Anode Block Research Articles

DEVELOPMENT OF THE DEVICE FOR CONTROLLING AND MEASURING THE SUPPLY OF WORKING GAS FOR LABORATORY TESTING OF THE ELECTRIC PROPULSION THRUSTERS

The object of the research is a device for measuring, controlling, and indicating the flow rate of working gas during laboratory testing of electric propulsion systems for space applications. The problem lies in the need to ensure high accuracy in controlling and measuring the flow rates of working gas for such devices. The obtained results include: analysis of existing industrial flow meters that could be used in development; proposed structural and functional diagrams of the device; experimental investigations into the accuracy of the developed device. Based on the analysis of parameters of the most common flow meters for development, the Bronkhorst F-201CV-100-AAD-22-V regulator was selected. Based on the selected regulator, a device was developed with a 32-bit ARM architecture. This architecture provides for the use of floating-point calculations, easy reprogramming of the device, and fast indication of values displayed on the indicator. The device features galvanic isolation between the control bus and the UART port of the microcontroller. The device allows for regulation, measurement, and indication of the flow rate of working gas into the anode block and hollow cathode during testing of Hall thrusters. Using the device allows for recommendations regarding the design of onboard systems for supplying working fluid to electric rocket propulsion systems. Based on the presented development and conducted research, laboratory prototypes of the devices were manufactured. The measurement error throughout the entire range of working gas flow rates does not exceed 0.7%. The overall error of the stand control and measurement system for working gas flow rates is up to 3%. The developed device provides measurement accuracy that satisfies the developers of electric propulsion systems.

Operation characteristics of a ten-cavity magnetron with TE11 mode extracted through compact diffraction output

We present the design of a ten-cavity magnetron extracting TE11 mode through compact diffraction output (DO). The effect of the DO length and the depth of the vane on the performance of the ten-cavity magnetron are investigated to design a compact diffraction structure. By adjusting the length of DO and the depth of the tapered cavities to provide a proper Qe, the output power and power conversion efficiency have been improved. Simulation results of the magnetron with compact DO (the length of the DO is about half an operation wavelength) show that the microwave power of 3.0 MW with a high conversion efficiency of 62% at 2.4 GHz is achieved under an applied voltage of 56 kV and a fixed axial magnetic field of 0.24 T. In addition, the length of the anode block is designed longer than the cathode to arrange the permanent magnet, which has been preliminary designed.

LOW POWER HALL THRUSTER ST-22 WITH PERMANENT MAGNETS


 
 
 The results of the design, development and testing of the laboratory model of the Hall Thruster ST- 22 are presented. The main attention in the development of the thruster was focused on the optimization of the magnetic field in the accelerating channel of the thruster. When choosing a constructive thruster diagram, it was proposed to use constant magnets and a non -magnetic ring in a magnetic system. The proposed constructive features of the thruster made it possible to exclude a magnetic screen from its design, which led to the simplification of the structure and reduce its mass. Laboratory tests of the ST-22 thruster were carried out when changing the discharge voltage in the range of 160-260 V, as well as with three different values of the mass flow rate of Xenon submitted to the anode - 0.4, 0.5, 0.6 mg/s. In the course of laboratory investigation of the ST-22 Hall thruster, the following characteristics were determined: current-voltage characteristics of the discharge in the acceleration channel of the thruster; the dependences of thrust and specific impulse on the mass flow rate of the working substance and the discharge voltage, as well as the value of the efficiency of the anode block of the thruster on the discharge voltage. As a result of laboratory tests, it was shown that at input power of 100 W, the discharge voltage 215 V and the working substance flow through the anode unit 0.6 mg/s, the thruster provides the thrust value of 7 mN, the discharge current of 0.47 A, a specific impulse of 950 s, and efficiency 33%. The values of the specific impulse and the thruster efficiency were given taking into account the mass flow rate of the working substance in the cathode-compensator. The thruster provides sustainable operation in the range of power consumption of 50 - 100 W and it was designed to use small spacecraft on board, which on board have appropriate electric power.
 
