The Experts below are selected from a list of 19023 Experts worldwide ranked by ideXlab platform
L. Bárdoš - One of the best experts on this subject based on the ideXlab platform.
-
Radio frequency powered spiral Hollow Cathodes
Vacuum, 2020Co-Authors: L. Bárdoš, Hana BarankovaAbstract:Abstract Potential usage of the radio frequency (RF) spiral Hollow electrodes in comparison with the compact Hollow Cathodes was examined for coating and other surface processing treatments. Most properties were found similar to the compact RF Hollow Cathodes. The non-conventional shapes of spiral Hollow Cathodes can be suitable for the inner coating in narrow tubes and pipes. Small diameter spiral Cathodes can generate focused high-density ion flux capable of rapid etching of the substrate.
-
Optimization and performance of atmospheric Fused Hollow Cathodes
Vacuum, 2013Co-Authors: Hana Barankova, L. BárdošAbstract:Experimental results on the atmospheric Hollow cathode plasma generation and performance, using a special configuration with tunable wall separations, are presented. The influence of the gas and type of the power used for generation on the optimum size of the cathode slit is investigated. The experimental results are in agreement with the Hollow cathode model. The plasma source/plasma reactor design is of utmost importance for control of plasma-chemical kinetics. An example of the atmospheric Hollow cathode plasma application for the NOx conversion is given. The energy consumption and plasma characteristics are discussed.
-
On Dimensions of Atmospheric-Pressure Hollow Cathodes
IEEE Transactions on Plasma Science, 2007Co-Authors: Daniel Söderström, Hana Barankova, L. BárdošAbstract:The Hollow cathode is known as a source of high-density plasmas. This property is due to the Hollow-cathode effect (HCE), which can be explained by the oscillations of fast electrons between repelling potentials of opposing space-charge sheaths. At atmospheric pressure, one should be able to create an HCE by adjusting the dimension of the Hollow cathode. Experiments show that the dimensions could be as large as 500, so that the sheath thickness may be on the order of 100. Theoretical models of the atmospheric-pressure sheaths based on the conventional Child-Langmuir approach give the sheath thicknesses on the order of 10, which contradicts the experiments. We introduce here a new model which takes into account three groups of electrons: slow, fast, and secondary. By adding a group of fast and secondary electrons, we show that the sheath thickness increases as compared with only slow electrons present.
-
Hollow cathode and hybrid plasma processing
Vacuum, 2006Co-Authors: Hana Barankova, L. BárdošAbstract:Abstract Generation and features of the radio frequency (rf) Hollow cathode discharge (HCD) and its transition into the Hollow cathode arc (HCA) are described. Rf linear Hollow Cathodes for generation of plasma over large areas and suitable for further scale-up are presented. Examples of surface processing and coating by PVD, both by HCD and HCA, are given. The hybrid reactor, combining Hollow cathode and microwave plasmas, integrates features of both and provides more options to control plasma characteristics and consequently properties of deposited films. The rf Hollow Cathodes can be operated in both, PVD and PE CVD regimes, depending on process parameters. These regimes can even be combined within one process. New concepts of fused Hollow cathode (FHC), microwave antenna (MWA) and Hybrid Hollow electrode activated discharge (H-HEAD) cold atmospheric plasma sources are introduced. The FHC with its modular concept can be used for gas conversion, cleaning and for surface treatment of temperature-sensitive materials at ambient atmosphere. The H-HEAD cold atmospheric plasma source, capable of generating plasma plumes more than 15 cm long, enables treatment of 3-d and complex geometry objects even at low gas flows.
