THE NONLINEAR ION-TRAP .3. MULTIPOLE COMPONENTS IN 3 TYPES OF PRACTICAL ION-TRAP

A general analytical method is introduced to study quantitatively the multipole components of potential fields in three types of practical ion trap with finite electrode size: (a) the truncated Paul ion trap; (b) the truncated ion trap with modified hyperbolic angle; (c) the truncated ion trap with stretched end-cap distance. Surface charge densities on ring and cap electrodes and capacitances of ion traps are calculated. The analysis point out different properties of the three electrode structures, and presents a potential distribution which allows the study of ion motion in these practical ion traps.