the study of the interaction of plasma and materials. This article outlines some features of the developed experimental installation designed for the investigation of surface–plasma interactions. The primary components of the linear plasma installation include an electron-beam gun with a LaB6 cathode, a plasma-beam discharge chamber, an interaction chamber, a target device, and an electromagnetic system comprising electromagnetic coils. The KAZ-PSI unit enables continuous plasma generation using hydrogen, deuterium, helium, argon, and nitrogen. The electron density of the plasma is in the range of about 1017–1018 m−3 and the electron temperature is in the range of 1 to 20 eV. The incident ion energy is regulated by applying a negative potential of up to 2 kV to the target. Experiments on the irradiation of tungsten with helium plasma were carried out using the KAZ-PSI installation for the first time. This article presents the research findings on the structure and properties of tungsten relative to the temperature of helium plasma irradiation. Alterations in roughness, microstructure, hardness, modulus of elasticity, and erosion of the tungsten’s surface following helium plasma irradiation at varying temperatures were examined. The study’s results indicate that helium plasma irradiation induces changes in the morphology of the tungsten’s surface, creating surface relief due to sputtering by helium ions, as well as the formation of blisters. Mechanical testing revealed that after irradiation at T = 500 °C, there was an increase in hardness of up to 10%, and a slight decrease in modulus of elasticity. And after irradiation at T = 900 °C and T = 1300 °C, both hardness and elastic modulus decreased with rising temperature. The tungsten surface erosion evaluation results showed that the degrees of surface erosion increase with increasing target temperature.

Surface Degradation of Thin-Layer Al/MgF2 Mirrors under Exposure to Powerful VUV Radiation.

Thin-layer Al/MgF2 coatings are currently used for extraterrestrial far-UV astronomy as the primary and secondary mirrors of telescopes (such as "Spektr-UF"). Successful Hubble far-UV measurements have been performed thanks to MgF2 on Al mirror coatings. Damage of such thin-layer coatings has been previously studied under exposure to high-energy electrons/protons fluxes and in low Earth orbit environments. Meanwhile, there is an interest to test the stability of such mirrors under the impact of extreme radiation fluxes from pulsed plasma thrusters as a simulation of emergency onboard situations and other applications. In the present studies, the high current and compressed plasma jets were generated by a laboratory plasma thruster prototype and operated as effective emitters of high brightness (with an integral overall wavelength radiation flux of >1 MW/cm2) and broadband radiation. The spectrum rearrangement and hard-photon cut-off at energy above Ec were implemented by selection of a background gas in the discharge chamber. The discharges in air (Ec ≈ 6 eV), argon (Ec ≈ 15 eV) and neon (Ec ≈ 21 eV) were studied. X-ray diffraction and reflectometry, electron and atomic force microscopy, and IR and visible spectroscopy were used for coating characterization and estimation of degradation degree. In the case of the discharges in air with photon energies of E < 6 eV, only individual nanocracks were found and property changes were negligible. In the case of inert gases, the energy fraction was ≈50% in the VUV range. As found for inert background gases, an emission of such hard photons with energies higher than the MgF2 band gap energy of ≈10.8 eV caused a drastic light-induced ablation and degradation of the irradiated coatings. The upward trend of degradation with an increasing of the maximum photon energies was detected. The obtained data on the surface destruction are useful for the design of methods for coating stability tests and an understanding of the consequences of emergencies onboard space research stations.

Numerical simulation of thermo-throttle for iodine flow rate control in multidirectional plasma thruster

Background: Recently, a new direction in the field of electric propulsion has emerged – the multidirectional plasma thrusters. These thrusters are capable of producing propulsive forces in multiple directions. The thrusters are proposed to be used for orbit maintenance and alterations, formation flights, and interplanetary flights of space artificial objects ranging in size from CubeSats to fusion-powered interplanetary spacecraft. In this paper, the results of numerical simulation of the iodine propellant supply system for the multidirectional plasma thruster are presented. Methods: The geometry and temperature parameters of propellant supply system various elements are varied to determine the stable modes of iodine propellant ejection into the gas discharge chamber of the thruster. The temperatures of the thermo throttle and filter are found to ensure iodine mass flow rate in the range of 0.1 to 1.5 mg/s. The thermo throttle and filter temperatures are altered in the range of 65 to 200 °C and 65 to 100 °C, correspondingly. Results: The mass flow rate is critically dependent on the filter temperature and iodine saturated vapor pressure, as well as the filter and throttle geometries. The required values of iodine flow rate have been achieved by using the throttle with a diameter of 0.5 mm and a length of 60 mm and a filter with 56 holes, each hole diameter is 0.2 mm, and temperature from 90 C to 200 C. Conclusions: According to the data obtained, the iodine storage and supply system is preferably equipped with a thermos throttle, which provides precise control of the flow rate, as well as reduces sharp jumps of the flow rate when the temperature of the filter changes. Preferred filter geometry: 56 holes, each hole 0.2 mm in diameter.

Influence of plasma grid bias on the beam extraction of RF driven negative hydrogen ion source

In the negative hydrogen ion sources, the positive bias of the plasma grid with respect to the discharge chamber is often used to suppress co-extracted electrons. Because most of the co-extracted electrons are magnetically deflected onto the extraction grid, the difference between the extraction and acceleration current (i.e., Iext − Iacc) is commonly used to represent the number of co-extracted electrons. In the single-driver RF negative ion source at ASIPP, the variation of Iext − Iacc with the plasma grid bias voltage was accidentally found to have different trends with and without the Cs seeding. When the current density of Iacc (regarded as JH-) was larger than 120 A/m2 during Cs conditioning, the Iext − Iacc fell first and then rose with the increasing bias voltage. The previous research results from NIFS that the beam optics were changed by the bias voltage can be used to explain the phenomenon. In this paper, the electron temperature (Te) in front of the plasma grid was found to increase from the Langmuir probe measurement, when the bias voltage was higher than a threshold of 4.5 V to the float potential. Interestingly, the bias voltage corresponding to the trough of Iext − Iacc was higher than the float potential—a similar value of 4.1 V to the threshold of Te increasing. Since the negative hydrogen ions are easily destroyed by the high-energy electrons, the increasing of Te may also cause the change of beam optics and the increase in co-extracted electrons. The electron energy distribution function was used to explain the change of plasma parameters in front of the plasma grid.

Linear plasma device for the study of plasma-surface interactions

In the research and production company "PlasmaScience" (Ust-Kamenogorsk, Kazakhstan) a new laboratory linear plasma installation KAZ-PSI (Kazakstan plasma Generator for Plasma Surface Interactions) for studying the interaction of plasma with material has been developed and built. The article describes some features of the developed experimental setup for the study of surface-plasma interactions. The main elements of the linear plasma setup are an electron-beam gun with a LaB6 cathode, a plasma-beam discharge chamber, an interaction chamber, a target device, and an electromagnetic system consisting of electromagnetic coils. The KAZ-PSI facility allows generating continuous plasma of hydrogen, deuterium, helium, argon and nitrogen. The electron density of the plasma is in the range of the order of 1017 -1018 m-3 and the electron temperature is in the range of 1 to 20 eV. The incident ion energy is controlled by applying a negative bias of up to 2 kV to the target. Experiments on irradiation of tungsten with helium plasma were carried out for the first time at the KAZ-PSI facility. The paper presents the results of studies conducted to study changes in the tungsten mixture. The results have shown that after helium plasma irradiation the morphology of tungsten surface changes and relief is created on the surface due to atomisation of the surface by helium ions, as well as due to the formation of blisters.