-
performance of radio frequency Hollow Cathodes at low gas pressures
Surface & Coatings Technology, 2003Co-Authors: L. Bárdoš, Hana Barankova, Yu A LebedevAbstract:Abstract Typical Hollow Cathodes (HC) have distances between opposite inner walls in a millimeter range and can operate at gas pressures of approximately 0.1–10 Torr (13.3–1333 Pa). This is because the pressure and the cathode geometry must fulfill the condition for the Hollow cathode effect, based on electron exchange between opposite walls. In this paper, we report on the performance of the radio frequency powered cylindrical and linear HC, with the gas flowing through the cathode, at the mTorr (0.1 Pa) pressure range typical for magnetron sputters or arc evaporators. Operation of simple cylindrical HC with inner diameters exceeding 10 mm was possible at pressures down to 0.9 mTorr (0.12 Pa) in argon. The plasma ion density did not exceed magnitude of 10 9 cm −3 . However, a plasma density as high as 5×10 11 cm −3 was measured 15 cm below 16 cm long linear Magnets-in-Motion (M-M) HC in mTorr pressure range. The M-M Cathodes can be used as an efficient sputtering/evaporation source for large area PVD of films or incorporated into different hybrid PVD and PE CVD plasma systems with conventional sources for production of new quality coatings.
Ioannis G. Mikellides - One of the best experts on this subject based on the ideXlab platform.
-
recent progress in research and development of Hollow Cathodes for electric propulsion
Reviews of Modern Plasma Physics, 2019Co-Authors: Dan R. Lev, Daniela Pedrini, Ioannis G. Mikellides, Dan M Goebel, Benjamin A. Jorns, Michael McdonaldAbstract:Electric thrusters are finding increasing usage worldwide in spacecraft applications. Significant progress has been made in recent years in the modeling and performance of thermionic Hollow Cathodes used in flight thrusters, such as Hall and ion thrusters, or other types of plasma sources, such as for technological plasmas. The recent progress is surveyed in this paper through the discussion of six areas: Hollow cathode modeling and simulation, low-current Hollow Cathodes, high-current Hollow Cathodes, heaterless Hollow Cathodes, new thermionic insert materials, and plasma oscillations. This includes descriptions of Hollow cathode designs capable of < 1 A to over 300 A, advances in electron emitter and heating/starting technologies, and modeling and simulation of the plasma properties, thermal behavior and instabilities in the discharge. Advances in the understanding and technology in these areas and challenges that still need to be addressed and solved are discussed.
-
Recent progress in research and development of Hollow Cathodes for electric propulsion
Reviews of Modern Plasma Physics, 2019Co-Authors: Dan R. Lev, Daniela Pedrini, Ioannis G. Mikellides, Dan M Goebel, Benjamin A. Jorns, Michael S. McdonaldAbstract:Electric thrusters are finding increasing usage worldwide in spacecraft applications. Significant progress has been made in recent years in the modeling and performance of thermionic Hollow Cathodes used in flight thrusters, such as Hall and ion thrusters, or other types of plasma sources, such as for technological plasmas. The recent progress is surveyed in this paper through the discussion of six areas: Hollow cathode modeling and simulation, low-current Hollow Cathodes, high-current Hollow Cathodes, heaterless Hollow Cathodes, new thermionic insert materials, and plasma oscillations. This includes descriptions of Hollow cathode designs capable of
-
effects of viscosity in a partially ionized channel flow with thermionic emission
Physics of Plasmas, 2009Co-Authors: Ioannis G. MikellidesAbstract:The flow of the partially ionized gas inside thermionic Hollow Cathodes spans a diverse range of theoretical disciplines in plasma physics and fluid mechanics. Understanding and predicting the evolution of such flows has many practical implications because Hollow Cathodes are critical components of electric propulsion systems used onboard scientific and commercial spacecraft presently in space or in the mission planning stages. As space missions become more demanding of the propulsion system in terms of throughput, understanding and predicting failure mechanisms of the system becomes imperative. Two-dimensional numerical simulations of the partially ionized gas generated by a thermionic Hollow cathode have been performed to quantify the effects of viscosity inside the cylindrical channel of the device. A comparison of the inviscid and fully viscous flow fields shows that viscosity has a significant impact on the atomic species and a lesser effect on the ions. The internal pressure is determined to be more...