 

Optimization Using Backtracking Search Algorithm for the Design of Magnetron Anode Block and Pill-Box RF Window

Optimization Using Backtracking Search Algorithm for the Design of Magnetron Anode Block and Pill-Box RF Window

Anodal Block in Evaluation of Nerve Conduction Changes in Anesthetized Rats: Preclinical Non-Randomized Experimental Study

Background. There is currently no gold standard for functional assessment of nerve regeneration. Different researchers use various methods to assess the functionality of the regenerated nerve directly and indirectly. Indirect methods have the advantage of being minimally invasive, and the benefit of direct methods is recording the signal directly in the nerve.Objectives. To identify significant parameters of neurogram changes in the sciatic nerve in an anaesthetized rat when the anode block is applied and to evaluate neurography as a method for functional assessment of nerve regeneration.Methods. A series of experiments was performed on 10 anaesthetized rats. A DC anode was placed on the exposed sciatic nerve, more proximal and more distal to the recording electrodes, and a common cathode in the form of a needle was introduced into one of the forelimbs. Needle nichrome electrodes were introduced into the nerve using a manipulator. An original neurogram and a neurogram against anode activation were recorded by closing the DC circuit of different voltages to block the afferent signal, efferent signal and afferent and efferent signals simultaneously.Results. When the anodal block of different voltages was applied to the afferent signal, efferent signal, and afferent and efferent signals simultaneously in all 10 experiments, the frequency-amplitude characteristics of the neurogram changed significantly as compared to the original neurogram. The amplitude of the neurogram increased considerably, while the frequency decreased, though not so dramatically. The changes in amplitude and frequency parameters were revealed to depend on the voltage value. In most cases, this relationship was directly proportional to the amplitude and inversely proportional to the frequency.Conclusion. Considering the nature of the dynamics of the neurogram when exposed to the anodal block, the most significant parameter of its change is the amplitude. Changes in nerve fibre composition during its regeneration after damage cause changes in afferent and efferent signals, which is likely to be displayed in the neurogram as compared to the initial state. Thus, the anodal block can be used as a model of nerve damage, and the analysis of the dynamics of neurogram parameters — as a method for functional assessment of nerve regeneration.

Equivalent circuit approach for the design of hole and slot bare anode block of magnetron

Magnetron is a high-power microwave source with high demand among vacuum devices. Before the design, validating it with other methods gives confidence to the designer. An equivalent circuit analysis is developed for a 16 vanes hole and slot structure yielding the design parameters, hole radius, slot length, slot width, and anode height. This method is adopted to calculate the cavity resonant frequencies preferable over the field equations, simulation, and fabrication. From inductance and capacitance definition, dispersion equation of the anode block is derived for each mode. The equivalent circuit approach is validated with the simulation to verify consistency. The resonant frequency relative difference of these two methods is 1.46%. The inductance and capacitance changes are observed by parametric variation of these structure dimensions. Strapping causes the frequency shift from 3.1685 to 2.217 GHz, and change in the cavity resonant frequency with the strap depth and strap height are plotted.

Sodium lignosulphonate decomposing accumulated byproducts of quasi-solid aluminum-air batteries

Quasi-solid Al-air batteries with hydrogels are regarded as a promising power source because of their high specific capacity, small-scale bulk, high ionic conductivity and no leakage. However, increasing accumulations of byproducts on the interface between Al anode and solid-state electrolyte block discharging performance and lifespan of the batteries. Here, we firstly present a way of sodium lignosulphonate as a chelating agent for Al-air batteries, forming coordination compounds and decomposing discharging byproducts, where the coordination compounds can make aluminum ions transfer from anodic surface into the interior of hydrogel electrolyte. Compared to Al-air batteries without additive sodium lignosulphonate, the lifespan of the battery with sodium lignosulphonate can be prolonged by 124.6% at a current density of 1 mA cm−2. Additionally, the battery can output high power density of 46.3 mW cm−2 at 56 mA cm−2, and the maximum specific battery capacity of 2161.67 mA h g−1 is achieved at 20 mA cm−2. The use of coordination compounds to decompose and migrate discharging byproducts is not only available for Al-air batteries but for other metal batteries.

