Effect of Segmented Electrode Length on the Performances of an Aton-Type Hall Thruster

The influences of the low-emissive graphite segmented electrode t）laeed near the channel exit on the discharge characteristics of a Hall thruster are studied using the particle- in-cell method. A two-dimensional physical model is established according to the Hall thruster discharge channel configuration. The effects of electrode length on the potential, ion density, electron temperature, ionization rate and discharge current are investigated. It is found that, with tile increasing of the segmented electrode length, the equipotential lines bend towards the channel exit. and approximately parallel to the wall at the channel surface, the radial velocity and radial flow of ions are increased, and the electron temperature is also enhanced. Due to the conductive characteristic of electrodes, the radial electric field and the axial electron conductivity near the wall are enhanced, and the probability of the electron-atom ionization is reduced, which leads to the degradation of the ionization rate in the discharge channel. However, the interaction between electrons and the wall enhances the near wall conductivity, therefore the discharge current grows along with the segmented electrode length, and the performance of the thruster is also affected.

Numerical study on the electron-wall interaction in a Hall thruster with segmented electrodes placed at the channel exit

Electron-wall interaction is always recognized as an important physical problem because of its remarkable influences on thruster discharge and performance. Based on existing theories, an electrode is predicted to weaken electron-wall interaction due to its low secondary electron emission characteristic. In this paper, the electron-wall interaction in an Aton-type Hall thruster with low-emissive electrodes placed near the exit of discharge channel is studied by a fully kinetic particle-in cell method. The results show that the electron-wall interaction in the region of segmented electrode is indeed weakened, but it is significantly enhanced in the remaining region of discharge channel. It is mainly caused by electrode conductive property which makes equipotential lines convex toward channel exit and even parallel to wall surface in near-wall re- gion; this convex equipotential configuration results in significant physical effects such as repelling electrons, which causes the electrons to move toward the channel center, and the electrons emitted from electrodes to be remarkably accelerated, thereby increasing electron temperature in the discharge channel, etc. Furthermore, the results also indicate that the discharge current in the segmented electrode case is larger than in the non-segmented electrode case, which is qualitatively in accordance with previous experimental results.

Study on the influences of ionization region material arrangement on Hall thruster channel discharge characteristics

There exists strong interaction between the plasma and channel wall in the Hall thruster,which greatly affects the discharge performance of the thruster.In this paper,a two-dimensional physical model is established based on the actual size of an Aton P70 Hall thruster discharge channel.The particle-in-cell simulation method is applied to study the influences of segmented low emissive graphite electrode biased with anode voltage on the discharge characteristics of the Hall thruster channel.The influences of segmented electrode placed at the ionization region on electric potential,ion number density,electron temperature,ionization rate,discharge current and specific impulse are discussed.The results show that,when segmented electrode is placed at the ionization region,the axial length of the acceleration region is shortened,the equipotential lines tend to be vertical with wall at the acceleration region,thus radial velocity of ions is reduced along with the wall corrosion.The axial position of the maximal electron temperature moves towards the exit with the expansion of ionization region.Furthermore,the electron-wall collision frequency and ionization rate also increase,the discharge current decreases and the specific impulse of the Hall thruster is slightly enhanced.

Dielectric barrier micro-plasma reactor with segmented outer electrode for decomposition of pure CO_(2)

Four coaxial cylinder dielectric barrier discharge micro-plasma reactors were designed for the noncatalytic decomposition of pure CO_(2) into CO and O_(2) at low temperature and ambient pressure.The influence of segmented outer electrodes on the electrical characteristics and the reaction performance was investigated.Experimental results indicated that the introduction of segmented outer electrodes can significantly promote the decomposition of CO_(2).Encouragingly,the highest conversion of 13.1% was obtained at an applied voltage of 18 kV,which was a substantial increase of 39.4% compared to the traditional device.Compared with other types of dielectric barrier discharge plasma reactors,the proposed segmented outer electrode micro-plasma reactor can give a higher CO_(2) conversion and acceptable energy efficiency.The increase in conversion can be attributed mainly to the enhanced corona discharge caused by the fringe effect at electrode edges,the increase in energy density and the increase in the number of micro-discharges.In addition,detailed electrical characterization was performed to reveal some trends in the electrical behavior of proposed reactors.