-
Tungsten and barium transport in the internal plasma of Hollow Cathodes
Journal of Applied Physics, 2009Co-Authors: James E. Polk, Ioannis G. Mikellides, Ira Katz, Angela M. CapeceAbstract:The effect of tungsten erosion, transport and redeposition on the operation of dispenser Hollow Cathodes was investigated in detailed examinations of the discharge cathode inserts from an 8200 hour and a 30,352 hour ion engine wear test. Erosion and subsequent re-deposition of tungsten in the electron emission zone at the downstream end of the insert reduces the porosity of the tungsten matrix, preventing the flow of barium from the interior. This inhibits the interfacial reactions of the barium-calcium-aluminate impregnant with the tungsten in the pores. A numerical model of barium transport in the internal xenon discharge plasma shows that the barium required to reduce the work function in the emission zone can be supplied from upstream through the gas phase. Barium that flows out of the pores of the tungsten insert is rapidly ionized in the xenon discharge and pushed back to the emitter surface by the electric field and drag from the xenon ion flow. This barium ion flux is sufficient to maintain a barium surface coverage at the downstream end greater than 0.6, even if local barium production at that point is inhibited by tungsten deposits. The model also shows that the neutral barium pressure exceeds the equilibrium vapor pressure of the impregnant decomposition reaction over much of the insert length, so the reactions are suppressed. Only a small region upstream of the zone blocked by tungsten deposits is active and supplies the required barium. These results indicate that Hollow cathode failure models based on barium depletion rates in vacuum dispenser Cathodes are very conservative.
-
insert heating and ignition in inert gas Hollow Cathodes
IEEE Transactions on Plasma Science, 2008Co-Authors: Ira Katz, Ioannis G. Mikellides, Dan M Goebel, James E. PolkAbstract:An extensive 2-D computational model of the fundamental ionization and transport processes that occur inside electric propulsion Hollow Cathodes has been developed over the last few years. The computed charged-particle fluxes from the plasma to the internal cathode surfaces have been used as input to a rudimentary Hollow-cathode thermal model also developed recently. It is shown that, in Hollow Cathodes with a very small diameter orifice, the plasma density peaks inside the orifice and that the cathode is heated primarily by the orifice plate which is, in turn, heated by the plasma inside the orifice and along the orifice plate. As the orifice diameter increases the peak plasma density moves upstream of the orifice with ions and electrons contributing to the heating of both the orifice plate and the insert. In Hollow Cathodes with a very large diameter orifice the plasma extends along much of the insert, the plasma density peaks well within the insert region, and the cathode is heated primarily by ion bombardment of the insert. By solving a 2-D axisymmetric boundary value problem, it is also shown that when a voltage is applied between the ends of a long cylindrical channel the potential in the absence of the plasma falls almost by one order of magnitude with each radius downstream of the entrance. The implication is that Cathodes with orifices of large length-to-radius ratio will be harder to ignite.
Dan M Goebel - One of the best experts on this subject based on the ideXlab platform.
-
recent progress in research and development of Hollow Cathodes for electric propulsion
Reviews of Modern Plasma Physics, 2019Co-Authors: Dan R. Lev, Daniela Pedrini, Ioannis G. Mikellides, Dan M Goebel, Benjamin A. Jorns, Michael McdonaldAbstract:Electric thrusters are finding increasing usage worldwide in spacecraft applications. Significant progress has been made in recent years in the modeling and performance of thermionic Hollow Cathodes used in flight thrusters, such as Hall and ion thrusters, or other types of plasma sources, such as for technological plasmas. The recent progress is surveyed in this paper through the discussion of six areas: Hollow cathode modeling and simulation, low-current Hollow Cathodes, high-current Hollow Cathodes, heaterless Hollow Cathodes, new thermionic insert materials, and plasma oscillations. This includes descriptions of Hollow cathode designs capable of < 1 A to over 300 A, advances in electron emitter and heating/starting technologies, and modeling and simulation of the plasma properties, thermal behavior and instabilities in the discharge. Advances in the understanding and technology in these areas and challenges that still need to be addressed and solved are discussed.