The recycling of pure metallic indium from waste LCD screens by a combined hydro-electrometallurgical method

The Liquid Crystal Display (LCD) panels were removed and crushed to be leached. Sulphuric acid of 0.25 M H2SO4 was found best for relatively fast reactions and selectivity, recovering >99% of the indium from the indium‑tin oxide (ITO) layers, while >95% of the tin content was left in the solid residue. As potential impurities, Sn, Fe, Mn, Ni, Zn, Bi, Pb, Al and Cu were analysed in the solutions and in the final product. Synthetic solutions of larger volumes corresponding to the obtained leachate were used for developing the purification and metal recovery steps. Metallic indium was extracted selectively from the solution by cementation on Al plates. The purity of the primary indium deposit was controlled by increasing the temperature to 50–60 °C and keeping the pH in the 0.25–0.5 range, while the aluminium consumption was close to the stoichiometric value. The cemented sponge was vacuum-melted to produce an indium anode block of >99.9% purity for electrorefining. According to the galvanostatic and potentiodynamic results, the optimal electrolyte conditions were found as 50 g/dm3 In, 1 M free Cl− ions, pH 1. The cathodic deposition of Zn, Mn, and Fe was negligible; however, the prior removal of Cu and Sn from the solution is required for producing high-purity indium. Generally, increasing the cathodic current density in the range of 150–600 A/m2 enhanced the purity of the cathodes, while a maximum pH 2 value should be assured. Chloride ion concentration strongly influences the deposit morphology.

PIC simulations of a frequency agile multicavity relativistic magnetron using irregular ring metamaterials driven by a transparent cathode

The design of an agile 5° irregular ring metamaterial for a 24-cavity relativistic magnetron with diffraction output (MDO) using single-stepped cavities for frequency switching is presented. By inserting six pieces of 5° irregular ring metamaterials in place of the traditional 5° vanes of a slow wave structure, the operating frequency can be tuned. When U = 400 kV high voltage is applied, with an applied magnetic field B = 0.36 T, the operating mode can be switched from the TE41 mode with a frequency of 2.585 GHz to the TE31 mode with a frequency of 2.282 GHz. The 24-cavity anode block is an electromagnetic medium which can support the operating mode working under its cutoff frequency, and the insertion of the irregular ring metamaterials alters its dispersion relation. The results suggest a new technique to achieve frequency agility by changing the dispersion relation of the electromagnetic system using a metamaterial unit cell. This work seeks to design a compact high power microwave source for a narrowband directed microwave wave beam that is suitable for frequency agility.

Thermal Design of Megawatt Power-Level X-Band Coaxial Magnetron

Thermal analysis of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${X}$ </tex-math></inline-formula> -band high-power (~2 MW) coaxial magnetron is presented. The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${X}$ </tex-math></inline-formula> -band magnetron is used for a medical linear accelerator (LINAC). The performance of LINAC depends on the RF performance of the magnetron. This magnetron consists of an oxygen-free copper anode with 40 vanes coupled with the coaxial cavity, cooling channels, and an indirectly heated oxide-coated cathode. The operating temperature of the cathode is about 850 °C, while the tungsten heater temperature is greater than 1800 °C. Therefore, the thermal design of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${X}$ </tex-math></inline-formula> -band magnetron is a challenging task and it is essential for reliable operation. This article deals with the step-by-step thermal design procedure for each part of this magnetron. The analytical (MATLAB code) calculation of heater temperature for various heater voltages is also carried out for verification of simulation results. By analyz- ing the temperature uniformity on the emitting surface of the cathode and the effect of the heat film coefficient, it was found that the maximum temperatures on the magnetron anode block, cathode surface, and heater are 220 °C, 1045 °C, and 1842 °C, respectively, for an applied 5-L/min flow rate of water cooling.

