4/30/2023 0 Comments Diode cathode anode![]() ![]() The three groups, along with the associated plasma discharge and energy transfer mechanisms, are presented via a discussion of long-standing technologies like arcjet thrusters, magnetoplasmadynamic thrusters, pulsed plasma thrusters and ion engines, as well as Hall thrusters and variants. Plasma thrusters are classically grouped into three categories according to the thrust generation process: electrothermal, electrostatic and electromagnetic devices. Subsequently, the influence of the power source type and characteristics on the mission profile is discussed. ![]() This article first describes the fundamentals of EP: momentum conservation and the ideal rocket equation, specific impulse and thrust, figures of merit and a comparison with chemical propulsion. Although the development of EP goes back to the 1960s, the technology potential has just begun to be fully exploited because of the increase in the available power aboard spacecraft, as demonstrated by the very recent appearance of all-electric communication satellites. Electric thrusters, also termed ion or plasma thrusters, deliver a low thrust level compared to their chemical counterparts, but they offer significant advantages for in-space propulsion as energy is uncoupled to the propellant, therefore allowing for large energy densities. This contribution presents a short review of electric propulsion (EP) technologies for satellites and spacecraft. Temperature measurements performed with thermocouples reveal that the LaB6 insert is moderately heated during the cathode operation (about 1600 ☌ at 19 A), except for the lowest mass flow rate. Particular attention was paid to the identification of the discharge mode (spot versus plume) through spectral analysis of discharge current waveforms. Electrical parameters and temperature of several parts, including the LaB6 insert, were collected and analyzed in order to investigate the possibility of operating the cathode in an extended range of discharge current with respect to its nominal condition (5 A at 0.4 mg.s⁻¹). The paper presents the characterization of the LaB6 cathode operated at xenon mass flow rates between 0.2 and 0.6 mg.s⁻¹ with discharge currents ranging from 2 A to 19 A. The cathode design is based on the direct heating of a flat disk lanthanum hexaboride (LaB6) insert to emit electrons. A laboratory model of a 5 A-class cathode has been experimentally studied in the so-called diode configuration with a flat metal anode. Changes in plasma property were also noticed, the cathode-anode gap increase inducing lower plasma density and higher electron temperature in the cathode plume.Ĭathodes are electron sources used for gas ionization and ion beam neutralization in Hall thrusters. It was demonstrated that an increase in the cathode-anode gap induces the discharge mode transition from spot mode, corresponding to lower gap values, to plume mode, corresponding to higher gap values. ![]() Particular attention was paid to the identification of the discharge mode and mode transition based on spectral analysis of discharge current waveforms. Both electrical and plasma parameters were collected and analyzed in order to highlight the main changes in cathode discharge when the cathode-anode gap was increased. For this purpose, the cathode was operated at 4 A and 0.6 mg s⁻¹ and at 10 A and 0.6 mg s⁻¹, while the cathode-anode gap was increased from 20 mm to 70 mm. Apart from the operating envelope and discharge mode (spot versus plume) differentiation, the influence of anode position on cathode discharge mode was studied. The paper reports the characterization of the LaB6 cathode operated at xenon mass flow rates between 0.4 and 1.0 mg s⁻¹ with discharge currents ranging from 2 A to 12 A. Electron emission is achieved using a heating element in direct contact with the insert. The core of the cathode is a flat disk lanthanum hexaboride (LaB6) insert. A laboratory model of a 5 A-class cathode was experimentally studied in diode configuration with a disk anode.
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