Mass spectrometer with crossed electric and magnetic fields

The merits of a mass spectrometer with crossed electric and magnetic fields are discussed. The electric field is assumed to be a toroidal one (field index c) and the magnetic field homogeneous. In the case c=-1 the stigmatic double focusing is obtained and the Barber's rule holds. If the toroidal electric field is produced by a cylindrical condenser having a pair of Matsuda plates, the directional focusing can be adjusted by changing the electric potential applied to the Matsuda plates and the velocity focusing can be adjusted by changing the ratio of electric and magnetic fields independently to each other. Therefore, all focal adjustments can be done electrically and no mechanical adjustment is necessary. This type of mass spectrometer works also as a single focusing apparatus under very weak magnetic field if appropriate potentials are applied to the condenser electrodes and Matsuda plates.