Theory and Practice of Creating a Two Energy Outputs Magnetron

This paper presents the methodology for 3-D simulation and design of the magnetron with two energy outputs. The principal functionality of the modified magnetron, both theoretically and experimentally, has been determined. The central distinguishing feature of this magnetron (for example, unlike the conventional magnetron with one output) is the availability of second energy output in the anode block. The mathematical models of both the resonant anode block and the electron-wave interaction are described. The dispersion characteristics of the anode block for cavities various geometries are given. It is supposed that forming the total RF field in the interaction space results from the interference of RF fields excited severally in the resonant anode block consisting of the small and large cavities (resonators). For PIC-simulation of electron-wave interaction in the dual-output magnetron, the non-linear system of equations is stated as a self-consistent system containing the equation of motion (for electron stream), the equation of excitation (for RF field), and Poisson’s equation for calculating the space-charge field. The fundamental feature of the self-consistent system of equations is a new algorithm for determining the Coulomb interaction forces. The implementation of the mathematical model made it possible not only to gain new knowledge about the physical processes in the magnetron but also to determine its output characteristics. On operating frequency of ∼ 13.34 GHz, at an anode voltage of 495 V, a magnetic field of ∼ 0.25 T, and with air cooling of the magnetron, there were obtained the following limiting values: the RF output power of ∼ 14.6 W and the power conversion efficiency of ∼ 40.8%. The use of the second energy output allowed extending the magnetron’s functionality and implementing the modes of the frequency tuning (adjunction) and its stabilization. The simulation results are in good agreement with the experiment. To the 100th anniversary of magnetron

S-Band GW-Level Relativistic Magnetron Operating at Relatively Low Applied Voltage

To realize miniaturization of high-power microwave (HPM) systems, a high-efficiency GW-level relativistic magnetron (RM) operating at a relatively low applied voltage is presented, which does not require a large high-energy pulsed power source. An eight-cavity anode block with rectangular vanes is adopted. The resonators in the anode block, where the high-frequency energy is directly stored, are enlarged by introducing rectangular vanes. The microwave extraction is accomplished by a step-like diffraction output, which benefits the compact magnet system design. In experiments, several transparent cathodes have been employed to investigate the cathode effects on the magnetron performance, including cathode configurations, cathode endcaps, and emission length. With the optimal cathode, the proposed RM can radiate microwave power of 1.1 GW with a power conversion efficiency of 51% at 2.72 GHz when the applied voltage is around 380 kV and the axial magnetic field is 0.44 T.

An advanced relativistic magnetron operating with a split cathode and separated anode segments

We report the successful operation of an advanced relativistic magnetron made up of separate anode segments and fed by a split cathode as suggested by Leopold et al. [Phys. Plasmas 27, 103102 (2020)]. A split cathode has the advantage that the emitter is placed outside the interaction region so that the cathode plasma does not cause pulse shortening. We find that the split cathode-fed magnetron performs as well as a common explosive emission plasma cathode but without the appearance of microwave pulse shortening during ∼200 ns while the pulsed generator is at its maximum power. The angular magnetron segments facilitate longitudinal slits in the magnetron's anode block, which allows for fast magnetic field penetration. This drastically decreases the power requirements of the pulsed generator feeding the axial insulating magnetic field producing solenoid and does not affect the operation of the magnetron. This results not only in a compact system but also in overall high electrical efficiency and the possibility to operate the relativistic magnetron in a repetitive mode.

