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We compare time-averaged and time-varying measured and computed ion velocity distribution functions in a Hall effect thruster for typical operating conditions. The ion properties are measured by means of laser induced fluorescence spectroscopy. Simulations of the plasma properties are performed with a two-dimensional hybrid model. In the electron fluid description of the hybrid model, the anomalous transport responsible for the electron diffusion across the magnetic field barrier is deduced from the experimental profile of the time-averaged electric field. The use of a steady state anomalous mobility profile allows the hybrid model to capture some properties like the time-averaged ion mean velocity. Yet, the model fails at reproducing the time evolution of the ion velocity. This fact reveals a complex underlying physics that necessitates to account for the electron dynamics over a short time-scale. This study also shows the necessity for electron temperature measurements. Moreover, the strength of the self-magnetic field due to the rotating Hall current is found negligible. [ABSTRACT FROM AUTHOR]

A hybrid fluid-particle model has been used to study the properties of a double-stage Hall effect thruster where the channel is divided into two regions of large magnetic field separated by a low-field region containing an intermediate, electron-emitting electrode. These two features are aimed at effectively separating the ionization region from the acceleration region in order to extend the thruster operating range. Simulation results are compared with experimental results obtained elsewhere. The simulations reproduce some of the measurements when the anomalous transport coefficients are adequately chosen. However, they raise the question of a complete separation of the ionization and acceleration regions and the necessity of an electron-emissive intermediate electrode. The calculation method for the electric potential in the hybrid model has been improved with respect to our previous work and is capable of a complete two-dimensional description of the magnetic configurations of double-stage Hall effect thrusters. [ABSTRACT FROM AUTHOR]

The origin of anomalous electron transport across the magnetic field in the channel of a Hall effect thruster has been the subject of controversy, and the relative importance of electron-wall collisions and plasma turbulence on anomalous transport is not clear. From comparisons between Fabry-Pérot measurements and hybrid model calculations of the ion velocity profile in a 5 kW Hall effect thruster, we deduce that one and the same mechanism is responsible for anomalous electron transport inside and outside the Hall effect thruster channel. This suggests that the previous assumption that Bohm anomalous conductivity is dominant outside the thruster channel whereas electron-wall conductivity prevails inside the channel is not valid. [ABSTRACT FROM AUTHOR]

An improvement of the neutral gas injection in order to increase the Hall thruster lifetime capabilities is demonstrated using a two-dimensional model. An additional atom injection through the channel ceramics in a region located between the ionization and the acceleration zones leads to an efficient ionization of the neutral flux, with a flattening of the plasma density and potential profiles in the radial direction. Thanks to this modified injection of the atom flow, a focusing electric field is produced, reducing the ion flux impacting on ceramic walls. [ABSTRACT FROM AUTHOR]

Hall effect thrusters (HETs) are ion sources used for satellite station keeping and orbit raising. In Single Stage HETs, the same electric field is responsible for electron heating and ion ac- celeration. We present a new HET concept where ionization and acceleration are separated in two different stages. This double stage HET allows for a more versatile operation and a separate control of thrust and specific impulse. [ABSTRACT FROM AUTHOR]