Magnetic immersion field emission electron gun systems capable of reducing aberration of electrostatic lens

Abstract

A magnetic immersion field emission electron gun has a vacuum vessel having a central axis in a predetermined direction, a cathode arranged along the central axis of the vacuum vessel for generating an electron beam, an anode for forming an electron beam path by accelerating a generated electron beam in the central axis direction, an electrostatic lens arranged between the cathode and anode for generating an electric field which focuses an accelerated electron beam toward the central axis, a magnetic field generating element arranged around the electron beam path for generating a magnetic field for focusing the electron beam in order to preventing a diameter of the electron beam from expansion by an aberration of the electrostatic lens, and a moving mechanism for moving the magnetic field generating element at a position where a peak point of a strength of the magnetic field generated by the magnetic field generating element coincides with a portion where the aberration of the electrostatic lens becomes most conspicuous. The electron gun having such a configuration can provide an effect of reducing a spherical and chromatic aberration by efficiently providing a lens characteristic to the electrostatic lens even though the entire length of electrostatic lens is long.

Dependencies are inferred from the claim text.