In the thin lens limit, aberrations are impulsive forces which vary as some higher power of the two transverse directions. Aberration coefficients for quadrupoles.
L is the length and f is the focal length.
Type f 2 LA f 2 LB Elect. Under this condition, and using the fact that from eqn. Now we simply use eqn. Application Formulas like eqn. For example, simply adding together the emittance growths of individual quadrupoles will yield an incorrect result.