Joseph P Conley

US Patent:

48475025, Jul 11, 1989

Filed:

Aug 11, 1987

Appl. No.:

7/084062

Inventors:

James G. Bradley - Altadena CA
Joseph M. Conley - La Canada CA
David B. Wittry - Pasadena CA

Assignee:

The United States of America as represented by the Administrator of the
National Aeronautics and Space Administration - Washington DC

International Classification:

H01J 302

US Classification:

250396ML

Abstract:

An electron beam source having a single electron optical axis is provided with two coplanar cathodes equally spaced on opposite sides from the electron optical axis. A switch permits selecting either cathode, and a deflection system comprised of electromagnets, each with separate pole pieces equally spaced from the plane of the cathodes and electron optical axis, first deflects the electron beam from a selected cathode toward the electron optical axis, and then in an opposite direction into convergence with the electron optical axis. The result is that the electron beam from one selected cathode undergoes a sigmoid deflection in two opposite directions, like the letter S, with the sigmoid deflection of each being a mirror image of the other.