US 6,674,068 B1Granted

Time-of-flight (TOF) mass spectrometer and method of TOF mass spectrometric analysis

AssigneeJEOL Ltd.

InventorYoshihiro Kammei

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Abstract

There is disclosed a time-of-flight (TOF) mass spectrometer using microchannel plates (MCPs), that are prevented from saturating even if strong ion pulses hit the microchannel plates. Usually, the saturation would result in a dead time, removing parts of the produced mass spectrum and shortening the lifetimes of the microchannel plates. An intermediate ion detector is mounted at the spatial focusing point of a reflectron TOF-MS spectrometer portion to measure the current values of ion pulses arriving from an external ion source, as well as the elapsed times since start of travel of the ion pulses. Information obtained by the measurement is fed back to the final ion detector. Thus, the gain of the final ion detector is controlled before the ion pulses reach the final ion detector. This prevents saturation of the final ion detector. The invention can also be applied to a TOF mass spectrometer using pulsed ionization and to an electrostatic sector field TOF mass spectrometer.

Claims16

Dependent claims

A time-of-flight (TOF) mass spectrometer comprising:

an ion source for emitting ion pulses;
a time-of-flight mass spectrometer region through which the ion pulses emitted from the ion source travel;
a final ion detector for detecting incident ion pulses which have traveled a given distance through said region and have been dispersed into plural ion pulses according to flight velocity;
a flight time-measuring portion for measuring times taken for the dispersed ion pulses to reach the final ion detector since departure from the ion source;
an intermediate ion detector mounted in said time-of-flight mass spectrometer region and acting to detect current values of said dispersed ion pulses before reaching the final ion detector;
a measuring means for measuring elapsed times of the dispersed ion pulses reaching the intermediate ion detector since departure from the ion source;
means for forecasting flight time at which the dispersed ion pulses will reach the final ion detector based on the measured elapsed times since the departure from the ion source;
and
a saturation-preventing means for controlling the gain of the final ion detector according to the current values of the dispersed ion pulses detected by the intermediate ion detector and according to the forecast times of arrival of the dispersed ion pulses at the final ion detector in step with arrival of the dispersed ion pulses to prevent the dispersed ion pulses from saturating the final ion detector.

6 more elements

Dependencies are inferred from the claim text.