Abstract: A charged-particle source for generating a charged-particle comprises a sequence of electrodes, including an emitter electrode with an emitter surface, a counter electrode held at an electrostatic voltage with respect to the emitter electrode at a sign opposite to that of the electrically charged particles, and one or more adjustment electrodes surrounding the source space between the emitter electrode and the counter electrode. These electrodes have a basic overall rotational symmetry along a central axis, with the exception of one or more steering electrodes which is an electrode which interrupts the radial axial-symmetry of the electric potential of the source, for instance tilted or shifted to an eccentric position or orientation, configured to force unintended, secondary charged particles away from the emission surface.

Abstract: A charged-particle source for generating a charged-particle comprises a sequence of electrodes, including an emitter electrode with an emitter surface, a counter electrode held at an electrostatic voltage with respect to the emitter electrode at a sign opposite to that of the electrically charged particles, and one or more adjustment electrodes surrounding the source space between the emitter electrode and the counter electrode. These electrodes have a basic overall rotational symmetry along a central axis, with the exception of one or more steering electrodes which is an electrode which interrupts the radial axial-symmetry of the electric potential of the source, for instance tilted or shifted to an eccentric position or orientation, configured to force unintended, secondary charged particles away from the emission surface.