Oscillation-Modes Of Stationary Plasma Thruster And Their Factors

Stationary Plasma Thruster (SPT) as one kind of hall thruster will be used broadly in spaceflight, it can provide power for satellites control, orbit transfer and so on. The low frequency oscillation (LFO) of discharge current has notable effect on the life-span of the thruster and the EMC of the satellites. Therefore the mechanism of the oscillation is being paid high attention by many research teams. The waveform of discharge current changes from LFO to chaotic oscillation under some conditions. Chaotic oscillation has small amplitude and broad spectrum. In this dissertation, the two modes of oscillation were researched by both examination and emulator, the details are followings:A test platform was built for internal tests of SPT. The float potential and ion saturation current under the two oscillations-modes were synchronically measured at different internal position of SPT. The control rule of the magnetic configuration and the oscillation modes was given. It proved that the distribution of potential in chaotic oscillation mode was better than the one in LFO mode. The current measured at different positions were not synchronization. The ion velocity was given.One-dimensional hydrodynamic model was improved. The relationship between ion density and conductance was added to the model. The numerical calculation results of the improved model better matched the experimental results on the waveform of discharge current and internal electric field. The dynamic data of many internal parameters were shown by the calculated results.A more quantificational method, improved false nearest neighbors, was applied to study the chaotic oscillation. The oscillations-modes of the discharge current were distinguished between different ionization rate and different atom density. The results show that the ionization source term was the result of the transformation of the oscillations-modes. Then the basic control mechanism of ionization source term over the oscillation-modes was expounded.Both of the current pulse during ignition process and the residual impulse during shutdown process were studied. The numerical results shown that it was the avalanche ionization of the propellant, which the channel was full of, that led to the current pulse and the residual impulse results from the volume effect.