Mass spectrometer

Abstract

In an ion detector, power supplies (through) generating independently controllable voltages are provided to respectively apply voltages to first to fifth dynodes (through), a final dynode (), and an anode () in a secondary electron multiplier (). Furthermore, the signal from the anode () is extracted, and the signal from the fifth dynode (), which has a low electron multiplication rate, is extracted. These two signals are concurrently converted into digital values, taken in by a data processing unit (), and stored in a data storage unit (). When a mass spectrum is created in the data processing unit (), the two detected data for the same time are read out and the presence or absence of signal saturation or waveform deformation is determined from the values of one of the detection data. If there is a high probability of signal saturation, the detection data based on the signals in the intermediate stages are selected, and the level of the selected data is corrected. The application of independent voltages to the secondary electron multiplier () makes the signal saturation less likely to occur. Even if saturation temporarily occurs, an unsaturated signal can be reflected in the mass spectrum.