-
Recent progress in research and development of Hollow Cathodes for electric propulsion
Reviews of Modern Plasma Physics, 2019Co-Authors: Dan R. Lev, Daniela Pedrini, Ioannis G. Mikellides, Dan M Goebel, Benjamin A. Jorns, Michael S. McdonaldAbstract:Electric thrusters are finding increasing usage worldwide in spacecraft applications. Significant progress has been made in recent years in the modeling and performance of thermionic Hollow Cathodes used in flight thrusters, such as Hall and ion thrusters, or other types of plasma sources, such as for technological plasmas. The recent progress is surveyed in this paper through the discussion of six areas: Hollow cathode modeling and simulation, low-current Hollow Cathodes, high-current Hollow Cathodes, heaterless Hollow Cathodes, new thermionic insert materials, and plasma oscillations. This includes descriptions of Hollow cathode designs capable of
-
note improved heater design for high temperature Hollow Cathodes
Review of Scientific Instruments, 2017Co-Authors: M S Mcdonald, Alec D Gallimore, Dan M GoebelAbstract:We present an improved heater design for thermionic Cathodes using a rhenium filament encased in a boron nitride ceramic sleeve. This heater is relatively simple to fabricate, yet has been successfully used to reliably and repeatably light a lanthanum hexaboride (LaB6) Hollow cathode based on a previously published design without noticeable filament degradation over hundreds of hours of operation. The high decomposition temperature of boron nitride (2800 C for inert environments) and melting point for rhenium (3180 C) make this heater especially attractive for use with LaB6, which may require operating temperatures upwards of 1700 C. While boron nitride decomposes in air above 1000 C, the heater was used only at vacuum with an inert gas discharge, and no degradation was observed. Limitations of current state of the art cathode heaters are also discussed and compared with the rhenium-boron nitride combination.
-
reduction of energetic ion production in Hollow Cathodes by external gas injection
Journal of Propulsion and Power, 2013Co-Authors: Emily Chu, Dan M Goebel, Richard E. WirzAbstract:Studies of the Hollow-cathode discharge have shown the existence of energetic ions at high-discharge currents that are likely responsible for the high erosion rates observed on the cathode keeper electrode. This work examines the effect of neutral gas injection in the discharge plume of a 250 A lanthanum hexaboride Hollow cathode on the production of energetic ions to determine the conditions that yield cathode operation and life. Two different gas injector types are used to deliver neutral gas into the discharge plume and a retarding-potential analyzer is used for ion energy measurements. The flow splits between the cathode internal and external flows, and the number and locations of the external gas injection sites are examined as a function of the discharge current. It is found that increasing discharge current increases the energetic ion production at any given flow rate or injection location. External gas injection reduces energetic ion production for constant cathode flow, with collimated gas-jet in...
-
insert heating and ignition in inert gas Hollow Cathodes
IEEE Transactions on Plasma Science, 2008Co-Authors: Ira Katz, Ioannis G. Mikellides, Dan M Goebel, James E. PolkAbstract:An extensive 2-D computational model of the fundamental ionization and transport processes that occur inside electric propulsion Hollow Cathodes has been developed over the last few years. The computed charged-particle fluxes from the plasma to the internal cathode surfaces have been used as input to a rudimentary Hollow-cathode thermal model also developed recently. It is shown that, in Hollow Cathodes with a very small diameter orifice, the plasma density peaks inside the orifice and that the cathode is heated primarily by the orifice plate which is, in turn, heated by the plasma inside the orifice and along the orifice plate. As the orifice diameter increases the peak plasma density moves upstream of the orifice with ions and electrons contributing to the heating of both the orifice plate and the insert. In Hollow Cathodes with a very large diameter orifice the plasma extends along much of the insert, the plasma density peaks well within the insert region, and the cathode is heated primarily by ion bombardment of the insert. By solving a 2-D axisymmetric boundary value problem, it is also shown that when a voltage is applied between the ends of a long cylindrical channel the potential in the absence of the plasma falls almost by one order of magnitude with each radius downstream of the entrance. The implication is that Cathodes with orifices of large length-to-radius ratio will be harder to ignite.
