Ion Extraction System Research Articles

Mathematical modeling of the ion extraction system of a radio-frequency ion source

In order to ensure space debris removal from the near-Earth space, the world scientific community is developing various technical means potentially capable of transporting the spent spacecraft to disposal orbits. The so-called Ion Beam Shepherd is among them. According to this method, in order to transfer momentum efficiently from an ion beam generated by a radio-frequency ion source mounted on board a service spacecraft, it is necessary to ensure the generation of an ion beam with the minimum divergence angle. In order to provide generation of a highly collimated ion beam for a system of contactless removal of technogenic space debris, an ion extraction system was modeled with the aim to study the influence of its geometric parameters on the angle of ion beam divergence at the ion source exit plane. Based on the preliminary study, a model of 28 full factorial experiment was developed for two types of electrodes in an ion extraction system. The regression coefficients have been defined that allow, without performing a large array of numerical studies, to assess the influence of various geometric parameters on the ion beam divergence angle.

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.

An Experimental Study of an Ion Thruster with Electrodes of an Ion-Extraction System Made of a Fine-Structure Carbon–Carbon Composite

An Experimental Study of an Ion Thruster with Electrodes of an Ion-Extraction System Made of a Fine-Structure Carbon–Carbon Composite

An Experimental Study of an Ion Thruster with Electrodes of an Ion-Extraction System Made of a Fine-Structure Carbon–Carbon Composite

This article presents the results of 1000-h tests of a radiofrequency ion thruster (RFIT) with electrodes of an ion-extraction system made of carbon–carbon composite material based on the non-woven carbon frame. The quality of the surface of the thruster IES accelerating electrode being the key element of the RFIT from the lifetime point of view was assessed by visual examination and scanning electron microscopy. The maximum depth of erosion cavity on the accelerating electrode surface was determined. Electrode-surface elemental analysis was performed by the method of electron-probe microanalysis.

Design method and construction of the Schwarzschild microscope with high numerical aperture for secondary ion mass spectrometry.

The Schwarzschild microscope is suitable for sample navigation in secondary ion mass spectrometry (SIMS) because of its advantages of a simple structure, large working distance, and good coordination with the ion extraction system. The high numerical aperture (NA) of the microscope significantly reduces diffraction effects, but the resulting high-order geometric aberrations seriously affect the imaging quality. In this paper, a novel design method of the Schwarzschild microscope with a high NA (0.47) was proposed. The aberration distributions and compensation methods were investigated through tolerance analysis. The results showed that the tilt and decenter tolerances become the dominant factors limiting the spatial resolution, which could only be improved by ensuring the alignment accuracy of mirrors. Finally, the spatial resolution of the microscope in the home-built SIMS reached 2.19 µm.

Computational and experimental study of an ion injector of a weakly divergent ion beam for implementing a method for removing space debris objects by an ion beam

Attention to the method of removing large space debris objects by impacting them with an ion beam has not waned over the past 10 years. The application of this method to the space debris removal from the protected area of the Geostationary Earth Orbit (GEO) seems to be the most effective. This is due to a low energy consumption for removing an object to a safe orbit with ΔV≃11 m/s, which allows the removal of several objects by a single spacecraft. A service spacecraft can be developed for this purpose based on the TelSat geostationary communication satellite technology. At the same time, one of the problematic issues remains that is the development of an injector of a weakly divergent ion beam. The ion beam divergence during injection into the vacuum occurs under the insuperable influence of the ambipolar electric field acting in the beam volume. At the same time, the beam behavior depends on the initial divergence angle stipulated by the conditions of beam formation by the electrostatic acceleration system. This paper considers the results of calculated and experimental studies for the peculiarities of the formation of an ion beam in an ion extraction system with slit and round apertures. The dependence of the initial divergence half-angle on the beam perveance for both geometries was defined. In the operation of the injector designed for the space debris removal, it is necessary to ensure stability of the geometry of the ion-extraction system, which is subject to uneven thermal loading. The resulting thermomechanical deformations of the grids in the technology of ion thrusters are parried by giving the grids a plate shape. Therefore, flat grids made of a carbon-carbon composite material of a new type were used in experiments, which avoided noticeable deformations. The results of experimental investigation of the prototype of ion injector with two configurations of carbon grids (with round and slit perforation) and with the initial divergence half-angle of 2°-4° are given in this paper. The thrust control of an ion beam by changing of the screen grid potential under the condition of a constant beam perveance is considered. It is shown that such regulation is associated with a change in the Mach number, which affects the beam divergence. As an example, the calculation of the dependence of the coefficient k on the distance to the removing object is given, which is considered to be a spent satellite SUPERBIRD-A.

