Solutions for discharge chamber sputtering and anode deposit spalling in small mercury ion thrusters

Power, J. L.; Hiznay, D. J.

doi:10.2514/6.1975-399

Cited by 13 publications

(5 citation statements)

References 4 publications

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“…Accumulated sputter deposited material extending about 200 /-lm into screen grid holes is thought to have caused deflection of ions onto the accelerator grid resulting in damage observed at 5 locations during the accelerated wear test described in Reference [10]. Methods to mitigate problems associated with flakes have been developed [13]. Adhesion of sputtered films is enhanced when the surface has been roughened or films are deposited on a fine wire mesh.…”

Section: Rouge Holesmentioning

confidence: 99%

Post-Test Analysis of the Deep Space 1 Spare Flight Thruster Ion Optics

Anderson

Sengupta

Brophy

2004

40th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit

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The Deep Space 1 (DSl) spare flight thruster (FT2) was operated for 30,352 hours during the extended life test (ELT). The test was performed to validate the service life of the thruster, study known and identify unknown life limiting modes. Several of the known life limiting modes involve the ion optics system. These include loss of structural integrity for either the screen grid or accelerator grid due to sputter erosion from energetic ions striking the grid, sputter erosion enlargement of the accelerator grid apertures to the point where the accelerator grid power supply can no longer prevent electron backstreaming, unclearable shorting between the grids causes by flakes of sputtered material, and rouge hole formation due to flakes of material defocusing t he ion beam. Grid g ap decrease, which increases the probability of electron backstreaming and of arcing between the grids, was identified as an additional life limiting mechanism after the test. A combination of accelerator grid aperture enlargement and grid gap decrease resulted in the inability to prevent electron backstreaming at full power at 26,000 hours of the ELT. Through pits had eroded through the accelerator grid webbing and grooves had penetrated through 45% of the grid thickness in the center of the grid. The upstream surface of the screen grid eroded in a chamfered pattern around the holes in the central portion of the grid. Sputter deposited material, from the accelerator grid, adhered to the downstream surface of the screen grid and did not spall to form flakes. Although a small amount of sputter deposited material protruded into the screen grid apertures, no rouge holes were found after the ELT.

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Section: Rouge Holesmentioning

confidence: 99%

Post-Test Analysis of the Deep Space 1 Spare Flight Thruster Ion Optics

Anderson

Sengupta

Brophy

2004

40th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit

View full text Add to dashboard Cite

show abstract

“…These atoms will be resputtered from cathode-potential surfaces that are not well shielded by magnetic elds, and they will tend to accumulate on anode-potential surfaces. 54 This accumulation can, after long periods of operation, result in akes of sputtered, electrically conducting material that can detach and drift into the grids. When this happens, arcing and even shorting between the grids occurs.…”

Section: Miscellaneous Lifetime Considerationsmentioning

confidence: 99%

Ion Thruster Development Trends and Status in the United States

Wilbur

Rawlin

Beattie³

1998

Journal of Propulsion and Power

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The current interest in ion thrusters for near-Earth and deep-space missions has occurred because of long-term development efforts yielding an understanding of the physical phenomena involved in thruster operation and hardware that is suited to a wide range of missions. Features of state-of-the-art thrusters are described in terms of the various physical processes that occur within them. Tradeoffs that must be considered to arrive at thruster designs suited to commercialization are discussed.

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“…1 ' 2 Present mercury thruster designs incorporate features that reduce the failure hazard posed by sputter erosion 3 ; these measures appear to be adequate for small (8-cm-diameter) thrusters, but further improvement is needed in large (30-cm-diameter) thrusters intended for primary-propulsion application. Details of the discharge processes that cause sputter erosion have, however, remained largely unexplored.…”

Section: Introductionmentioning

confidence: 98%

Discharge-Chamber Sputtering in Mercury Ion Thrusters

Williamson

Hyman

1978

Journal of Spacecraft and Rockets

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Discharge-chamber sputter erosion has been investigated in two electron-bombardment mercury ion thrusters at 8-cm and 12-cm beam diameter (respectively, the SIT-8 and the SIT-12 thrusters). Sputter erosion is found to be concentrated primarily on the screen electrode and is due primarily to singly charged mercury ions, Hg + . A model of discharge-chamber sputter-erosion has been developed that predicts erosion rates that are in good agreement with observed rates. A three fold reduction in the rate of total mass erosion has been achieved in both the SIT-8 and SIT-12 thrusters by biasing the thruster shell (including screen electrode) at keeper potential rather than at cathode potential.

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Solutions for discharge chamber sputtering and anode deposit spalling in small mercury ion thrusters

Cited by 13 publications

References 4 publications

Post-Test Analysis of the Deep Space 1 Spare Flight Thruster Ion Optics

Post-Test Analysis of the Deep Space 1 Spare Flight Thruster Ion Optics

Ion Thruster Development Trends and Status in the United States

Discharge-Chamber Sputtering in Mercury Ion Thrusters

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