The paper looks into the applicability of two models of Coulomb interactions - space charge interaction and two particles interaction - for image distortion calculations in the SCALPEL projection system. In contrast to [1-3], the paper takes into consideration the electron beam structure which is determined by the image structure, focusing and vignetting conditions. The calculations show that with the increasing electron current the space charge interaction becomes stronger than two particle interactions. In a qualitative sense spherical aberrations caused by Coulomb interactions are the same in the both models. The inference is that a Coulomb decrease in resolution in this particular system is largely due to space charge interactions. The calculations of the central point spread show that the resolution can be increased several times by correctly choosing the location of the image plane. With the beam energy of 10 kV and current of 50 mA the highest resolution is 25 nm.

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