Langmuir Probe Measurements Within the Discharge Channel of the 20-kW NASA-300M and NASA-300MS Hall Thrusters

NASA is presently developing a high-power, high-efficiency, long-lifetime Hall thruster for the Solar Electric Propulsion Technology Demonstration Mission. In support of this task, studies have been performed on the 20-kW NASA-300M Hall thruster to aid in the overall design process. The ability to incorporate magnetic shielding into a high-power Hall thruster was also investigated with the NASA-300MS, a modified version of the NASA-300M. The inclusion of magnetic shielding would allow the thruster to push existing state-of-the-art technology in regards to service lifetime, one of the goals of the Technology Demonstration Mission. Langmuir probe measurements were taken within the discharge channels of both thrusters in order to characterize differences at higher power levels, as well as validate ongoing modeling efforts using the axisymmetric code Hall2De. Flush-mounted Langmuir probes were also used within the channel of the NASA-300MS to verify that magnetic shielding was successfully applied. Measurements taken from 300 V, 10 kW to 600 V, 20 kW have shown plasma potentials near anode potential and electron temperatures of 4-12 eV at the walls near the thruster exit plane of the NASA-300MS, verifying magnetic shielding and validating the design process at this power level. Channel centerline measurements on the NASA-300M from 300 V, 10 kW to 500 V, 20 kW show the electron temperature peak at approximately 0.1-0.2 channel lengths upstream of the exit plane, with magnitudes increasing with discharge voltage. The acceleration profiles appear to be centered about the exit plane with a width of approximately 0.3-0.4 channel lengths. Channel centerline measurements on the NASA-300MS were found to be more challenging due to additional probe heating. Ionization and acceleration zones appeared to move downstream on the NASA-300MS compared to the NASA-300M, as expected based on the shift in peak radial magnetic field. Additional measurements or alternative diagnostics will be needed to verify peak electron temperatures in the NASA-300MS and compare them with model predictions.

[1]  Hani Kamhawi,et al.  Ion Current Density Study of the NASA-300m and NASA-457mv2 Hall Thrusters , 2013 .

[2]  I. Mikellides,et al.  Magnetic Shielding of the Acceleration Channel Walls in a Long-Life Hall Thruster , 2010 .

[3]  J. Haas.  Low perturbation interrogation of the internal and near -field plasma structure of a Hall thruster using a high -speed probe positioning system. , 2001 .

[4]  A. Gallimore,et al.  Plasma Potential Measurements in the Discharge Channel of a 6-kW Hall Thruster , 2008 .

[5]  N. Hershkowitz,et al.  Measurement of plasma potential using collecting and emitting probes , 1988 .

[6]  I. Mikellides,et al.  Design of a Laboratory Hall Thruster with Magnetically Shielded Channel Walls, Phase I: Numerical Simulations , 2011 .

[7]  J. Linnell.  An evaluation of krypton propellant in Hall thrusters , 2007 .

[8]  Hani Kamhawi,et al.  Numerical Simulations of a 20-kW Class Hall Thruster Using the Magnetic-Field-Aligned-Mesh Code Hall2De , 2011 .

[9]  Hani Kamhawi,et al.  Performance and Thermal Characterization of the NASA-300MS 20 kW Hall Effect Thruster , 2013 .

[10]  Rohit Shastry,et al.  Experimental Characterization of the Near-Wall Region in Hall Thrusters and its Implications on Performance and Lifetime. , 2011 .

[11]  Alec D. Gallimore,et al.  Langmuir Probe Measurements in the Discharge Channel of a 6-kW Hall Thruster , 2008 .

[12]  A. Lichtenberg,et al.  Principles of Plasma Discharges and Materials Processing , 1994 .

[13]  Hani Kamhawi,et al.  Performance Test Results of the NASA-457m V2 Hall Thruster , 2013 .

[14]  Brittany D. Drenkow,et al.  Laser-Induced Fluorescence of Singly-Charged Xenon inside a 6-kW Hall Thruster , 2009 .

[15]  David H. Manzella,et al.  NASA's 2004 Hall Thruster Program , 2013 .

[16]  Hani Kamhawi,et al.  Fairfield Plume Measurement and Analysis on the NASA-300M and NASA-300MS , 2013 .

[17]  I. Mikellides,et al.  Design of a Laboratory Hall Thruster with Magnetically Shielded Channel Walls, Phase III: Comparison of Theory with Experiment , 2012 .

[18]  Hani Kamhawi,et al.  Farfield Plume Measurement and Analysis on the NASA-300M , 2013 .

[19]  H. Kamhawi,et al.  Plasma Potential and Langmuir Probe Measurements in the Near-Field Plume of the NASA-457mv2 Hall Thruster , 2013 .

[20]  I. Mikellides,et al.  Design of a Laboratory Hall Thruster with Magnetically Shielded Channel Walls, Phase II: Experiments , 2012 .