Electrostatic cylinder lenses III: three element asymmetric voltage lenses

For Pt. II see ibid., vol. 5, 150 of 1972. The potential distribution inside three equidiameter coaxial cylinders separated by finite distances has been derived and used to calculate the focal lengths, mid focal lengths and spherical aberration coefficients of some triple cylinder lenses having three different voltages applied to them. The lenses have the length of the central cylinder equal to its diameter or to half its diameter. Data are presented for such lenses with the middle potential both higher and lower than the outer potentials.