Patent ID: 6492640
Filing Date: 2002-12-10
Classification: H01J

Abstract:
A mass spectrometer provided with an ionization device, wherein the ionization device comprises:an ionization chamber, a filament situated near the ionization chamber for emitting thermoelectrons for ionizing molecules in the ionization chamber, a trap electrode situated near the ionization chamber at a side opposite to the filament for accelerating the thermoelectrons by a potential difference between a potential of the filament and that of the trap electrode, said trap electrode capturing the thermoelectrons passing through the ionization chamber, first current measuring means connected to the trap electrode for measuring a trap current flowing by the thermoelectrons reaching the trap electrode, second current measuring means connected to the filament for measuring a total current flowing by the thermoelectrons emitted by the filament, current control means connected to the filament for controlling a heating current flowing through the filament so that one of the trap current and the total current becomes a predetermined value, and abnormality diagnosis means connected to the first and second current measuring means and the filament, said abnormality diagnosis means measuring current values of the first and second current measuring means in conditions that the filament is energized and not energized to determine abnormality based on the measured current values.