Hana Barankova - One of the best experts on this subject based on the ideXlab platform.
-
Radio frequency powered spiral Hollow Cathodes
Vacuum, 2020Co-Authors: L. Bárdoš, Hana BarankovaAbstract:Abstract Potential usage of the radio frequency (RF) spiral Hollow electrodes in comparison with the compact Hollow Cathodes was examined for coating and other surface processing treatments. Most properties were found similar to the compact RF Hollow Cathodes. The non-conventional shapes of spiral Hollow Cathodes can be suitable for the inner coating in narrow tubes and pipes. Small diameter spiral Cathodes can generate focused high-density ion flux capable of rapid etching of the substrate.
-
Optimization and performance of atmospheric Fused Hollow Cathodes
Vacuum, 2013Co-Authors: Hana Barankova, L. BárdošAbstract:Experimental results on the atmospheric Hollow cathode plasma generation and performance, using a special configuration with tunable wall separations, are presented. The influence of the gas and type of the power used for generation on the optimum size of the cathode slit is investigated. The experimental results are in agreement with the Hollow cathode model. The plasma source/plasma reactor design is of utmost importance for control of plasma-chemical kinetics. An example of the atmospheric Hollow cathode plasma application for the NOx conversion is given. The energy consumption and plasma characteristics are discussed.
-
On Dimensions of Atmospheric-Pressure Hollow Cathodes
IEEE Transactions on Plasma Science, 2007Co-Authors: Daniel Söderström, Hana Barankova, L. BárdošAbstract:The Hollow cathode is known as a source of high-density plasmas. This property is due to the Hollow-cathode effect (HCE), which can be explained by the oscillations of fast electrons between repelling potentials of opposing space-charge sheaths. At atmospheric pressure, one should be able to create an HCE by adjusting the dimension of the Hollow cathode. Experiments show that the dimensions could be as large as 500, so that the sheath thickness may be on the order of 100. Theoretical models of the atmospheric-pressure sheaths based on the conventional Child-Langmuir approach give the sheath thicknesses on the order of 10, which contradicts the experiments. We introduce here a new model which takes into account three groups of electrons: slow, fast, and secondary. By adding a group of fast and secondary electrons, we show that the sheath thickness increases as compared with only slow electrons present.
-
Hollow cathode and hybrid plasma processing
Vacuum, 2006Co-Authors: Hana Barankova, L. BárdošAbstract:Abstract Generation and features of the radio frequency (rf) Hollow cathode discharge (HCD) and its transition into the Hollow cathode arc (HCA) are described. Rf linear Hollow Cathodes for generation of plasma over large areas and suitable for further scale-up are presented. Examples of surface processing and coating by PVD, both by HCD and HCA, are given. The hybrid reactor, combining Hollow cathode and microwave plasmas, integrates features of both and provides more options to control plasma characteristics and consequently properties of deposited films. The rf Hollow Cathodes can be operated in both, PVD and PE CVD regimes, depending on process parameters. These regimes can even be combined within one process. New concepts of fused Hollow cathode (FHC), microwave antenna (MWA) and Hybrid Hollow electrode activated discharge (H-HEAD) cold atmospheric plasma sources are introduced. The FHC with its modular concept can be used for gas conversion, cleaning and for surface treatment of temperature-sensitive materials at ambient atmosphere. The H-HEAD cold atmospheric plasma source, capable of generating plasma plumes more than 15 cm long, enables treatment of 3-d and complex geometry objects even at low gas flows.