Simulation and Design of Rising-Sun Anode Blocks for Magnetrons with Two Outputs of Energy

This paper presents the simulation results of the oscillation modes excited in the interaction space of an anode block of a magnetron and the azimuthal distributions of a longitudinal electric component of the RF field for either of the excited modes. Using CST code, there were considered available anode blocks with different configurations of the resonators: a rising sun anode block and a rising sun hole-and-slot anode block. The dispersion characteristics and distributions of the azimuthal components of the RF field for different geometrics of their cavities as applied to the X- and Ku-bands are given. The condition of acceptable separation both in frequency and in phase velocity between the operating JV/2 -mode (or 7T-mode) and neighboring (JV/2 - l)-mode has been determined. It suggested that the mechanism of forming the total RF field connects with possible interference of the RF fields excited severally in the resonant system consisting of the small and large cavities. The features design of the magnetrons with two energy outputs is presented, and their application in practice is determined. The results of the simulation are in good agreement with the experiment.

An Improved Compact and High-Efficiency Relativistic Magnetron With TE11 Mode Radiation

An improved compact and high-efficiency A6 relativistic magnetron (RM) with axial extraction is proposed and studied by numerical simulations. Compared with the conventional design, two pairs of diametrically opposite cavities (four cavities) of the anode block are tapered onto the horn antenna for TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode radiation with high output efficiency. Due to the cutoff radius of the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode is the smallest in the circular waveguide, the diameter of the output waveguide could be reduced obviously. And the total axial length of the horn antenna could also be shortened accordingly. At the same time, a semitransparent cathode is used for quick startup and efficient beam-wave interaction. Results of the 3-D particle-in-cell (PIC) simulations show that over 1.25 GW output power with TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode is obtained at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${S}$ </tex-math></inline-formula> -band, when the electron beam voltage is 600 kV and the applied axial guiding magnetic field is 0.54 T. And the efficiency exceeds 66%. Simulation results also show that the output efficiency of the proposed RM keeps almost unchanged between 550 and 620 kV with fixed guiding magnetic field.

Study of influence of the charge granulometric composition on the quality of burned anodes

Many factors affect the quality of produced anodes: composition and grade of raw materials, recipe, technology, operating parameters, the granulometric composition of charge materials etc. The most significant influence is from the last factor. The article provides research results on the effect of fine fractions on the quality of anodes. The research object is charge of different granulometric composition used to produce anodes at the Kazakhstan Electrolysis plant in Pavlodar. Six types of anode mass with different granulometric composition were prepared for the experiment. The anode mass was made of petroleum coke, pitch, recycled anodes, and dust from filters and grinder produced during coke treatment. Several properties of the specimens were studied. In total, six specimens were made and, specimen № 4 drew particular attention. Its granulometric composition is as following: coarse fractions – 25 %, medium fractions – 20%, fine fractions (grinder dust) – 50 %, and filter dust – 5 %. The results showed that some specifications of anodes, like gas permeability and apparent density that affect anode consumption, are improved as the fineness of dust grinding. For instance, the addition of dust fraction in the charge increases anode density from 1.542 to 1.639 kilogram per cubic decimeters and decreases gas permeability from 1.01 to 0.78 nPm. In addition, the presence of dust fraction minimizes the porosity of the anode block. The results of the investigation help adjust the optimal recipe of anode mass to obtain high-quality anodes.

Compact High Efficiency Relativistic Magnetron With TE11 Mode Output

A compact high-efficiency GW-level <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${S}$ </tex-math></inline-formula> -band relativistic magnetron (RM) with TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode output is proposed. In order to achieve high efficiency and high power, an eight-cavity slow wave system with rectangular vanes is adopted, which can provide a larger resonant system where the high-frequency energy is directly stored. All cavity axial extraction (ACAE) is applied with four 90° sector waveguides arranged azimuthally around the anode block. The four 90° sector waveguides play a significant role in converting sector waveguide TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode to circular waveguide TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode. The entire tube is designed without any increase in the radial dimension, which is propitious to a compact and lightweight magnet system design. In particle-in-cell (PIC) simulations, the proposed rectangular vane-type 8-cavity (R8) RM with ACAE can generate a microwave power of 2.1 GW with a pure TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode at the frequency of 2.475 GHz when the applied voltage is 460 kV and the axial magnetic field is 0.46 T, and the power conversion efficiency is 68.4%.

