Chromatic aberrations of three-electrode transaxial mirrors

The authors have previously given the cardinal elements and geometric aberration coefficients for three-electrode transaxial electrostatic mirrors with two-plate electrodes for energy-separation and focusing of parallel and divergent beams of charged particles. They considered both concave and convex mirrors, and they found the conditions under which second-order stigmatic focusing with respect to the angles of divergence of the beam is achieved in two mutually orthogonal directions. In the present paper they give the chromatic aberration coefficients for these mirrors