Digitally controlled deflection of an electron beam with a miniature octupole unit

The paper describes results of preliminary investigations of an octupole deflecting-focusing system, comprising a miniature unit of two diaphragms: a focusing diaphragm divided into eight segments with an octupole axial symmetry and a screening diaphragm. They are electrically isolated and can be mutually biased up to  ±4 kV with focusing voltage, while an isolated sample stands for the third electrode of a unipotential focusing lens. The octupole unit is steered by a digital, eight-channel electronic control system with isolated output circuits, enabling high-voltage bias of the octupole focusing diaphragm. The system is destined for handling an ion beam from a coaxial ion micro-source in scanning electron microscopy or an electron beam in a prospect electron optical micro-device. Preliminary tests conducted with a JSM-840 scanning electron microscope proved that the quasi-planar deflecting and focusing system (2.5 mm thick, at a distance of 3 mm to the sample) is capable at operating with acceptable imaging errors. Further, the electronic control system and the software fully meet the requirements. (paper)