FOURIER TRANSFORM MASS SPECTROGRAPH

PROBLEM TO BE SOLVED: To improve the availability factor of a Fourier transform mass spectrograph by providing a controller controlling the current flowing in an electron emitting filament on the mass spectrograph. SOLUTION: A sample gas is guided into an analyzer cell 2 from a feed pipe 44, and it is ionized by a filament 2b and the electron beam emitted toward a collector Q. Cyclotron resonance occurs on the ionized sample gas on the plane perpendicular to the magnetic field. An output signal is sent from a receiving electrode R in the analyzer cell 2 to an electronic circuit outside a vacuum chamber 11 by the cyclotron resonance. An electric signal is sent from a vacuum detector 33 in the vacuum chamber 11 to an external vacuum gauge 36, and the degree of vacuum is determined by the vacuum gauge 36. A degree of vacuum signal is sent from the vacuum gauge 36 to a comparator 38. The comparator 38 compares the degree of vacuum with the set value of the degree of vacuum stored in the comparator 38, turns a relay on when the degree of vacuum is the set value or below, and turns the relay off when the degree of vacuum is the set value or above. When the degree of vacuum becomes the set value or below, the relay in a controller cuts off the current of a filament 43.