Исследование высокочастотного ионного двигателя с прямоточной конфигурацией разрядной камеры

The paper describes a zero-dimensional balance mathematical model of a radio-frequency ion thruster with a ramjet discharge chamber and considers the case when the propellant is fed into the ionization chamber but is able to outflow through the ion-extraction system as well as through the inlet channel of the atmosphere gases intake device. Nitrogen was considered as the propellant. The mathematical model is distinctive as it takes into account the propellant dissociation and the influence of atmosphere gases intake device. The paper also gives the results of the first experiments with a laboratory model of the thruster. The comparison between the calculated and experimental data made it possible to obtain the discrepancies of less than 15 percent, which indicates the applicability of the developed mathematical model for a qualitative analysis of the processes occurring in the thruster.

Two-rod-antenna microwave injection system for production of circularly polarized microwaves in cylindrical ECRIS cavities

In the design of Electron Cyclotron Resonance Ion Sources (ECRIS) three topics generally need to be addressed: (i) The feed of a microwave to generate a plasma, (ii) the creation of a magnetic field guiding the charged particles, and (iii) the design of an ion extraction system. In this report, we concentrate on improvements of aspect (i), a new microwave injection system introduced to the Dresden ECRIS 2.45M, a permanent-magnet 2.45 GHz ECRIS, applied, e.g., for the production of proton currents in medical particle therapy. The improvements include the replacement of its one-rod antenna system by two rod antennas on one cross-sectional circle of the cylindrical ECRIS cavity positioned under an angle of 90° towards each other. Feeding two microwave signals with a relative phase shift of 90°, a right-hand circularly polarized wave can be created inside the cavity to efficiently heat the electrons. Basic considerations, simulations, and results from first experiments are presented.

Ion Source—Thermal and Thermomechanical Simulation

The main purpose of this work is to conduct ground development testing of the ion source intended for use the space debris contactless transportation system. In order to substantiate the operating capability of the developed ion source, its thermal and thermomechanical simulation was carried out. The ion source thermal model should verify the ion source operating capability under thermal loading conditions, and demonstrate the conditions for ion source interfacing with the systems of the service spacecraft with the ion source installed as a payload. The mechanical and mathematical simulation for deformation of the ion source ion-extraction system profiled electrodes under thermal loading in conjunction with the prediction of the strained state based on the numerical simulation of the ion source ion-extraction system units, making it possible to ensure the stability of the ion source performance. Good agreement between the thermal and thermo-mechanical ion source simulation results and experimental data has been demonstrated. It is shown that the developed ion source will be functional in outer space and can be used as an element of the space debris contactless transportation system into graveyard orbits.

Reversible Electrochemical Tuning of Ion Sieving in Coordination Polymers.

Membrane-based ion separation is environmentally friendly, energy-efficient, and easy to integrate, being widely used in water desalination and purification systems. With the existing separation technologies, it is yet difficult to achieve real time, in situ, and reversible control of the separation process. Here, we design and fabricate a Prussian blue (PB) coordination polymer based membrane with uniform and electrochemically size-tunable subnanopores. The ion separation can be significantly and reversibly modulated through the electrochemical conversion between PB and Prussian white (PW). The permeation rates of small hydrated metal ions (Cs+ and K+) obviously increase upon switching from PB to PW, while the permeation rates of large hydrated metal ions (Li+, Na+, Mg2+, and La3+) remain constant. The membrane selectivity of small hydrated ions to large hydrated ions can be increased by more than 2 times during the electrochemical switch, which could be assigned to the slightly larger crystal size (e.g., pore window size) of PW than PB. The present approach provides a new strategy for constructing tunable seawater desalination and ion extraction systems.

Ionic Liquid-Based Dye for Highly Sensitive Optical Sensing Based on FRET and Ion Extraction System Using Plasticized PVC Membrane

Ionic Liquid-Based Dye for Highly Sensitive Optical Sensing Based on FRET and Ion Extraction System Using Plasticized PVC Membrane

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.

