Ion Beam Divergence Characteristics of Three-Grid Accelerator Systems

Aston, G.; Kaufman, H. R.; Wilbur, P. J.

doi:10.2514/3.61063

Cited by 29 publications

(6 citation statements)

References 3 publications

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“…2,3 It is instructive to compare the magnitude of the divergence measurements presented herein with the values that would have been predicted from these previous studies. 2,3 It is instructive to compare the magnitude of the divergence measurements presented herein with the values that would have been predicted from these previous studies.…”

Section: Comparison With Previous Divergence Datamentioning

confidence: 58%

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Probe for measuring ion beam angular distribution

Kahn

Kaufman

Phillips

et al. 1996

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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Low energy ion beam mixing as a tool for multilayer xray mirror fabricationA new type of ion beam probe is described that measures the angular distribution of energetic ions and, through their sputtering effects, energetic neutrals as well. This probe does not require either complicated motion actuators or very sensitive electrical measurements in the adverse environment of an ion beam, but instead performs the measurement through the sputter etching of a multilayer sample with contrasting metal colors. This probe was tested and found to provide a half-width at half-maximum reproducibility of about Ϯ0.3 deg. After use, the probe sample provides a permanent record of the angular distribution of the ion beam at the target location tested. Because no electrical contacts are required, the probe can even be attached to a moving stage to measure the effective angular distribution of an ion beam while being carried through a complicated planetary pattern. Using this probe, the low divergence and paraxial beam from an ion source with 30 cm flat graphite grids were documented. This probe, in conjunction with profiles obtained with a Faraday probe, allows full global and internal ion beam characterization. It is significant that the minimum divergences obtained in this investigation were 40-60 percent lower than the minimum divergences obtained from earlier tests with small arrays of apertures.

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Section: Comparison With Previous Divergence Datamentioning

confidence: 58%

“…2,3 This was done using a small array of grid apertures and measuring the ionbeam envelope at a distance that was large compared to the size of the ion optics. 2,3 This was done using a small array of grid apertures and measuring the ionbeam envelope at a distance that was large compared to the size of the ion optics.…”

Section: Introductionmentioning

confidence: 99%

Probe for measuring ion beam angular distribution

Kahn

Kaufman

Phillips

et al. 1996

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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“…7for three different values of the ratio Ig/ds. It is clear from this figure that operation that larger le/ds is desirable to minimize It is also known that larger values of le/& generally result in smaller beam divergence angles[22].…”

mentioning

confidence: 89%

“…and the theoretical maximum perveance is [22], For Xe with a mass of mi = 2 . 1 8~1 0 -~~ kg,' the theoretical maximum perveance is, P , , = 4.77x10-' AN3"…”

Section: Cex Ions That Hit the Hole Wallsmentioning

confidence: 99%

Numerical Simulations of Ion Thruster Accelerator Grid Erosion

Brophy¹,

Katz²,

Polk³

et al. 2002

38th AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

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The highly successful demonstration of ion propulsion on Deep Space 1 has stimulated the study of more demanding applications of ion propulsion. These future applications require ion thrusters capable of providing significantly greater specific impulses and total impulses than the current state-of-the-art Higher specific impulses aggravate the known wear out mechanisms of the ion accelerator system. Computer simulations of the ion accelerator system operation and erosion are essential tools for the development of ion thrusters to meet the demand for higher specific impulse and longer life. Two-dimensional and three-dimensional computer codes have been developed at JPL and are used provide insight to the processes limiting the life of the accelerator grid. The 2D code was used to identify a key feature of operation at high Isp. That is, as the beam voltage is increased the energy of the charge-exchange ions hitting the hole walls increases in proportion to the beam voltage and more rapidly than the increase in the magnitude of the accelerator grid voltage. This has serious implications for the design of long-life, high specific impulse thrusters, and these implications are discussed herein. Another important parameter is the fraction of charge exchange ions created downstream of the accelerator grid that return to the grid. Our calculations show that these ions form the pits and

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“…[2][3][4][5] One of the main issues in the ion beam generation research has been raising the beam flux by optimizing the grid hole diameter, the grid gap, the grid voltage distribution, and the source plasma density. [6][7][8][9][10] Even though a considerable progress has been made in optimizing these physical conditions, a higher ion beam flux is still in demand without a warranty for further improvement. A different approach and the fundamental physics understanding may now be needed for further advances in this field.…”

Section: Introductionmentioning

confidence: 99%

Numerical study of the plasma wall-bias effect on the ion flux through acceleration grid hole

Park

Chang

2010

Physics of Plasmas

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In the extraction of ion beams from a source plasma through a grid acceleration structure, one of the key improvement issues is the fluence of the ion flux. Theoretical research has usually been focused on the structure of the grid system and the distribution of the electrostatic voltages over the grid layers. In the present work, using a self-consistent computer simulation between the plasma source, sheath potential, and the grid system, the effect of the source-wall biasing on the fluence of the ion flux through a three-grid acceleration system has been examined. It is found that a strongly positive wall-biasing can significantly enhance the ion flux by improving the shape of the plasma sheath potential meniscus at the entrance to the grid hole structure.

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Ion Beam Divergence Characteristics of Three-Grid Accelerator Systems

Cited by 29 publications

References 3 publications

Probe for measuring ion beam angular distribution

Probe for measuring ion beam angular distribution

Numerical Simulations of Ion Thruster Accelerator Grid Erosion

Numerical study of the plasma wall-bias effect on the ion flux through acceleration grid hole

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