-
performance of radio frequency Hollow Cathodes at low gas pressures
Surface & Coatings Technology, 2003Co-Authors: L. Bárdoš, Hana Barankova, Yu A LebedevAbstract:Abstract Typical Hollow Cathodes (HC) have distances between opposite inner walls in a millimeter range and can operate at gas pressures of approximately 0.1–10 Torr (13.3–1333 Pa). This is because the pressure and the cathode geometry must fulfill the condition for the Hollow cathode effect, based on electron exchange between opposite walls. In this paper, we report on the performance of the radio frequency powered cylindrical and linear HC, with the gas flowing through the cathode, at the mTorr (0.1 Pa) pressure range typical for magnetron sputters or arc evaporators. Operation of simple cylindrical HC with inner diameters exceeding 10 mm was possible at pressures down to 0.9 mTorr (0.12 Pa) in argon. The plasma ion density did not exceed magnitude of 10 9 cm −3 . However, a plasma density as high as 5×10 11 cm −3 was measured 15 cm below 16 cm long linear Magnets-in-Motion (M-M) HC in mTorr pressure range. The M-M Cathodes can be used as an efficient sputtering/evaporation source for large area PVD of films or incorporated into different hybrid PVD and PE CVD plasma systems with conventional sources for production of new quality coatings.
Daniela Pedrini - One of the best experts on this subject based on the ideXlab platform.
-
recent progress in research and development of Hollow Cathodes for electric propulsion
Reviews of Modern Plasma Physics, 2019Co-Authors: Dan R. Lev, Daniela Pedrini, Ioannis G. Mikellides, Dan M Goebel, Benjamin A. Jorns, Michael McdonaldAbstract:Electric thrusters are finding increasing usage worldwide in spacecraft applications. Significant progress has been made in recent years in the modeling and performance of thermionic Hollow Cathodes used in flight thrusters, such as Hall and ion thrusters, or other types of plasma sources, such as for technological plasmas. The recent progress is surveyed in this paper through the discussion of six areas: Hollow cathode modeling and simulation, low-current Hollow Cathodes, high-current Hollow Cathodes, heaterless Hollow Cathodes, new thermionic insert materials, and plasma oscillations. This includes descriptions of Hollow cathode designs capable of < 1 A to over 300 A, advances in electron emitter and heating/starting technologies, and modeling and simulation of the plasma properties, thermal behavior and instabilities in the discharge. Advances in the understanding and technology in these areas and challenges that still need to be addressed and solved are discussed.
-
Recent progress in research and development of Hollow Cathodes for electric propulsion
Reviews of Modern Plasma Physics, 2019Co-Authors: Dan R. Lev, Daniela Pedrini, Ioannis G. Mikellides, Dan M Goebel, Benjamin A. Jorns, Michael S. McdonaldAbstract:Electric thrusters are finding increasing usage worldwide in spacecraft applications. Significant progress has been made in recent years in the modeling and performance of thermionic Hollow Cathodes used in flight thrusters, such as Hall and ion thrusters, or other types of plasma sources, such as for technological plasmas. The recent progress is surveyed in this paper through the discussion of six areas: Hollow cathode modeling and simulation, low-current Hollow Cathodes, high-current Hollow Cathodes, heaterless Hollow Cathodes, new thermionic insert materials, and plasma oscillations. This includes descriptions of Hollow cathode designs capable of
-
Triple Langmuir Probes Measurements of LaB6 Hollow Cathodes Plume
Frontiers Media S.A., 2019Co-Authors: Giulia Becatti, Daniela Pedrini, Fabrizio Paganucci, Bhargav Kasoji, Mariano AndrenucciAbstract:Lanthanum hexaboride Hollow Cathodes represent a viable option for high power Hall effect thruster applications, under development for the next generation of manned and robotic interplanetary missions. In this scenario, SITAEL and the University of Pisa are actively developing high current Hollow Cathodes capable of providing discharge current in the range 10–100 A to be coupled with high power Hall effect thrusters. The cathode design is based on an in-house theoretical model of the internal sections of the cathode, recently integrated with a simplified model of the cathode plume. Despite the application of Hollow Cathodes on flight and laboratory model Hall effect thrusters, many questions remain unsolved. In particular, issues related to onset of instabilities, due to plume mode or ion acoustic turbulence, are still unclear, while it is known that they