Excited state population density and spontaneous emission probabilities ХеI plasma of Hall Thruster

Аuthors

Krivoruchko D. D.^*, Skrylev A. V., Skorokhod E. P.^**

Moscow Institute of Physics and Technology (National Research University), 9, Institutskiy per., Dolgoprudny, Moscow region, 141701, Russia

*e-mail: daria.krivoruchko@phystech.edu
**e-mail: e.p.skorohod@mail.ru

Abstract

In the bginning of the paper a low-temperature xenon plasma of Hall Thruster (HT) was investigated by spectroscopic measurements in the 250‒1100 nm range. More than 50 xenon atoms (Xe I) transitions were explored. A measure light power emitted by the plume at optical range was found to be about 0,5 W.

The spontaneous emission probabilities (Einstein coefficients) for xenon atom were calculated at the Coulomb approximation (~800 transitions). The obtained results were compared with the results of other authors. By analysis the Hall thruster spectrum Xe I excited state concentrations were identified for 25 terms use getting Einstein coefficients.

According to Maxwell’s electrons and Boltzmann distribution the value of excited state concentrations as a function of their energy is a line with line inclination equal to , where – ionization potential from ground state. However, the obtained excited state distribution is poorly approximated by linear dependence and more resembling «swarm» distribution. Measured spectral lines intensities have little differences for each location of collection optics. That could be conditional on heterogeneity of HT plume. However, the mode of the excited state population density persist. That gives evidence of plasma beyond the thruster exit plane common character and unfitness local thermodynamic equilibrium or Coronal model for describe HT plume plasma. In other words, one needs multilevel kinetic model allowing calculate excited state population density which agrees with experimental results for identification electron and nuclear temperature and concentrations.

Keywords:

xenon, phototransition probabilities (Einstein coefficient) XeI, Hall Thruster excited plasma states concentraions

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