Abstract
Image aberrations of various different magnetic sector type mass spectrometers are calculated and compared. Four second order aberration coefficients Aαα, Ayy, Ayβ and Aββ are important. The third order aberration coefficients are sufficiently small. The old proposals for Aαα = 0 yield very large aberrations for Ayy, Ayβ and Aββ due to the influence of fringing field. The image aberrations of 90° and 60° sector type with symmetric arrangement are rather small. Several ion optical systems for a better single focusing mass spectrometer are proposed (for instance, φm = 130°, ε1 = ε2 = 55°, Aγ/γm = 3).
