Mattauch-Herzog Type Mass Spectrograph with a Two Stage Electrostatic Field

Abstract

The most important advantage of the Mattauch—Herzog type mass spectrograph is double focusing for all masses. One disadvantage, however, is the fact that the energy slit cannot control the velocity spread (β) independently of beam divergence (α). This disadvantage is removed by substituting a two-stage electrostatic field for the usual single one. General formulae for determining the distances between the elements of the optical system are derived. Combinations of two cylindrical electrostatic fields with equal radii are chosen as a practical example. The condition to be fulfilled for a physically significant solution and the resolving power of this system are discussed. The study of the second-order aberrations shows that α2 focusing for all masses can be achieved under suitable conditions. In addition, α β and β2 aberrations can be made to vanish simultaneously at a point on the focal plane. The design parameters are numerically computed and tabulated for several favorable examples. The total image defect is calculated for a typical example, and found to be very small for a wide range of masses.