Electrostatic cylinder lenses II: Three element einzel lenses

For Pt. I see ibid., vol. 4, 625 of 1971 The potential distribution inside three equidiameter coaxial cylinders separated by finite distances has been used to calculate the focal lengths, mid focal lengths and spherical aberration coefficients of some triple cylinder einzel lenses. The lenses considered have the length of the middle cylinder equal to its diameter or to half its diameter. Data are presented for such lenses with the middle cylinder at either a higher or lower potential than the outer cylinders over a large range of voltage ratios.