Effect of preionization in Aton-type Hall thruster on low frequency oscillation

Abstract

It was found through the experiments made with an Aton-type Hall thruster that some of the propellant was ionized in the buffer chamber by “quick electrons.” This ionization is called “preionization” to discriminate it from the ionization in the discharge channel. The effect of preionization on low frequency oscillation was experimentally studied by changing the electric field intensity in the buffer chamber. The relationship between low frequency oscillation and preionization ratio was investigated through numerical simulation using a one-dimensional quasineutrality hydrodynamic model. The results obtained indicate that the amplitude of low frequency oscillation decreases as the preionization ratio increases. It was found through the analysis and numerical simulation of the physical process of low frequency oscillation that the positive feedback of electron density was the main cause of low frequency oscillation. The increase of preionization ratio decreases the amplitude of the feedback variation thereby reducing the amplitude of low frequency oscillation.

Effect of ionization distribution on the low frequency oscillations mode in Hall thrusters

“…This mode was also used to study the effects of pre-ionization and magnetic field strength on the low frequency oscillation. 9,13 The fundamental assumptions also can be found in Refs. 2, 6, and 9.…”

“…With the positive and negative feedback dominating alternately, the atom-front moves forward and backward periodically while the discharge current increases and decreases periodically. 9 The region of atom-front movement determines the scope of ionization region fluctuation. Though the atom ionization number density measured through spectrograph is steadystate characteristic, a narrow distribution of atom ionization number density shows that the ionization region (or the atomfront) moved in a small range.…”

“…1 Boeuf and Garriguse commented by saying that low frequency oscillation was associated with a small oscillation of the production zone location and of the front of neutral atoms, which was described as the "breathing" of the neutral flow. 8 This "breathing" of the neutral flow was also described as an exhibition of positive and negative feedback dominating alternately in the discharge channel by Yu et al 9 Based on the model in Ref. 8, Chable and Rogier pointed out that the low frequency oscillation was due to the coupling between ion current and self-consistent electric field, and it was known as Buneman's instability.…”

Modulating action of low frequency oscillations on high frequency instabilities in Hall thrusters

“…1 The low frequency oscillations are observed as a small oscillation of the production zone location and of the front of neutral atoms, which is described as the "breathing" of the neutral flow. 8 This "breathing" of the neutral flow is also described as an exhibition of positive and negative feedback dominating alternately in the discharge channel by Yu et al 9 Though the low frequency oscillations are commented at different angles, these oscillations are commonly referred to breathing oscillations 10 following a back-and-forth motion of the ionization front in numerical simulations. 7,8 With the development of experimental approach 11,12 and the surge of interest in the basic physics of Hall thrusters, the researches are conducted over a wide frequency range in the recent years.…”

Effect of Preionization on the Erosion of the Discharge Channel Wall in a Hall Thruster Using a Kinetic Simulation

“…The major cause of the low-frequency oscillation is the unstable ionization process resulting from the slow supplementing rate of the propellant [15]. The low-frequency oscillation has an adverse effect on the power processing unit, lowers its efficiency, and reduces the durability and stability of its operation [16]. Therefore, it is vital to develop an innovative thruster design to minimize the oscillation.…”