Anticipated performance of achromatic quadrupole focusing systems when used with liquid metal ion sources

Journal Article · Sun Jul 01 04:00:00 EDT 1990 · Journal of Vacuum Science and Technology, A (Vacuum, Surfaces and Films); (USA)

DOI:https://doi.org/10.1116/1.576578· OSTI ID:6687895

Harriott, L R; Brown, W L; Barr, D L ^[1]

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1. AT T Bell Laboratories, Murray Hill, New Jersey 07974 (USA)

Current focusing systems for producing finely focused ion beams from liquid metal ion sources (LMIS) using axially symmetric electrostatic lenses are limited by chromatic aberration due to the relatively high ({similar to}10 eV) energy spread inherent in LMIS. The highest current densities achievable are in the range of 1--5 A/cm{sup 2} at energies above 20 keV. In this paper, we discuss the use of achromatic quadrupole lenses to overcome the limitation due to energy spread. These lenses require both magnetic and electrostatic focusing elements. Lens acceptance angles are limited by the electrode positions and by the necessary magnetic gradients. The coefficients relating image distance to lens excitation of some of the elements in the quadrupole multiplet are found to be much larger than in electrostatic systems. These factors combine to require excitation stabilities as high as 1 part per million in order to achieve current densities more than 10 A/cm{sup 2}, although such performance can be expected at beam energies of 5 keV or below.

• OSTI ID: 6687895
• Journal Information: Journal of Vacuum Science and Technology, A (Vacuum, Surfaces and Films); (USA), Journal Name: Journal of Vacuum Science and Technology, A (Vacuum, Surfaces and Films); (USA) Vol. 8:4; ISSN JVTAD; ISSN 0734-2101
• Country of Publication: United States
• Language: English

Related Subjects

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Molecular & Chemical Physics-- Beams & their Reactions
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
AMP BEAM CURRENTS
BEAM CURRENTS
BEAM EXTRACTION
BEAMS
CURRENT DENSITY
CURRENTS
ELEMENTS
ENERGY RANGE
FLUIDS
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ION BEAMS
ION SOURCES
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KEV RANGE 01-10
LIQUID METALS
LIQUIDS
METALS
MULTIPOLES
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QUADRUPOLES