Effects of Internally Mounted Cathodes on Hall Thruster Plume Properties

Hofer, Richard R.; Johnson, L. K.; Goebel, Dan M.; Wirz, Richard E.

doi:10.1109/tps.2008.2000962

Cited by 36 publications

(22 citation statements)

References 22 publications

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“…The vacuum chamber has a total xenon system pumping speed of ∼200 000 l/s and produces a background pressure of 1.6 × 10 −5 torr at the nominal xenon flow rate of ∼21 mg/s at the 6-kW operation point. At this background pressure, ingestion from background gases is negligible [33]. The vacuum chamber is lined with graphite panels to reduce the amount of back sputtered material on the thruster and diagnostics.…”

Section: Experimental Apparatusmentioning

confidence: 99%

Conducting Wall Hall Thrusters

Goebel¹,

Hofer

Mikellides³

et al. 2015

IEEE Trans. Plasma Sci.

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A unique configuration of the magnetic field and channel geometry near the wall of Hall thrusters, called magnetic shielding, has recently demonstrated the ability to significantly reduce the erosion of the boron nitride (BN) walls and extend the life of Hall thrusters by orders of magnitude. The ability of magnetic shielding to minimize interactions between the plasma and the discharge chamber walls in regions where erosion typically occurs has for the first time enabled the replacement of insulating walls with conducting materials without loss in Hall thruster performance. It is important to note that this is not a thruster with anode layer (TAL) where the walls are at or near cathode potential, but is a Hall thruster configuration where the walls are near the anode potential. The BN rings in the 6-kW H6 Hall thruster were replaced with graphite that self-biased to near the anode potential during operation. The thruster efficiency remained over 60% (within 2% of the baseline BN configuration) with a small decrease in thrust and increase in Isp typical of magnetically shielded Hall thrusters. The graphite wall temperatures decreased significantly compared with both shielded and unshielded BN configurations, leading to the potential for higher power operation. Eliminating ceramic walls makes it simpler and less expensive to fabricate a thruster to survive launch loads, and the graphite discharge chamber radiates more efficiently, which increases the power capability of the thruster compared with conventional Hall thruster designs.Index Terms-Hall effect devices, plasma propulsion.

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Section: Experimental Apparatusmentioning

confidence: 99%

Conducting Wall Hall Thrusters

Goebel¹,

Hofer

Mikellides³

et al. 2015

IEEE Trans. Plasma Sci.

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show abstract

“…The vacuum chamber has a total xenon system pumping speed of approximately 200,000 l/s and produces a background pressure of 1.6x10 -5 torr at the nominal xenon flow rate of about 21 mg/s at the 6kW operation point. At this background pressure, ingestion from background gases is negligible [32]. The vacuum chamber is lined with graphite panels to reduce the amount of back sputtered material on the thruster and diagnostics.…”

Section: Experimental Apparatusmentioning

confidence: 99%

Conducting Wall Hall Thrusters

Goebel

Hofer

Mikellides

et al. 2013

49th AIAA/ASME/SAE/ASEE Joint Propulsion Conference

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A unique configuration of the magnetic field near the wall of Hall thrusters, called "magnetic shielding", has recently demonstrated the ability to significantly reduce the erosion of the boron nitride (BN) walls and extend the life of Hall thrusters by orders of magnitude. The ability of magnetic shielding to minimize interactions between the plasma and the discharge chamber walls has for the first time enabled the replacement of insulating walls with conducting materials without loss in Hall thruster performance. The boron nitride rings in the 6 kW H6 Hall thruster were replaced with graphite that self-biased to near the anode potential during operation. The thruster efficiency remained over 60% (within two percent of the baseline BN configuration) with a small decrease in thrust and increase in Isp typical of magnetically shielded Hall thrusters. The graphite wall temperatures decreased significantly compared to both shielded and unshielded BN configurations, leading to the potential for higher power operation. Eliminating ceramic walls makes it simpler and less expensive to fabricate a thruster to survive launch loads, and the graphite discharge chamber radiates more efficiently which increases the power capability of the thruster compared to conventional Hall thruster designs. Nomenclature g = acceleration of gravity Isp = specific impulse ! ˙ m p = total propellant mass flow rate T = thrust P T = Total input power P d = Discharge power P mag = Power into the magnets

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“…Visual observations, shown in Figure 3, also reveal that thrusters with external cathodes are typically surrounded by a "halo" as the electrons collide with background gases causing neutral emission [58]. These interactions are virtually absent when internal cathodes are used.…”

mentioning

confidence: 96%

“…Indeed, studies of Hall thrusters with internally mounted cathodes have shown this is the most energetically favorable configuration and provides for a high-level of performance primarily through decreased plume divergence and improved cathode coupling [16,38,39,[58][59][60][61][62][63]. Visual observations, shown in Figure 3, also reveal that thrusters with external cathodes are typically surrounded by a "halo" as the electrons collide with background gases causing neutral emission [58].…”

mentioning

confidence: 99%

Finite Pressure Effects in Magnetically Shielded Hall Thrusters

Hofer¹,

Anderson²

2014

50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference

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We describe the effects of finite pressure in a large vacuum facility on a magnetically shielded Hall thruster using internally and externally mounted cathodes. A numerical model of the pumping system was first used to guide the placement of an ionization gauge and an auxiliary propellant injector used for increasing the backpressure. The laboratory model H6MS Hall thruster was operated at 300 and 800 V discharge voltage, 2-20 A discharge current, and 0.6-9.0 kW discharge power at pressures calibrated for xenon from 2.4 to 100 uTorr-Xe. The hollow cathode was located in three positions: internally mounted on thruster centerline and two external mounts outside of the magnetic circuit. Performance variations exceed that expected from ingestion of background gas in all configurations but were still consistent with prior studies of unshielded Hall thrusters. Magnetic field strength, cathode location, and magnitude of discharge oscillations can greatly affect the apparent level of ingestion, which suggests that mechanisms other than ingestion of background gas affect the pressure sensitivity of the discharge. In particular, cathode location is shown to have a profound influence on the measured performance and stability. When the internally mounted cathode is used, the plasma response is shown to be much less sensitive to pressure changes than when an externally mounted cathode is employed. Our results suggest that high-power Hall thrusters using internally mounted cathodes minimize the effects of finite pressure on performance and stability, providing a path for reliably correlating ground tests with flight performance.

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Effects of Internally Mounted Cathodes on Hall Thruster Plume Properties

Cited by 36 publications

References 22 publications

Conducting Wall Hall Thrusters

Conducting Wall Hall Thrusters

Conducting Wall Hall Thrusters

Finite Pressure Effects in Magnetically Shielded Hall Thrusters

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