An electromagnetic/electrostatic dual cathode system for electron beam instrumentsA method of providing cathode redundancy which consists of two fixed cathodes and uses electromagnetic and/or electrostatic fields to direct the electron beam to the electron optical axis is presented, with application to the cathode system of the Scanning Electron Microscope and Particle Analyzer proposed for NASA's Mariner Mark II Comet Rendezvous/Asteroid Flyby projected for the 1990s. The symmetric double deflection system chosen has the optical property that the image of the effective electron source is formed above the magnet assembly near the apparent position of the effective source, and it makes the transverse positions of the electron sources independent of the electron beam energy. Good performance of the system is found, with the sample imaging resolution being the same as for the single-axis cathode.
Document ID
19870047441
Acquisition Source
Legacy CDMS
Document Type
Conference Proceedings
Authors
Bradley, J. G. (Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Conley, J. M. (California Institute of Technology Jet Propulsion Laboratory, Pasadena, United States)
Wittry, D. B. (Southern California, University Los Angeles, CA, United States)
Albee, A. L. (California Institute of Technology Pasadena, United States)