A Rectangular Vane-Type Relativistic Magnetron With Diffraction Output

In this article, a GW-level and high-efficiency $S$ -band eight-cavity relativistic magnetron with diffraction output (MDO) is proposed. A rectangular profile vane-type anode block is adopted to increase the volume of resonators, which leads to a promising higher output power. In particle-in-cell (PIC) simulations, the proposed eight-cavity MDO generates 2.5 GW output power with a power conversion efficiency of 70% when the applied voltage is 460 kV and the axial magnetic field is 0.44 T. The operation mode, $\pi $ -mode, oscillates at 2.75 GHz. The proposed eight-cavity MDO generates an RF output power over 2 GW in a wide range of voltages and magnetic fields, which exhibits its reliable performance in $\pi $ -mode.

Suppression of Spurious Cavity Modes Using Lossy Dielectric Material in X-Band Tunable Coaxial Pulse Magnetron

This article presents the electromagnetic and particle-in-cell (PIC) simulation results of an X-band coaxial magnetron obtained using commercially available 3-D simulation tools CST particle studio. The operating frequency of the magnetron is 9.5 GHz with the tuning range of 8.5-9.5 GHz and the output power of 200 kW. It is observed by simulation that stable operation is not possible without eliminating the spurious cavity modes. For this purpose, the inner wall of the anode block has been loaded with the lossy dielectric material in the form of an annular cylinder having dielectric permittivity 23 and loss tangent 0.24. When the anode wall is loaded with lossy dielectric material, eight space charge spokes are observed during the stable operation of the magnetron which correspond to π-mode of operation in a coaxial magnetron having 16 vanes. A clear oscillation spectrum with a single peak is observed at 9.350 GHz with no other noticeable peaks. The radiated output power obtained in simulations is about 235 kW, with an anode voltage of 23 kV and an anode current of 30 A. The applied external magnetic field is 0.36 T and the corresponding efficiency of the magnetron operation is ~34%. The frequency tunability of the magnetron and the effect of frequency variation on the output power of the magnetron have also been studied by varying the length of the outer coaxial cavity. The frequency has been varied from 8.65 to 9.577 GHz and the corresponding variation in the output power is about 16%.

Low-Voltage Kᵤ-Range Magnetron With Two Outputs of Energy: Design Features and Main Advantages

This article presents a design of the low-voltage ${K}_{u}$ -range magnetron with two outputs of energy: an active with matched load and a passive that is matched with a load having reactive impedance and providing frequency tuning (or its adjustment). Studying the magnetron is carried out in continuous and pulsed modes under the following input operating parameters: an operating anode voltage varied in a range of 450–500 V, a magnetic field of 0.25 T, a pulse length of 5–20 $\mu $ s, a pulse repetition rate between 100 and 300 Hz, and the magnetron weight ~0.85 kg subject to air cooling. The results of computer modeling the mode spectrum of a cold resonant anode block of the magnetron show that the separation between the operating N/2-mode and the closest low-voltage (N/2-1)-mode is ~1.6 GHz. Under these conditions, it is shown that the maximum frequency tuning of the cold resonant anode block is ~250 MHz. It is shown that the results of experimental studies of frequency tuning in the magnetron depend on the value of reactive loading in the second (passive) output. The limiting value of the frequency tuning range of the “hot” magnetron is ~110 MHz, providing an output average power of 15 W at ~36% efficiency. The available results of computer modeling are in good agreement with the experiment data. The implementation of the mode of frequency tuning enables to extend the functionality of the magnetron and a range of tasks that can be solved.