High-Specific Impulse Hall Thrusters, Part 1: Influence of Current Density and Magnetic Field

Abstract

A laboratory-model Hall thruster with a magnetic circuit designed for high-specific impulse (2000-3000 s) was evaluated to determine how current density and magnetic field affect thruster operation. Results have shown for the first time that a minimum current density and optimum magnetic field shape exist at which efficiency will monotonically increase with specific impulse. At the nominal mass flow rate of 10 mg/s and between discharge voltages of 300 and 1000 V, total specific impulse and total efficiency ranged from 1600 to 3400 s and 51 to 61%, respectively. Comparison with a similar thruster showed how efficiency can be optimized for specific impulse by varying the shape of the magnetic field. Plume divergence decreased from a maximum of 48 deg at 400 V to a minimum of 35 deg at 1000 V, but increased between 300 and 400 V as the likely result of a large increase in discharge current oscillations. The breathing-mode frequency continuously increased with voltage, from 14.5 kHz at 300 V to 22 kHz at 1000 V, in contrast to other Hall thrusters where a sharp decrease of the breathing-mode frequency was found to coincide with increasing electron current and decreasing efficiency. These findings suggest that efficient, high-specific impulse operation was enabled through the regulation of the electron current with the applied magnetic field. . Associate Fellow AIAA. η t = total efficiency θ = azimuthal coordinate direction ∇ z B r = axial gradient of the centerline radial magnetic field

Study on the Relation Between Discharge Voltage and Magnetic Field Topography in a Hall Thruster Discharge Channel

“…Much work has been done to determine the quantitative relations between the magnetic field strength and voltage on optimal operating conditions [4][5][6][7][8]. Recently, Gawron et al studied the influence of above two factors on the acceleration layer features using experimental and numerical methods, and proposed that both the magnetic field strength and applied voltage have an impact upon the accelerating potential profile [9].…”

Experimental Characterization of a Micro-Hall Thruster

“…The shape of the main peak is relatively broad in comparison to what is seen in larger, higher power thrusters [28][29][30], as shown in Fig. 13.…”

Magnetic field deformation due to electron drift in a Hall thruster

“…The standard deviation values in the simulation results are 0.4 and 2.7 for 5 mg/s and 15 mg/s anode flow rate, respectively. In the actual thruster, the oscillation of discharge current is different than this simulation results [26][27][28] The simulation just gives an order of magnetic deformation as Hall current. The actual magnetic deformation caused by the Hall current should correlate with the work condition of thruster.…”