Quantitative spectroscopic studies of a pulsed plasma microthruster (Electric propulsion).

摘要

The absolute intensity of the emission spectra emitted from a PPT plume was studied from both experimental measurements and theoretical analysis to investigate its interference with an optical sensor/signal. The results were also used to estimate the absolute radiant-energy emitted from the PPT plume to compare with the input energy for the energy-budget analysis.; Initially the radiating species in the PPT plume were identified by the spectroscopic measurements. For the identified species, the absolute intensity was obtained in three methods. In the first method, the intensity was experimentally measured with the quantitative spectroscopic apparatus to provide the experimental intensity. In the second method, the intensity was theoretically calculated with the experimental results assuming the observed plasma to be spatially uniform and temporally constant for simplification to provide the spatially and temporally uniform (STU) semi-empirical theoretical intensity. In the third method, the intensity was theoretically calculated independently from the experimental results using the MACH2 magnetohydrodynamic code to provide the spatially and temporally nonuniform (STN) fully theoretical intensity.; The STU theoretical intensity has reasonable agreement with the experimental intensity to capture the trend although the STU values are larger by up to four times. This discrepancy was reduced by STN theoretical intensity which predicted well the experimental value. Using the result of the experimental intensity and the STN theoretical intensity, the radiant energy was estimated. The experimental and the theoretical radiant energies increase with the input energy in an approximately linear fashion. The result indicates that the radiative loss due to the spontaneous line emission in the range of 400 to 700 nm is at most 0.02% of the input energy.; The comparisons of absolute intensity measurements and calculations of radiant energy based on MACH2 MHD simulations indicate that such simulations can provide adequate guides for estimating the amount of radiation from PPTs.