Progress in low energy high intensity ion implantation method development

New results on the equipment development and advancement of the method of high-intensity ion implantation of metal, gases and low-energy semiconductors providing a long range effect of dopants penetration are presented in the article. The results of the research and development of plasma-immersion systems for the formation of ion beams with a current density of tens and hundreds of mA/cm2, a beam current exceeding 1 A at kilovolt accelerating voltages using ion extraction and beam focusing systems as part of a sphere or cylinder are shown. A comparative analysis of various systems, their advantages and disadvantages depending on the purpose are presented.The concept of low energy high intensity ion implantation (LEHI3) method is described. The features of the method as applied to the problems of deep modification of the microstructure and operational characteristics of metals and alloys are analyzed. The report presents the results of experimental studies of LEHI3 of aluminum, titanium, nitrogen into various structural materials. The possibility of ion doping of materials at depths of several tens and hundreds of micrometers is shown. Data are presented on the changes in the elemental composition, microstructure and properties of various materials depending on the ion current density of 10–500 mA/cm2, ion energy, implantation temperature and irradiation fluence of 1018–1022 ion/cm2.Based on the analysis of the obtained experimental data, the directions of further research are discussed in the framework of the development of the physical and technological foundations of the LEHI3 method of material properties modification at depths that are orders of magnitude greater than the projective ranges of ions.

On the Passage of Radiant Fluxes out of Discharge Plasma in Ion Sources through Openings in Ion-Extraction Systems

In ion sources, up to a third of the power released in a plasma discharge is carried away from the plasma in the form of ultraviolet radiation. Two main mechanisms for the formation of radiation are considered: radiation from excited atoms of the propellant and from ion-electron recombination coming out of plasma onto the surface bordering the discharge. The radiation-absorption coefficients of perforated electrodes of ion-extraction systems are determined.

Procedure of Predicting the Lifetime of the Accelerating Electrode of an Ion-Extraction System of a Gas-Discharge Ion Source

The state of studies on determination of the lifetime of ion thrusters (IT), including their methodology, is analyzed. The erosion of the accelerating electrode (AE) of an ion-extraction system caused by charge-exchange ions is a critical process responsible for the IT lifetime. It is shown that the quickest and most accurate information on the nature of AE erosion and rate at the initial test stage can be obtained by a method based on the use of multilayer coatings, consisting of several pairs of optical contrast materials, preliminarily applied to the AE surface. The method allows the use of simple photographic devices for recording the erosion pattern and is especially efficient in the case of a highly nonuniform nature of erosion. The calculation procedure is presented for the parameters of diagnostic multilayer coatings, including the optimal layer thickness and total coating thickness, which allow data to be obtained on the surface erosion profile and rate, and on the charge-exchange ion current density distribution with the highest resolution during the given test time.

Two-Electrode Ion-Extraction System of a Radio-Frequency Ion Source: Numerical and Experimental Studies of Erosion of the Accelerating Electrode

The results of numerical and experimental studies of the erosion rate of the accelerating electrode of an ion thruster are presented. When the ion beam propagates beyond the edge of the thruster, the process of resonant charge-exchange leads to the formation of slow ions in the engine volume. Under the action of negative electric potential of the accelerating electrode, ions bombard the electrode surface which faces the outgoing beam. Erosion due to the bombardment of the accelerating electrode by charge-exchange ions is the main factor limiting the ion-thruster lifetime. A 25-layer coating of optically contrasting copper and chromium layers, which is applied to the outer electrode surface, is used to diagnose the sputtering rate. The total time of exposure is 14 h. The time dependence of the growing cavity depth is obtained by recording the cavity profile every 3–5 hours. The results obtained in the experiment are used as the initial data for the numerical 3D modeling of multilayer-coating erosion under conditions corresponding to the experiment. Based on the results, the lifetime of the test thruster is estimated at 13 800 hours in respect to the wear of the titanium electrode at its potential of –500 V.

