Abstract: An ion source for a quadrupole mass spectrometer comprises, from the upstream end to the downstream end in the axis of the quadrupole, an ionization chamber with heated filament and electrostatic field associated with an electron-optical system provided with an electron convergence device. A uniform magnetic field is superimposed on the electrostatic field of the ionization chamber. The electron-optical system comprises a first extraction electrode having a downstream surface which is at least approximately spherical, a second coaxial electrode in the form of a disk having a central orifice of relatively substantial width and, at a short distance, a third electrode in the form of a disk having a relatively small central orifice, the potentials of the electrodes being so adjusted as to form hemispherical equipotential surfaces between the first and the second electrode.

Abstract: A mass spectrometer with quadrupole filter comprises a spectrometer chamber containing the ion source, its associated electron optical system, and a quadrupole filter. The chamber is designed in the form of a hollow sleeve closed at one end by a removable leak-tight cover mounted on a longitudinally-sliding motor-driven carriage which also supports the ion source and its optical system. The carriage is capable of selective displacement in translational motion between a closed position in which the ion source is in the work position and the cover is in the closed position, and an open position in which the carriage projects outside the casing at least to a partial extent and allows access to the ion source and its associated optical system.