Ion optics of probe-forming systems on the base of magnetic quadrupole lenses with conical aperture

Abstract

This paper describes the performance of probe-forming systems based on a new type of magnetic quadrupole lens with a conical aperture (MQL CA). The main difference in the MQL CA from the conventional quadrupole lens with a cylindrical aperture is that the poles in it are not parallel to the lens axis and positioned at a certain angle. The basic advantage of such a lens is that the conical angle of the aperture allows the profile of the longitudinal distribution of the main components of the quadrupole field to be changed. It provides for the changing of the focal length value, displacement of the principal plane relative to the centre of the lens and aberration variations depending on the conical angle. A theoretical study of the ion optics of the probe-forming systems consisting of a triplet MQLs CA was carried out. A comparison of the systems with MQLs CA and conventional systems based on the magnetic quadrupole lens (MQL) with a cylindrical aperture shows the possibility of increasing the acceptance of the first due to using the new type of lens.