Radiant energy – With charged particle beam deflection or focussing – Magnetic lens
Patent
1975-03-17
1976-10-05
Smith, Alfred E.
Radiant energy
With charged particle beam deflection or focussing
Magnetic lens
H01J 3700
Patent
active
039846873
ABSTRACT:
A shielded magnetic lens and deflection yoke structure for an electron beam column which minimizes aberrations in the lens system caused by winding asymmetry in the field coil, as well as aberrations due to eddy currents created within the magnetic circuit of the lens by interaction with the field of the deflection yoke. The shield includes a polepiece structure for the magnetic electron lens generally comprising a hollow cylinder formed of a plurality of precisely machined magnetic discs stacked concentrically with precisely machined nonmagnetic discs in alternating sequence with the lens coil positioned adjacent the periphery of the cylinder and the deflection yoke positioned within the cylinder or proximate to either end thereof. In one preferred embodiment of the invention the magnetic discs are formed of a nonconductive material such as ferrite and the nonmagnetic discs are formed of alumina.
REFERENCES:
patent: 2469165 (1949-05-01), Hillier
patent: 2637000 (1953-04-01), Page
patent: 2859363 (1958-11-01), Leisegang et al.
patent: 3736423 (1973-05-01), Katagiri et al.
patent: 3812365 (1974-05-01), Le Poole
"A New Concept of Superimposed Deflection and Projection for Probe-forming Electron-Beam Systems", Pfeiffer, Eighth International Congress of Electron Microscopy, CanBerra, 1974 vol. 1, pp. 56-57.
Loeffler Karl H.
Pfeiffer Hans C.
Anderson B. C.
Galanthay Theodore E.
International Business Machines - Corporation
Smith Alfred E.
Thomson James M.
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