Electron beam focussing method having beam displaced using electrical acceleration field/magnetic field combination providing desired focussing point position using equipotential plane

摘要

The electron beam (28) focussing method has an electron source (16) with the beam displaced from the propagation axis (Z). An electrical acceleration field is created along the axis. A magnetic field (B) is created along the propagation axis and cooperates with the electrical field to create a desired focussing point using the equipotential plane (48,50).