A multi-stage cylindrical mirror analyzer incorporates a primary radiation source, such as an electron gun, disposed internally and along the axis of the multi-stage analyzer. The gun includes all of the optical elements for producing a well defined beam, correcting aberration thereof and scanning the beam on a sample. The components of the gun are distributed along the axial length of the analyzer. Aberration of the scanned beam due to traversal of a subsequent lense is minimized by placing the pivot point of the deflected beam trajectory substantially at the center of the lense. The greater dispersion of the multi-stage analyzer and the unit magnification thereof permit proportionately greater exit aperture dimensions, whereby a wider field of view may be realized.