High-spatial-resolution image reconstruction-based method for measuring electron temperature and density of the very near field of an applied-field magnetoplasmadynamic thruster

Abstract

A method based on image reconstruction is proposed for measuring the electron temperature ( T e ) and density ( n e ) distribution of the axisymmetric low-temperature argon plasma plume of applied-field magnetoplasmadynamic thrusters (AF-MPDTs). The method uses a complementary metal–oxide–semiconductor camera with narrowband filters of 460 and 500 nm to obtain the raw projection images in specific wavelength ranges. An image reconstruction method is developed to construct relative emission intensity profiles. The electron temperature distribution can be obtained by combining the relative emission intensity ratio of two profiles with a simple argon kinetic model. The electron density distribution can be calculated by constructing a function of relative emission intensity containing T e and n e . To verify the feasibility of this method, we diagnosed a very near field plume of a 15 kW AF-MPDT and obtained the distribution of parameters with a spatial resolution of 0.23 mm. The results show that the maximum T e and n e are located on the centerline near the exit plane of the thruster and decrease with both radial and axial distances. The second peak appears in the radial direction of both the T e and n e distributions, while their zones do not overlap. A comparative analysis of measurement results obtained by this method and the Langmuir probe method is performed to prove its accuracy. Moreover, this measurement method has the advantages of high spatial resolution and the ability to diagnose high-density and magnetized plasma. This method can be also applied to other optically thin axisymmetric low-temperature argon plasmas.

Temperature measurement and simulation analysis of heaterless hollow cathode during start-up process

“…Its sensitivity range (350-700 nm) corresponds to most of the spectral lines of the xenon ions rather than those of atoms. The relative emission intensity is positively correlated with electron temperature and ion density [26]. The V-I characteristics of the anode and keeper are also recorded during this process.…”

A xenon collisional-radiative model applicable to electric propulsion devices: III. Determination of the ionization fraction in low-temperature xenon plasma by using ionic and atomic 6p lines

“…As a non-invasive method, optical emission spectroscopy (OES) is widely applied in the diagnostics of the electron temperature [27][28][29][30], the electron density [31,32], and the gas temperature [33,34]. Combined with the spectral imaging method, OES can obtain sub-millimeter-level spatially-resolved distributions of the above-mentioned plasma parameters [35,36]. The literature shows that the spectral lines of ionic and atomic species have been observed simultaneously in argon, krypton, xenon, and iodine plasmas [37][38][39][40], and the emission lineratios of the ionic and atomic species are related to the ionization fraction [41,42].…”

A plasma equilibrium model for rapid estimation of SF-MPDT performance

“…In the early rise period of MPDT development, SF-MPDT is the most commonly type [3], whose structure and operating principles are shown in the figure 1(a). During the operation of SF-MPDTs, electric arcs are formed by discharging between the cathode and the anode, which ionizes the propellants, among others, H 2 , N 2 , Ar, Xe, Li [4], producing a high-temperature, high-density plasma. There will be a large radial current (~kA) passing through the plasma, which will generate a circumferential induced magnetic field between the cathode and the anode, and an axial Lorentz force is generated through the interaction between the magnetic and the current [5].…”