Ion beam divergence characteristics of two-grid accelerator systems

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

doi:10.2514/3.7538

Cited by 85 publications

(48 citation statements)

References 8 publications

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“…29 The systematic errors come from several places. The angle of the ion beam source to the magnetic field could deviate 1°or 2°f rom the expected 15°.…”

Section: -7mentioning

confidence: 99%

Measurements of classical transport of fast ions

et al. 2005

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To study the fast-ion transport in a well controlled background plasma, a 3-cm diameter rf ion gun launches a pulsed, ϳ300 eV ribbon shaped argon ion beam parallel to or at 15°to the magnetic field in the Large Plasma Device ͑LAPD͒ ͓W. Gekelman, H. Pfister, Z. Lucky, J. Bamber, D. Leneman, and J. Maggs, Rev. Sci. Instrum. 62, 2875 ͑1991͔͒ at UCLA. The parallel energy of the beam is measured by a two-grid energy analyzer at two axial locations ͑z = 0.32 m and z = 6.4 m͒ from the ion gun in LAPD. The calculated ion beam slowing-down time is consistent to within 10% with the prediction of classical Coulomb collision theory using the LAPD plasma parameters measured by a Langmuir probe. To measure cross-field transport, the beam is launched at 15°to the magnetic field. The beam then is focused periodically by the magnetic field to avoid geometrical spreading. The radial beam profile measurements are performed at different axial locations where the ion beam is periodically focused. The measured cross-field transport is in agreement to within 15% with the analytical classical collision theory and the solution to the Fokker-Planck kinetic equation. Collisions with neutrals have a negligible effect on the beam transport measurement but do attenuate the beam current.

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“…29 The systematic errors come from several places. The angle of the ion beam source to the magnetic field could deviate 1°or 2°f rom the expected 15°.…”

Section: -7mentioning

confidence: 99%

Measurements of classical transport of fast ions

et al. 2005

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“…This assumption is derived from the variation of the accel grid hole radius having little effect on beam divergence angle. 14) This indicates that the variation of the cross-sectional area of the ion beam is negligible during operation even if the accel grid hole diameter is enlarged by charge exchange ion erosion.…”

Section: Model 221 Assumptionmentioning

confidence: 99%

“…The lifetime scaling equation (14) indicates that the duration before causing the electron backstreaming strongly depends on the beam current (proportional to i B 5/3-8/3 ). Based on this characteristic, the life of the grid optics is prolonged by a reduced beam current.…”

Section: Design Guide From Lifetime Scaling Lawmentioning

confidence: 99%

See 1 more Smart Citation

A Scaling Law of the Life Estimation of the Three-Grid Optics for an Ion Engine.

Nakano

Tachibana

Arakawa

2002

Trans. Japan Soc. Aero. S Sci.

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A scaling law on the wear of three-grid optics is proposed for the lifetime estimation of ion engines. The charge exchange ions erode the accel grid holes; therefore, the reduced retarding potential results in electron backstreaming, which is the end of life of the three-grid optics. The arithmetic formulas are induced by use of the space-charge-limited current density law and a newly introduced parameter called the modified effective acceleration length. The model is based on the following scenario of grid life: (1) Charge exchange ion erosion enlarges the accel grid hole diameter, (2) which shortens the modified effective acceleration length between the screen and accel grids and (3) reduces the retarding potential to keep the beam current constant under the space-charge limited flow. The characteristic of the proposed formulas is that the lifetime of the three-grid optics strongly depends on the beam current and the accel grid voltage. The correlation between the arithmetic formulas and the numerical simulations showed good qualitative agreement with one another in all regions of the normalized perveance per hole and achieved quantitative consistency in its high value.

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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 two-grid accelerator systems

Cited by 85 publications

References 8 publications

Measurements of classical transport of fast ions

Measurements of classical transport of fast ions

A Scaling Law of the Life Estimation of the Three-Grid Optics for an Ion Engine.

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

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