Aberration properties of the quadrupole triplet with a line source for a micro-probe optics

The aberration properties of the quadrupole triplet with a line source has been investigated theoretically under the pseudo- stigmatic condition with the high demagnification. The aperture and chromatic aberration coefficients were calculated numerically using the general formulae of orthogonal system. The aperture aberration coefficient in the narrow direction of the line source is four order of magnitude larger than the aberration in the long direction. By providing the aperture electrodes close to the second quadrupole lens, the aperture aberration can be coincided with the aberration in the long direction. It has been apparent that by correction of the aperture aberrations, the quadrupole triplet with a line source can achieve the micro probe of around 0.1 μm which is limited by the chromatic aberrations.