Reduction of Energetic Ion Production in Hollow Cathodes by External Gas Injection

Chu, E.; Goebel, Dan M.; Wirz, Richard E.

doi:10.2514/1.b34799

Cited by 38 publications

(28 citation statements)

References 16 publications

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“…3 Keeper erosion, on the other hand, is still considered anomalous. This is because keeper sputtering results from impact by ions from the cathode plume with energies that far exceed the cathode discharge voltage, [4][5][6][7][8][9][10][11] yet there is no classical reason why such high energy ions should exist. The erosion from these anomalous ions is becoming an increasingly important concern in light of new NASA programs that are calling for higher power electric propulsion missions with extended duration.…”

Section: Introductionmentioning

confidence: 99%

Investigation of Energetic Ions in a 100-A Hollow Cathode

Jorns¹,

Mikellides

Goebel

2014

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

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The role of ion acoustic turbulence in the formation of high-energy ion tails in the plume of a 100-A LaB6 hollow cathode is experimentally and theoretically examined. At fixed flow rate and varying discharge current, single-point measurements of fluctuation intensity in the cathode plume are taken and compared to ion energy measurements. It is shown that for high discharge current the formation of energetic ions is correlated with the amplitude of the ion acoustic turbulence. Two-dimensional maps of background plasma parameters and wave turbulence are made at the highest discharge current investigated, 140 A. A simple, one-dimensional quasilinear model for the interaction of the ion energy distribution with the ion acoustic turbulence is employed, and it is shown that the energy in the measured wave turbulence is sufficiently large to explain the formation of ion tails in the cathode plume. Mitigation techniques for minimizing the amplitude of the turbulence are discussed.

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Section: Introductionmentioning

confidence: 99%

Investigation of Energetic Ions in a 100-A Hollow Cathode

Jorns¹,

Mikellides

Goebel

2014

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

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“…The other benefit that can be attained from the this additional injected flow is a reduction in the keeper erosion rate as was shown by Chu et al 14 Figure 1 shows the location of the auxiliary propellant feed line with respect to the HiVHAc thruster and cathode 1 assembly. Tests were performed for thruster operating throttle points that were outlined in Table 1.…”

Section: Auxiliary Flow Variation Testmentioning

confidence: 79%

“…16,17 Additionally, it has been shown that external gas injection (similar to the auxiliary flow injection scheme) reduces energetic ion production by the keeper which will increase cathode life. 14 The increase in discharge current and American Institute of Aeronautics and Astronautics thrust with increased auxiliary flow is partly due to the ingestion of the additional neutral propellant, changes to the location of the discharge may also be contributing to the change in thruster performance and behavior. For all the test conditions, the total thrust efficiency and specific impulse decreased with increased auxiliary flow rate.…”

Section: Discussionmentioning

confidence: 98%

Investigation of the Effects of Cathode Position on the Performance and Operation of the High Voltage Hall Accelerator

Kamhawi¹,

Huang²,

Haag³

2014

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

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Space Propulsion Technology office is sponsoring NASA Glenn Research Center (GRC) to develop a 4 kW-class Hall thruster propulsion system for implementation in NASA science missions. Tests were performed within NASA GRC Vacuum Facility 5 at background pressure levels that were six times lower than what has previously been attained in other vacuum facilities. A study was conducted to assess the impact of varying the cathode-to-anode flow fraction and cathode position on the performance and operational characteristics of the High Voltage Hall Accelerator (HiVHAc) thruster. In addition, the impact of injecting additional xenon propellant in the vicinity of the cathode was also assessed. Cathode-to-anode flow fraction sensitivity tests were performed for power levels between 1.0 and 3.9 kW. It was found that varying the cathode flow fraction from 5 to approximately 10% of the anode flow resulted in the cathode-to-ground voltage becoming more positive. For an operating condition of 3.8 kW and 500 V, varying the cathode position from a distance of closest approach to 600 mm away did not result in any substantial variation in thrust but resulted in the cathode-to-ground changing from -17 to -4 V. The change in the cathode-to-ground voltage along with visual observations indicated a change in how the cathode plume was coupling to the thruster discharge. Finally, the injection of secondary xenon flow in the vicinity of the cathode had an impact similar to increasing the cathode-to-anode flow fraction, where the cathode -to-ground voltage became more positive and discharge current and thrust increased slightly. Future tests of the HiVHAc thruster are planned with a centrally mounted cathode in order to further assess the impact of cathode position on thruster performance.

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“…This anode gas injector is also known to reduce the oscillation level in the cathode plume and the local production of energetic ions that tend to sputter the keeper face and anode wall. 11,12 The area expansion ratio of the plasma from the hollow cathode orifice to the anode is on the order of 20 to 30, so the discharge is stable and well behaved over a large range in discharge current and plasma densities. In addition, the higher neutral gas pressure downstream of the cathode orifice in the new Pi, compared to the constant axial pressure in the flat disk PISCES cathode source, provides additional protection of the insert from contamination by metallic components that might be sputtered or evolved in the system.…”

Section: Iia Plasma Source Designmentioning

confidence: 98%

The Plasma-Material Interactions Facility at UCLA

Matlock

Conversano

Goebel

et al. 2013

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

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A new device has been constructed for the investigation of interactions between engineered materials and a plasma in the regime relevant to electric propulsion. The facility is comprised of a cylindrical vacuum chamber with a flange-mounted, hollow cathode plasma source running perpendicular to the chamber axis. The plasma source delivers unmagnetized ions and thermal, magnetized electrons to a cooled target mounted on the opposing flange. The ion energy impacting the surface is controlled by the sample bias relative to the plasma potential, which is maintained near the chamber potential. This paper discusses the major aspects of the plasma source design and presents preliminary measurements of the plasma parameters achieved to date.

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Reduction of Energetic Ion Production in Hollow Cathodes by External Gas Injection

Cited by 38 publications

References 16 publications

Investigation of Energetic Ions in a 100-A Hollow Cathode

Investigation of Energetic Ions in a 100-A Hollow Cathode

Investigation of the Effects of Cathode Position on the Performance and Operation of the High Voltage Hall Accelerator

The Plasma-Material Interactions Facility at UCLA

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