can affect the overall performance of the cathode and thruster unit. This paper focuses on the experimental investigation of the cathode plume by means of measurements of the main plasma parameters, at different operating conditions and for different cathode geometry. Two Cathodes were investigated, namely HC20 and HC60, designed to be coupled with SITAEL's HT5k and HT20k (5 kW- and 20 kW-class) Hall effect thrusters. The Cathodes were mounted in stand-alone configuration with an auxiliary cylindrical anode. The experimental campaign was performed using triple Langmuir probes as plasma diagnostic system. The probes were mounted on scanning mechanisms to measure the plume parameters at various radial and axial distances from the keeper exit. General trends of electron temperature, plasma potential and plasma density are reported in terms of discharge current, mass flow rate and cathode orifice geometry. The results highlight that the cathode plate orifice selection affects the plume mode onset, giving the possibility to extend the stable mode of cathode operation in the current range required by the thruster
-
sitael Hollow Cathodes for low power hall effect thrusters
IEEE Transactions on Plasma Science, 2017Co-Authors: Daniela Pedrini, Fabrizio Paganucci, Tommaso Misuri, C Ducci, Mariano AndrenucciAbstract:Low-power Hall effect thrusters (HETs) belong to a class of electric thrusters with an operating power lower than 500 W. The application of this class of HETs is suited for small satellites for telecommunications and Earth observation missions. Sitael is active in this field, through the development of two HETs, HT100, and HT400, belonging to a power class of 100 and 400 W, respectively. HT100 is a permanent-magnet thruster operating in the 100- to 250-W range, providing thrust between 4 and 13 mN, and specific impulse between 900 and 1400 s. HT400 operates in the 350- to 750-W range, providing thrust between 20 and 45 mN, and specific impulse between 1300 and 1700 s. Two Cathodes have been developed and tested, referred to as HC1 and HC3, conceived for HT100 and HT400, respectively. Both Cathodes are based on Sitael heritage in theoretical modeling and experimental activities for the development of such devices, and rely on lanthanum hexaboride emitters. HC1 is a cathode designed to provide a discharge current in the 0.3-1 A range, operating in steady-state conditions at mass flow rates between 0.08 and 0.5 mg/s of xenon. HC3 was designed for the range 1-3 A of discharge current, with 0.08-0.5 mg/s of mass flow rate. Both HC1 and HC3 have an expected lifetime higher than 10 4 h, based on the rate of material evaporation from the emitter surface, computed with the aid of a theoretical model developed to guide the cathode design. Experiments were carried out, including preliminary characterization campaigns, of each of the two Cathodes and HET-cathode coupling tests. The collected data are presented and discussed with reference to the model predictions, showing a good agreement between theoretical and experimental results.
-
development of Hollow Cathodes for space electric propulsion at sitael
Aerospace, 2017Co-Authors: Daniela Pedrini, Fabrizio Paganucci, Tommaso Misuri, Mariano AndrenucciAbstract:Hollow Cathodes are electron sources used for the gas ionization and the beam neutralization in both ion and Hall effect thrusters (HETs). A reduction of power and propellant consumption from the cathode is particularly needed in small satellite applications, where power and mass budgets are inherently limited. Concurrently, the interest in high-power HETs is increasingly fostered for a number of space applications, including final positioning and station-keeping of Geostationary Earth Orbit (GEO) satellites, spacecraft transfers from Low Earth Orbit (LEO) to GEO, and deep-space exploration missions. As such, several Hollow Cathodes have been developed and tested at Sitael, each conceived for a specific power class of thrusters. A numerical model was used during the cathode design to define the geometry, in accordance with the thruster unit specifications in terms of discharge current, mass flow rate, and lifetime. Lanthanum hexaboride (LaB6) Hollow Cathodes were successfully developed for HETs with discharge power ranging from 100 W to 20 kW. Experimental campaigns were carried out in both stand-alone and coupled configurations, to verify the operation of the Cathodes and validate the numerical model. The comparison between experimental and theoretical results are presented, offering a sound framework to drive the design of future Hollow Cathodes.