Iodide ion trapping polypyrrole film: Selective capture of iodide ions by electrochemically switched ion extraction (ESIE) process

Effective extraction of iodide ions (I−) from low-concentration brine or radioactive wastewater remains a great challenge. In this study, an electroactive I− trapping polypyrrole film (PPy/I− film) was fabricated via a facile one-step electrodeposition method and used in a novel and effective electrochemically switched ion extraction (ESIE) system for capture of I− from dilute aqueous solutions. Herein, the PPy/I− film displayed superior performance owing to the special I− trapping efficiency. The extraction capacity as high as 287 mg/g was achieved in 5 ppm KI solution, and the separation factors for I−/Cl−, I−/Br−, I−/SO42−, I−/PO43− were 6.93, 22.16, 15.92, 7.92, respectively. Moreover, the desorption efficiency of I− from the PPy/I− film extracted with I− was approximately 100% even after several repeated cycles. It manifested that the present ESIE system with the PPy/I− film had efficient extraction capacity, remarkable selectivity and excellent recyclability, which could be applied in the extraction of I− from the dilute industrial solutions.

Development of a test bench of 2.45 GHz ECR ion source for RFQ accelerator

The optimization of beam quality at the entrance of a RFQ system requires a test bench for the optimization of the ion source and beam parameters. The aim of this test bench is to produce a 5 mA proton/deuterium beam with rms normalized emittances lower than 0.2 π ⋅mm⋅mrad for the 5 MeV RFQ. This bench consists of an indigenously developed permanent magnet based 2.45 GHz ECR ion source with three electrode ion extraction system and a LEBT to match the beam for the injection into the RFQ. The LEBT system has been designed using TRACEWIN© code. The LEBT parameters have been optimized in order to maximize the beam transmission through the RFQ.The ECR ion source test bench has been setup and operated up to 50 kV. Deuterium ion beam of 9.8 mA is extracted from the test bench.This paper presents the design of the test bench, results of latest extracted ion beam.

3D Printing of Ion Optics for Electric Propulsion

Additive manufacturing is rapidly opening its way into many areas of the aerospace industry, where different 3D printing technologies are finding niche applications in which they do not only simplify the process and allow shorter lead times, but also the particularities of these new fabrication methods yield new material properties that enhance the component and can lead to higher performance and longer service life of an aerospace system. Although rapid manufacturing processes are being tested for in-space manufacturing and are commonly used to fabricate UAV parts and some spacecraft subsystems with 3D printed components have been tested in space, little research has been conducted on the potential application of these techniques to electric thrusters. This paper presents the study conducted on the application of selective laser melting, a powder bed fusion technology, to the fabrication of ion engine grids and the challenges faced during the process. The first proof of concept and its optimization are described. Later, the development of the selective laser melting process for molybdenum, the study of the 3D printed materials’ properties, their direct application to ion extraction systems, and the tests of additively-manufactured ion optics are described. It was found that 3D printed grids can be accurately fabricated with titanium and molybdenum, that they perform similar to conventional optics in short tests, that the selective laser melting process allows certain control of the coefficient of thermal expansion of the output and that this fabrication method allows the reproduction of sputtering erosion patterns. Future research in this direction will cover sputtering tests of selectively-laser-melted samples and the additive manufacturing of carbon-carbon grids.

Solvent Water Content as a Factor in the Design of Metal Ion Extraction Systems Employing Ionic Liquids

ABSTRACTIn the extraction of strontium nitrate from aqueous nitric acid solutions into a series of hydrophobic N-(1-hydroxyalkyl)-N’-alkylimidazolium bis[(trifluoromethyl)sulfonyl]imides by dicyclohexano-18-crown-6, a correlation has been demonstrated between the conditional extraction constant of strontium (K’ex,Sr) and the concentration of water in the equilibrated ionic liquid (IL) phase. Despite the absence of a hydroxyl group on the IL cation, essentially the same relationship is observed for the analogous N,N’-dialkylimidazolium ILs. In both instances, the correlation is attributed to the coextraction of the hydrated nitrate ion and its solvation by the hydrated diluent. Transitions of water in the attenuated total reflectance-infrared spectra of the ILs are consistent with the existence of multiple states of water. The extraction efficiency for a given water content is greater for the ILs examined than for conventional solvents (i.e., n-alcohols). When coupled with existing knowledge of the factors influencing cation partitioning into ILs, these results provide insight into the IL structural characteristics required to effect efficient metal ion extraction from acidic media.