A simple double focusing mass spectrometer of new type

A new ion optical system is proposed for a simple double focusing mass spectrometer. The apparatus consists of a parallel plane condenser, a doublet electrostatic Q lens and a simple homogenous magnet having pole pieces of rectangular shape. (rsub(m)=30cm, phisub(m)=300, epsilon'=epsilon''=150). A weak magnetic field (approximately 5000 gauss) is sufficient to analyze ions of A approximately 1000 because rsub(m) is large. Stigmatic double focusing is obtained by the doublet Q lens and the plane condenser. The adjustment of the energy focusing as well as the directional focusing can be achieved by changing potentials on the electrodes of two Q lenses. Therefore, no mechanical adjustment is necessary at all. Several examples of suitable parameters are shown, and the method of the electrical focus adjustment is explained. The second order focusing character is also described. (author)