This book (Practical Electron Microscopy and Database) is a reference for TEM and SEM students, operators, engineers, technicians, managers, and researchers.
 

=================================================================================

Macroscopic fields in EMs are produced by macroscopic elements, including the solenoids, magnetic multipoles or by the voltages applied to conducting devices, for example cylinders or apertures.

Multipoles of higher-order than 3 do not produce 3rd-order spherical aberrations at all and elements of lower order than 2 disturb the spherically symmetric paraxial optics.